Turbine Engine Starting; Ignition; and Shutdown Flashcards
What is the function of a turbine engine starting system?
To uniformly accelerate the engine from rest to a rpm at which the gas flow through the turbine section provides sufficient torque to drive the compressor at idle rpm.
What is the most common type of starter used on large modern turbofan engines?
An air turbine starter.
What are the sources of bleed air to the air turbine starter?
An APU, another engine or from a ground compressed air source.
When/how is an air turbine starter disengaged?
Automatically by a starter clutch at a pre-determined rpm.
Why is a uniform rate of acceleration required during engine start?
To uniformly accelerate the engine from rest to a rpm at which the gas flow through the turbine section provides sufficient torque to drive the compressor at idle rpm, thereby avoiding a hung start.
What is the most positive indication of light-up (light-off) during a turbine engine’s start cycle?
The most positive indication of light-up (light-off) during a turbine engine’s start cycle is an increase in the turbine temperature, however it is measured and displayed - EGT, ITT etc.
What is “self-sustaining” rpm?
The rpm at which the starter has cut-out and the turbine is able to accelerate on its own.
What actions should be taken if the turbine or exhaust gas temperature is rising rapidly to exceed or nearly exceed the specified limits?
If a hot start is experienced, the fuel flow to engine should be shut off immediately and the engine should be dry motored to reduce the turbine or exhaust gas temperature.
What is a hot start?
A hot start is a start or attempted start where the turbine or exhaust gas temperature is rising rapidly to exceed, or nearly exceed the specified limits.
What are the potential causes of a hot start?
- Excessive fuel flow/excessive fuel to air ratio.
- A starter that is slow to accelerate the compressor /turbine spool.
- A starter that cuts out too early.
- Low battery voltage.
What actions are usually recommended in the event of a hot start?
Shut off the fuel supply and continue to dry motor the engine.
What is the main indication of a hung start?
Very slow or no increase in rpm.
What actions are usually recommended in the event of a hung start?
Shut off the fuel supply, discontinue the start cycle and continue to dry motor the engine.
What are the indications of a compressor stall during start?
The indications of a compressor stall during start are the same as for any compressor stall, i.e. a popping or banging noise, fluctuating rpm indications and rapidly increasing turbine or exhaust gas temperature.
What actions are usually recommended in the event that an engine stalls during start?
Shut off the fuel supply and continue to dry motor the engine.
