Helicopter 1

How is a helicopter usually considered regarding stability?. Statically unstable, dynamically stable. Statically stable, dynamically unstable. Statically and dynamically stable.

What force is blade speed associated with?. Gyroscopic force. Centrifugal force. Aerodynamic drag.

What causes the coning angle of the blades?. Lift acting alone. Centrifugal force and lift. Drag and lift.

What determines the magnitude of the coning angle?. Blade twist along the span. Relationship between centrifugal force and lift. Rotor RPM only.

What stalls first on a helicopter rotor system?. Advancing blade. Both blades simultaneously. Retreating blade at high pitch angles.

What phenomenon is corrected by blade flapping?. Gyroscopic precession. Dissymmetry of lift. Transverse flow effect.

What is associated with the Coriolis effect?. Collective pitch changes. Blade lead-lag movement. Cyclic feathering.

8. How do fully articulated rotors compensate for Coriolis effect?. Through underslinging. Through rigid rotor hubs. Through lead-lag hinges.

How do semi-rigid rotors compensate for Coriolis effect?. Through lead-lag hinges. Through underslinging. Through drag braces.

What is the purpose of a helicopter blade flapping hinge?. Allow blade to twist for pitch control. Allow advancing blade to flap up, reducing angle of attack. Allow blade to move in-plane to absorb vibration.

What is the purpose of a helicopter lead-lag hinge?. Allow blades to move vertically. Allow blades to move in-plane to compensate for Coriolis effect. Adjust blade pitch automatically.

What is blade twist called?. Incidence gradient. Twist angle. Pitch sweep.

What is the variation in incidence between root and tip?. Pitch differential. Twist angle. Root transition.

What is translational lift and when does it occur?. Improved tail rotor thrust; 5–10 mph. Improved engine efficiency; 20–30 mph. Improved rotor efficiency; 15–20 mph.

What is transverse flow effect?. More downwash in aft portion of disc. More downwash in forward portion of disc. Equal downwash across disc.

What happens in vertical steady flight?. Lift + thrust > weight + drag. Lift + thrust = weight + drag. Lift alone equals weight.

Why are cyclic inputs applied before desired direction?. To avoid Coriolis effect. Because of gyroscopic precession. To balance coning angles.

How is the skin of a metal rotor blade attached to the spar?. Riveted. Bonded. Clamped.

The skin of metal blades functions as: A primary structural load path. An aerodynamic surface and abrasion shield. A counterweight.

What are tow pins on a wooden rotor?. Grip bolt alignment points. CG and center of pressure markers. Balance weights.

What is the mixer box used for?. Combines cyclic, collective, and throttle inputs mechanically. Adds weight to stabilize the rotor head. Mixes engine air and fuel Respuesta: a.

22. Why is the driven swashplate attached to the mast?. To remain stationary. So it rotates with the main rotor. To allow pitch-change rods to disconnect.

What type of bearing is found in pitch-link rod ends?. Tapered roller bearings. Sleeve bearings. Spherical bearings.

What is the purpose of conical elastomeric bearings?. Provide electrical insulation. Absorb high axial and radial loads with limited motion. Increase blade twist.

What type of gear is most used in helicopter transmissions?. Spur gear. Spiral bevel or helical. Worm gear.

Mast bumping is associated with which system?. Rigid rotor. Fully articulated. Semi-rigid.

Ground resonance affects which system?. Fully articulated. Rigid. Semi-rigid.

What is the most common system in small helicopters?. Rigid. Fully articulated. Semi-rigid.

Why is a semi-rigid rotor underslung?. To improve drag characteristics. To reduce Coriolis stress and increase rigidity. To increase blade twist.

What rotor head uses under-slinging?. Fully articulated. Semi-rigid. Rigid.

What causes a 1:1 vertical vibration?. Out-of-track blade. Chordwise imbalance. Tail rotor aerodynamic stall.

What causes a 1:1 lateral vibration?. Low rotor RPM. Bad damper on fully articulated system. Excessive blade twist.