12. Helicopter aerodynamics, structures and systems - Q&A

Retreating blade stall symptoms in a helicopter typically include:

• nose-up pitching, vibration, and a roll toward the retreating blade side as the retreating blade loses lift capacity
• immediate loss of all rotor thrust resulting in an uncontrollable descent regardless of the pilot control actions taken
• a smooth and gradual reduction in forward speed with no vibration or unusual control response from the pilot input

Relative airflow over a helicopter blade

• increases at the tip.
• is unaffected by blade position.
• increases at the root.

Over-pitching the main rotor causes

• a reduction in RPM.
• an increase in RPM.
• a decrease in coning angle.

A helicopter is hovering and the pilot applies right pedal. Assuming the main rotor rotates anti clockwise viewed from above, the helicopter will

• descend, unless the pilot applies more collective pitch.
• descend, unless the pilot inches the throttle open.
• ascend, unless the pilot decreases rotor RPM.

How is the next database on the FMC activated?

• Manually on the ground.
• Automatically by due date.
• Manually in the air.

If the pitot and static pipe lines were cross connected at the instrument panel connection, application of pressure to the pitot head would cause the

• altimeter reading to increase, vertical speed indicator to indicate descent.
• altimeter reading to decrease, vertical speed indicator to indicate descent.
• altimeter reading to decrease, vertical speed indicator to indicate climb.

The intermediate gearbox is

• an epicyclic gearbox.
• a bevel gearbox.
• a reduction gearbox.

When the rotor blade increases its angle of attack, the centre of pressure

• does not move.
• moves rearwards.
• moves forward.

The main rotor stabiliser bar hydraulic dampers have been set too stiff. This would cause

• too much stability and over sensitive controls.
• too much stability and less sensitive controls.
• instability and over sensitive controls.

Solidity of the rotor is the ratio of the

• blade area to disc area.
• all up weight to blade area.
• all up weight to disc area.

In straight and level flight, the forward air speed is controlled by the

• cyclic stick and the throttle.
• cyclic stick and the collective lever.
• collective lever and the throttle.

Which part of the rotor disc produces the most lift during forward flight?

• The mid-span portion.
• The front portion.
• The rear portion.

The coning angle of the rotor blades is the angle between

• the horizontal and the rotor blades.
• the rotor blades and the tip path plane.
• the normal axis and the rotor blades.

A redundant structure is

• on-condition structure.
• a safe-life structure.
• a failsafe structure.

A cold air unit allows for cabin temperatures to be

• a little more than ambient air temperature.
• lower than ambient air temperature despite compression heating.
• same as ambient temperature, despite compression heating.

A pneumatic indicator takes its indications from

• compressor inlet.
• reservoir.
• compressor outlet.

Compressibility error in a pitot head is caused by

• misalignment of pitot head.
• blockage in the pitot tube.
• compression of air in the tube at high speed.

What does a Decca Navigation system operate on?

• Very High Frequency.
• High Frequency.
• Low Frequency.

A helicopter tail rotor is fitted to

• counteract engine torque and provide a rapid turn facility.
• counteract main rotor torque and provide normal directional control.
• permit directional control.

How do the rotors turn on a co-axial rotor system?

• They counter-rotate on a common shaft.
• Both rotate in the same direction on a common shaft.
• They counter-rotate on separate shafts.

What is the advancing blade on a helicopter doing?

• Going to the highest point.
• Increasing in lift.
• Increasing in drag.

A helicopter is hovering and the pilot applies right pedal. Assuming the main rotor rotates anti clockwise viewed from above, the helicopter will

• descend, unless the pilot applies more collective pitch.
• descend, unless the pilot inches the throttle open.
• ascend, unless the pilot decreases rotor RPM.

Lift generated by a blade is proportional to the

• relative airflow and the angle of attack.
• aircraft airspeed and angle of attack.
• relative airflow and the pitch.

The stalling speed of an helicopter blade

• does not change.
• is increased when the helicopter is heavier.
• is increased when the helicopter is lighter.

On a helicopter, what is vortex ring state?

• Tip vortex build-up in a powered vertical descent.
• Tip vortex interference at high forward speed.
• Ground vortex interference when hovering close to the ground.