Accident Stemme S10-VT N389BD,
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ASN Wikibase Occurrence # 289776
 
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Date:Friday 30 August 2013
Time:19:15 LT
Type:Stemme S10-VT
Owner/operator:512 Horses Inc
Registration: N389BD
MSN: 11-066
Year of manufacture:2001
Total airframe hrs:600 hours
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: Substantial
Category:Accident
Location:Mackinaw City, Michigan -   United States of America
Phase: Approach
Nature:Private
Departure airport:Waukegan Memorial Airport, IL (UGN/KUGN)
Destination airport:Hessel, MI (5Y1)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot reported that the motor-glider was on a long, straight-in visual approach to land when he heard a very loud "bang" in the front of the motor-glider followed by a severe vibration. The pilot shut down the engine and made a forced landing to a field. A postaccident examination of the aircraft revealed that the flexible disk on the front of the driveshaft had disconnected. Only one of the three bolts that connected the disk to the driveshaft remained partially installed. No evidence of Loctite or torque paint was found on the bolt. The bolt's threads were rusted, and the bolt's head was digging into the gearbox housing. The second bolt was sheared off, and the third bolt was missing.

A review of maintenance records revealed that the motor-glider's most recent annual inspection was completed about 1 month before the accident. According to the manufacturer's maintenance manual, a mechanic was required to check the tightness of the bolt connections of the flexible disk on the front side of the drive shaft. It is likely that the mechanic improperly inspected the bolts that connected the flexible joint to the front side of the driveshaft during the last annual inspection, which resulted in the ultimate failure of these components.

The maintenance records also revealed that, during the last annual inspection, Federal Aviation Administration Airworthiness Directive (AD) 2006-19-08, which required inspection for deformations and cracks in the exhaust pipes and the replacement of any damaged exhaust pipes found, had not been properly complied with when a weld repair was made to the No. 1 exhaust pipe. The mechanic's failure to not properly comply with the AD and the operator's failure to ensure that the AD was complied with were not causal to the accident; however, because the AD was not complied with, the motor-glider was not considered airworthy.

Probable Cause: The mechanic's failure to inspect the tightness of the bolts that connected the flexible disk to the driveshaft, which resulted in the failure of these components.

Accident investigation:
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Investigating agency: NTSB
Report number: CEN13LA524
Status: Investigation completed
Duration: 1 year
Download report: Final report

Sources:

NTSB CEN13LA524

Location

Revision history:

Date/timeContributorUpdates
05-Oct-2022 18:01 ASN Update Bot Added

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