CADH Practice Cards 6 Flashcards
Random Questions/Statements for Exam preparation
The Centre of Pressure of an aerofoil is …
a point along the chord line of an aerofoil through which the resultat of total reaction of all aerodynamic forces is said to act
During an autorotative approach the cyclic is moved aft, the first effect is to …
reduce rate of descent
On a helicopter with a semirigid rotor system, the rotor can …
flap and feather, but not drag
Ground Effect is most useful when …
hovering at High DA and High Altitude at high gross weight
Refer to diagram
The vector labelled B is …
relative airflow
Diagram is of the autorotative drive region
The rotational airflow is defined as …
the component of relative airflow parallel to the plane of rotation, caused by the rotation of the blades
During autorotation, best range is achieved by …
low rotor RPM, high collective pitch at best range speed
The five factors affecting the lift produced by an aerofoil are …
- the shape and design
- the angle of attack
- the density of the air flowing around the aerofoil
- the speed of the air relative to the aerofoil
- the surface area of sthe aerofoil
The Centre of Gravity of an aerofoil is …
the point on the aerofoil through which weight acts
Refer to diagram
The vector labelled D is …
lift
The diagram is of the autorrotative drive region
The induced flow is defined as …
the component of relative airflow at right angles to the plane of rotation.
The aerofoil design which has a limited movement of the centre of pressure with changes in lift production is …
symmetrical
The possibility of vortex ring state is greatest when …
on a very steep descent at high power
It is desirable to limit the movement of the centre of pressure of a helicopter rotor blade to …
prevent large twisting forces on the aerofoil which would make control forces high
To minimise tail rotor drift you can …
tilt the mast
During power off autorotation at high altitude, you notice a higher than normal rotor RPM. This is probably caused by …
a higher than normal rate of descent
The effect of an increase in the induced flow for a given pitch angle in a rotor system is …
decreased agnle of attack
Refer to vector diagram -
The letter corresponding to the pitch angle is …
B
The angle of attack of an aerofoil is defined as …
the smaller angle between the chord line and the relative airflow
Navigation computers, charts and tables do not allow for the effect of humidity in density altitude computations. If humidity is higher …
density altitue will increase
The pitch angle is defined as …
the acute angle between the Plane of Rotations and the chord line
Tail rotor roll occurs as a result of …
a turning couple between the main rotor hub and the tail rotor axis of rotation
Generally speaking, is induced flow in a rotor system desirable or undesirable?
undesirable
The component of total reaction acting along the axis of rotation is called …
rotor thrust
The aerodynamic force acting perpendicular to the relative airflow is known as …
lift
The pitch angle of a rotor blade is the smaller angle between the …
blade chord and the plane of rotation
The component of total reaction acting in the plane of rotation opposite to torque is called …
rotor drag
The component of total reacstion acting parallel to the relative airflow is called …
drag
The torque is the force required to balance the …
rotor drag
Positive static stability in a aircraft is demonstrated when …
it is deflected from its intended parth by an external force, and will initially return towards its intended path when the external force is removed
Torque is produced by
the engine
In the lift formula, Rho represents …
air density
Total rotor thrust is defined as …
the combined rotor thrust of all the blades acting along the axis of rotation
The rotor RPM will decay (reduce) if …
rotor drag exceeds torque from the engine
The angle of attack will increase if …
pitch is increased
In the lift formula, V represents …
velocity
Negative Dynamic stability is demonstrated when …
the aircraft oscillates divergently
Consider the position of the power required curve at MSL, as density height increases the relative postion of the curve will …
move up and to the right
The components you would expect to find in a ‘Soft in Plane’ rotor head are …
elastomeric drag bearings
