The ppt used in class

2. SPEED = DISTANCE / TIME
Three types of speeds:
• AIRSPEED: Rate of change of position in relation to
time, of air molecules as they are flowing though
a certain passage
• GROUNDSPEED: Relative velocity an aircraft has
in relation to the ground. (Being the ground
considered still)
• RELATIVE SPEED: Relative change of position
between any two objects

6. DEFINITION: The one measure by the pitot-static
system without any corretions
INSTRUMENT ERROR: All inaccuracies shown on
an airspeed indicator due to the inherent
imperfections of the instrument. (Frictions,
readablity, timming, accuracy, scale reading,…).
Usually considered negligible

7. DEFINITION: Airspeed shown on an airspeed indicator
whenever the actual incoming from the pitot-static
system indication is corrected for INSTRUMENT
ERROR.
The one actually shown on a usual ASI
POSITION ERROR: Missinterpretation of the real airspeed
due to the fact of the pitot-static system’s incoming not
being undisturbed. (Drifting, turbulence, water,
maneuvreing,…). Taken into account for certain
maneuvres and situations

8. DEFINITION: Sometimes called Rectified airspeed
(RAS) Stands for the IAS corrected for position
error.
DENSITY ERROR: Due to the fact of the Pitot-Static
system only being able to measure dynamic
pressure the systems takes into account a
constant value for the air density. This mistake
increases as density decreases, and so, as
altitude increases. ≈2% each 1000ft AMSL

9. DEFINITION: Calibrated Airspeed (CAS) of an airflow
taking into account compressibility of the air.
Must take into account that the air is taken as not
compressible bellow ≈300Kts
DENSITY ERROR: Density varies in accordance with the
Ideal Gases Formula P/ℓ = MRT.
So temperature and pressure will affect the
airspeed indicator reading
If ∆T > 0  ∆ℓ < 0 ASI will read a lower speed
If ∆P > 0  ∆ℓ < 0 ASI will read a lower speed

10. DEFINITION: Airspeed relative to the airmass in which
the aircraft is actually flying.
The EAS corrected for density error.
½ ℓ EAS² = ½ ℓh TAS²
0
NOTE: Must understand that density thermodinamyc
charateristics vary in a “known” way through the
atmosphere

11. DEFINITION: Adimensional number that relates the
actual airspeed of a body to the speed that the
sound would have inside the airmas (with its
thermodinamyc charateristics) through wich the
body is moving.
TAS
M
LSS TAS
M
38 .92 T (º K )
LSS 38.92 T (º K )