SIFT Principles of Helicopter Flight Questions and Answers 2

Question 1

What is 'translational lift' in helicopter aerodynamics?

Accepted Answer

The extra lift generated when forward airspeed improves rotor efficiency at around 16-24 knots

Answer

The lift provided by the horizontal stabilizer during cruise flight

Answer

The increase in tail rotor lift needed for forward flight

Answer

The lift generated by the fuselage in high-speed forward flight

Question 2

What is 'autorotation' in helicopter flight?

Accepted Answer

An unpowered descent where aerodynamic forces keep the rotor spinning to enable a safe landing

Answer

Automatic stabilization of the rotor speed by the governor

Answer

Flying the helicopter using only the tail rotor for propulsion

Answer

The automatic rotation of the rotor during engine start

Question 3

What causes 'torque roll' tendency in a single-rotor helicopter?

Accepted Answer

The main rotor's reaction torque trying to rotate the fuselage opposite to the rotor

Answer

Gyroscopic precession from the spinning rotor

Answer

Dissymmetry of lift in forward flight

Answer

Center of gravity shifts during fuel burn

Question 4

What is 'retreating blade stall' and when does it occur?

Accepted Answer

Stall of the retreating blade at high forward airspeeds when it cannot generate sufficient lift

Answer

Stall of all rotor blades during hovering in high density altitude

Answer

Stall caused by the pilot lowering the collective too rapidly

Answer

Stall of the tail rotor blades during sharp turns

Question 5

What is 'effective translational lift (ETL)' and how does it affect hover performance?

Accepted Answer

The speed at which a helicopter achieves maximum efficiency, approximately 16-24 knots, improving hover-out-of-ground-effect capability

Answer

A measure of lift efficiency that decreases in ground effect

Answer

The lift generated by the horizontal stabilizer during forward flight

Answer

The maximum lift available at sea level standard conditions

Question 6

What is 'density altitude' and how does it affect helicopter performance?

Accepted Answer

Pressure altitude corrected for temperature, representing air density; high density altitude reduces helicopter performance

Answer

The altitude above the highest terrain feature in the area

Answer

The altitude above sea level as indicated on a standard altimeter

Answer

The altitude calculated using only humidity corrections