Serious incident de Havilland Canada DHC-8-102 N923HA, Sunday 12 January 1992

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Date:	Sunday 12 January 1992
Time:	16:18 LT
Type:	de Havilland Canada DHC-8-102
Owner/operator:	USAir Express
Registration:	N923HA
MSN:	99
Total airframe hrs:	9965 hours
Engine model:	P&W PW120A
Fatalities:	Fatalities: 0 / Occupants: 33
Other fatalities:	0
Aircraft damage:	Minor
Category:	Serious incident
Location:	Baltimore, MD - United States of America
Phase:	Initial climb
Nature:	Unknown
Departure airport:
Destination airport:	Charlottesville, VA
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
AS THE GEAR & FLAPS WERE RETRACTED AFTER TAKEOFF, THE #1 ENGINE LOW FUEL PRESSURE WARNING LIGHT ILLUMINATED. AT ABOUT 400' AGL, A "LOUD BANG" WAS HEARD FOLLOWED BY A #1 ENGINE FIRE WARNING INDICATION. THE ENGINE WAS SHUT DOWN & BOTH FIRE EXTINGUISHING BOTTLES WERE DISCHARGED. THE FLIGHTCREW EXTENDED THE LANDING GEAR BY USING THE ALTERNATE SYSTEM & MADE A NO-FLAP EMERGENCY LANDING. THEY USED EMERGENCY BRAKES, BUT DIRECTIONAL CONTROL WAS LOST & THE AIRCRAFT EXITED THE SIDE OF THE RUNWAY & STOPPED WITH THE FIRE EXTINGUISHED. AN EXAM OF THE #1 ENGINE AREA REVEALED A FAILED LOW FUEL PRESSURE WARNING SWITCH SNUBBER & FIRE DAMAGE TO THE ENGINE, NACELLE & WHEELWELL. THERE WAS EVIDENCE THAT DURING INSTALLATION, THE LOW FUEL PRESSURE WARNING SWITCH SNUBBER WAS TORSIONALLY DEFORMED, THEN FATIGUE & SUBSEQUENT FAILURE OCCURRED. GAPS IN THE FIREWALL ALLOWED LEAKING FUEL (SPRAY) TO ENTER THE HOT SECTION & IGNITE. THIS RESULTED IN AN EXPLOSION & FIRE. FIRE PROPAGATION RESULTED IN BURNED WIRES TO THE #1 STANDBY HYDRAULIC PUMP & A RUPTERED #2 SYSTEM HYDRAULIC LINE.

Probable Cause: IMPROPER INSTALLATION OF THE LOW FUEL PRESSURE WARNING SWITCH SNUBBER ON THE #1 ENGINE, RESULTING IN FATIGUE FAILURE OF THE SNUBBER, A FUEL LEAK (SPRAY), AND SUBSEQUENT EXPLOSION/FIRE DAMAGE. A FACTOR RELATED TO THE INCIDENT WAS: INADEQUATE DESIGN OF THE FIREWALL, WHICH ALLOWED FUEL VAPORS TO MIGRATE TO THE HOT SECTION OF THE ENGINE.

Accident investigation: