Part 107, explained · Last reviewed October 25, 2026 against the eCFR and faa.gov. UAV Campus is not affiliated with the FAA.
How does a wing make lift (Bernoulli or Newton)?
Both. Bernoulli's principle: as the speed of air increases its pressure decreases, so faster air over the curved top of the wing lowers the pressure there. Newton's third law: the airfoil forces air downward, and the equal reaction forces the airfoil upward. The FAA says lift is based on Newton's laws and Bernoulli's principle.
Sources: FAA-H-8083-25C ch. 4, Theories in the Production of Lift · FAA-H-8083-25C ch. 4, Bernoulli's Principle of Differential Pressure
What the FAA handbook says
FAA-H-8083-25C ch. 4, Theories in the Production of Lift
Generating this force called lift is based on some important principles, Newton's basic laws of motion, and Bernoulli's principle of differential pressure.
FAA-H-8083-25C ch. 4, Bernoulli’s Principle of Differential Pressure
Bernoulli’s Principle states that as the velocity of a moving fluid (liquid or gas) increases, the pressure within the fluid decreases. This principle explains what happens to air passing over the curved top of the airplane wing.
FAA-H-8083-25C ch. 4, Airfoil Design
An airfoil is shaped to cause an action on the air, and forces air downward, which provides an equal reaction from the air, forcing the airfoil upward.
FAA-H-8083-25C ch. 11, Aircraft Performance (equilibrium in level flight)
When an aircraft is in steady, level flight, a condition of equilibrium must prevail. An unaccelerated condition of flight is achieved when lift equals weight, and the powerplant is set for thrust equal to drag.
Sources: FAA-H-8083-25C ch. 4, Theories in the Production of Lift · FAA-H-8083-25C ch. 4, Bernoulli’s Principle of Differential Pressure · FAA-H-8083-25C ch. 4, Airfoil Design · FAA-H-8083-25C ch. 11, Aircraft Performance (equilibrium in level flight)
Exam traps
- In straight, level, unaccelerated flight, lift equals weight (and thrust equals drag); lift does not have to exceed weight to keep an aircraft flying.
- Bernoulli's principle says that as the velocity of a moving fluid increases, the pressure within the fluid decreases.
- The handbook says the lift shares of the upper and lower surfaces are not constant values: they vary with flight conditions and wing design.
- Lift is more complex than a pressure difference between a longer upper surface and a shorter lower one: many symmetrical airfoils, with no longer upper surface, still produce lift.
Try it: practice questions
Similar to the FAA test, not the actual test questions.
Practice question 1
A stall occurs when the smooth airflow over the unmanned airplane’s wing is disrupted and the lift degenerates rapidly. This is caused when the wing
- A exceeds its critical angle of attack.
- B exceeds the maximum speed.
- C exceeds maximum allowable operating weight.
Show the answer
Answer: A. exceeds its critical angle of attack.While the traditional wisdom dictates that this happens at slow airspeed, when the nose of the aircraft is high, this can happen at any speed. If you apply abrupt pitch-up controls, the angle of attack can reach the critical number where the airflow separates and the aircraft stalls. Remember also that the angle of attack is the difference between the chord line and the relative wind (or direction of motion of the aircraft). When the aircraft reaches maximum speed, the wing will still produce lift, but structural failure can occur (the aircraft wouldn’t be strong enough to go that fast). If the aircraft exceeds its maximum allowable operating weight, structural damage or failure is also a possibility.)
FAA source: FAA-H-8083-25C ch. 5, Stalls
Practice question 2
How would high density altitude affect the performance of a small unmanned aircraft?
- A Decreased performance.
- B Increased performance.
- C No change in performance.
Show the answer
Answer: A. Decreased performance.Density Altitude is the altitude corrected for non-standard pressure and non-standard temperatures. A high density altitude means your UAS will “feel” like it’s operating at a higher altitude, hence the performance will be diminished.
FAA source: FAA-H-8083-25C ch. 11, Density Altitude
Is lift mostly from the top or the bottom of the wing?
The handbook says it is neither accurate nor useful to assign specific percentages to the upper and lower surfaces. The shares are not constant and vary with flight conditions and wing design.
Source: FAA-H-8083-25C ch. 4, Airfoil Design