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ASN Wikibase Occurrence # 42956
Last updated: 22 January 2021
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Date:06-DEC-1991
Time:15:30
Type:Silhouette image of generic GLAS model; specific model in this crash may look slightly different
Glasair II RG
Owner/operator:private
Registration: N614LS
C/n / msn: 763
Fatalities:Fatalities: 1 / Occupants: 1
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Category:Accident
Location:Nuevo, CA -   United States of America
Phase: Unknown
Nature:Unknown
Departure airport:Redlands, CA (L12)
Destination airport:
Investigating agency: NTSB
Narrative:
THE AIRPLANE COLLIDED WITH RUGGED TERRAIN AFTER A LOSS OF ENGINE POWER. IT STRUCK THE NORTH FACE OF 20 DEG SLOPE OF AN EAST-WEST RIDGE, JUST BELOW THE CREST. THE AIRPLANE THEN SLID ABOUT 20 FT DOWN THE SLOPE WHERE A POST-IMPACT FIRE DESTROYED THE PLANE. AN EXAM OF THE ENGINE SPARK PLUGS REVEALED THE #1 & #3 CYLINDER SPARK PLUG GAPS WERE BRIDGED WITH CINDER-LIKE DEPOSITS WITH METALLIC GLOBULES STARTING TO FILL THE FIRING END CAVITY & WORN CENTER ELECTRODES. ACCORDING TO THE SPARK PLUG MANUFACTURER, SEVERELY FOULED PLUGS WILL OPERATE COLDER CAUSING MISFIRES, AND WILL ALSO MISFIRE AT HIGHER POWER BECAUSE OF THE CONDUCTIVE NATURE OF THE DEPOSITS AT ELEVATED TEMPS. BRIDGED GAPS WILL SHORT OUT THE SPARK PLUG. SUCH A MALFUNCTIONED PLUG WILL MISFIRE AT ALL POWER SETTINGS IN A MANNER SIMILAR TO A OIL FOULED PLUG. BRIDGED GAPS BRIDGED BY BEADED LEAD GLOBULE WILL NOT CLEAR UP BY ENGINE OPERATION & CAN BE CORRECTED ONLY BY REPLACING THE MALFUNCTIONING SPARK PLUG WITH A SERVICEABLE UNIT. THE ACDNT TIME WAS ESTD BE AT 1530 PST. CAUSE: THE FAILURE OF THE PILOT TO PERFORM PREVENTATIVE MAINTENANCE ON THE AIRPLANE'S POWERPLANT WHICH RESULTED IN A LOSS OF PERFORMANCE DURING AN UNKNOWN PHASE OF OPERATION. CONTRIBUTING TO THE ACCIDENT WAS FOULED SPARK PLUGS AND THE PARTIAL LOSS OF AIRCRAFT PERFORMANCE.

Sources:

NTSB: http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001212X18612


Revision history:

Date/timeContributorUpdates
24-Oct-2008 10:30 ASN archive Added
21-Dec-2016 19:24 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]

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