PLT005: Density Altitude
What code PLT005 covers, why the FAA tests it, and how to study Density Altitude before your checkride.
Calculate aircraft performance - density altitude
What this means for your checkride
Density altitude is pressure altitude corrected for nonstandard temperature: the altitude the air actually behaves like to the wing, propeller, and engine. It rises with heat, elevation, and humidity, and it, not the number under the altimeter, is what governs how the airplane performs.
Density altitude ties temperature, pressure, and field elevation straight to takeoff distance, climb rate, and true airspeed, so the FAA tests whether you can compute it and predict its effect before you commit to a departure.
Candidates often treat field elevation as the performance number. On a hot day a low-elevation airport can have a density altitude thousands of feet higher than its actual elevation, and performance degrades to match.
Where to study it
Practice questions on this code
Real questions from the Aviator IQ bank that test this exact area. Answer each to see the correct choice, the full rationale, and the FAA source.
Which combination of conditions produces a high density altitude and the greatest loss of airplane takeoff and climb performance?
Which combination produces the greatest required landing distance and the most critical energy dissipation on the brakes?
Oral checkride defense
A code on your report is an area the examiner can revisit. Here is how an examiner might probe it, and how to explain it out loud.
It's a 95 degree afternoon at a 5,000 foot field. Walk me through how density altitude affects this takeoff.
Explain that heat and elevation thin the air, so density altitude can sit well above 8,000 feet. That means a longer ground roll, a weaker climb, and a higher true airspeed for the same indicated airspeed. Reference the POH performance chart for the actual numbers and state your planned abort point on the runway.
How do you find density altitude, and why not just use field elevation?
Start with pressure altitude (set 29.92 and read the altimeter, or correct field elevation), then correct for temperature above standard using a chart or E6B. Field elevation ignores temperature and humidity, so on a hot, humid day the airplane performs as if it were thousands of feet higher than the field.
A code on your test report is an area of deficiency. An authorized instructor must review it with you and endorse that review before you take the practical test, and the examiner may revisit it during the oral. Study it until you can explain it out loud, not just recognize the answer.