Indication and Monitoring
What this domain tests
You must interpret EGT, N1/N2, torque, fuel flow, vibration and oil indications, and know what to do when a limit is exceeded.
Core rules
- EGT is measured at turbine inlet or interstage; it is the best indicator of turbine stress. N1 and N2 are percentage speeds; N1 usually relates to thrust, N2 to core speed.
- Torque is used on turboprops and turboshafts; on turbofans, EPR or N1 may be the thrust parameter.
- Vibration is measured in mils or inches per second; a rising trend can indicate fan imbalance, bearing wear or FOD.
- Exceedances: note the value, duration, phase of flight and OAT; land or shut down as required; make a written report.
Worked example
At takeoff, EGT redline is 900°C. The gauge shows 925°C for about 3 seconds before settling at 880°C. This is a transient exceedance. Reasoning: record the peak and duration, because maintenance needs to assess hot-section damage; a brief overshoot may be acceptable under the maintenance manual, but it must be documented. Do not simply continue as if nothing happened.
Traps
- Treating N1 and N2 as interchangeable.
- Ignoring a slow vibration trend because the reading is below the redline.
- Reading a digital gauge without checking the trend or the associated parameter.
- Assuming a redline exceedance is automatically an engine change; the manual defines the action.
Key points
- EGT indicates turbine stress; N1 and N2 are percentage speeds.
- Torque is used on turboprops; EPR or N1 on turbofans.
- A vibration trend can reveal imbalance, bearing wear or FOD.
- Record exceedance value, duration, phase and OAT.
- A redline exceedance may still be acceptable under the manual, but must be documented.