Stemme Gmbh & S10-VT N389BD

Summary

On 31 August 2013 at about 01:15 local time, a Stemme Gmbh & S10-VT registered N389BD, operated by 512 Horses Inc, was involved in an accident near Mackinaw City, Michigan, United States. 2 people were on board and one was seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

31 August 2013 at 01:15

Classification

Accident

Location

Mackinaw City, Michigan, United States

Coordinates

45.7678, -84.7347

Aircraft

Stemme Gmbh & S10-VT

Registration

N389BD

Category

Glider

Year built

2001

Engines

1

Operator

512 Horses Inc

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Waukegan → Hessel

Aircraft damage

Substantial

Weather

VMC

Light

Dusk

NTSB number

CEN13LA524

1 person was seriously injured.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB 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.

Quoted verbatim from the NTSB record.