PLT242: The Four Forces
What code PLT242 covers, why the FAA tests it, and how to study The Four Forces before your checkride.
Recall forces acting on aircraft - lift / drag / thrust / weight / stall / limitations
What this means for your checkride
This is the balance of the four forces, lift, drag, thrust, and weight, and how the wing produces lift until the critical angle of attack, beyond which it stalls regardless of airspeed or attitude. It also covers the structural limitations that cap how much load the airframe can take.
Understanding that a stall is about angle of attack, not speed, is fundamental to flying safely, so the FAA tests the force balance, the critical angle of attack, and the load limits.
The deepest misconception is that an airplane stalls only at low speed. A wing stalls whenever it exceeds the critical angle of attack, which can happen at any airspeed or attitude, including a high-speed accelerated stall in a steep turn.
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.
The angle of attack (AOA) is the acute angle between which two references?
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.
Name the four forces in level flight and how they relate.
Lift, weight, thrust, and drag. In steady, unaccelerated level flight lift equals weight and thrust equals drag, so the airplane is in equilibrium. Change one, such as adding power, and it accelerates or climbs until the forces rebalance.
Define angle of attack and why it, not speed, causes a stall.
Angle of attack is the angle between the chord line and the relative wind. Lift rises with AOA up to the critical angle; past it the airflow separates and the wing stalls. Because that critical angle is fixed, a stall can happen at any airspeed or attitude.
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.