Boeing B-29 Superfortress Familiarization and Maintenance Manual,Part 4.pdf

Boeing B-29 Superfortress Familiarization and Maintenance Manual,Part 4.pdf
COMMUNICATIONS 8-29 A I R P L A N E
COMMUNICATIONS TABLE OF CONTENTS PAGE COMMUNICATIONS (GENERAL) -------------------------------------- 2 COMMUNICATION SYSTEM______________________________________________ 3 RADIO OPERATOR'S STATION__________________________________________ 5 COMMAND RADIO RECEIVERS__________________________________________ 6 COMMAND RECEIVER CONTROL_____________________________________ 7 COMMAND RADIO TRANSMITTER ------------------------------------- 8 COMMAND TRANSMITTER CONTROL_______________________________ 9 COMMAND MODULATOR ------------------------------------------------- 11 LIAISON RADIO, SCR-287-------------------------------------------------- 12 LIAISON RECEIVER ------------------------------------------------------------ 12 LIAISON TRANSMITTER BC 375c______________________________________ 14 LIAISON TUNING UN IT ____________________________________________________ l 5 TRAILING ANTENNA -------------~------------------------------------------ l 8 RADIO COMPASS ~ECEIVER SCR-269G______________________________ 19 RADIO COMPASS CONTROL BOX_______________________________________ 19 RAD10 COMPASS UN IT______________________________________________________ 20 LOOP ANTENNA -------------------------------------------------------------- 23 MARKER BEACON RECEIVER (RC-43A)______________________________ 24 BLIND LANDING RADIO RC- l 03________________________________________ 25 RADIO BLIND LANDING RECEIVER______________________________________ 25 BLIND LANDING RECEIVER CONTROL BOX________________________ 26 DINGHY RADIO TRANSMITTER_______________________________________ ______ 27 IFF IDENTIFICATION RADIO SCR-695_______ ._______________________ 28 AIRBORNE RECOGNITION RADIO ARR SCR-515________________ 29 PORTABLE FREQUENCY METER SCR-21 l _____________________________ 30 INTERPHONE EQUIPMENT RC-36 _____ _____ ___ ___ ____________________ 31 INTERPHONE DYNAMOTOR ... ________________________________________ 32 INTERPHONE AMPLIFIER _ _ _________ -·------------------------------- 32 INTERPHONE CIRCUIT_ ---- -----------·· -- --- ---------------. 35
RESTRICTED 8-29 FAMILIARIZATION ANO MAINTENANCE COMMUNICATIONS While radio in general has been considered to deal primarily with communications, its uses have been multiplied and greatly diversified, especially in regard to aircraft radio. Aircraft radio may be classified according to use under one or more of the following six types: Communications Landing Navigation Identification Distress Location COMMUNICATIONS: This class comprises equipment performing the function of communication from the airplane to the ground, from one airplane to another and between various members of the crew in the same airplane {interphone). Communication is carried on either by voice. CW (continuous wave) or MCW {tone). Frequencies may vary from a few hundred kilocycles to IO or 20 megacycles. NAVIGATION: Radio compasses, marker bea- cons, and radio (absolute) altimeters are included in this classification. The radio compass indicates the airplane's heading with respect to the radio station being received, but does not indicate its heading with respect to true or magnetic north. Marker beacon transmitters are the "milestones of the air" and reception of their signals indicates the airplane's progress along a radio range or "beam." Radio altimeters indicate the clearance (height) of the airplane above the terrain and not the height of the airplane above sea level as is shown by the pressure, or barometric type, altimeter. IDENTIFICATION: The purpose of identification radio is to distinguish between friendly and enemy aircraft. This identification is used by the pilot to identify another airplane, or by a ground station to identify a passing airplane. DISTRESS: The emergency sea rescue (dinghy) transmitter, a small self-powered unit, sends out a distress signal to enable rescue parties to locate the crew after abandoning ship. LANDING: Included in this classification are components of blind landing systems by means of which the airplane may be successfully landed under zero ceiling conditions. Such radios indicate to the pilot the airplane's height above the ground, and its ground track in relation to the airport runway. LOCATION: This classification includes the equipment popularly known as radar. These radios, of a confidential nature, have a variety of uses. such as locating other aircraft. Radio equipment in the Model B-29 airplane consists of the following: Designation Type Classification Command Set SCR-274- N Communication Liaison Set SCR-287 Communication Frequency Meter SCR-211 Communication lnterphone Equipment RC-36 Communication Filter Equipment RC-198 Communication Radio Compass SCR-269-G Navigation Marker Beacon RC-43A Navigation Blind Landing RC-I 03 Landing Emergency Sea Rescue SCR-578 Distress IFF SCR-695 Identification With Signal Corps equipment, the first code model number of the item. The last letter is the group consisting of one, two, or three letters is series designation and indicates a modification the designation of the type of equipment. SCR of the model.Therefore,SCR-274-N means Sig- means "Signal Corps Radio." A Signal Corps nal Corps radio, model 274, modification N. In radio generally comprises radio components general, items of the same model number, but designated RC, or basic components designated BC. These components are further sub- with different series numbers, are interchange- divided into individual items, such as: plugs able. However. care should be taken in inter- (designated PL), couplings (designated MC), changing these items, as occasionally the series insulators (designated IN), etc. The two or letter has been used for items not completely three numerals following the dash indicate the interchangeable. 1 COMMUNICATIONS
RESTRICTED NOTES
RESTRICTED A IFF RADIO MANUAL DETONATOR SWITCHES IFF RADIO CONTROL SWITCHES (TWO) ON PILOT'S INSTRUMENT PANEL: RADIO COMPASS B INDICATOR, INSTRUMENT LANDING RADIO INDICATOR, MARKER BEACON AMBER SIGNAL LIGHT C LIAISON TRANSMITTER DYNAMOTOR D LIAISON RADIO TRANSMITTER E LIAISON RADIO ANTENNA TUNER F RADIO COMPASS RELAY SHIELD G TRAILING ANTENNA FAIRLEAD CONTROL H LIAISON RADJO RECEIVER COMMAND RADIO TRANSMITTERS J COMMAND RADIO ANTENNA TRANSFER RELAY K COMMAND RADIO RECEIVERS L COMMAND RADIO MODULATOR AND DYNAMOTOR CO-PILOT'S RADIO COMPASS CONTROL BOX M N 0 p Q R s T u V w X y z LIAISON RADIO ANTENNA TRANSFER SWITCH INTERPHONE DYNAMOTOR INTERPHONE AMPLIFIER IFF RADIO SPARE-PLUG-IN TRANSMITTER TUNING UNITS (2) LIAISON RADIO TRAILING ANTENNA INDICATOR IFF RADIO CONTROL BOX FREQUENCY METER RADIO COMPASS CONTROL BOX RADIO COMPASS INDICATOR JACK BOX IFF RADIO IMPACT DETONATOR SWITCH DETONATOR CIRCUIT WARNING LIGHTS WHIP ANTENNA OR PLUG STOWED HERE ~ -· , ; WHIP ANTEN N' ~ " 3 1 ~ .......... • • • ••• , TRAILING ANTENNA LIAISO •• • •• COMMAND RADIO ANTENNA . . ...•. ....... COMMAND RADIO TRANSMITTER CONTROL BOX COMMUNICATION SYSTEM COMMUNICATIONS SIDE GUNNER'S JACK BOX 8-29 F"AMILIARIZATl □ N -AND MAINTENANCE TAIL GUNNER'S JACK BOX DINGHY RADIO TRANSMITTER - - - SPARE-PLUG-IN TRANSMITTER TUNING UNITS (4 LIAISON RADIO TOP GUNNER 1 S JACK BOX 3
8 - 29 NOTES F' A M I LI A R I Z A T 'I O N ANO MAINTENANCE
:a > 1:::9 - 0 0 c-:, -a c::, '" :I: :a :I: C: > ::z -I c-:, 0 :a:- :a --I .. c::, en ::z ~ en -I > -I - 0 :z c.n ( COMMAND TRANSMITTERS COMMAND RECEIVERS LIAISON ANTENNA TUNING UNIT LIAISON ANTENNA TRANSFER SWITCH LIAISON RECEIVER LIAISON TRANSMITTER COMMAND ANTENNA TRANSFER RELAY ( LIAISON TRANSMITTER DYNAMOTOR (PARTIALLY SHOWN) REMOTE TUNING SHAFTS COMMAND MODULATOR UNIT INTERPHONE AMPLIFIER ( COMMAND ANTENNA INSULATOR ---INTERPHONE DYNAMOTOR IFF IMPACT SWITCH ___) IFF DESTROYER CIRCUIT LIGHTS ~--INTERPHONE JACK BOX ------ RADIO COMPASS CONTROL BOX DESTROYER PLUG '------DESTROYER PLUG RECEPTACLE TRAILING ANTENNA REEL CONTROL BOX 1 RADIO COMPASS TUNING CABLE GEARBOX RADIO COMPASS INDICATOR LIAISON TUNING UNIT (2) STOWAGE TRAILING ANTENNA FAIRLEAD CONTROL MICROPHONE CORD SWITCH )>"IJ z )> 0 l: Ir ~; z;i:i -; - fl1 N z ► )>-i z- nD fl1 z .
RESTRICTED DYNAMOTOR TUNING DIAL B-29 ANTENNA TERMINAL TUNING SHAFT CONNECTION FAMILIARIZATION AND MAINTENANCE ALIGNING KNOB COMMAND RADIO RECEIVERS PURPOSE: Command set SCR-274-N is the pilots' communication system for short-range voice communication between the airplane and ground stations, usually used when requesting landing information: or between aircraft, to enable a flight commander to give instructions to various members of the flight. RECEIVER: The equipment used in the B-29 airplane consists of three receivers and two transmitters. Receiver BC-453-A covers 190 to 550 kilocycles; receiver BC-454-A covers 3.0 to 6.0 megacycles; and receiver BC-455-A covers 6.0 to 9.1 megacycles. These three receivers, located above the radio operator's station, are remotely-controlled by the pilot through a radio control box BC-450-A mounted on the pilot's engine control stand, aft of the throttles. This box contains three sets of controls, a set for each of the receivers. Each set consists of a gain (volume) control, a tuning control, a signal switch, and a channel selector. The gain control and tuning control are of the conventional types. The signal switch has three positions-CW- OFF-MCW, corresponding to "continuous wave.'' "off" and "modulated continuous wave. 11 The switch is usually turned to the MCW position to receive modulated radio signals. For continuous wave signals, the switch is turned to the CW position. Unmodulated code or CW signals consist of a keyed carrier signal, heard as a series of clicks in the receiver, which are generally unintelligible. However, with the signal switch at CW, a beat .frequency oscillator in the receiver applies an audio tone to the carrier making the signal readily intelligible. The receiver channel selector switch, labeled A-0-B, is sometimes referred to as the 11 Tel" switch. Two audio channels, through which the output of the three receivers may be heard, are labeled A and Bchannels. 6 COMMUNICATIONS
RESTRICTED PHONE SWITCH (SEE PHONE JACKS) GAIN CONTROL--- EMISSION SELECTOR SWITCH B-29 ELECTRICAL CONNECTOR F"AMILIARIZATICN AND MAINTENANCE ~-,;::a,,,,..-PHONE JACKS TUNING CABLE CONNECTION ··•-"'"""' "l' -------TUNING CABLE ELECTRICAL CONNECTO~---- CONNECTIONS COMMAND RECEIVER CONTROL The receivers may be coupled to these channels in any combination. However, since the receiver is generally heard through the interphone system, and the interphone system is connected only with channel A, these switches should be left in the A position. If it is desired to turn a receiver on and let it warm up to "stand by", the channel switch may be placed in the mid position. In this position, the audio output will not be heard. When it is desired to hear the audio output, the control should be returned to the A position. Remote tuning of the receivers by the radio control box is accomplished mechanically by three flexible shafts. All other control intercon- nections are electrical. MAINTENANCE: Tuning dials are provided on each section of the radio control box BC-450 and on the face of each receiver. Check occasionally to see that the dials on the control box agree with the dials on their respective receivers. If the dials do not agree, adjustment can be made by disconnecting the flexible shaft at the receiver, noting the receiver dial reading, and then turning the control box dial to correspond with this reading. The shaft may again be coupled and the readings should then agree. The only adjustment necessary on the receiver is the antenna alignment. The aligning procedure is as follows: Tune a receiver to its highest frequency. Adjust the antenna input circuit for maximum background noise, using the ALIGN INPUT knob on the lower left of the receiver face. The adjustment will be correct for all lower frequencies of this receiver. COMMUNICATIONS 7
RESTRICTED ANTENNA TERMINAL-- ANTENNA COUPLING ADJUSTMENT TUNING DIAL--- 8-29 FAMILIARIZATION AND MAINTENANCE ANTENNA '!!fl---------lNDUCTANCE ADJUSTMENT COMMAND RADIO TRANSMITTER TRANSMITTER: Transmitting equipment consists of two transmitters and a modulator-power supply unit. The transmitters are: BC-457, covering 4.0 to 5.3 megacycles, and BC-459, covering 7.0 to 9.1 megacycles. Other transmitters may be substituted when frequencies outside these ranges are required. The transmitters are located above the radio operator's station, forward of the command receivers, and are remotely-controlled by the radio control box BC-451, at the pilot's station. This control box is mounted on th·e side of the airplane at the left of the pilot's instrument panel. The controls provided are: a switch for COMMUNICATIONS
RESTRICTED EMISSION SELECTOR----..,, MICROPHONE JACK----- B-29 FAMILIARIZATION AND MAINTENANCE ----TRANSMITTER SELECTOR "----ON-OFF SWITCH ::------ELECTRICAL CONNECTOR COMMAND TRANSMITTER CONTROL turning on the transmitter tube filaments, a transmitter selector switch to select the transmitter to be operated, and an emission (TONE- CW-VOICE) selector switch. A key on the top of the box may be used by the pilot for code (CW) communication. However, CW communication is usually handled by the radio operator employing the liaison set. There are three controls on the face of each transmitter: the tuning control, the antenna inductance, and the antenna coupling. Each of these controls is equipped with a friction lock. Before using, these controls must be preset to the desired frequency. The selected frequency is set on the tuning control and the control is locked. The antenna coupling and antenna inductance controls are each tuned to give the greatest antenna current. Antenna current is indicated on the meter in the antenna relay shield which is mounted above the command transmitters. This antenna current indicator is not calibrated, and indicates only relative COMMUNICATIONS 9
RESTRICTED values. Tuning should be done with the transmitter control box emission switch in the CW position. The setting must not be changed when switching to the TONE or VOICE positions. The key or button on the top of the transmitter control box has two motions: up and down, and rotary. When the key is rotated clockwise, as viewed from above. it will be screwed down and held there, so that, with the emission switch in the CW position, only a continuous wave, or unmodulated signal, is sent. Turning the key counter-clockwise permits it to remain up so that the transmitter may be used for sending signals by means of the key. With the emission switch in the TONE position. these signals will be modulated with a I000-cycle audio tone. The emission switch will usually be left in the VOICE position. In this way modulation by means of the pilot's microphone {or other interphone stations) may be placed on the carrier so that oral signals may be sent and the transmitter operated by the microphone switch. This is a "push-to-talk" system and the transmitter is on the air only during the time the microphone button is held down. When this button is pressed, the antenna relay switches 8-29 FAMILIARIZATION AND MAINTENANCE the antenna from the receiver to the transmitter, and the modulator dynamotor starts rotating. This furnishes high-voltage tube plate current to the transmitters. This dynamotor is in operation only during transmission (VOICE position). The command receiver and transmitter are connected to each of the interphone stations throughout the airplane. When the desired transmitter has been selected by the pilot by means of the transmitter selector switch on his control box, any crew member may modulate the transmitter or may listen to the signals received. Power for the command radio is supplied from the DC power bus in the radio compass relay shield, behind the engineer's instrument panel. No fuse for the command radio is provided in this shield. Three I0-ampere fuses, one for each receiver, are located at the back of the receiver rack under metal caps labeled FUSE. There are two 20-ampere fuses in the modulator, one at each end of the dynamotor. There are no fuses in the transmitters, as the circuit to the transmitter is fused by one of the fuses on the dynamotor. 10 COMMUNICATIONS
RESTRICTED 8-29 f"AM I LIAR IZATI □ N AND MAINTENANCE COMMAND MODULATOR The antenna for the command radio extends from the top of the airplane aft of bulkhead 218, upward and aft, to the top of the vertical fin. An insulator is placed near the center of this antenna, limiting its length to 34 feet to permit proper antenna loading throughout the frequency range. MAINTENANCE: When the receiving or transmitting equipment does not function properly, or respond to any of the adjustments pre- viously mentioned, replace the unit not operating properly. Adjustments in the interior of the radio require special equipment and should be attempted only by authorized personnel at the proper maintenanee depot.s. COMMUNICATIONS 11
RESTRICTED AUTOMATIC- MANUAL GAIN CONTROL JACKS------< BEAT FREQUENCY ADJUSTMENT 8-29 FAMILIARIZATION AND MAINTENANCE -----DIAL LIGHT RHEOSTAT :;:.--- ANTENNA TERMINAL 14--GROUND TERMINAL LIAISON RECEIVER LIAISON RADIO, SCR-287 GENERAL DESCRIPTION: The liaison radio consists basically of a single, long-range transmitter and receiver. This equipment is intended to be operated at the radio operator's station only, although the pilot and co-pilot, in addition to the radio operator, may modulate the transmitter. All crew stations have access to •the audio output of the receiver. Power for the liaison radio set is obtained from the radio compass relay shield. The liaison receiver is fused within the set, and the liaison transmitter has its fuses in the liaison dynamotor filter shield. NOTE: The equipment should never be operated while the cover of this shield is removed. The fuse for the trailing antenna reel motor is in the forward bomb bay door solenoid shield, underthe wing center section. This fuse must be rated at IO amperes. 12 COMMUNICATIONS
RESTRICTED RECEIVER: Radio receiver BC-348 is mounted on the radio operator's table. It is a 6-band, superhetrodyne receiver, covering a frequency range of .5 to .5 megacycles and 1.5 to 18.0 megacycles. No remote control is provided. Controls on the face of the receiver are as follows: Receiver switch, CW beat oscillator switch, crystal switch, volume control, beat oscillator frequency control, band switch, tuning control, dial light control, and antenna alignment control. The power switch is labeled AVC-OFF-MVC. OPERATION: The receiver is operated by turning the switch either to AVC, "automatic volume control", or MVC1 11 manual volume con- trol11 • The switch is usually kept in the MVC posi- +ion while tuning in a station. The automatic volume control (AVC position) is used only to regulate the gain or volume of the receiver after the station has been fully tuned in. The crystal switch is used to increase receiver selectivity, enabling two adjacent radio sta- 8-29 FAMILIARIZATl □ N ANO MAINTENANCE tions to be separated. The crystal narrows the signal channel width to 2 kilocycles. The CW oscillator switch controls a beat frequency oscillator similar to the one used in the command set. This oscillator is used to apply a tone (beat frequency) to a continuous wave signal so that the code characters may be intelligible. The beat oscillator frequency control knob varies the pitch of the tone to suit the radio operator. The dial light knob adjusts a rheostat control- ling the brilliance of the tuning dial lights. Adjust the antenna alignment control to give a maximum signal when the receiver is tuned to 2.9 megacycles. Although the audio output of this receiver is usually monitored through the interphone fack box, the radio operator's headset extension cord may be plugged directly into either of the two telephone jacks on the front of the receiver. COMMUNICATIONS 13
RESTRICTED ELECTRICAL CONNECTORS EMISSION SELECTOR SWITCH ON-OFF SWITCH B-29 FAMILIARIZATION AND MAINTENANCE R. F. - MODULATOR FILAMENT CHECK SWITCH LIAISON TRANSMITTER BC375C TRANSMITTER: Liaison radio transmitter BC-375 is mounted on the cabin sidewall, forward of the radio operator's table. No remote control is provided. The transmitter must be adjusted locally by the radio operator to be placed in operation. The transmitting components are: the transmitter, dynamotor, antenna tuning unit, and seven alternate plug-in tuning units. In addition to the tuning unit ordinarily installed in the transmitter, four are stowed in the aft pressurized compartment at the left of the upper rear turret, and two are stowed under the radio operator's table. Each tuning unit provides the transmitter with a different frequency range and is interchangeable with any other unit. 14 COMMUNICATIONS
- -- - - RESTRICTED SNAPSLIDES OSCILLATOR TUNING---- 8-29 FAMILIARIZATION AND MAINTENANCE CALIBRATION CHART LIAISON TUNING UNIT CAUTION: Very high voltages are present, which, if proper precautions are not observed, can prove fatal. The transmitter should never be operated unless its cover is in place. This caution must be complied with in operating the dynamotor, since it contains the same high voltages. Three meters, located on the face of this transmitter, show antenna current, total plate current, and filament voltage. There is also a pilot light in the filament circuit. Filament voltage is controlled by the ON-OFF switch on the face of the equipment. NOTE: To allow the filaments to heat up and the tubes to attain proper operating temperature, turn this switch to the ON position a short time before the equipment is to be operated. When a new transmitter has been placed in the airplane, several preliminary adjustments are required. These adjustments are outlined in the Air Forces publication relating to the equipment and should be followed in detail. OPERATION: Before placing the transmitter in operation, select the proper transmitter tuning unit for the desired frequency. CW operation may then be obtained as follows: Place the signal switch on CW. From the calibration chart on the front of the transmitter tuning unit, set the band change switch, the MO tuning control, and the PA tuning control for the desired frequency. Set the antenna coupling switch D on point I. NOTE: The band change switch does not appear on the plug-in tuning units TU-7 to TU- I0 inclusive. COMMUNICATIONS 15
RESTRICTED When the ON-OFF switch is placed in the ON position, the dynamotors should start and the MO and PA filaments light. After sufficient time has elapsed, press the test key or the transmitting key. The vacuum tubes will draw plate current as indicated by the total plate current meter. Immediately check the PA tuning for resonance by varying the control slightly until minimum total plate current is indicated. When the PA circuit is properly resonated, the total plate current will be from 80 to 110 milliamperes. Next, tune the antenna to resonance by varying the length of the antenna, using the antenna reel control box. Antenna resonance is indicated by a reading of current on the antenna current meter, and by an increase in total plate current. Increase in plate current is the more sensitive indication of approaching antenna resonance. When the antehna is tuned to resonance, the total plate current reading will be somewhat higher than the off resonance value. If the plate current is below 200 to 220 milliamperes, increase the coupling to the antenna by placing antenna coupling control D on a higher point, and retune the antenna circuit. When finally adjusted, the total plate c~rrent should be from 200 to 220 milliamperes. If necessary, retune the circuit slightly, keeping the PA dial · (control C) in resonance to stay within the plate current limits. The equipment should now be delivering rated power output, and communication may be carried on by operating the transmitter key on the radio operator's table. To shut down the equipment, place the ON- OFF switch in the OFF position. 8-29 f"AMILIARIZATI ON AND MAINTENANCE To operate the equipment for voice transmission, assuming it is in CW operation, the following procedure is recommended: Note the value of total plate current for CW operation. Then, place the signal switch in the VOICE position, and by means of the modulator bias adjustmentin the tube compartment, adjust until the total plate current, with the microphone switch depressed, is approximately 20 to 35 milliamperes higher than for CW. The modulator tubes are now biased for class B operation, and radio phone communication may be carried on. After the equipment has been adjusted for voice operation, place the signal switch on TONE for tone transmission. The total plate current on TONE will be between 300 and 350 milliamperes. In the radio compass junction shield, aft of the engineer's panel on the cabin right hand sidewall, a switch is marked MONITOR and NOR- MAL. This switch should be left in the NORMAL position. In this positionr the transmitter automatically silences the receiver when the transmitter is in operation. This is accomplished by a relay within the transmitter. When the transmitter is placed on the air, the side tone from the transmitter is sent through the interphone audio channel and may be heard by all crew members. When the transmitter is in operation and it is desired to keep the receiver on the air (e.g. checking frequency), place this switch in the MONITOR positio~. In this position, when the transmitter is sending, the receiver remains operative, allowing monitoring of various frequencies during transmission. No side tone then 16 COMMUNICATIONS
b;-=== ~ - - RESTRICTED will be injected in the liaison audio system and no side tone will be heard by the crew members. ANTENNAE: The antenna system for the liaison radio consists of two separate antennae: the trailing antenna extending from the right hand side of the forward bomb bay, and an auxiliary antenna. The auxiliary antenna lead extends from a point aft of bulkhead 218 near the top, of the forward bomb bay to a point on the top surface of nacelle number 3 fairing. This antenna uses the airplane skin as an aerial and is employed while the airplane is on the ground or flying in formation, when the trailing antenna cannot be used. Two controls are provided for the operation of the trailing antenna. The first control (cable) 1 located under the radio operator's table, is a lever which may be raised or lower.ed. With the lever in the UP position, the trailing antenna fairlead is faired flush with the skin of the bomb bay. When the lever is placed in the LOWER position, the rear end of the fairlead extends approximately IO inches from the skin of the airplane, allowing it to extend well into the slip- stream to aid in reeling out the antenna wire. Inside the bomb bay, next to the fairlead, is the type RL-42A antenna reel containing 250 feet of antenna wire. A weight on the end of the wire aids in pulling out the trailing antenna, and prevents whipping of the trailing end. This reel is controlled by antenna reel control box BC-461 on the radio operator's instrument panel to the right of the operator. The reel control box has a switch for reeling out, reeling in, or stopping the reel. A footage indicator, (tally dial) indicates revolutions of the antenna reel, and since the circumference of ~~- B-29 FAMILIARIZATION AND MAINTENANCE the reel is approximately one foot, numbers on the counter show approximately the number of feet of antenna wire extended. This enables the radio operator to select the approximate length of antenna for resonance before tuning · the transmitter. The length of the antenna should be either ~ wave or quarter wave, whichever can best be obtained from the available length of antenna wire. The counter has a reset knob which is turned to set the counter to zero when the wire is completely reeled in. Check occasionally to I see if any error has developed in the dial reading. A warning light is on when the antenna is reeled out and the landing gear is extended, warning the radio operator of the impending landing. When the antenna has been completely reeled in, the light goes out, showing that the antenna is safe for the landing. Limit switches on the antenna re.el prevent im- proper reeling in or out of the antenna wire. These limit switches operate on tension instead of displacement or length of the wire. The antenna wire will not reel out unless the tension on the wire is equal to IO to 12 ounces: while the wire is being reeled in, the tension must be less than 15 pounds. When the weight is completely reeled in against the fairlead and this tension is exceeded, the "in" limit switch opens, pre- venting further rotation of the antenna reel. MAINTENANCE: A maintenance kit, type ME-57, containing spare wire and a spare antenna weight is located in section 42, on the right side of the airplane, above the trailing antenna reel. This equipment is used if the antenna wire is broken off. The trailing antenna wire should not be spliced, as splices will not go through the fairlead system. COMMUNICATIONS 17
RESTRICTED 18 SUPPORT BRACKET REEL DRIVE MOTOR } ) ) ? .J . ~ EXTERIOR VIEW TRAILING ANTENNA COMMUNICATIONS 8-29 F'AMILIARIZATl □ N AN □ MAINTENANCE
RESTRICTED DIAL LIGHT BAND SWITCH-- TUNING DIAL DIAL LIGHT RHEOSTAT GREEN LIGHT "CONTROL" INDICATOR B-29 FAMILIARIZATION AND MAINTENANCE TUNING METER DIAl LIGHT ---CONTROL VOLUME LOOP DRIVE SWITCH ---"CONTROL" BUTTON - - - - SPARE DIAL LIGHTS - - - OPERATION SWITCH RADIO COMPASS CONTROL BOX - - - ~ RADIO COMPASS RECEIVER SCR-269G PURPOSE: This radio direction finding device indicates the direction of the radio station received with respect to the heading of the airplane. GENERAL DESCRIPTION: The set is composed primarily of a receiver, two control boxes (one each for the co-pilot and the radio operator) 1 and a switching relay, two indicators (one each for the pilot and the radio operator). and a motor-driven loop antenna. The receiver tunes frequencies between 200 and 1750 kilocycles, in three separate bands. Each control box (BC-434) has the following controls similar in operation to those of the liaison receiver: band switch, tuning control, light control, and volume control. In addition, there are: an "operation" switch, loop drive switch and a "control" button. COMMUNICATIONS 19 =
RESTRICTED B-29 FAMILIARIZATION AND MAINTENANCE LOOP ANTENNA CONNECTION CW-VOICE SWITCH WHIP ANTENNA CONNECTION RADIO COMPASS UNIT OPERATION: The "operation" switch has four positions - OFF-COMPASS-ANTENNA- LOOP. To place the equipment in operation, turn the switch in one of the three operating positions and note whether or not the green indicator light is on. If this light is not on, press the control button to gain control of the radio compass receiver. If this button should be pressed again, or if the button on the other control box is pressed, the control will be returned to the other station. Each time a control button is pressed, control of the receiver is trans- ferred from one box to the other. The desired band is selected with the band switch and the tuning control rotated until the desired station is tuned. Proper tuning is indicated by a maximum clockwise reading of the tuning meter. When the station has been tuned in properly, the radio compass indicators on the radio operator's table, and on the pilot's instrument panel, indicate the station's direction. The instrument reading is the relative direction of the radio station measured in degrees clockwise from the direction in which the airplane is heading. That is, 90 degrees will be to the right, 180 degrees to the rear and 270 degrees to the left 20 COMMUNICATIONS
RESTRICTED of the airplane. As the tuning control is slowly rotated to tune across the band, the indicator points in directions corresponding to the heading of each station as it is tuned in. When the "operation" switch is placed in the ANTENNA position, the indicator is not operative and the radio may be used as a conventional receiver. When the "operation" switch is placed in the LOOP position, the antenna loop may be rotated either to the left or right by means of the LOOP drive switch. The indicators show the loop antenna position. When the switch is pushed in and then turned, the loop rotates rapidly for a coarse adjustment; if it is not pushed in, the switch will rotate the loop very slowly to permit fine adjustment. Radio compass loop LP-21, located on top of the forward bomb bay, has an internal compensating mechanism (cam) adjusted to correct for the distortion caused by the airplane's metallic structure so that the loop indicators will indicate the true position of the radio station. If it becomes necessary to replace the loop in the field, take care to adjust the compensating cam in the new loop as directed in the instruction book. The compensation required applies to only the B-29 airplane and must be the same as the compensation applied in the loop originally installed. The loop housing is a closed structure, having only one vent where air may enter or leave, as motivated by the variation in pressure when the airplane ascends or descends. The air from the vent passes through a rubber tube to a dehydrator on the upper left side of the forward bomb bay. B-29 FAMILIARIZATION AND MAINTENANC E The dehydrator consists of a plastic tube containing silica gel crystals. Silica gel absorbs moisture from the air entering the loop. When the silica gel is dry, it is blue in color, but as moisture is absorbed, the silica gel gradually turns pink. Pink silica gel should be removed and reactivated by heating in a shallow pan at approximately 300 degrees Fahrenheit, until the blue color is restored. This may be done 15 to 20 times before it becomes necessary to replace the silica gel. The radio compass also employs a whip-type sense antenna which protrudes upward through the skin of the forward pressurized compartment, aft and to the left of the upper forward turret. This antenna may be removed in flight by rotating the handle at its base one-half turn to the left, and retracting it through the hole in the airplane's skin. To maintain cabin pressure when this antenna has been withdrawn, a plug is provided for insertion in the hole. This plug hangs on a hook at the inboard side of the navigator's cabinet. When the hole is plugged, the antenna may be hung on this hook. The sense antenna is used when the operation switch is in the COMPASS position. If this antenna is not in place, the indicator will turn continuously in one direction and the compass will not "home" on any station. The antenna is not needed when the switch is in the LOOP position, but it is required when the switch is in the ANTENNA position. All but the tuning connections between the control boxes and the compass receiver are electrical, the tuning being accomplished by means of flexible shafts. A flexible shaft from each of the control boxes is routed under the COMMUNICATIONS 21
RESTRICTED radio operator's table, and through the pressure seal in the station 218 bulkhead. From there, it is carried by another shaft to the receiver itself. Check the alignment of this tuning system occasionally by turning the tuning control (on the control box) counter-clockwise to its extreme limit, until a mechanical stop is felt. At this point, a line, marked ALIGN, should coin- cide with the dial index. If the marks do not line up, uncouple the tuning shaft and turn the tuning control until these points do line up and then recouple the shaft. Radio compass relay BK-22 is located in the radio compass relay shield. This relay switches control of the compass receiver from one control box to the other. The relay also acts as a terminal block for various interconnecting wires. One of two fuses in this relay, marked AC IO amperes, is for alternating current, and the other, marked DC IO amperes, is for direct current. In some models of the radio compass, either 2-ampere or 20-ampere fuses were originally installed. The correct fuse for radio compass SCR-269G used in the B-29 is IO amperes. The proper receiver is type BC-433G; receivers of earlier series than G will not operate in the B-29 airplane. CAUTION: Both the receiver and the wiring can be seriously damaged if an attempt is made to substitute any receiver other than BC-433G. To supply power to the radio compass, the airplane's inverter switch on the engineer's panel must be turned either to the NORMAL or the ALTERNATE position. Power for operating the marker beacon receiver is obtained from the B-29 F"AMIL.IARIZATl □ N AND MAINTENANCE radio compass. This receiver is in operation whenever the radio compass is on. In the field, the only other adjustment on the radio compass that might be necessary is an adjustment of the sensitivity control on the front of the receiver. The receiver is located near the top of the forward bomb bay to the left of the tunnel directly aft of bulkhead 218. Adjustment is made with a screw driver. The sensitivity adjustment is divided into two operations: adjustment of automatic sensitivity, and of threshold sensitivity. Threshold sensitivity is a background noise adjustment.To adjust, set the op~ration switch to ANTENNA and the AUDIO control to maximum. With the engines running, tune the receiver to a "dead" portion of the dial where no signal is heard. Adjust THRESHOLD SENSI- TIVITY so the noise is not objectionable. Chee~, by tuning in distant stations, to make sure that sufficient sensitivity remains. Automatic sensitivity is a measure of the hom- ing action of the loop. When this is adjusted low, the loop is sluggish, particularly when near the angle of the station direction. When the automatic sensitivity adjustment is at the high end, the loop is too sensitive and tends to hunt back and forth around the correct value of the azimuth of the station. The AUTO SENSITIVITY should be adjusted until the hunting is approximately I degree on each side of the station. This adjustment should be accomplished with the operation switch on COMPASS and the receiver tuned to a station more than IO miles distant. 22 COMMUNICATIONS
RESTRICTED LOOP BASE---- MOUNTING--------.<! HOLES COMPENSATING CAM ELECTRICAL CONNECTORS AUTOSYN TRANSMITTER - - WRENCH~ , .--~-,· COMPENSATING CAM----- LOOP DRIVE MOTOR ----;; LOOP ANTENNA COMMUNICATIONS 8-29 FAMILIARIZATION ANO MAINTENANCE - - ~ - 23
RESTRICTED 8-29 FAMILIARIZATION AND MAINTENANCE .,;::;:::...----ANTENNA COAXIAL CABLE TERMINAL TUNING SET SCREWS ELECTRICAL CONNECTOR MARKER BE AC ON RECEIVER (RC-43A) GENERAL DESCRIPTION:The marker beacon receiver indicates the passage of the airplane over Civil Airways and similar marker beacon stations. It is located below the wing center section, on the left hand sidewall of the body between the bomb bays. The equipment consists of a fixed frequency receiver operating on 75 megacycles: a resonant, horizontal antenna; and an indicator light on the pilot's instrument panel. It is placed in operation by turning on the radio compass. When the airplane passes over a marker beacon station, the indicator light on the pilot's instrument panel flashes according to the signals sent out from the ground transmitter. This signal is coded in I, 2, or 3 dashes, identifying the station. There are no further controls for this equipment, and after it has been placed in operation, no adjustment is required.Tuning set screws are on the face of the receiver panel. However, adjustment of these screws requires the use of a test oscillator and should be made only at a maintenance depot. Frequent inspection of the marker beacon antenna is necessary, as the antenna is exposed to the personnel walking around the airplane and is easily broken. Dirt or foreign matter collect- ing on the insulator (where the lead end goes throuqh the skin on the bottom of the airplane) should be removed, as it reduces the sensitivity and range of the equipment. 24 COMMUNICATIONS
= RESTRICTED TEST METER J A C K - - - - - - - - - - 8-29 FAMILIARIZATION AND MAINTENANCE -------ANTENNA CONNECTION ------ELECTRICAL CONNECTOR RADIO BLIND LANDING RECEIVER BLIND LANDING RADIO RC-103 GENERAL DESCRIPTION: This specialized radio receiver assists the pilot in making blind ap- proaches to a landing field equipped with the proper localizer transmitters. The complete radio equipment should be considered as SCR-570, of which radio receiving equipment RC- I03 is a part. The equipment consists of a receiver, a dynamotor, an antenna, a control box, and an indicator. The indicator on the pilot's instrument panel consists of a set of crossed point- ers which show the airplane's relation to a predetermined glide path beam radiated by the airport's special transmitters. The vertical pointer swings from one side to the other to indicate any horizontal deviation from the proper approach ground track, while the other pointer moves up or down to indicate any deviation in a vertical direction from the proper approach glide path. The control box, at the left of the pilot, has an ON-OFF switch, a band selector, and a gain or volume control. The receiver is located behind the pilot at the forward end of the navigator's table. The Alford loop (horse- shoe) antenna is located on top of the for- COMMUNICATIONS 25
RESTRICTED ON-OFF SWITCH l__ GAIN CONTROL 8-29 FAMILIARIZATION AND MAINTENANCE ----------HEADPHONE JACK BLIND LANDING RECEIVER CONTROL BOX ward bomb bay, aft of the radio compass loop. Radio receiver BC-733 is a directional receiver only. No glide path receiving equipment is installed but is being developed and will be installed later. Therefore, at present only the vertical cross hair in the indicator will operate. OPERATION: To operate this equipment, turn the ON-OFF switch, in the control box, to the ON position. Next, turn the band selector switch to one of the six bands which corre- sponds to the frequency on which the localizer transmitter is operating. The gain or volume control adjusts the audio level of the signal as heard in the interphone system. The signal consists of two tones-one 90 cycles and the other 150 cycles. The relative volumes of these two tones indicate the airplane's location with respect to the proper ground track. However, the visual indicator should be followed to obtain the exact reading. Fuses for this equipment are located in the fuse box forward of the receiver. 26 COMMUNICATIONS
RESTRICTED TUNING CRANK SOCKET CAP 8-29 F"AMILIARIZATION ANO MAINTENANCE INDICATOR LAMP------ - - - SPEED INDICATOR LAMP KEY JACK - GROUND CONNECTION----------- -----ANTENNA REEL COVER . DINGHY RADIO TRANSMITTER GENERAL DESCRIPTION: This transmitting equipment is generally referred to as the dinghy transmitter. This radio equipment is intended for operation after the airplane has been abandoned. It is contained in a canvas bag stowed in the rear unpressurized compartment, over the entrance door. The bag contains a parachute which will safely carry this equipment to earth if thrown overboard during flight. As the equipment is cast overboard, the parachute ring must be pulled, otherwise the parachute will not open. This equipment is waterproof and will float. An instruction book for this radio set is contained in a waterproof container within the canvas bag. This equipment consists of a transmitter, an antenna, two rubber balloons for raising the antenna, two hydrogen generators for pro- ducing hydrogen for the balloons, and a box kite. The hydrogen generators are designed to operate when immersed in water. The transmitter is a fixed frequency type tuned to the emergency distress channel of 500 kilocycles and sends out a continuous SOS signal when the operating crank is turned. The automatic alarm distress signal may also be transmitted. Code messages may be sent out by means of a push button key in the transmitter base. COMMUNICATIONS 27
RESTRICTED 8-29 F"AMILIARIZATl □ N AND MAl ' NTENANCE IFF IDENTIFICATION RADIO SCR-595 PURPOSE: This radio set is a confidential type and is used for the purpose of identifying the aircraft to a ground radar station, which is transmitting interrogating signals. The IFF radio returns the proper signal to the interrogating station, indicating the friendly intent of the aircraft. LOCATION: The IFF equipment consists of a receiver-transmitter, an antenna, a control box, an indicator light, a detonator switch, and two control switches. The receiver- transmitter is located under a removable floor panel on the starboard side of the center pressurized compartment at approximately Station 650. The antenna is located. just aft of the aft bomb-bay, slightly to starboard of the bottom center line. It is an AN-95-( ) mast which projects downward a distonce of approximately 14 inches. The control box is located at the top of the vertical support for the radar operat- or's rack facing inboard, at Station 760. The indicator lights are mounted immediately above the receiver-transmitter, along side the gravity detonator switch. The manual pushbutton detonator switch box is located on the top of the pilot's instrument panel. The two control switches are also located on top of the pilot's instrument panel. GENERAL DESCRIPTION: This radio is a piece of confidential equipment and it is quite important that it not fall into the hands of unauthorized persons. In order to prevent this occurring when the airplane lands in hostile territory, either through crash landing or otherwise, a detonator is placed inside the receiver, which, when set off, will explode and destroy the internal wiring and components of the receiver. This detonator is not of a sufficient strength to blow up the set completely, endangering the personnel of the aircraft, but is of a sufficient size to satisfactorily .destroy the interior wiring of the set. This detonator is operated in one of two ways. One way is manually, by the pilot. The manual detonator switch located on top of the pilot's instrument panel, is composed of two push buttons. When both of these pushbuttons are pressed at the same time, the circuit is completed through the detonator, which then explodes. Inadvert- ent pressing of one of these buttons at a time will not complete the circuit, thereby insuring that the detonator will not accidentally go off. The other means of operating the detonator is by the gravity switch. This switch is a pendulum type switch and is located on the radio operator's instrument panel. When the airplane makes a forced landing, deceleration of approximately l0-l 3G's or 10-13 times the normal gravitational acceleration will trip this switch and cause the detonator to explode. This deceleration must be in a horizontal direction as a vertical deceleration will have no effect on the switch. (Horizontal and vertical directions are made with reference to the fuselage of the aircraft.) The detonator itself is installed in the front ·face of the receiver and is connected by means of Plug PL-177. This plug should never be installed in the detonator until the aircraft actually leaves the ground, and should be removed before landing, if landing is effected in a friendly region. Before this plug is ever inserted in a detonator, the indicator lights should be examined. These indicator lights, located on the radio operator's' instrument panel, are in parallel with the detonator 28 COMMUNICATIONS
RESTRICTED circuit and will be on if there is any voltage at the detonator plug. Either light will indicate a voltage. In the event that this plug is alive, or voltage exists there, it should not under any circumstances be placed in the detonator or serious damage may result to the person so doing. The circuit should be occa- sionaIly checked with the plug removed to see if the gravity switch_ , when tripped, will light the indicator light and also to see whether the manual switch will also light the indicator lights. The equipment may be tu med on from either of the two locations, either the pilot's instrument panel control switch, or the control box located on the radio operator's instrument paneI. Th i s co n t r o I box a Iso co n ta i n s a selector switch which has six positions. These positions indicate the coding that the receiver-transmitter will send out to identify the aircraft. The employment of this selector switch will be directed by the local operations office, wherever the a i rcraft is station. ed. There is also another code available, known as the emergency code. This code is placed in operation by means of the switch on the radio control box or by an emergency switch on top of the pilot's instrument panel. This switch is used only in case of an emergency and as directed by the operations officer. This gives a different type of coding, which will be received by the ground radar station. There are two fuses for this equipment, one being found in the radar junction box and labeled as the IFF fuse, and the other fuse is B-29 FAMILIARIZATION AND MAINTENANCE in the battery solenoid shield, located in the rear unpressurized section, just ahead of the auxiliary power plant. This fuse is used in conjunction with the battery switch circuit and the reason is that in the event of a crash land- rng, the pilot will open the master switch, which breaks all of the circuits _ on the airplane, with the exception of the one battery switch circuit. This circuit must not be broken so that current will be available for the detonator when the airplane actually crashes. This fuse is also labeled as the IFF fuse. It fuses the detonator circuit only, while the fuse in the radar junction box fuses the receiver itself. INTERCHANGEABILITY: The radio SCR-595 is completely interchangeable with SCR-695, and uses the same mounting brackets for the radio receiver and control panel. The operation of either piece of equipment in the B-29 airplane is identical. The SCR-695 radio has an .a.ddi- tional band known as the "G" band which usually would be controlled by an additional toggle switch and pushbutton switch, which would be operated by the pilot. However, the Army Air Forces has determined that this employment will be made by fighter-type aircraft only, and will not be used in bombers. Therefore, since the additional feature of the SCR-695 radio is not utilized, its operation is identical with the SCR-595 radio. AIRBORNE RECOGNITION RADIO ARR SCR-515 This equipment is not installed, although pro- visions for installation were made in some of the earlier B-29 airplanes. If this radio equipment is installed in the future, complete operating instructions will be released. COMMUNICATIONS 29
RESTRICTED ANTENNA POST------ HEAD PHONE JACKS CRYSTAL SWITCH 8-29 FAMILIARIZATION AN □ MAINTENANCE -------FREQUENO DIALS ----<ORRECTION KNOB ---FREQUENCY BAND SWITCH ,-----ON-OFF SWITCH PORTABLE FREQUENCY METER SCR 211 PURPOSE: The frequency meter provides a means of accurately checking the tuning of the command and liaison receiver and transmitter. LOCATION: This item is stowed forward on the floor at the radio operator's station of bulkhead 218. GENERAL DESCRIPTION: The frequency meter =-=-=--====- -- ------ is a self-contained, battery-operated unit re- quiring no connection with the airplane's power supply. The antenna consists of a short length of wire not over 2 or 3 feet long. This wire should run parallel to the transmitter or receiver lead-in, although this may not be necessary in most cases. The wire must never be connected directly to the transmitter or the receiver antenna. 30 COMMUNICATIONS - -
I RESTRICTED l@=- - -__ - - - -- - - - _-_ ----~~~ - - 8-29 - - FAMILIARIZATION AND MAINTENANCE ~ - - -_ ~----=-- __ -== - -- - ---- -=- OPERATION: To operate the frequency meter, plug the headset into the phone jack; then, turn the power and crystal switches ON. Allow the instrument to warm up for at least 20 minutes. Before attempting to make any frequency adjustments, correct the calibration of the heterodyne oscillator by comparison with the crystal oscillator at the crystal check point nearest the desired frequency. This comparison may be made at many points over the calibrator range, by employing the fundamental or harmonic frequencies of either or both oscillators. Comparison between the two oscillators is effected by rotating the heterodyne tuning controls through a portion of the corresponding frequency range to obtain "zero beat" at the desired crystal check points. The beat tone may be heard in the headset when plugged into the phone jack. To correct the heterodyne oscillator before setting on any desired frequency within the calibrated range, proceed as follows: By reference to the high or low frequency indices on the front and rear covers of the calibration book, determine in which band the desired frequency is located, and set the frequency band switch to correspond. Also, from the frequency indices, ascertain the page on which the desired frequency is listed and turn to it. The nearest crystal check point is noted in red at the bottom of that page, together with its dial setting. Set the heterodyne oscillator dials to agree with this crystal check point dial setting. A beat note (tone} will probably be heard in the phones, as an ab- sence of beat note occurs only under three conditions: when the heterodyne oscillator is exactly on calibration (zero beat), when it is so far off calibration that the beat frequency is above audibility, or when the equipment is defective. However, if no tone is heard, either of the first two conditions may be determined by rotating the corrector dial to the point where the tone becomes audible, and notinq the direction of change. If the third condition is. the cause, no tone will be heard at any point in the entire heterodyne oscillator range. With the heterodyne oscillator dials set on the desired crystal check point setting, adjust the heterodyne oscillator frequency as close as possible to the crystal oscillator frequency by turning the corrector dial only. When the operator has become familiar with the equipment, this adjustment can be made to pre- cisely zero beat. MAINTENANCE: Check the condition of the batteries in the frequency meter case at frequent intervals and at least once each six months if the meter has not been in operation. When swelling of batteries is noticed, they should be replaced immediately, as further swelling may damage the case and make removal of the swollen batteries difficult. To facilitate operation, the frequency meter is usually moved to the radio operator's table when in use. INTERPHONE EQUIPMENT RC-36 PURPOSE: All crew stations are connected through an interphone system, making inter- communication possible, and allowing various members of the crew to operate the radio equipment. GENERAL DESCRIPTION: lnterphone equipment receives power from the radio compass relay shield, aft of the engineer's panel. The equipment consists of 11 jack boxes BC-366, an interphone amplifier BC-347, and a dynamotor PE-86. Headsets HS-23 and microphones T-30 may also be considered as part of this equipment. OPERATION: Located on the face of jack box BC-366 are a volume, or gain, control and a switch. This switch has the following positions, reading from Jeft to right: COMPASS-LIAI- SON-COMMAND-INTERPHONE-CALL. The switch may remain in each of the first four COMMUNICATIONS 31 - -
RESTRICTED INTERPHONE DYNAMOTOR positions, but it w_ill not remain in the CALL position. This position is "momentary" only and, when released, the switch will flip from this position to the INTERPHONE position. When the jack box switch is placed in the COMPASS position, the audio output of the radio compass receiver is hearc:J in the headphones. Similar results are obtained for the LIAISON and COMMAND positions; however, on these two positions, when the liaison or command transmitter is operating, the output of the transmitter is heard. This occurs in the LIAISON position only when the liaison monitoring switch in the radio compass relay shield is in the NORMAL position. When this switch is in the MONITOR position, the output of the transmitter is not heard, and the receiver audio output is heard continuously. In the INTERPHONE position, the volume r------- B-29 F AMI LI AR IZ A TI O N ANO MAIN TE NAN CE =--==== ~ - -~- --=---'-- ~ INTERPHONE AMPLIFIER control is inoperative; that is, the interphone volume has a fixed level and cannot be re- duced by the volume control. The compass, liaison, and command audio channels are coupled directly to the audio output of those sets. The interphone channel is connected to the output of the interphone amplifier. The interphone amplifier and the interphone dynamotor are located at the radio operator's station, aft of the command modulator. The interphone dynamotor runs continuously when' the airplane's DC power supply is on. No switch has been provided to turn off the interphone dynamotor or the interphone amplifier. The interphone fuse (15-ampere) is in the radio compass relay shield, aft of the engineer's panel. When a crew member has his jack box in the COMPASS, LIAISON or COMMAND posi- L - -- -- --- - §==f=j 32 COMMUNICATIONS
RESTRICTED +ion, and another crew member wishes to call him, the calling crew member places his interphone jack box switch in the CALL position and speaks to gain attention. In the CALL position, the output of the interphone amplifier is connected in parallel with the output of all the receivers. The low impedance of the interphone amplifier effectively short-circuits the outputs of the compass, liaison and command receivers. Thus only the interphone is heard. The low impedance of the interphone amplifier effectively short-circuits the output of the receivers, rendering them momentarily inoperative, and allowing the interphone amp Ii fie r audio output to be heard alone. The CALL position is made momentary to prevent all the other receivers from be ing short- circuited if an operator should accidentally leave his switch in that position. All microphones are connected to the interphone jack boxes through microphone switches. This presents a "push-to-talk" system in which the microphone button is depressed if the operator's voice is intended to be heard over the system. The microphone switch must also be depressed when it is desired to modulate the liaison and command radio transmitters. These transmitters are normally operated through the jack box in the same manner as the interphone system. The micropho,,e circuit has two wires and a ground wire. When the microphone button is depressed, the two wires are connected to the ground wire. One wire completes the microphone circuit and the other wire completes the keying circuit of the transmitter. If the microphone button is depressed while the switch is on the COMPASS position, it has no effect on the system, either on the audio channel or on the compass receiver. B-29 F"AMILIARIZATION ANO MAINTENANCE In the interphone CALL position, the button must be depressed; in this case, it completes only the circuit of the microphone, and the keying circuits have no effect. Jack boxes are provided at the following stations: bombardier, on the cabin right sidewall, ahead of the co-pilot's instrument panel; pilot, on the pilot's oxygen panel, at the left of the pilot's station; co-pilot, on the co-pilot's oxygen panel, at the right of the co-pilot's station: engineer, on the engineer's oxygen panel, at the right of the engineer's station, (on the engineer's left as he faces aft): navigator, on the navigator's data cabinet, on the left side of the airplane, aft of the navigator; radio operator, on the radio operator's instrument panel at bulkhead 2181 above the radio operator's table; top gunner, hanging from the top of the cabin, aft and to the left of the upper sighting station; left gunner, on the left sidewall of the cabin, above and forward of the left sighting blister; right gunner, on the right sidewall of the cabin, above and forward of the right sighting blister; relief ere~, on the left side of bulkhead 834 aft of the lower left bunk; tail gunner, on the tail gunner's oxygen panel on the right sidewall of his compartment. Headsets and microphones are provided at all crew stations in the airplane with the exception of the relief crew station. The following stations have microphone switch and cord assembly CD-318: bombardier, engineer, radio operator, navigator, left gunner, right gunner, relief crew and tail gunner. Microphone switch buttons for the pilot and co-pilot are installed in the control wheels. They are operated by the pilot's right thumb and the co-pilot's left thumb, respectively enabling either pilot to hold a thumb on the microphone button and keep the other hand COMMUNICATIONS 33
RESTRICTED NOTES B - 29 f"AMILIARIZATION AND MAINTENANCE
RESTRICTED NOTES
RESTRICTED B-29 FAMILIARIZATION 'A N D M A I N T E NA N C E INTERPHONE 3 2 1 DYNAMOTOR •ii INTERPHONE AMPLIFIER 7654321 .·-r . il::.fK 1 E COMMAND RADIO PL-Q-64 C Y MODULATOR 1 9, l: f PL-153 LR 7 ,------, MOTOR- -lffl--GENERATOR ~--------- 2 1 3 ~cR-4 --------.,..,LR"""' 8 .-----------+,-~Kr34 KEY I r---+----------=--------;"'-tKK-23 MICj HEAD SET LLl +200 VOLT-S GROUND +28 VOLTS INTERPHONE DYNAMOTOR PE-86 COMMAND RADIO TRANSMITTER CONTROL BOX -MK 6~ PILOT'S FILTER INTERPHONE SYSTEM £"- COMMON GROUND COMMAND RECEIVER AUDIO COPILOT'S FILTER r LIAISON RECEIVER AUDIO LR37 • • MONITOR r-+-.....,_.,,....,,..--=-""""_ _....... 7 SWITCH I RC123 • • _ 16 CR-3 ~ LIAISON RADIO TRANSMITTER --t--RECEIVER FUSE (15 AMP.) 1 RADIO COMPASS+ - - - - RECEIVER AUDIOJ ---~P183 .___RA_D_I_O_C_O_M_P_A_S_S__, 28 VOLT D.C. + RELAY SHIELD RECEIVER RACK COMMAND RADIO 8 9 7 11 , LIAISON RADIO PL-l5J l tr ..'.__~KEY STATION646 I 7 11 I CR -16~ ---------. • ~ ~----CONNECTOR S - - ff TIP RING G SLEEVE "'":~ 11 ~Jr MICROPHONE7l"' SWITCH MICROPHONE PLUG AND SWITCH TIP SLEEVE PLUG STA 8 A,,. - 1 ·- CR-lSJI ·= ,,1_ :' ... , I _ 2• - . -:_ ,L ,_ - ,- 11_"'-+---------+--C,..---------+-oi.------___;;_.--c; 3 , _ ~ :3 ,_,_ - l!..-s 4 - 7 = - --{:4 ,_ ~ - - ~ - B - - C~ 5 ~---t-t-+-+-ic::,=>--t---t--+--+--+-+-iiC::::-------+-i~-+--,o--+-----+---+-+--+-1~>--~1-t++-----.,:.---f'*:.s~-+-+-t°'"""-t++-+------+-+---.=:~-------t-T""1'0i---------+---t-tCJ-~----;-<;: 6..,..... ----t-1-;-;--t--'1(-;Jt----;-----1----;--t-t-+--,C,:::,---------;-;-+--1-+--,ot----;---t-t-+-t-t-,1C---t+t-+f----..J._~:6~-+-+-t-te'->T--t++-+------+-+--t-t:=:..-------,-----,...-t-1°"""-------+--t-t-1C-.--------< ] • j I I) - - - ~ - D:: E... ... II - - 8. -r----:. :8 9..,..... ---T""1-;---t-t-+-+--t--J10'-----"1----t--t-t-t-1----p----t-i~-t-t-+-+-+-,D---t---t-+-+-ir+--+-~-,c+----f{_'Tj.;...9-+-t-+-+-t-t-+--fl'-:::>or-+------+-+--t~~=(r-------+---+-+-+-+---C-:>r-----+---+-+-+-+---C.,---::-< lOet---+-t-+-+-~+-+-+-,c~--+-+-+-+-+--+-,o---+-1~+-.....,.._+-+-1--,c>--1------1-4-+-1~4----l-cx- '' - - - ~ - - - F,,. G-: - - - - ·- ·- - H: ic:=1------+-+-+-+-+-..:=;~------t---t---t---t--t----K-Jr-----+-+-+--+-+----+0~ _!.!..:...,....---t-t-;--t-t-+-+-+--t-+--,,o&---+-+-+-+-+--~t-ic>---+-i~-t-t-+-+-+-+-+-~---+CJ'--+-11-++---+-.fcx,_ - - - ·- ,- - NAVIGATOR I,2 3 ; 5 6 7 s 910111 PILOT I, 23 4 s6, a91·0,11 I1 2 34 5 67 8 910111 COPILOT ' • ' • • t ' 1 2 3 4 5 6 7 8 9 1011 I, 2 3 4 5 6 ; a910111 RADIO OPERATOR BOMBARDIER ENGINEER TUBE VT-99- rll- I .-- 1 2 3 4 INPUT_J t JU OUTPUT~ +28 VOLT MICRO- PHONE SUPPLY +28 VOLT HEATER 5 6 7 [lLHIGH VOLTAGE PLATE SUPPLY GROUND GROUND HEATER INTERPHONE AMPLIFIER BC-347 1 ,nn; 1 VOLUME -+ CONTROL ... z 0,;() 0 0 0 0 0 0 0 0 0 1 '2 3 4 5 1 2 3 4 5 000000 000000 ? 7 ~ 9 1 10 lil 6 7 8 9 10 11 a::.I:o-JJ---+--1..l,IIJ J?:JN. c~~fss coi~1 ~D c TERMINAL STRIP RADIO OPERATOR--~ TERMINAL STRIP ENGINEER COPILOT .-----A------.,-------..--IN_C_R_E_A...,.SE,_O_U_T_P_U--.T BOMBARDIER 0 0 1 2 MIC. : PHONE INTERPHONE D INTERNAL CONNECTIONS FOR VARIOUS SWITCH POSITIONS MIC. "= PHONE CALL E EXTERIOR OF JACK BOX INTERPHONE JACK BOX BC-366 <? PHONE 7"-=-= 2• 3- 4- s- 6 7. 8. 9 10- ....1L. LEFT GUNNER INTERPHONE CIRCUIT COMMUNICATIONS 1 .2 - - 3 - - 4 - -5 - -6 •7 •8 -9 - 10 - - 11 - UPPER GUNNER - 11 i 3456 ;8910111 11 i 34 56 78910111 RELIEF CREW RIGHT GUNNER UPPER GUNNER LEFT HAND GUNNER TAIL GUNNER----- RELIEF CREW TAIL GUNNER 35
B- 29 NOTES F"AMI LIARIZATION AND MAINTENANCE
RESTRICTED on the throttle while operating the command radio during taxiing. Otherwise, the operation at these stations is the same as for the other stations. At the top gunner's station, the microphone button is installed in the right hand sight control grip, enabling the gunner to operate the push button without removing his hand from the sight grip. Connections for the top gunner's station are routed through a slip ring assembly in the base of the upper gunner's seat, allowing his seat to make several complete turns to the left or right without entangling the interphone wires. Connections are made to the upper gunner's jack box by plugs PL-55 and PL-68 for the headset and microphone circuits, respectively, by wires running under the floor to the slip ring assembly. Wires from the top of the slip ring lead upward through the top ~unner's seat assembly, and terminate in the microphone button in the upper sight grip. Jacks JK-48 and JK-26 at the end of each of two flexible cord assemblies are fastened to the top gunner's seat. Jack JK-48 receives the plug from microphone T-30, and jack JK-26 receives the plug from headset HS-23. All interphone stations, except the pilot and co-pilot, also have a headset extension cord composed of a plug PL-55 inserted in the phone jack of each jack box, and a flexible cord terminating at the other end in jack JK-26, to connect with headset HS-23. The pilot and co-pilot employ a different arrangement as described under Filter Equipment. B-29 FILTER EQUIPMENT RC-198: F"AMILIARIZATICN AND MAINTENANCE Filter equipment consists of two identical filter and switch box combinations mounted on the pilot's and co- pilot's oxygen panels, respectively. These filters are connected internally with the audio channel in the pilot's and co-pilot's jack boxes: and therefore, do not require plug PL-68 to be inserted in the microphone jack position on the jack boxes. For connection through the headset HS-23, the filter FL-8, has a flexible cord attached, terminating at the opposite end in a jack JK-26, (for the headset plug). The filter FL-8 has a switch with three positions-RANGE- VOICE-BOTH: it is normally left in the BOTH position. However, the audio output of the various receivers may also be heard with the switch in the VOICE position. This filter, also known as the range filter, is used in conjunction with the radio ranges (beams) operated by the Civil Airways within the United States. From these radio range stations, N and A code signals are received when the airplane is to the left or right of the beam. When the airplane is on the beam, the N and A code signals overlap, giving a continuous tone in the headphones. Range stations operate on various channels in the low frequency band but the modulat- ing tone always has a frequency of 1020 cycles per second. These range stations broadcast the N and A code signals continuously, but periodically the carrier wave is further modulated by voice, transmitting weather reports and instructions. However, confusion some- COMMUNICATIONS 37
RESTRICTED times results when this voice modulation is heard at the same time as the code signals. Range filter FL-8 enables the pilot to select the modulation to which he wishes to listen. With the filter switch in the RANGE position, the filter passes only audio frequency of I020 cycles per second. This removes most of the voice modulation, enabling the pilot to con- centrate on the range signals. When the filter switch is placed in the VOICE position, it rejects frequencies of 1020 cycles per second. This prevents range signals from garbling the voice modulation, enabling the speech to be readily understood. When the filter switch is placed in the BOTH position, both voice and range signals may be heard at the same time. The pilot's and co-pilot's filters are independent and are operated in- dividually. LOW IMPEDANCE HEADSETS HS-33: Although this equipment is not used in early B-29 airplanes, it may be installed in later airplanes. Headsets in the British theater of operations are standardized on low impedance and confusion resulted when American equipment was used there. Since the low impedance headset gives better operation than the high _ impedance headset (HS-23} used in the United States, the low impedance headset was standardized. Low impedance headset HS-33 is identified by a red plug (PL-354) on the short headset cord connected to one of the headphones. On the high impedance set, the plug (PL-54) is black. When used with the present interphone equipment, the low impedance headset requires an impedance matching adapter M-385. This adapter may be plugged into the headphone jack on the jack boxes. It is a 8-29 FAMILIARIZATION AND MAINTENANCE small box incorporating plug (PL-55} to match the headphone jack of the jack box and a jack to accommodate the headset plug (PL-55}. The jack spring in jack box BC-366 is strong enough to hold the weight of this adapter. Plug PL-55 of the headset extension cord, formerly inserted directly into the jack box, is now inserted into the adapter, connecting the adapter in series with the headphone circuit. The low impedance headset HS-33 is then plugged into jack JK-26, on the opposite end of the headset extension cord. This arrangement is used for all interphone stations except the pilot and co-pilot. At these two stations, since the headset extension cord connects with filter FL-8 instead of the jack box, a different arrangement is used. · The cord from filter FL--8 is approximately one foot long, terminating in jack JK-26. Jack JK-26 is then placed on the plug portion of the adapter, which is placed upright. Adapter M-385 is secured along the side of filter FL-8 by a length of wraplock or similar fa bric. The headset extension cord, formerly connected with the filter FL-8, must then be equipped with a plug PL-55. In turn, this plug is inserted in the jack of the adapter M-385. THROAT MICROPHONES: Microphones should be worn as high as possible on the throat. Take care that the microphone does not slip down below the "Adam's apple." When a microphone is worn low, only low tones are heard from the throat, and these are unintelligible over the interphone. In warm, humid climates or on long ocean flights, perspiration or salt spray may enter the microphone units. These have a destruc- tive action on the units and care should be exercised to prevent their entry. 38 COMMUNICATIONS
8-29 A I R P L A N E :E .... ... .. ► ~ ..... - Ct
0 I L SYSTEM TABLE OF CONTENTS PAGE GENERAL DESCRIPTION --------------------------------·---------------..-------- 2 01L SYSTEM (Perspective) ___________.:_______________________________ ______ __ 3 INBOARD NACELLE OPERATIONAL DIAGRAM____________________ 5 OUTBOARD NACELLE OPERATIONAL DIAGRAM_____________ ___ 6 Y ORAiN COCK___________________________ __________-----------------------__________ 9 0 IL TANK -------------------------------------- -------------------------------- ------10 OIL TEMPERATURE REGULATOR__________________________________________ l 2 01L TEMPERATURE CONTROL_____________________________________________ 14 OIL DILUTION SOLENOID___________________________________________________ l 7 OIL TEMPERATURE REGULATOR WIRING DIAGRAM____________ 18 OIL TEMPERATURE CONTROL______________ _____ __________________ _________ 19 OIL COOLER FLAP ACTUATOR______________ _________________________________20 OIL TEMPERATURE CONTROL DIAGRAM______________________ --- _____22 OIL TEMPERATURE BULB CIRCUIT________ _ _ _ _________________________ _____2J OIL QUANTITY GAGE CIRCUIT__________________ _________________ _ __________24
[ RESTRICTED B-29 FAMILIARIZATION ANO MAINTENANCE OIL SYSTEM GENERAL DESCRIPTION: The lubricant recommended for the R-3350-23 engine is S.A.E. 60, grade 1120, specification AN-VV-0-446A. This oil has a flash point of 490 degrees Fahren- heit. Oil consumption is .025 pound per brake horsepower per hour at normal rated power and speed (2000 brake horsepower at 2400 rpm with a manifold pressure of 43.5 inches of mercury), and .015 pound per brake horsepower per hour at 70 percent normal rated power and 89 percent normal rated speed. The engine lubrication system is of the dry sump type in which oil is returned from the engine sumps to an external tank by scavenger pumps. Oil is supplied to the moving parts of the engine by pressure pumps. Each engine is provided with two pressure pumps and three scavenger pumps. All of the moving parts of the engine are pressure lubricated except the piston rings, wrist pins, crankshaft main bearings, the propeller thrust and radial load bearings, and the valve operating mechanisms of the lower cylinders. These parts are lubricated either by oil sprayed from jets or fed from pressure supplied wells. Each engine has two oil pump and sump housings. The front pump and sump housing is attached to a pad on the lower side of the crankcase front section. It has a scavenger pump, a pressure pump, oil strainers, a pressure relief valve, an oil filter, and an oil check valve. The front pressure and scavenger pumps are on the same pair of gear shafts. Because the length of the pressure pump gears is proportionately less than the length · of the scavenger pump gears, the scavenger pump has twice the capacity of the pressure pump. The scavenger pump is located below the pressure pump in the bottom of the front sump housing. The rear pump and sump housings are attached to a mounting pad at the lower side of the supercharger rear housing. This sump incorporates two scavenger pumps and one pressure pump. In this housing, there are also oil strainers, an oil filter, a pressure relief valve, and an oil check valve. The check valves prevent return flow from the oil tank to the sumps when the engine is not in operation. The rear pressure pump is the middle pump of the three pumps in the rear sump housing. The two pumps at either side of the pressure pump are the rear scavenger pumps. A fitting at the rear sump housing of each engine connects the line from the oil manifold to the rear pressure pump inlet. A line external to the engine, also leading from this fitting, passes between the lower cylinders and connects to the inlet of the front pressure pump. Oil entering the inlet side of the rear pressure pump is discharged into a chamber to the right of the pump gears. The rear oil pressure relief valve is in this chamber. When the oil pressure exceeds the relief valve setting, excess oil is by-passed back to the inlet side of the pressure pump. The relief valve is adjusted by a screw on the aft side of the rear sump. The relief valve adjusting screw is protected by a cup and secured by a lock nut. Turning the screw clockwise increases the oil pressure. One turn of the screw raises or lowers the oil pressure approximately 10 pounds per square inch. Adjustment of the front oil pressure relief valve is made in the same manner as for the rear valve. Both pump pressures should be set to relieve at 70 pounds per square inch, as measured by a gage at the test connection on the left side of the front sump and the rear oil pressure gage on the engineer's instrument panel. The front oil pressure transmitter line runs to a connection at the rear of the propeller governor housing. Because of the pressure drop between the front pump and the propeller governor, the front oil pressure indicator will read only 35 pounds per square inch although the pressure at the front test connection is the required 70 pounds per square inch. Both pump pressures may be set to relieve at approximately 70 pounds per square inch by backing off the adjusting screws one and one-half turns from full bottom. This serves as a first approxima- tion, as the engine must be stopped to adjust the front oil pressure. A cylindrical screen type filter is located in both the front and the rear sumps to remove foreign particles from the inlet oil. These strainers must be installed carefully to avoid crushing the screen. Screens should be removed periodically and cleaned with un- leaded gasoline. Two cylindrical screens in the rear sump remove impurities from the outlet oil before it goes to the oil cooler. 2 OIL SYSTEM
RESTRICTED NOTES
RESTRICTED REAR ENGINE OIL PUMP PRESSURE TRANSMITTER IDENTIFICATION BANDS / OIL SYSTEM IS IDENTIFIED BY YELLOW BANDS ON THE TUBING. CABIN SUPERCHARGER REGULATOR TO POWER SECTION NEAR BREATHER TUBE OIL DILUTION SOLENOID EN61NE FRONT OIL PUMP OIL TO ENGINE CHECK VALVE OIL SUPPLY 01 L RETURN IL...,._---'-'----'--'-....;.....:a.-==-====.1 OIL PRESSURE M M M M M M OIL DILUTION PROPELLER FEATHERING ( i I I I t I I I DRAIN~ M M M M M M PROPELLER FEATHERING PUMP MANIFOLD CABIN SUPER- CHARGER OIL FILTER NACELLE No. 2 (INBOARD) l'Y'DRAIS CABIN SUPER- CHARGER COCK ENGINE OIL NOSE PRESSURE TRANSMITTER OIL SYSTEM OIL SYSTEM OIL PUMP PRESSURE TRANSMITTER --- FNGINE FRONT OIL PUMP OIL TO ENGINE MANIFOLD B- 2 9 F"AMILIARIZATION ANO MAINTENANCE No. 2 AND 3 NACELLE OIL SUPPLY INSTALLATIONS ARE IDENTICAL No. 1 AND 4 NACELLE OIL SUPPLY INSTALLATIONS ARE IDENTICAL OIL SUPPLY TANK "Y" DRAIN COCK COOLER OIL DILUTION SOLENOID ENGINE OIL NOSE PRESSURE TRANSMITTER 3
B- 29 NOTES F"AMI LIARIZATICN AND MAINTENANCE
RESTRICTED OIL DILUTION SOLENOID L_,jl ~ I IDENTIFICATION BAND . ,_,,,,'/ (?;~- NOSE ENGINE OIL OIL TANK~ / .I · ~---·: ..· .-.·:', "Y" DRAIN COCK J '··; 01:L SYSTEM OIL SYSTEM B-29 FAMILIARIZATION ANO MAINTENANCE ELECTRICAL CONNECTION - - - · REAR I ENGINE OIL--....... ~·1• PRESSURE TRANSMITTER - - CARBURETOR ~-----__,OIL SUPPLY ..___________, OIL RETURN ::::============::::: VENT-LINE a:11ca=-=i PROPELLER FEATHERING • • ■ ■ •PRESSURE TRANSMITTER - - - - • OIL DILUTION LINE INBOARD NACELLE • • • :t • • • 5
RES IR ICJ_E_Q_ 6 ELECTRICAL CONNECTIONS TO OIL DILUTION SWITCHES TO PROPELLER !GOVERNOR I OIL MANIFOLD IDENTIFICATION BAND ,,A/•"' ~.,, "Y" DRAIN COCK 0 IL SYS TE·M OIL SYSTEM B- 2 9 f'"AMILIARIZATION AND MAINTENANCE ELECTRICAL CONNECTION I REAR ll ENGINE OIL - - - . PRESSURE TRANSMITTER Ji_ CARBURETOR ________. OIL SUPPLY ■ ■ ■ ■ •PROPELLER FEATHERING ■ ■ ■ ■ •PRESSURE TRANSMITTER - - - - • OIL DILUTION LINE OUTBOARD NACELLE
RESTRICTED Each engine has its own individual oil system. The oil systems are similar except that some airplanes are equipped with engine-driven cabin superchargers which employ the engine oil of the inboard system for speed regula- tion. (See Cabin Supercharger illustration.) All scavenged oil in the engines is pumped to the oil outlet connections on the rear of the engines by the two scavenger pumps in the rear sump housing, and the scavenger pump in the front sump housing. Oil forward of the rear row of cylinders drains into the front sump. Oil to the rear of the front row of cylinders, but forward of the distribution chamber, drains through a passage into the lower part of the rear s~mp. Oil to the rear of the distribution chamber drains to the upper part of this sump. From the nose scavenger pump, a line leads aft between two of th~ lower cylinders in the front and rear banks into a fitting on the rear sump. From the sump fitting (marked OUT), a line continues aft to the oil temperature regulator. Each outboard engine oil temperature regulator is located in the bottom of the nacelle, aft of the firewall. The inboard oil temperature regulators are located in the bottom of the nacelles, forward of the wheel well. The oil temperature regulators maintain the temperature of the oil constant at approximately 70 degrees Centi- grade. From the oil temperature regulators, lines conduct the oil to the return port of the oil tanks. Eighty gallons of oil for each engine are contained in self-sealing oil tanks in each nacelle, forward of the firewalls. The tanks are similar except that they are shaped differently to facilitate installation. Each tank has a hopper that serves as an oil warming tube during engine starting and cold weather op-eration. Oil returning to the tank spirals downward inside the hopper and flows into the oil sump at the bottom center of the tank. The warm oil flowing through the hopper gradually heats the remaining oil in the tank. As oil is con- sumed by the engine, and the hopper tube oil level drops, the reservoir of oil outside the hopper tube flows into the hopper through B-29 FAMI LIARIZATICN ANO MAINTENANCE an opening in the bottom of the hopper. An oil line leads from the sump to the Y drain cock in the bottom of the nacelle. Since the Y drain cock is at the lowest point in the system, it is used to drain the entire oil system. However, its primary purpose is to drain water from the system. Under some climatic conditions, considerable water will condense in the oil tank. The water, being heavier than the oil, settles to the lowest point in the system. This water can be drained from the tank sump and the Y drain cock and should be checked occasionally. A closer check for water in the system should be made during cold weather as the water may freeze in the fitting when the airplane is on the ground and restrict or stop the oil supply to the engine. Check for water several times after the engine is stopped so that condensate water may be removed as it collects in the drain cock, before it has time to freeze. From the oil drain cock, the oil line ru'ns forward to the oil manifold in the bottom of the nacelle, aft of the engine mount. The oil manifolds in the outboard nacelles have two outlet fittings and the oil manifolds in the inboard nacelles have three outlet fittings. The most forward fitting of each manifold outlet leads to the propeller feathering pump. The second manifold outlet leads to the engine oil pumps. The third manifold outlet on the inboard engine oil systems leads to the cabin superchargers (if they are installed). Following the second line leading from the oil manifold, the line enters the rear of the engine below the engine accessory section at the fitting marked IN. From this fitting, an oil line continues forward between pairs of the lower engine cylinders to the nose oil pump located below the engine nose section. The oil supply line to the nose oil pump is the larger of the two lines leading forward to the nose section. The smaller line is the scavenger line for the nose section. From the most forward outlet of the oil manifold, a line leads to the inlet side of the propeller feathering pump mounted in the lower left side of the nacelle near the engine mount. OIL SYSTEM 7
RESTRICTED The inlet and the outlet fittings on the propeller feathering pumps are plainly marked. The pumps are high pressure gear types driven by electric motors. The pumps are in operation only during feathering or unfeath- ering of the propellers. (See Propeller Feath- ering Pump illustration.) From the third manifold outlet in the inboard engine oil systems, lines 11/4 inch in diameter lead to the engine-driven cabin superchargers. (For operation of the cabin supercharg- chargers, see Cabin Supercharger illustration.) From the outlet of each cabin supercharger, a line 1 1/◄ inch in diameter continues to a Puro- lator filter mounted at the lower right hand side of the nacelle, in front of the cabin supercharger. This Purolator filter is similar to that illustrated in the Hydraulic System section. The flow of warm oil enters the outer part of the filter housing and passes through the filtering element to the outlet port. If the filter element becomes clogged, a spring- loaded relief valve opens when a differential pressure of 11 to 13 pounds per square inch is reached. The unfiltered oil then continues to flow through the unit until the filter element has been cleaned. The filter element will not pass particles larger than .0035 inch. A handle at the top of the unit permits turning the filter element against two metal scrapers to dislodge impurities collected on the element. These impurities settle to the bottom of the unit and can be drained by removing the filter sump plug. From the oil filter, the cabin compressor return oil line tees into the oil line from the engine scavenger pumps to the oil temperature regulator. Airplanes not equipped with cabin superchargers have plugs in the fittings on the oil manifolds and the scavenger lines. Each engine oil tank is vented to the atmosphere through its corresponding engine. A vent line 1/4 inch in diameter connects the outboard tank vent fitting to the engine accessory case. The tanks of the inboard nacelles equipped with cabin superchargers B- 2 9 f"AMILIARIZATION AND MAINTENANCE have the same vent arrangement as the outboard tanks, plus two additional vent lines teeing from the vent line between the tank and the engine accessory case. One of the additional vent lines leads to the breather tube on top of the engine supercharging section. The remaining vent connects to the cabin supercharger. An oil temperature bulb which transmits the temperature of the oil leaving the tank to an indicator on the engineer's instrument panel is located in the tank oil sump. There are two pressure transmitters for each engine - an engine rear section transmitter and an engine nose section transmitter. In- dicators for both transmitters are on the engineer's panel. The engine rear section transmitter is locai-ed in the top right hand side of each nacelle at station O on the shock mounted autosyn panel. The line leading from the transmitter connects to the pressure connection on the rear sump housing. The nose section transmitter is located on the left side of the nacelle, aft of the engine mount, below and forward of the left hand nacelle access opening. This transmitter is connected to the pressure connection at the propeller governor. Both transmitter oil lines are in areas warmed by the engine, reducing the possibility of oil congealing and causing incorrect pressure indications. A solenoid operated oil dilution valve is installed in each oil system between the carburetor and the Y drain cock. Operating an oil dilution switch on the engineer's control stand energizes the oil dilution solenoid, opening the valve, permitting fuel to flow from the carburetor fuel strainer chamber in- to the Y drain fitting and into the oil line to the engine. The addition of fuel lowers the viscosity of the oil in the engine, facilitating starting in cold weather. After the engines are warmed up, the fuel vaporiz.es and es- capes through the engine vent line. After about 30 minutes of operation, all the fuel will have evaporated allowing the oil to re- gain its original viscosity. 8 OIL SYSTEM
RESTRICTED MOUNTING - - - - HOLE LOCKWIRE----- B-29 GASOLINE FROM OIL DILUTION SOLENOID F'AMI LIARIZATION AND MAINTENANCE OIL FLOW FROM TANK PORT A / OIL FLOW OUT TO ENGINE HOLE DRILLED--------~ PART No. 3706114 AIR CORPS THRU STEM [DRAIN SHOWN CLOSED] Y DRAIN PURPOSE: To provide a means for draining the oil system. This valve also provides a fuel inlet for dilution of the oil for cold weather starting. LOCATION: A Y drain cock is located aft of the left turbosupercharger in each nacelle. COCK PORT C DRAIN OVERBOARD OPERATION: To open the drain valve, cut the lockwire and turn the valve 90 degrees in a clockwise direction. The valve is completely closed when its handle is in a horizontal position. OIL SYSTEM 9
RESTRICTED RETURN FLOW FROM ENGINE L ( SHELL HOPPER OIL PURPOSE: The oil tanks serve as reservoirs of oil for the engine, the propeller feathering pump, and the cabin supercharger. LOCATION: An oil tank is located on the forward side of the firewall of each nacelle, about two feet above the bottom of the nacelle. GENERAL DESCRIPTION~ The oil tanks are of the self-sealing type made by the Goodyear Tire & Rubber Co. Their size was determined 8-29 FAMILIARIZATION ANO MAINTENANCE --ELECTRICAL CONNECTION TO OIL GAGE OIL OIL FLOW GAGE .----------TO ENGINE FLOAT TANK by the range of the airplane {I gallon of oil to every 14 gallons of fuel). Each has a capacity of 80 U.S. gallons with an expansion space equal to IO gallons. The construction of the self-sealing oil cells is different from that of self-sealing fuel cells. • From the outside to the inside, the cell structure is made up as follows: .13 inch of square woven fabric impregnated with black syn- thetic rubber for strength; .09 inch of red chemigum which is resistant to aromatics; and .06 inch of square woven black fabric. 10 OIL SYSTEM
RESTRICTED An aluminum shell encloses and supports the cell. It is constructed in three sections-the upper or top portion which is .05 inch 2S 1 /4 hard aluminum, the middle section and the bottom or lower portion which are .125 inch 2S 1 /4 hard aluminum. The shell is fastened to the firewall by 16 bolts. The three sections of the tanks are supported on the forward side by a lateral beam. Rigid- ity of the cell is obtained by two fore and aft braces bolted to the ends of two lateral braces to form a rectangular support. The tank header unit, a casting located at the top of the tank, contains a port for the return oil and a port for the vent line between the tank and the engine. An oil quantity transmitter (liquidometer) is mounted on one end of the tank header. The arm of an internal oil gage float is attached to the bottom of the transmitter. The amount of oil in the tanks may be read on the liquidometer oil quantity indicator on the engineer's panel. A hopper in each tank provides a channel for the circulating oil and accelerates the heating of the remaining oil in the tank. This also allows warm oil from the engine to pass through the main body of oil in the tank without losing too much heat during engine starting. It hds the additional effect of confining diluted oil to the vicinity of the hopper. The return oil from the engine enters the hopper through an off-center port on the tank header and spirals downward toward the outlet, this action throwing any oil sludge against the wall of the hopper. Air bubbles caused by foam- ing oil rise along the center of the hopper and escape through the vent fitting on the tank header. The hopper consists of an aluminum tube 5V2 inches in diameter, tapering to 3¼ inches at the ends. It extends from the inlet port at the top of the tank to the outlet port at the bottom. Two elliptical holes at the top of the hopper provide an overflow, and a vent for the main body of the tank. As the oil passes through the hopper, it warms the cold oil next to it. A non-turbulent flow of oil is maintained at the bottom of the hopper by means of four fins that rise into the tube from the lower end of the hopper. The lower end of the hopper rests on the oil tank sump, providing a small opening in the hopper for oil to seek its own level. As the engine consumes oil, B- 2 9 F"AMILIARIZATIIJN ANO MAINTENANCE warm oil flows into the hopper and into the sys.tern. The oil outlet extends from the sump partially into the bottom of the hopper, providing a trap for sludge particles. The oil tank sump contains the two-inch diameter outlet for oil flow to the engine, a drain cock, and a type A-24 oil temperature resistance bulb. The bulb is mounted so that the oil passes through the bulb fitting as it flows to the engine. This transmits the temperature of the oil entering the engine to an oil temperature indicator on the engineer's instrument panel. The oil tank sump has a drain-cock connected to a 1 /4 inch diameter line through which water or sludge collected at the bottom of the sump can be drained to the outside of the nacelle. MAINTENANCE: The tank should be cleaned and flushed at each fourth engine change and at all engine changes made necessary by engine failure in which metal particles have circulated through the oil system. The tank need not be removed for this operation. Use steam for cleaning and flushing if such equipment is available; if not, use kero- sene. Take care to remove all collected sludge or foreign matter adhering to the internal cell support. OIL TANK REMOVAL: I. Remove the bottom half of the nacelle from station 0 to the firewall. 2. Remove the access door above the oil tank. 3. Disconnect the header unit on top of the tank and the attached lines, both oil and electric. 4. Disconnect the filler cap unit and the attached lines. 5. Remove the stiffeners located inside the cell. 6. Remove the tank sump from the bottom of the tank shell. · 7. Remove the bottom half of the tank shell and the cell will slide out. CAUTION: Do not collapse the cells when they are cold and inflexible. To facilitate handling, collapsing, and installation, place cells in a room having a temperature of 70 to 80 degrees Fahrenheit. Installation of the oil tank is accomplished by reversing the removal procedure. OIL SYSTEM 11
RESTRICTED MOUNTING HOLE INLET PART No. 6E-10358 AlRESEARCH OUTLET PLUG GASKET------ BY PASS VALVE 53-75 PSI THERMOSTAT ARM ELECTRICAL CONNECTOR OVERRIDE SWITCH PRESSURE ADJUSTMENT SCREW B-29 FAMILIARIZATION ANO MAINTENANCE ---CONTACT ARM ADJUSTMENT CONTACTS ~~....... SPIRAL HOUSING PASSAGE A OIL TEMPERATURE REGULATOR PURPOSE: To automatically and electrically control the position of the oil cooler exit flap. LOCATION: An oil temperature regulator is mounted on the side of each oil cooler. OPERATION: This unit consists of two sections: One section contains four valves which provide three routes of oil travel through the cooler and regulator (see OIL TEMPERA- TURE CONTROL): the ·second section consists of a mechanism which automatically controls the position of the oil cooler exit flap. The automatic feature may be disconnnected and the flap position controlled directly by the engineer by means of switches on his panel. When the75PSI (pounds per square inch)valve is open, the oil from the inlet port flows through this valve and into the cooler muff. 12 OIL SYSTE.M
RESTRICTED This valve provides the only entrance to the cooler. It remains in a full open position unless a pressure of 53 PSI or over is built up due to congealed cold oil in the cooler. The valve starts to close at 53 PSI and is completely closed at 75 PSI. Mounted on the same stem as the 75 PSI valve so that it starts to open at 53 PSI is another valve which affords a by-pass passage for the oil flow directly to the outlet port. Oil pressure on this by-pass valve is the acting force which moves both valves against the spring. The opposite face of this valve is exposed to the atmosphere. Passage A leads oil to the spring-loaded pressure override piston. When an oil pressure difference of 23 to 25 PSI is reached between the inlet and outlet ports, the piston de- presses the override switch which in turn energizes the motor, closing the cooling air exit flap. The middle valve is the 25 PSI or·muff valve. It is spring-loaded to open when a pressure of 25 PSI or more is exerted against it. This is the only direct outlet fr.:>m the cooler muff into the regulator outlet chamber. This valve is normally closed when the oil in the cooler is warm. The third valve is the 2 PSI or check valve. It is spring-loaded and will open at a pressure of 2 PSI. When the oil is circulating through the cooler core, this valve is open, as it is the only outlet from the core into .+he regulator. The flow from the by-pass, muff or check valves is directed past the bi-metallic spiral which either contracts or expands, depend- ing on the temperature of the oil. Movement of this spiral actuates a contact arm which can move over five contacts governing a 8 - 2 9 F'AMILIARIZATION AND MAINTENANCE total of seven positions of the exit flap: full open, full closed and five intermediate positions (see Oil Temperature Regulator Wiring Diagram). The oil temperature regulator is set to main-· tain a temperafore of 70 degrees Centigrade. The exit flap is completely closed when the temperature of the oil is below 65 degrees Centigrade. The exit flap starts to open at 65 degrees Centigrade and is fully open when the oil temperature reaches 77 degrees Cen- tigrade. Approximately 30 seconds is required for the exit flap to travel from the open to the closed position. On the engineer's switch panel; four, four- position (OPEN, CLOSED, AUTOMATIC or OFF) switches control the position of the exit flaps. The exit flap motors may be operated manually to open and to close the flaps, thus allowing the engineer to directly control the passage of air through the cooler. In the AUTOMATIC position, the oil cooler exit flap is controlled automatically by the oil temperature regulator unit. ADJUSTMENT: If a change in the control temperature of 70 degrees Centigrade is desired, any oil cooler outlet temperature from 38 degrees to 98 degrees Centigrade may be obtained by resetting the contact arm adjust.. men+. The arm is turned counterclockwise for higher outlet temperatures up to 98 degrees Centigrade. Temperatures referred to are those indicated at the engineer's panel. The temperature is obtained at the outlet fitting on the tank sump. Before any large adjustments are made on the .oil temperature regulators, the oil temperature bulb and indicator circuit should be checked for accuracy. - -~---= OIL SYSTEM 13
RESTRICTED 34 P .S. I. VALVE FOR ENGlNES WITH CABIN COMPRESSOR 25 P. S. I. VALVE FOR ENGINES WITHOUT CABIN COMPRESSOR - - - - - - PRESSURE SAFETY BY-PASS VALVE---------- STARTS OPENING AT 53 POUNDS PER SQUARE INCH FULLY OPEN AT 75 POU NOS PER SQUARE INCH 75 P.S.I. VALVE STARTS CLOSING AT 53 POUNDS PER SQUARE INCH FULLY CLOSED AT 75 POUNDS PER SQUARE INCH OIL FROM ENGINE - - - - RETURN TO OIL RESERVOIR------- LEGEND - HOT ENGINE OIL - ENGINE OIL BY-PASSING COOLER c==::J OIL COOLED BY FLOW THRU MUFF r:=:::=J OIL COOLED TO ENGINE OPERATING TEMPERATURE P. S. I.= POUNDS PER SQUARE INCH AIR FLOW THRU OIL COOLER 8 - 2 9 FAMILIARIZATION ANO MAINTENANCE Bl-METALLIC SPIRAL ~ PRESSURE OVERRIDE Ill~ PISTON ACTUATES SWITCH AT 33 POUNDS PER SQUARE INCH FOR ENGINES WITH CABIN COMPRESSORS. ACTUATES SWITCH AT 25 POUNDS PER SQUARE INCH FOR ENGINES WITHOUT CABIN COMPRESSORS. OIL TEMPERATURE CONTROL 14 OIL SYSTEM

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Boeing B-29 Superfortress Familiarization and Maintenance Manual,Part 4.pdf