Hydraulic Actuator

Technical Information

Catalogue No: C0311
Category: Flight Control
Object Type: Actuator
Object Name: Hydraulic Actuator
Part No: 204 Mk1
Serial No: 37671
Manufacturer: HM Hobson
Division: Unknown
Year of Manufacture:
Width (mm):
Height (mm):
Depth (mm):
Weight (g):
Location: Archive Object Store

Powered Flying Control
Type 204 Mk 1
Serial 37671


On aircraft linear actuators may be used for flight control surfaces, wing flaps, and spoilers. Hydraulics deliver a great deal of power without taking up too much space or weight, meant that they massively help pilots in undertaking necessary mechanical tasks without using too much energy.
The other advantages of hydraulics are the quick response to the demands that may be placed upon the system. They are also reliable and reasonably easy to maintain. Because they do not use electricity, there is no chance of a shock hazard, and the chances of being a fire hazard are low, which makes them a safer option than other equivalent systems.
Perhaps the main advantage of a hydraulic system is that they can handle a practically unlimited amount of work due to the immense force they can produce. This is all the more important in modern day aircraft.
Hydraulic fluid is pumped from a reservoir, either by an electric, or engine driven pump. It is filtered to keep it clean, and then passes through a selector valve, which relieves extra pressure.
Once it reaches the linear actuator, the fluid power is turned into work by a piston. This power is then used to move an aircraft system or flight control. These actuators can be either single or double acting, depending on the requirements of the system, meaning that the fluid can be applied to one or both sides of the actuator. The selector valve allows for the fluid direction to be controlled, which is necessary for operations such requiring extension and retraction.
The actuating cylinder also contains a reduction gear, which allows it to control the rotating motion to what is needed within the system. Previously, systems would use steel cables connected by pulleys to control motion. The cables that connected the controlling mechanism, such as the pedals, to the controlled surface, such as the rudder, would be subject to expansion due to temperature changes. Hydraulic systems though, are capable of controlling motion without worrying about such concerns, as they do not operate in an environment that is not open to the atmosphere. This means that hydraulic systems not only provide better control for the pilots using them, but also increase response times, making them an imperative part of aerospace engineering.

This linear actuator was made by Hobson and was probably acquired at Rochester for demonstration of a Flight Control system.

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