Airplane Actuators 240

Actuators are used to convert the hydraulic pressure into mechanical movement.


  1. Single acting
  2. Double acting unbalanced
  3. Double acting balanced

Hydraulic gadgets

  1. hydraulic motor – is a form of of rotary actuator. Hydraulic fuses are located near anti-skid module on top of the wheel well. They block lines in vulnerable areas if a serious fluid leak should occur.
  2. non- return valve – it acts like a diode , its also known as a check valve or non-reversible valve.
  3. Restrictor valve – permits fluid flow in one direction and full flow in other direction.
  4. Selector valve – is used to direct fluid to the appropriate side of an actuator or motor and provide a return path for fluid displaced from the other side.
  5. Shuttle valve – allows an alternate system to operate services.
  6. Sequence valves – are fitted in the landing gear hydraulic circuit to ensure that the gear and doors open and close in the correct sequence
  7. Hydraulic power pack -A hydraulic power pack is a small unit that consists of an electric pump, filters, reservoir, valves, and pressure relief valve.

A typical actuating cylinder consists of a cylinder housing, one or more pistons and piston rods, and some seals. works more like a reciprocating compressor only in this case hydraulic fluid is used.


  1. Linear actuators
  2. rotary actuators

actuators are responsible of controlling movement of rudders, elevators, ailerons, leading edge flaps, trailing edge flaps, slats, spoilers e.t.c. They use hydraulic fluid known as skydrol, Def stan 91-48 as shown in my seals & pipelines article.

An actuating cylinder also contains a reduction gear which allows it to control the rotating motion which is needed within the system.

actuators work together with motors in an aeroplane in case of hydraulic system failure. although they can manually be activated and repaired if both system fail. The actuators achieve very high dynamic forces but have a low weight and fit into small spaces. They  have to withstand ambient conditions such as high vibration and cycling temperature.

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