FAA Flight Instructor Airplane (FIA)Performance, Weight and BalanceEasy
A pilot is preparing for takeoff from an airport at 5,000 ft field elevation on a hot, humid afternoon. Compared to a standard-day takeoff at the same field elevation, the resulting high density altitude will most likely:
- AOnly affect engine performance, not aerodynamic performance
- BIncrease takeoff distance and decrease climb performance
- CHave no effect on performance because true airspeed remains constant
- DDecrease takeoff distance and increase climb performance
Show answer & explanationAnswer & explanation
Correct answer: B. Increase takeoff distance and decrease climb performance
High density altitude means the air is less dense, so the engine produces less power, the propeller is less efficient, and the wings produce less lift at a given airspeed. This combination lengthens the takeoff roll and reduces the rate of climb.
Why the other options are wrong
- A. Both engine power and aerodynamic lift are reduced, not just engine performance.
- C. True airspeed actually increases for a given indicated airspeed, but lift and thrust still decrease.
- D. Opposite of the actual effect; high DA always degrades performance.
Density Altitude
Pressure altitude corrected for nondstandard temperature; represents the altitude the airplane 'feels' it is performing at.
- High temperature, humidity, and altitude all increase density altitude
- High DA reduces engine power, propeller efficiency, and lift
- Always degrades takeoff, climb, and landing performance
Memory trick: Hot, High, Humid = Hurts performance