Starting and Engine Control Systems
Starting and Engine Control Systems tests the start sequence, the electronic or hydromechanical control, and the protections that prevent a hot or hung start. The examiner expects sequence logic, not just button-pushing.
Core rules
- Typical sequence: starter cranks, ignition on, fuel on, light-off, acceleration, starter cut-out, idle, generator online.
- The control schedules fuel to keep TGT within limits while accelerating; it may use N1, N2, TGT and rate of change.
- FADEC or EECU provides metering, limit protection, overspeed protection and fault recording; some installations retain hydromechanical backup.
- A hot start is a rapid TGT rise above limit, often from excess fuel or low airflow.
- A hung start is stagnation below idle, often from weak starter, low battery or fuel scheduling.
- Starter duty cycles protect the starter and battery.
Worked example
The start limit is 900°C TGT. At 35% N1 the TGT passes 930°C and is still rising at 40°C/s. The correct action is to abort: fuel off, ignition off, continue cranking to clear fuel vapour, then investigate. Do not wait for 1000°C to confirm the trend. Record the peak TGT and duration for the maintenance manual exceedance check.
Traps
- Continuing a start because the engine is almost there.
- Re-engaging the starter before the duty cycle expires.
- Assuming a hung start is always a fuel control fault.
- Forgetting to clear unburned fuel after an aborted start.
- Resetting a FADEC fault without recording it.