ASN Wikibase Occurrence # 38133
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| Date: | Sunday 1 May 1994 |
| Time: | 13:20 LT |
| Type: |  Mooney M20E |
| Owner/operator: | Verbosh, George M. |
| Registration: | N1905Y |
| MSN: | 288 |
| Year of manufacture: | 1964 |
| Total airframe hrs: | 4412 hours |
| Engine model: | Lycoming IO-360-A1A |
| Fatalities: | Fatalities: 2 / Occupants: 2 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Broomfield, CO -
 United States of America
|
| Phase: | Initial climb |
| Nature: | Private |
| Departure airport: | (KBJC) |
| (KBJC) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
SHORTLY AFTER TAKEOFF, THE PILOT REQUESTED CLEARANCE TO RETURN FOR AN IMMEDIATE LANDING. A WITNESS SAID THAT HE HEARD A METALLIC NOISE FROM THE PLANE AS IT PASSED OVERHEAD. HE SAID THE PILOT MADE A STEEP RIGHT BANK TO LAND ON RUNWAY 29L; HOWEVER, THE PLANE IMPACTED BETWEEN THE PARALLEL RUNWAYS. AN EXAM OF THE ENGINE REVEALED 2 FINGER-TIGHT CYLINDER BASE NUTS & UNDERTORQUED BASE NUTS & CRANKCASE THROUGH-NUTS. A TEARDOWN REVEALED THE CRANKSHAFT HAD FAILED FROM FATIGUE BETWEEN THE #3 & #4 CONNECTING ROD JOURNALS. A METALLURGICAL EXAM OF THE CRANKSHAFT REVEALED HIGH LOCALIZED STRESS-INDUCED FATIGUE CRACKS. THE ENGINE HAD ACCUMULATED 266 HRS OF FLIGHT TIME SINCE MAJOR OVERHAUL ON 1/11/91. THE PLANE HAD BEEN MODIFIED WITH 2 STC'S, 1 FOR INSTALLATION OF A RAYJAY TURBOCHARGER, ANOTHER FOR INSTALLATION OF A 'BLACKMAC' PROPELLER. THE HOLDER OF THE PROPELLER STC REPORTED THE COMPANY WOULD NOT HAVE INSTALLED THE PROPELLER ON A TURBOCHARGED ENGINE, SINCE CERTIFICATION VIBRATORY TESTS WERE ONLY MADE ON NORMALLY ASPIRATED ENGINES. AFTER INSTALLATION ON 1/17/91, THE PROPELLER WAS REMOVED ON 3/19/91 FOR STATIC BALANCE & 'RE-INDEX PROP #1 BLADE 180 DEGREES;' ON 3/28/91, IT WAS REMOVED FOR A BLADE ANGLE CHECK; AND ON 5/23/91, IT RECEIVED A DYNAMIC BALANCE.
Probable Cause: FATIGUE FAILURE OF THE ENGINE CRANKSHAFT; AND FAILURE OF THE PILOT TO MAINTAIN ADEQUATE AIRSPEED, WHILE MANEUVERING TO LAND, WHICH RESULTED IN A STALL AND COLLISION WITH THE TERRAIN. FACTORS RELATED TO THE ACCIDENT WERE: THE UNDESIRABLE ENGINE/PROPELLER VIBRATION, AND THE LOOSE CRANKCASE AND CYLINDER BASE NUTS.
Accident investigation:
 |
|
Sources:
NTSB FTW94FA141
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Oct-2008 10:30 | ASN archive | Added |
| 21-Dec-2016 19:23 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 10-Apr-2024 07:48 | ASN Update Bot | Updated [Time, Operator, Other fatalities, Phase, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
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