Flight Project

[luke1]

Can anyone help with my sons homework project.

How are hydraulics and pneumatics used on an air craft to operate moving parts ie landing gear, wing flaps

How do they design wing shapes and why

Thanks h

[eckhard]

Dear h,

Aircraft use hydraulic and/or pneumatic systems to move the gear and flaps by utilising the pressurised fluid (oil or air) acting on pistons and jacks to provide the motive force. The fluid is pressurised by pumps which are powered electrically or sometimes driven directly by the engine.

Wing design can be defined by two parameters – thickness and sweep angle. The choice of design is determined largely by the cruising speed of the aircraft and also by its main ‘mission’. A slow, small, propeller-driven passenger or cargo aircraft will have fairly thick, straight wings, which provide good lifting force at the low speeds associated with these types. A fast jet airliner will have thinner wings which are swept back, giving a faster cruise speed but on the other hand the need for complex flaps and slats to enable slower landing and take-off speeds. A supersonic fighter may have short, very thin wings or even a delta wing shape which gives the best performance at speeds above the ‘sound barrier’.

Hope this helps and good luck to luke 1 with his homework!

Eckhard

[Northbeach]

Eckhard’s summary is quite good.

Pneumatics or hydraulic fluid is pressurized either by the compression of air through the engine or running some sort of pump (mechanical/electric). The force under pressure is routed out to perform work, just as eckhard said, valves opening and closing causing pistons to move in one direction and then the other. To these actuators are connected things like landing gear, brakes, nose wheel steering, thrust reversers, leading edge and training edge devices (slats/flaps) and flight control surfaces (rudder, ailerons and elevators). The force under pressure is able to overcome the aerodynamic loads and achieve the desired flight control state.

The F-27 (Fokker/Fairchild Friendship-early designed turboprop with Rolls Royce engines) I flew decades ago did virtually everything with pneumatics; brakes, steering, and gear. The Boeing 737 I now fly uses hydraulics.

Pneumatics (hot compressed air from the engines called “bleed air”{prior to combustion}) is used to maintain cabin pressurization (after the air is filtered and cooled) and to keep the leading edges of the wings free from ice as well as parts of the engine intake area.

As automotive vehicles are designed for different purposes: the sanitation truck serves a completely different purpose from the Formula-1 racing machine so are wings designed for their intended purpose (and they will look just about as radically different).