Practice question 1
As the angle of attack increases, induced drag will
- A remain the same.
- B increase.
- C decrease.
Show the answer
Answer: B. increase.
FAA source: FAA-H-8083-25C ch. 5, Induced Drag
FAA-H-8083-25C, ch. 5
What is induced drag?
Induced drag is the price a wing pays for making lift. Here is what drives it, the exam traps and practice questions, with the FAA source under each answer.
What is induced drag and what makes it increase?
Induced drag is the drag that results from an airfoil developing lift. As angle of attack increases, induced drag increases proportionally. Because slower flight needs a higher angle of attack to support the weight, induced drag is greatest at low airspeed: it varies inversely with the square of the airspeed.
Source: FAA-H-8083-25C ch. 5, Induced Drag
What the FAA handbook says
FAA-H-8083-25C ch. 5, Induced Drag
The action of the airfoil that gives an aircraft lift also causes induced drag.
FAA-H-8083-25C ch. 5, Induced Drag
In any case, as AOA increases, induced drag increases proportionally. To state this another way—the lower the airspeed, the greater the AOA required to produce lift equal to the aircraft’s weight and, therefore, the greater induced drag. The amount of induced drag varies inversely with the square of the airspeed.
Sources: FAA-H-8083-25C ch. 5, Induced Drag · FAA-H-8083-25C ch. 5, Induced Drag
Exam traps
- As airspeed increases, induced drag decreases, because it varies inversely with the square of the airspeed.
- Parasite drag does the opposite: it increases as the square of the airspeed.
- Near the stalling speed total drag becomes greater, due mainly to the sharp rise in induced drag.
- If the angle of attack of a symmetrical airfoil were zero, there would be no pressure differential and no induced drag.
Try it: practice questions
Similar to the FAA test, not the actual test questions.
Practice question 2
As speed increases, induced drag will
- A remain constant.
- B decrease.
- C increase.
Show the answer
Answer: B. decrease.
FAA source: FAA-H-8083-25C ch. 5, Drag Curves / Induced Drag
What causes induced drag?
A pressure difference exists between the upper and lower surfaces of an airfoil flown at a positive angle of attack. Air spills around the wingtips and sets up vortices, and the resulting downwash bends the lift vector rearward, which is induced drag.
Source: FAA-H-8083-25C ch. 5, Wingtip Vortices