Flashcards in Jet Engine Deck (11):
What is a Hot start
When the EGT exceeds the safe limit of an aircraft, it experiences a “hot start.” This is caused by too much fuel entering the combustion chamber or insufficient turbine rpm.
What is a hung start
If the engine fails to accelerate to the proper speed after ignition or does not accelerate to idle rpm, a hung or false start has occurred. A hung start may be caused by an insufficient starting power source or fuel control malfunction.
What is EPR
An engine pressure ratio (EPR) gauge is used to indicate the power output of a turbojet/turbofan engine. EPR is the ratio of turbine discharge to compressor inlet pressure.
What is N1
N1 represents the rotational speed of the low pressure compressor and is presented on the indicator as a percentage of design rpm.
What is the parameter to set thrust between GE90 and Trent892?
GE -N1. RR-EPR
N readings are more reliable due to their independence from other measured parameters. The EPR, albeit its indication of thrust, on the other hand needs carefully positioned probes, which must provide both pressure and temperature data to a computer. This EPR control depends upon two probes providing minimum 4 data, in contrast to the N sensor which needs only rotational speed data from a single sensor. In case of an inability to control thrust using EPR, the thrust control system always falls back upon a more reliable N1.
Advantages of 3-spool
-each spool works at optimal speed ->fuel efficient
-easier to start because only one shaft to be turned
How does jet engine work?
The cycles occur continuously in the gas turbine
Major aircraft systems powered by hydraulics
Speed brakes and ground spoilers
Nose wheel steering
What is hydraulic system
The hydraulic fluid is pumped through the system to an actuator or servo. A servo is a cylinder with a piston inside that turns fluid power into work and creates the power needed to move an aircraft system or flight control. The selector valve allows the fluid direction to be controlled. This is necessary for operations such as the extension and retraction of landing gear during which the fluid must work in two different directions.
How is pressure supplied to hydraulics system? Where's the power come from?
Pressure is supplied through a pump. The pump provides a continuous flow of fluid which covert hydraulic pressure into mechanical energy.
The Boeing 777 is equipped with three hydraulic systems. Primary hydraulic power for the left and right systems is provided by two EDPs (engine driven pump)and supplemented by two on-demand ACMPs(AC motor pump). Primary hydraulic power for the center system is provided by two ACMP and supplemented by two on-demand air turbine-driven pumps (ADP). The center system provides hydraulic power for the engine thrust reversers, primary flight controls, landing gear, and f laps/slats. Under emergency conditions, hydraulic power is generated by the ram air turbine (RAT), which is deployed automatically and drives a variable displacement inline pump. The RAT pump provides flow to the center system flight controls.