Date: 202102
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: None
Flight phase: Parked
Aircraft component: APU
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Inspector; Lead Technician
Reporter qualification: Maintenance Powerplant; Maintenance Airframe; Maintenance Avionics
Human factors: Time Pressure; Distraction; Human-Machine Interface; Troubleshooting
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Maintenance
When detected: Other Maintenance
Result: Aircraft Aircraft Damaged; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Human Factors; Procedure; Aircraft
Primary problem: Procedure

Narrative: Aircraft X was an air return back into ZZZ; for the standby display cool fan malfunction causing the display screens to overheat. This aircraft was ferrying to ZZZ1 for a repair. During troubleshooting it was decided that the problem could be relays K7HK and K11HK in JB2. The relays were replaced per the AMM (Aircraft Maintenance Manual) CH24/ESPM (Electrical Standard Practices Manual) and did not fix the problem. The next likely part was the avionics cooling control panel; it was replaced per AMM CH21 and did fix the problem. Because I had removed JB2; a retest had to be performed per the AMM CH24. The first half of this complex task was done in the hangar. The second half requires the engines to be ran. Everything was checking out good per the AMM; until the final engine start. During the start sequence on the LH (Left Hand) engine everything seemed to be normal; then I received an APU Overtemp red warning message which distracted me from watching the LH engine parameters. After the APU Overtemp message cleared I noticed the LH engine ITT (Interstage Turbine Temperature) at 998 degrees. I immediately put the LH thrust lever to fuel cutoff and motored the engine until the ITT was below 120 degrees. The MDC (Maintenance Diagnostic Computer) engine exceedance history showed the LH engine to be at 1110 degrees for 10.6 seconds. This is the first time I have ever encountered 2 overtemp events or 2 red warning indications at the same time while working one of our aircraft. I was working hard to get this task done so the crew could move the aircraft yet that day; as they were standing by in the hangar to depart after repairs were completed. I must admit I did feel pressured and hurried; however I did complete the retest task per the AMM; with everything checking satisfactory. As for the engine hot start event; I really regret it happening. It seems like it was one of those situations that does not occur together all that often. I felt I was distracted and was task overloaded for maybe a second or two which played a factor in this unfortunate event.




Synopsis: Technician reported APU over temperature and engine over temperature simultaneously during post maintenance engine run ups.