ASN Wikibase Occurrence # 157058
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| Date: | Sunday 23 June 2013 |
| Time: | 14:43 |
| Type: |  Beechcraft A45 Mentor |
| Owner/operator: | Jet Test and Transport LLC |
| Registration: | N434M |
| MSN: | G-755 |
| Engine model: | Continental IO-550-B23B |
| Fatalities: | Fatalities: 2 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Near Boulder City Municipal Airport (KBVU), Boulder City, NV -
 United States of America
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | Chandler, AZ |
| North Las Vegas, NV (VGT) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot, who was also the mechanic for the airplane, had replaced all six cylinders on the engine during the airplane’s annual inspection; he reported that, 3 days before the accident, the engine was operated and ran well. On the day of the accident, he was returning the airplane to its home base following a maintenance inspection on the wings. The pilot was near the end of the flight when he contacted approach control and requested priority handling because an engine chip light had illuminated. Shortly thereafter, the pilot stated that the engine had lost power on a cylinder, and he declared an emergency. When the airplane was at 9,500 ft mean sea level, the pilot said that he was going to attempt to land at a nearby airport (elevation 2,201 ft). Before switching to the airport’s common traffic advisory frequency (CTAF), the pilot reported to the approach controller that the airplane was at 3,800 ft with the landing gear down and that the situation was under control. The pilot did not contact approach control again and did not broadcast over the CTAF. The airplane collided with terrain in a nose- low attitude about 1 mile west of the airport. Postaccident examination of the airframe revealed no evidence of mechanical anomalies that would have precluded normal operation.
Postaccident examination of the engine revealed that the No. 6 cylinder had separated, and no nuts were located on its through bolts. Magnified examinations of the bolt threads found the thread profiles intact and only locally distorted, consistent with the nuts not being present during the No. 6 cylinder separation, which appeared to be the result of the incorrect assembly of the cylinder at the last cylinder change. Fretting damage on the mounting pad was observed, which indicates looseness and movement between the cylinder and the case that resulted from inadequate preload in the fasteners either through insufficient initial torque or loss of torque during operation. Considering the short time since cylinder installation, it is likely that the cylinder fasteners, or at least some of them, were not correctly torqued at installation.
Probable Cause: The pilot/mechanic's loss of control during an emergency descent following a loss of engine power while in cruise flight. Contributing to the accident was the pilot/mechanic's incorrect assembly of the No. 6 cylinder at the last cylinder change, which resulted in a separation of the cylinder and the loss of engine power.
Accident investigation:
 |
|
Sources:
NTSB
ex.USAF/55-198.
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Jun-2013 12:58 | Alpine Flight | Updated [Aircraft type] |
| 24-Jun-2013 16:16 | Geno | Added [[Aircraft type]] |
| 24-Jun-2013 17:05 | harro | Updated [Aircraft type] |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 29-Nov-2017 08:46 | ASN Update Bot | Updated [Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
| 08-Feb-2022 14:09 | A.J.Scholten | Updated [Cn, Source] |
Corrections or additions? ... Edit this accident description
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