Principles of Helicopter Flight Flashcards
7 cards from real SIFT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Principles of Helicopter Flight flashcards as text
What happens to required tail rotor thrust as altitude increases?
Answer: It increases because the tail rotor must work harder in thinner air to produce the same anti-torque force
At higher altitudes, thinner air reduces tail rotor thrust efficiency, requiring higher pitch angles or limiting the anti-torque authority available to the pilot.
What is the difference between hovering in ground effect (IGE) and out of ground effect (OGE)?
Answer: OGE requires more power because the rotor cannot benefit from ground interference with downwash
OGE hovering requires significantly more power because the rotor operates without the efficiency benefit of ground effect, and density altitude OGE limits are lower than IGE limits.
What is 'LTE' (Loss of Tail Rotor Effectiveness) and under what conditions does it most often occur?
Answer: Reduced tail rotor authority during certain wind and power conditions, most often at low airspeeds in left crosswind or tailwind (for US helicopters)
LTE occurs when wind interferes with tail rotor effectiveness, particularly from certain wind azimuths during low-speed flight, reducing the pilot's ability to control yaw.
Why is it dangerous to reduce collective during a high-speed autorotation just before touchdown?
Answer: Reducing collective too early depletes rotor energy needed for the flare and cushioned touchdown
Rotor RPM stores inertial energy; reducing collective prematurely in autorotation bleeds this energy, leaving insufficient rotor kinetic energy for the flare and cushioned landing.
What is the purpose of the collective pitch control?
Answer: To simultaneously increase or decrease the pitch angle of all main rotor blades to control altitude and power
The collective changes the pitch of all main rotor blades equally and simultaneously, controlling the total lift generated and the helicopter's altitude.
What is 'compressibility effect' and at what rotor condition does it become significant?
Answer: Shock wave formation on advancing rotor blade tips at high forward airspeeds, causing drag rise and vibration
Compressibility effects occur when the advancing blade tip speed approaches the speed of sound, forming shock waves that dramatically increase drag and cause airframe vibration, limiting maximum airspeed.
In a coordinated turn, what control inputs does a helicopter pilot typically use?
Answer: Cyclic to bank, collective to maintain altitude, and pedals to coordinate yaw
A coordinated turn requires cyclic to establish the bank, increased collective to compensate for the reduced vertical lift component, and pedals to maintain coordinated (slip-free) flight.