FAA Aviation Mechanic Powerplant (AMP)Engine InspectionHard
A turbine engine's exhaust gas temperature (EGT) trend monitoring log shows the following at a fixed reference power setting: at engine installation, EGT was 905°C with a redline of 950°C. After 500 hours of operation at the same power setting, EGT has risen to 928°C. What does this trend indicate, and what is the current EGT margin?
- AThe engine has improved efficiency; current margin is 45°C
- BNo conclusion can be drawn without airspeed data; margin cannot be calculated
- CThe engine is gradually deteriorating; current margin is 22°C
- DThe engine is gradually deteriorating; current margin is 45°C
Show answer & explanationAnswer & explanation
Correct answer: C. The engine is gradually deteriorating; current margin is 22°C
EGT margin equals redline temperature minus actual EGT at the reference power setting: 950°C − 928°C = 22°C. The rising EGT trend at a constant power setting indicates gradual loss of internal engine efficiency (compressor/turbine deterioration), and the shrinking margin (from 45°C to 22°C) confirms this deterioration trend, which is used to schedule maintenance before the margin reaches zero.
Why the other options are wrong
- A. A rising EGT indicates deteriorating, not improving, performance.
- B. EGT trend monitoring at a fixed reference power setting does not require airspeed data.
- D. The margin has decreased from 45°C, not remained at 45°C.
EGT Trend Monitoring
Tracking exhaust gas temperature at a standard reference power setting over time to detect gradual turbine engine performance deterioration before reaching the EGT redline limit.
- EGT margin = redline temperature − actual EGT at reference power
- A shrinking margin over time indicates hot section or compressor deterioration
- Used to schedule engine removal/overhaul proactively
- Sudden EGT spikes (not gradual trend) may indicate a different fault, like FOD
Memory trick: Shrinking margin, aging engine — the gap to redline keeps closing.