PLT131: Ground Effect
What code PLT131 covers, why the FAA tests it, and how to study Ground Effect before your checkride.
Recall aircraft performance - ground effect
What this means for your checkride
Ground effect is the drop in induced drag when the wing is within about a wingspan of the surface, because the ground disrupts the wingtip vortices. It can let an airplane lift off or float before it truly has flying speed.
Ground effect explains float on landing and premature liftoff on takeoff, both common test and real-world scenarios, so the FAA checks that you know when it helps and when it hurts.
Pilots think ground effect adds lift. It mainly reduces induced drag; climbing out of ground effect increases drag, which is why an airplane forced off early can settle back onto the runway.
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.
Ground effect is significant only when the wing is close to the surface. It generally exists within approximately what height above the ground?
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.
What is ground effect and when does it matter?
Ground effect is the reduction in induced drag when the wing is within about one wingspan of the surface. It matters on takeoff and landing: the airplane can lift off below normal flying speed and settle when it climbs out of it, and on landing it produces float if I carry extra airspeed.
How can ground effect trick you on a soft or short-field takeoff?
Reduced drag lets the airplane become airborne prematurely. If I climb out of ground effect before reaching a safe climb speed, drag returns and the airplane may sink or stop climbing, so I stay in ground effect to accelerate to Vx or Vy before climbing away.
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.