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ASN Wikibase Occurrence # 43399
Last updated: 10 November 2020
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Date:17-JUN-1989
Time:17:30
Type:Silhouette image of generic C172 model; specific model in this crash may look slightly different
Cessna 172F
Owner/operator:private
Registration: N7939U
C/n / msn: 17251939
Fatalities:Fatalities: 1 / Occupants: 1
Other fatalities:0
Aircraft damage: Substantial
Category:Accident
Location:Vernon, AL -   United States of America
Phase: Landing
Nature:Private
Departure airport:Vernon, AL (M55)
Destination airport:
Investigating agency: NTSB
Narrative:
WITNESSES OBSERVED THE ACFT AT ABOUT 100 FT AGL WITH THE ENGINE SPUTTERING, MISSING. IT THEN CRASHED INVERTED IN A LARGE OPEN FIELD ABOUT 100 FT EAST OF A LINE OF TREES; ONE TREE HAD SEVERAL BRANCHES BROKEN NEAR THE TOP. ENG TEST/TEARDOWN REVEALED NO COMPRESSION #6 CYL; BOTTOM SPARK PLUG CENTER ELECTRODE MISSING; ELECTRODE DEBRIS IN EXHAUST VALVE SEAT/FACE. THE FAILED PLUG SHOWED EVIDENCE OF EXCESSIVE OPERATING TEMPERATURES AND PREIGNITION. LAST ANNUAL WAS 11/3/83, ABOUT 44 HRS PRIOR TO ACCIDENT. ALL PLUGS APPEARED TO HAVE BEEN RECENTLY CLEANED AND SERVICED; NONE OF THE REMAINING PLUGS EXHIBITED EVIDENCE OF DETONATION OR PREIGNITION. PILOT PERFORMED OWN MAINTENANCE AND ALSO REPORTEDLY MIXED OWN AUTO/AVIATION GASOLINE. CAUSE: IMPROPER MAINTENANCE OF THE SPARK PLUGS BY THE PILOT/MECHANIC WHICH RESULTED IN A PARTIAL LOSS OF ENGINE POWER, AND THE PILOT'S FAILURE TO CLEAR TREES DURING AN EMERGENCY LANDING IN AN OPEN FIELD RESULTING IN AN INADVERTENT STALL.

Sources:

NTSB: http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001213X28484


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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