Aerodynamic Forces

Question 1

DEF

tip path

Answer 1

The circular path described by the tips of rotor blades

Question 2

DEF

Tip path plane

Answer 2

The plane within which the tips of rotor blades travel. It is parallel to the plane of rotation which acts through the rotor head.

Question 3

How can a pilot change tip path plane?

Answer 3

a pilot my out of this plane for movement of the cyclic control

Question 4

DEF

axis of rotation

Answer 4

The line through the rotor head at right angles to the plane of rotation. blades actually rotate around this axis.

Question 5

What does POR stand for?

Answer 5

Plane of rotation

Question 6

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What is the shaft axis

Answer 6

The lion consistent with the rotor shaft mast.

Question 7

What is the disc area?

Answer 7

The area contained within the tip path plane. In flight, this area is not constant since it is affected by the coning angle of blades

Question 8

What is a chord?

Answer 8

The straight line between the blades leading Edge and its trailing Edge

Question 9

What is Blade angle (aka Pitch angle)?

Answer 9

The angular difference between the chord of a blade and the plane of rotation (POR).

Question 10

How can the pilot change the blade angle?

Answer 10

This angle may be altered by the pilot through movement of the collective lever or through cyclic control.

Question 11

DEF

Angle of attack

Answer 11

The angular difference between the code of a blade and a relative airflow

Question 12

What is coning?

Answer 12

Coning is an upward sweeping angle of the rotor blades as a result of lift and centrifugal force.

Question 13

DEF

Feathering axis

Answer 13

The straight-line axis between the root of the blade and it’s tip about which the blade can alter its blade angle

Question 14

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Feathering

Answer 14

The movement of a blade about it’s feathering axis.

Which results in pitch angle changes

Question 15

DEF

Disc loading

Answer 15

The gross weight of a helicopter divided by the disk area.

Question 16

Is disc loading constant during a flight?

Answer 16

No. A helicopters disc area is not constant in flight so it follows that disc loading cannot be a constant

Question 17

DEF

Blade loading

Answer 17

The gross weight of the helicopter divided by the combined area of the helicopter blades

Question 18

What units are used for disk loading?

Answer 18

Expressed as pounds per square inch (lb/sq inch) or kilograms per metre squared (kg/m^2)

Question 19

What units are used to express blades loading

Answer 19

Expressed as pounds per square inch (lb/sq inch) or kilograms per metre squared (kg/m^2)

Question 20

What is flapping?

Answer 20

Movement of a blade in the classical sense relative to the plane of rotation.

Question 21

DEF

Lead-Lagging

Answer 21

Movement of a blade forward or aft in the plane of rotation

Leading - would be on the leading edge moving forward

Lagging - on the other bit of the rotor blade

Question 22

Give some examples of rotor systems

Answer 22

Fully articulated rotor

Semi rigid rotor

Rigid rotor

Question 23

What is a fully articulated rotor

Answer 23

A rotor system allowing blades to flap, feather, and lead-lag, allowed by hinges or bearings

Question 24

Generally, where can you find a fully articulated rotor?

Give an example

Answer 24

In helicopters with more than 2 blades

Cabri G2 which has three blades

Question 25

What is a semi rigid rotor?

Answer 25

A rotor system that allows the blade to flap and feather but not lead lag.

Question 26

In what type of helicopter is a semi rigid rotor system usually found?

Answer 26

It is a common system used in two blade rotors

Question 27

What does a rigid rotor system allow on a helicopter

Answer 27

The blades to feather only