EGT Overlimit — Three Triggers and the Thrust-Dependent Threshold
Engine Indicating gave the EGT red line (920 °C) and limits; Start Faults covered the hot start; Stall/Surge the EGT spike. This article covers the in-flight EGT OVERLIMIT alert: its exact triggers — in particular how the threshold shifts with thrust setting (MCT) — and the handling principle.
1. EGT thresholds vary by phase and thrust
EGT is not a single threshold; it shifts with start / flight / thrust setting (gathering 10/18 + this article):
| Scenario | EGT threshold | Source |
|---|---|---|
| Ground start | amber limit 700 °C | 10/18 (DSC-70-90-40) |
| In flight (general) | amber limit 900 °C | 10 (DSC-70-90-40) |
| Red line | 920 °C | 10 |
| Low thrust (TLA < MCT) | OVERLIMIT at 850 °C | this article (PRO-ABN-ENG) |
2. EGT OVERLIMIT — three triggers
ENG 1(2) EGT OVERLIMIT — ANNUNCIATIONS Triggering Conditions: This alert triggers when: ‐ EGT is above 920 °C, or ‐ EGT is above 900 °C for more than 20 s, or ‐ EGT is above 850 °C when the throttle resolver angle is lower than MCT.
Per PRO-ABN-ENG, EGT OVERLIMIT triggers on any of: EGT > 920 °C; EGT > 900 °C for more than 20 s; EGT > 850 °C when the throttle resolver angle (TLA) is below MCT.
[!warning]- At low thrust 850 °C already triggers; high thrust tolerates up to 920 °C The third condition: TLA < MCT (low thrust) → EGT > 850 °C triggers (PRO-ABN-ENG). The logic: low thrust should not produce high EGT, so 850 °C is already abnormal (hinting at a combustion/component problem); high thrust (take-off/MCT) tolerates higher EGT (up to 900/920 °C). The same EGT value means different things at different thrust settings — 850 °C is a problem in cruise, normal at take-off.
3. Handling direction
The core handling direction is reduce thrust (retard the THR LEVER) to lower EGT; with abnormal parameters / a sustained exceedance → shut down (MASTER OFF, like the 22 branch). The full ENG EGT OVERLIMIT ECAM steps are in PRO-ABN-ENG (not invented here). An EGT spike often accompanies a surge (22).
| Phase | Read EGT |
|---|---|
| Start | > 700 °C amber → hot start (18) |
| Take-off/MCT | tolerates up to 900/920 °C |
| Cruise (< MCT) | > 850 °C → OVERLIMIT |
| EGT spike on advancing the lever | suspect surge (22) |
4. Counterintuitive point
[!warning]- The EGT threshold "depends on thrust setting" — not one fixed number Start 700 / flight 900 / red line 920 / low thrust (< MCT) 850 °C (DSC-70-90-40 + PRO-ABN-ENG). Judging an EGT exceedance must factor in the current thrust setting.
Self-test
[!note]- Q1. The three EGT OVERLIMIT triggers? EGT > 920 °C; > 900 °C for more than 20 s; > 850 °C with TLA < MCT.
[!note]- Q2. Why does 850 °C trigger at low thrust? Low thrust should not produce high EGT, so 850 °C is already abnormal; high thrust (take-off/MCT) tolerates up to 900/920 °C. Same value, different meaning by setting.
[!note]- Q3. The EGT thresholds by phase? Start 700 °C / flight 900 °C / red line 920 °C / low thrust (< MCT) 850 °C.
[!note]- Q4. The core handling direction? Reduce thrust (retard THR) to lower EGT; shut down if severe/abnormal (full steps in PRO-ABN-ENG).
Key takeaways
| Point | Detail |
|---|---|
| OVERLIMIT triggers | > 920 °C / > 900 °C·20 s / > 850 °C·TLA < MCT |
| Thresholds by phase | start 700 / flight 900 / red 920 / low thrust 850 |
| Handling | reduce thrust first, shut down if severe; spike suspects surge (22) |
References
- FCOM PRO-ABN-ENG — EGT OVERLIMIT three triggers (> 920 °C / > 900 °C·20 s / > 850 °C·TLA < MCT).
- FCOM DSC-70-90-40 (10) — EGT scale 0–1200 / red line 920 / limit start 700 · flight 900.
Independent study material, not an Airbus publication and not endorsed by the manufacturer. Always defer to the current operator FCOM, FCTM, and QRH for operational use.