Position Sensors

Question 1

List flight control surfaces and what direction they control

Answer 1

Ailerons - roll
Elevators - pitch
rudder - yaw

Question 2

What happens to the ailerons if aircraft rolls to the left

Answer 2

Left aileron goes up, reducing lift on this wing. Right aileron goes down, increasing lift on this wing. The difference in forces cause aircraft to roll

Question 3

What happens to the elevators if aircraft pitches up

Answer 3

Elevators go up, generating lift downwards on back of plane, so front of plane pitches up.

Question 4

What happens to the rudder if aircraft yaws to the left

Answer 4

rudder trailing edge is displaced to the left causing right force on back of plane, so front of plane turns left

Question 5

Where can slats and spoilers be found on an aircraft

Answer 5

Slats: found on leading edge of main wing
Spoilers: found just before flaps on main wing

Question 6

What are slats used for

Answer 6

At the leading edge of the wing to form a slot, smoothing out the airflow over the wing and delaying the onset of the stall

Question 7

What are spoilers used for

Answer 7

Are surfaces that can be extended on the wing to disrupt the air flow and create drag to act in the same manner as ailerons

Question 8

For hydraulic actuation, give equation for force and speed of a single rod actuator

Answer 8

Force = (PiA - Po(A-a))n

Pi - initial pressure, A - area of piston, a - area of piston rod, Po - other pressure, n - efficiency (>0.85)

Speed = (Q/A)*n

Q = inlet, n - efficiency (<0.98)

Question 9

For hydraulic actuation, give equation for force and speed of a double rod actuator

Answer 9

Force = (Pi - Po)(A - a) * n

Pi - initial pressure, A - area of piston, a - area of piston rod, Po - other pressure, n - efficiency

Speed = (Q/A-a)*n

Q = inlet, n - efficiency

Question 10

List three typical hydraulic actuator control methods

Answer 10

• mechanical signalling
• electrical signalling with servo valves
• electrical signalling with direct-drive motor

Question 11

What is the advantage of having a ‘more-electric’ aircraft

Answer 11

• significant weight and cost savings
• better overall energy efficiency
• improved reliability and maintainability

Question 12

Name two electromagnetic losses and two mechanical losses

Answer 12

Electromagnetic losses:
- copper and Iron losses

Mechanical losses:
Windage and friction

Question 13

Equation for electromechanical power conversion, both for motors and for generators

Answer 13

Motors:
(convert electrical to mechanical)

n = Mechanical Power/Electrical power * 100

Generators:
(convert mechanical into electrical)

n = Electrical power /Mechanical Power * 100

Question 14

Describe torque production mechanism in a single current carrying conductor

Answer 14

Single current is placed in magnetic field and force is exerted on the wire.
F = BILsin(alpha)

F - force, B - magnetic flux denisty, L - length, alpha - angle

for maximum force alpha = 90deg

Question 15

Describe torque production mechanism in a rotor conductor

Answer 15

Torque = 2BILr

r - radius of the rotor

(after 180deg turn, T = -2BILr)

Question 16

How is a continuous torque created in a rotor conductor

Answer 16

• the current polarity must be changed as the rotor rotates (commutation)
• done mechanically using brushes
• or electrically (brushless)

Question 17

List advantages of brushless format

Answer 17

• better cooling therefor higher torque/frame size

- elimination of brushgea/commutator

Question 18

List disadvantages of brushless format

Answer 18

• needs rotor position sensor

- more complex power electronic converter

Question 19

When is maximum acceleration of the load achieved

Answer 19

when motor inertia = load inferred inertia