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Which of these statements about a gust lock system are correct?

1. There is no need for a gust lock on irreversible flight controls.
2. There is no need for a gust lock on a fully manual flight control system.

  • A
    1 is incorrect, 2 is correct.
  • B
    Both 1 and 2 are correct.
  • C
    Both 1 and 2 are incorrect.
  • D
    1 is correct, 2 is incorrect.

Statement 1: There is no need for a gust lock on irreversible flight controls.
CORRECT: as in irreversible flight controls the control surfaces are attached to hydraulic actuators which will not move when an external force is exerted on the control surface.

Statement 2: There is no need for a gust lock on a fully manual flight control system.
INCORRECT: reversible flight controls will move by external or internal forces and are not held in place by anything, so strong winds could cause damage to the aircraft.

A gust lock or control lock, is an internal or external lock and may be fitted to the control surface or the cockpit control. These locks are made for when an aircraft is parked outside with strong or gusty winds these could move the control surfaces against their stops which could cause damage. If these are fitted to the cockpit control they might be made in a way that it is impossible to move the throttle until the control locks are removed.

Primary flight controls
Are controls which movement causes a rotation about one of the three axes of the aircraft, causing a change in the aircraft’s flightpath or attitude. The elevator, rudder and ailerons are considered to be the primary flight controls. The primary flight controls in a manually controlled system are reversible. This means that a force applied to the controls is a force which moves the control surface, and also a force which moves the control surface will move the pilot’s controls. This means that the air pressure on the control surface can be felt in the pilot’s controls. When the flight controls are fully power operated this is not the case and is called irreversible. This means that if there is a force moving the control surface this will not move the control columns, and there will be no natural feel on the controls.

Because of this there will need to be an artificial feel unit installed in a fully powered or irreversible control system. This artificial feel unit should apply force to the cockpit controls in proportion to the control deflection and in proportion to the aircraft’s speed.

This artificial feel system will also work with a trim system, but this works different than a normal trim surface does. A movement of the trimwheel will result in a movement of the electric trim actuator, and so the control surface, but not in the movement of the control column (this is for elevator control). It is different for aileron and rudder trim.

Elevator trim: zero force position of the control column does not change (control column/horn/stick does not move)
Aileron trim: zero force position changes (control wheel turns in the direction of the trim)
Rudder trim: zero force position changes (pedals move in the direction of the trim)

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