Hot Start Procedures
Definition
A hot start occurs when an aircraft engine—typically a turbine or jet engine—experiences abnormally high exhaust gas temperatures (EGT) during engine start-up, potentially exceeding manufacturer limits. This can lead to engine damage if not immediately addressed. A hot start usually results from early fuel introduction, slow rotation (N2), or insufficient airflow during light-off.
Purpose of Hot Start Procedures
- Detect and respond to an abnormal engine start condition
- Protect engine components from thermal damage
- Allow for safe recovery and restart attempts after a hot start
- Ensure compliance with manufacturer and regulatory procedures
Common Causes of a Hot Start
| Cause | Description |
|---|---|
| Premature fuel introduction | Fuel introduced before sufficient airflow (N2) is established |
| Weak starter performance | Starter fails to accelerate core fast enough to cool combustion |
| Hot ambient conditions | Reduce the cooling effect of air and raise baseline EGT |
| Residual heat | Recent shutdown may leave engine components already hot |
| Ignition system faults | Improper timing or delayed combustion may spike temperatures |
Hot Start Symptoms
| Indicator | Observation |
|---|---|
| EGT rise | Rapid, steep increase beyond limits during start |
| N2/N1 lag | Rotor speeds remain low or slow to stabilize |
| Smoke/smell | May be visible from exhaust in severe cases |
| Warnings | Engine monitoring system alerts or redlining gauges |
Immediate Hot Start Procedure (Typical Jet)
🚨 Memory Actions – Abort the Start
- Fuel lever/Cutoff switch — OFF
- Ignition switch — OFF
- Starter/Motor — ON (if required to cool engine)
- Motor for 20–30 seconds or per POH/AFM
- Monitor EGT drop to safe levels
- Allow cooldown, then assess whether a re-attempt is permitted
Always refer to the Aircraft Flight Manual (AFM) or QRH (Quick Reference Handbook) for aircraft-specific procedures.
Phraseology (If Coordinated with Ground Crew)
- “Abort start, hot start on engine two.”
- “Cutting fuel, request continued motoring.”
- “Stand by, engine cooling in progress.”
Prevention Tips
- ✅ Ensure starter air source is strong (APU or GPU)
- ✅ Wait for adequate N2 RPM before introducing fuel
- ✅ Monitor EGT closely during light-off
- ✅ Do not rush the sequence—follow the checklist exactly
- ✅ Use battery or APU voltage checks to verify starting power
If a Hot Start Occurs
- Log the event in the technical logbook
- Notify maintenance personnel immediately
- The engine may require borescope inspection or trend monitoring
- Do not attempt another start unless specifically approved
Difference: Hot Start vs. Hung Start
| Type | Description | Action |
|---|---|---|
| Hot Start | EGT exceeds limits | Cut fuel immediately |
| Hung Start | N2 fails to reach idle RPM | Abort start and cool down |
Tips for Pilots
- Know the EGT limits and start envelope for your aircraft
- Practice with simulated malfunctions in LearnATC or flight training devices
- Don’t hesitate to abort early—waiting often makes it worse
- Re-brief engine start actions before every first start of the day