Serious incident Boeing 737-222 N9015U, Monday 9 July 1984

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Date:	Monday 9 July 1984
Time:	14:15 LT
Type:	Boeing 737-222
Owner/operator:	United Airlines
Registration:	N9015U
MSN:	19053/34
Engine model:	P&W JT8D-17
Fatalities:	Fatalities: 0 / Occupants: 71
Other fatalities:	0
Aircraft damage:	None
Category:	Serious incident
Location:	Portland, OR - United States of America
Phase:	En route
Nature:	Passenger - Scheduled
Departure airport:	Portland, OR (KPDX)
Destination airport:	San Diego, CA (KSAN)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
AFTER TAKEOFF, THE ACFT WAS CLIMBING THRU ABOUT 4000 FT WHEN THE APU FIRE WARNING LIGHT ILLUMINATED. THE FLT CREW DISCHARGED THE FIRE EXTINGUISHING UNITS & REQUESTED AN EMERGENCY LANDING. A TEARDOWN OF THE APU REVEALED EVIDENCE THAT A HARD OBJECT WAS INJESTED INTO THE 1ST STAGE COMPRESSOR IMPELLER, BENDING 2 OF THE BLADES. THE OBJECT CONTINUED THRU THE ENG & IMPACTED THE EXDUCER BLADE. THE BLADE FAILED AT A CRACK & PENETRATED THE EXHAUST PIPE ASSEMBLY. HOT GASES THEN VENTED INTO THE COOLING AIR PASSAGE & OVERHEATED THE TAIL CONE & AFT PORTION OF THE APU.

Probable Cause:

Accident investigation: