Piper PA 46 350P N786MD

Summary

On 30 July 2017 at about 23:59 local time, a Piper PA 46 350P registered N786MD was involved in an accident near Tahlequah, Oklahoma, United States. 4 people were on board and 4 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

30 July 2017 at 23:59

Classification

Accident

Location

Tahlequah, Oklahoma, United States

Nearest airport

Tahlequah Municipal Airport (TQH)

Coordinates

35.9303, -95.0044

Aircraft

Piper PA 46 350P

Registration

N786MD

Category

Airplane

Year built

1998

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Joplin → Dallas

Aircraft damage

Substantial

Weather

VMC

Light

Dusk

NTSB number

CEN17LA292

4 people had minor injuries.

The total loss of engine power, which resulted from fatigue failure of two engine through bolts and the No. 2 cylinder attachment studs due to the lack of sufficient clamping force.

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

Read the full NTSB narrative

The private pilot reported that he was in cruise flight when the engine experienced a total loss of power. Oil covered the windshield and smoke filled the cockpit, making it difficult for him to see out of the airplane. He attempted to land at an airport but conducted a forced landing to a field about 300 ft short of the runway. The right wing separated from the fuselage when it hit a hay bale. The examination of the engine revealed a large hole in the engine case near the No. 2 cylinder. The engine maintenance records indicated that when the engine had a major overhaul about 8 years before the accident, the engine crankcase was repaired at a facility specializing in crankcase repairs. The facility typically used glass bead media to clean engine crankcases instead of "mildly abrasive organic substances" as required by the engine manufacturer. About 1 year before the accident, about 825 hours since the major overhaul, all 6 cylinders were replaced. The engine failure occurred about 198 hours after the cylinders were replaced. The metallurgical examination of the eight through bolts revealed that two of the through bolts and the No. 2 cylinder studs had fracture surfaces that were consistent with fatigue. The fatigue in the studs and through bolts likely resulted from insufficient clamping force due to insufficient torque applied to the attachment nuts during installation or could have developed in service as asperities on the clamping surfaces worked down over time, leading to a reduction in clamping force.

Quoted verbatim from the NTSB record.