Propellers and Thrust
A propeller creates thrust based on which law of physics?
Newton’s Third Law.
What section of a jet engine increases pressure using spinning blades?
The compressor.
Spiral slipstream striking the tail causes which tendency?
Corkscrew effect (left yaw).
Drag caused by the shape of an object is called what?
Form drag.
What is the drag equation?
D = (CD × ρ × V² × S) / 2.
Why do propeller blade tips move faster than the root?
They travel a longer distance in the same amount of time.
What turns the compressor in a jet engine?
The turbine via a connecting shaft.
What tendency occurs because the descending propeller blade on the right creates more thrust?
P-factor.
What type of drag is created by airflow mixing where components meet, such as at the wing root?
Interference drag.
In the drag equation, which variable has the largest effect on drag?
Velocity, because it is squared.
What major design feature helps equalize thrust along a propeller blade?
Blade twist (changing angle of attack from root to tip).
A turbofan differs from a turbojet because it uses what to produce extra thrust?
A large bypass fan.
According to Newton’s 3rd Law, engine/prop rotation causes the airplane to roll left. What is this called?
Torque reaction.
Parasite drag depends mainly on what variable?
Velocity squared.
If velocity doubles, drag changes by what factor?
Drag × 4.
What is the main tradeoff of a fixed-pitch “climb” propeller?
Great takeoff thrust, but less efficient cruise.
What are the five stages of jet engine operation?
Intake, Compression, Combustion, Turbine, Exhaust.
Gyroscopic precession appears strongest during which type of airplane motion?
Pitch changes (nose up or down).
What type of drag results from creating lift and forms wingtip vortices?
Induced drag.
What does ground effect do to induced drag?
It reduces it by weakening wingtip vortices.
Name three factors engineers can change along a blade to balance thrust.
Angle of attack (twist), camber, and surface area.
Why can’t propellers be used efficiently at very high speeds?
Propeller tips approach the speed of sound, becoming inefficient and creating shockwaves.
Name all four turning tendencies.
Corkscrew effect, Torque reaction, P-factor, Gyroscopic precession.
Describe how induced drag changes with airspeed, and why.
It decreases as speed increases, because producing the same lift requires a lower AOA at higher speeds.
What airspeed corresponds to minimum total drag and maximum glide range?
Best glide speed (the speed at which induced and parasite drag sum to the lowest point).