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ASN Wikibase Occurrence # 219246
Last updated: 20 November 2020
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Date:09-DEC-2018
Time:12:15
Type:Silhouette image of generic M20T model; specific model in this crash may look slightly different
Mooney M20K 231
Owner/operator:Private
Registration: N5756W
C/n / msn: 25-0822
Fatalities:Fatalities: 0 / Occupants: 4
Other fatalities:0
Aircraft damage: Substantial
Category:Accident
Location:NW of Lincoln Park Airport (N07), Lincoln Park, NJ -   United States of America
Phase: Landing
Nature:Private
Departure airport:Lincoln Park, NJ (N07)
Destination airport:Poughkeepsie-Dutchess County Airport, NY (POU/KPOU)
Investigating agency: NTSB
Narrative:
During cruise flight, the pilot noticed an increase in cylinder head temperature on two cylinders and unsuccessfully attempted to reduce the temperature. He reported that he soon heard "an explosion" and noted a hole in the engine cowling. He performed a forced landing to a golf course, during which the landing gear collapsed, which resulted in substantial damage to the right wing.
Postaccident examination of the engine revealed that the Nos. 1 and 2 connecting rods exhibited thermal discoloration consistent with a loss of lubrication. Additionally, the breakaway torques measured at 8 of the 12 through-bolts showed that they were below the manufacturer's specifications. The No. 2 main bearing saddles exhibited impingement damage, and the No. 2 bearing was partially rotated clockwise, which blocked the oil passages leading to the connecting rod bearings. The mating surfaces of the main bearing saddles had remnants of silk thread around the through-bolt holes, which was contrary to manufacturer guidance that prohibited placing silk thread in these areas. Given this information, it is likely that maintenance personnel applied silk thread to a prohibited area during an engine overhaul that occurred about 255.8 flight hours before the accident. This resulted in a loss of torque on the crankcase through-bolts, which allowed the No. 2 main bearings to shift, resulting in restriction of lubrication to that area and subsequent engine failure.

Probable Cause: Maintenance personnel's improper assembly of the engine during overhaul, which resulted in lubrication restriction due to a bearing shift and the subsequent engine failure.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20181209X33123&key=1

FAA register: https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=5756W%20

Accident investigation:
cover
  
Investigating agency: NTSB
Status: Investigation completed
Duration: 1 year and 6 months
Download report: Final report
Location


Images:


Photo: FAA

Revision history:

Date/timeContributorUpdates
09-Dec-2018 19:47 Geno Added
03-Jul-2020 12:39 ASN Update Bot Updated [Operator, Nature, Departure airport, Destination airport, Source, Narrative, Accident report, ]
03-Jul-2020 17:41 harro Updated [Destination airport, Source, Narrative, Photo, Accident report, ]

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