Case Study of Hydraulics/Pneumatics in Aeronautics
Fluid mechanics is used in the aeronautical industry for instrumentation and sensors, and for control. This includes:
· Primary flight control
o Elevator
o Rudder
o Ailerons
· Secondary flight control
o Flaps
o Spoiler
o Slats
· Utility systems
o Landing gear
o Brakes
o Gear steering
o Cargo and passenger stairs
· Instrumentation
o Air speed indicator
o altimeter
As these systems are so important in keeping the aircraft safe, most aircraft have two or three redundant hydraulic systems as a backup in case of failure.
Hydraulics are used as they are able to transmit high forces using a small volume of fluid. A similar system using an electric motor would be much heavier as the driving motor would need to be much larger to drive the mechanisms. Also an electric motor is too slow if used for the essential systems, looking after the craft’s yaw, pitch and roll adjustments. The steel cables that were used on aircraft were subject to thermal changes, which produced unexpected results due to the cable length being different to what is expected. As the hydraulic system is not open to the atmosphere, it does not have these issues.
Hydraulic power can also be converted to mechanical power through the use of an actuating cylinder (turbine). Modern aircraft use computers to actuate the hydraulic systems.
· Primary flight control
o Elevator
o Rudder
o Ailerons
· Secondary flight control
o Flaps
o Spoiler
o Slats
· Utility systems
o Landing gear
o Brakes
o Gear steering
o Cargo and passenger stairs
· Instrumentation
o Air speed indicator
o altimeter
As these systems are so important in keeping the aircraft safe, most aircraft have two or three redundant hydraulic systems as a backup in case of failure.
Hydraulics are used as they are able to transmit high forces using a small volume of fluid. A similar system using an electric motor would be much heavier as the driving motor would need to be much larger to drive the mechanisms. Also an electric motor is too slow if used for the essential systems, looking after the craft’s yaw, pitch and roll adjustments. The steel cables that were used on aircraft were subject to thermal changes, which produced unexpected results due to the cable length being different to what is expected. As the hydraulic system is not open to the atmosphere, it does not have these issues.
Hydraulic power can also be converted to mechanical power through the use of an actuating cylinder (turbine). Modern aircraft use computers to actuate the hydraulic systems.
An altimeter does not measure the craft’s altitude directly as such; rather it measures the atmospheric pressure and uses the differences in pressure to indicate the altitude. It is based on the theory that the weight of air above you in the atmosphere becomes less as you increase altitude. It uses the concepts espoused by Archimedes regarding hydrostatic pressure.