ASN Wikibase Occurrence # 37588
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| Date: | Wednesday 1 May 1991 |
| Time: | 06:53 LT |
| Type: |  Piper PA-31-310 Navajo B |
| Owner/operator: | John Westbrook |
| Registration: | N7407L |
| MSN: | 31-790 |
| Year of manufacture: | 1971 |
| Engine model: | Lycoming TIO-540-A2B |
| Fatalities: | Fatalities: 1 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Bennett, Arapahoe County, Colorado -
 United States of America
|
| Phase: | En route |
| Nature: | Executive |
| Departure airport: | Englewood, CO (APA |
| Des Moines, IA (KDSM) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
SHORTLY AFTER TAKEOFF, WHILE CLIMBING TO CRUISE ALTITUDE, THE PILOT REPORTED THE LEFT ENGINE COWL ASSEMBLY HAD COME OFF. WITNESSES OBSERVED THE AIRPLANE AT LOW ALTITUDE & NOTED THAT IT WAS 'YAWING, SPUTTERING, AND ROCKING BACK AND FORTH.' THEY INDICATED THE LEFT ENGINE WAS NOT RUNNING & THAT THE AIRPLANE BANKED SHARPLY TO THE RIGHT & DISAPPEARED BEHIND TREES BEFORE CRASHING. AN INVESTIGATION REVEALED THE LEFT PROPELLER HAD NOT BEEN FEATHERED. THE LEFT ENGINE COWLING WAS FOUND 1.8 MILES FROM THE ACCIDENT SITE. THE THREE PRIMARY (EYEBOLT) COWL FASTERERS ON THE OUTBOARD SIDE OF THE LEFT UPPER COWL WERE FOUND UNLOCKED & SEVEN OTHER COWL ATTACHING STUDS (SCREWS) WERE MISSING. THE COWLING HAD BEEN REMOVED 16 DAYS BEFORE THE ACCIDENT TO INSTALL AN OIL/AIR SEPARATOR. THIS WAS THE FIRST FLIGHT SINCE THAT WORK WAS PERFORMED. THE MECHANIC, WHO DID THE WORK, SAID HE NOTED SEVERAL COWL STUD FASTENERS WERE MISSING & THAT HE HAD NOTIFIED THE PILOT. THE PILOT WAS REPORTED TO HAVE REPLIED THAT HE HAD SOME FASTENERS & WOULD TAKE CARE OF THE PROBLEM.
Probable Cause: IN-FLIGHT SEPARATION OF THE LEFT ENGINE COWL ASSEMBLY THAT WAS NOT PROPERLY LATCHED, AND FAILURE OF THE PILOT TO MAINTAIN MINIMUM CONTROL SPEED, WHICH RESULTED IN HIS LOSS OF AIRCRAFT CONTROL. FACTORS RELATED TO THE ACCIDENT WERE: AN INADEQUATE PREFLIGHT INSPECTION, INADEQUATE MARKINGS/ALIGNMENT INDICATIONS TO ASSURE THAT THE COWL FASTENERS WERE LOCKED, AND AN INSUFFICIENTLY DEFINED PROCEDURE IN THE FLIGHT MANUAL FOR CHECKING THE COWL FASTENERS.
Accident investigation:
 |
|
Sources:
NTSB DEN91FA065
FAA register: 2. FAA: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=7407L
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Oct-2008 10:30 | ASN archive | Added |
| 29-Apr-2015 17:45 | Dr. John Smith | Updated [Time, Aircraft type, Operator, Location, Departure airport, Destination airport, Source, Narrative] |
| 29-Apr-2015 17:47 | Dr. John Smith | Updated [Narrative] |
| 21-Dec-2016 19:23 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 09-Oct-2017 22:57 | Dr. John Smith | Updated [Time, Source] |
| 21-Apr-2024 06:49 | ASN Update Bot | Updated [Time, Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
Corrections or additions? ... Edit this accident description
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