Specifications

DCS
[P-51D Mustang]
110
FLIGHT CHARACTERISTICS
Figure 89: Maximum Indicated Airspeed
Compressibility
Compressibility effects result in a loss of control over the aircraft as it approaches the speed of sound
and is the reason maximum IAS is reduced as altitude increases. The lift characteristics of the aircraft
are largely destroyed and intense drag develops. The stability, control, and trim characteristics of the
aircraft are affected. The tail buffets or the controls stiffen, or the aircraft develops uncontrollable
pitching and porpoising, or uncontrollable rolling and yawing, or any combination of these effects. If
the speed of the aircraft is allowed to increase out of control in a dive, either the terrific vibrations of
the sound barrier shockwaves cause structural failure or the aircraft crashes while still in the
compressibility dive.
In the P-51, the first effect of compressibility is a “nibbling” of the control stick, where it occasionally
jumps slightly in the pilot’s hand. If the airspeed is allowed to climb, this movement will increase into
a “walking” stick, where it moves uncontrollably forward and back, resulting in the characteristic
“porpoising” pitching moments of the aircraft. As the airspeed builds, this effect will become
increasingly violent.