FAA Commercial Pilot Airplane (CAX)Navigation and Flight PlanningMedium
An airport has a pressure altitude of 5,000 feet, but the outside air temperature is 35°C, well above the standard temperature of 5°C for that altitude. How will the resulting high density altitude affect the pilot's fuel planning for takeoff and climb to cruise altitude?
- AThere is no effect on fuel planning because fuel burn depends only on pressure altitude, not temperature
- BTakeoff distance and time-to-climb will increase, requiring additional fuel to be planned for the climb segment
- CFuel burn to climb will decrease because true airspeed increases with density altitude
- DThe airplane will reach cruise altitude faster, reducing the climb fuel requirement
Show answer & explanationAnswer & explanation
Correct answer: B. Takeoff distance and time-to-climb will increase, requiring additional fuel to be planned for the climb segment
High density altitude reduces engine and propeller efficiency, increasing takeoff roll and reducing climb rate. This means more time (and thus more fuel) is needed to reach cruise altitude, which must be accounted for in fuel planning.
Why the other options are wrong
- A. Density altitude, driven by both pressure altitude and temperature, directly affects performance and fuel burn.
- C. Higher TAS at altitude does not offset the reduced climb performance and increased fuel burn.
- D. Climb performance is degraded, not improved, at high density altitude.
Density Altitude Effect on Fuel Planning
High density altitude reduces engine, propeller, and aerodynamic performance, increasing takeoff distance and climb time, which increases fuel consumption during those phases.
- Density altitude = pressure altitude corrected for nonstandard temperature
- Higher density altitude reduces climb rate and increases takeoff roll
- Fuel planning must add margin for degraded performance on hot/high days
Memory trick: Hot and high, fuel goes bye-bye (uses more)