Understanding how an airplane works makes you a safer, more confident pilot, and it is exactly what your examiner probes on the oral exam. This hub explains the four forces of flight and walks through the major systems you operate every flight: the engine, propeller, flaps, and pitot-static instruments, plus what really happens in a stall.
Part of our Learn to Fly library. These topics come up constantly on the oral exam.
The four forces of flight
Every airplane in flight is acted on by four forces: lift (upward, from the wings), weight (downward, from gravity), thrust (forward, from the propeller), and drag (rearward, from air resistance). In steady, level flight they balance: lift equals weight and thrust equals drag. Change one and the airplane climbs, descends, accelerates, or slows.
How a wing makes lift
A wing produces lift by accelerating air over its surface and deflecting air downward, creating a pressure difference between the upper and lower surfaces. The key variable you control is the angle of attack, the angle between the wing and the oncoming air. Increase it and lift increases, up to a point. Exceed the critical angle of attack and the wing stalls, which is the subject of its own guide below.
The major systems you operate
- How an aircraft engine works
- How a propeller works
- How flaps work
- The pitot-static system
- Stalls and angle of attack
Why this matters
You do not need to be an engineer, but you do need to understand your airplane well enough to operate it correctly, recognize when something is wrong, and explain it to an examiner. A pilot who understands the systems handles surprises calmly, because they know what each control and instrument is actually doing.
Study tools
What you'll need
The FAA handbooks that explain how your airplane works, from PilotMall.com.
Frequently asked questions
What are the four forces of flight?
Lift, weight, thrust, and drag. In steady level flight, lift equals weight and thrust equals drag.
What actually makes an airplane fly?
The wing produces lift by accelerating and deflecting air, creating a pressure difference. The amount of lift depends largely on angle of attack and airspeed.
Do I need to understand systems for the checkride?
Yes. The oral exam covers how your airplane’s engine, propeller, flaps, and instruments work, and what to do when they fail.