# NTSB ERA19LA062: Mooney M20K, N5756W, Paramus, NJ, December 9, 2018 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: December 9, 2018, 12:15 local (17:15 UTC) - Place: Paramus, NJ - Coordinates: 40.946388, -74.089721 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.9464&lon=-74.0897&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Minor injuries - Injuries: 2 minor, 2 uninjured - Status: Completed, report June 29, 2020 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO, Continental Motors Inc. - NTSB case key (mKey): 98746 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA19LA062 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/98746/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=98746 - Page: https://openairdocs.org/ntsb/ERA19LA062 ## 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. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Mooney M20K, 4 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=5870220), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) - [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Mooney M20K, 4 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=5870220), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) - [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Maintenance personnel (probable cause); cases with it: [Mooney M20K, 2 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=5870220), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [Mooney M20K, 3 cases](https://openairdocs.org/ntsb-events/040/sequence.md?model=5870220), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Mooney M20K, 15 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=5870220), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Mooney M20K, 28 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=5870220), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis 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. ## Factual narrative On December 9, 2018, about 1215 eastern standard time, a Mooney M20K, N5756W, was substantially damaged during a forced landing near Paramus, New Jersey. The private pilot and a passenger received minor injuries, and two other passengers were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the cross-country flight, which originated from Lincoln Park Airport (N07), Lincoln Park, New Jersey, about 1200. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91 and had an intended destination of Hudson Valley Regional Airport (POU), Poughkeepsie, New York.According to the pilot, while in cruise flight, he noticed an increase in cylinder head temperature on two cylinders. He attempted to reduce the temperatures; however, he soon heard "an explosion," and noted a hole in the engine cowling. The pilot performed a forced landing to a golf course and during the landing roll, the airplane impacted a berm, became airborne again, and struck the ground resulting in the landing gear collapsing and substantial damage to the right wing. According to Federal Aviation Administration records, the airplane was manufactured in 1984 and was registered to the pilot in November, 2017. It was equipped with a Continental Motors Inc. TSIO-360-LB1, 210-hp, engine. According to the airframe maintenance logbook, the most recent annual inspection was performed on August 15, 2018, at a total time of 2,401.3 hours. According to the engine logbook, the engine was overhauled on January 11, 2016, at a total time of 2,185 hours. At the time of the accident, the Hobbs meter indicated 2,440.8 hours. The engine was examined at the manufacturer's facility under NTSB supervision. The examination revealed that the engine case was breached over the No. 2 cylinder. The oil sump was removed and metallic debris was noted. The oil filter was removed and disassembled, and metal was noted in the filter. The oil pump was examined and scoring was noted inside the pump housing. The crankcase was split and the No. 1 connecting rod was separated from the crankshaft, and the Nos. 1 and 2 connecting rods exhibited thermal discoloration. Further examination of the mating surfaces of the main bearing saddles had remnants of silk thread around the through-bolt holes (see figure 1). Figure 1. View of No. 2 main bearing saddle and No. 2 main bearing. Note remnants of silk thread. The break-away torque was measured for the through-bolts on the engine. Eight out of the 12 through bolt torque values were below the manufacturer's recommended torque values as can be seen in the engine teardown report in the public docket associated with this case. The through bolts associated with the Nos. 2 and 3 main bearings and measured between 172 in-lbs and 395 in-lbs, which was below the manufacturer specification of 590-610 in-lbs of torque. The No. 2 main bearing saddles exhibited impingement damage and the No. 2 bearing waspartially rotated clockwise, which blocked the oil passage to the connecting rod bearings. The engine manufacturer published a Service Information Letter (SIL) titled "Sealants, Lubricants, and Adhesives Authorized by CMI" in 1999 (revised September 16, 2014). This guidance, which was applicable at the time of the accident engine's overhaul stated that the when reassembling the crankcase halves, maintenance personnel should "...apply and position P/N 641543 (a continuous, single piece of grade 'D' silk thread on the 2-4-6 case half as specified (see Figures 5 through 8…). Ensure the free ends of your thread are covered by gaskets (except the nose oil seal)." Figure 2 below is from the SIL, and shows that the #2 main bearing saddle was one of four "prohibited" areas where silk thread should not be placed. Figure 2 – Areas where silk thread application is prohibited noted in red, which include the No. 2 main bearing saddle. The Continental Aircraft Engine Maintenance Manual, "Six Cylinder Engine Crankcase Threading," which was released in April 2016, just after the engine overhaul, stated, "Do not apply any form of sealant to the crankcase cylinder deck, chamfer, cylinder mounting flange, cylinder base O-ring, or cylinder fastener threads. The use of RTV, silicone, Gasket Maker or any other sealant on the areas listed above during engine assembly will cause a loss of cylinder deck stud or through-bolt torque. Subsequent loss of cylinder attachment load, loss of main bearing crush and/or fretting of the crankcase parting surfaces will occur. The result will be cylinder separation, main bearing movement, oil starvation and catastrophic engine failure." ## Aircraft - Registration: [N5756W](https://openairdocs.org/deregistered/N5756W-2021-04-03), registration cancelled 2021-04-03, S/N 25-0822, built 1984 (OpenAirDocs) - Reported make and model: Mooney M20K (No Series) - Registry model: [Mooney M20K](https://openairdocs.org/model/mooney-m20k) (registry code 5870220) (OpenAirDocs) - Category: Airplane - Serial number: 25-0822 - Year built: 1984 - Airframe hours: 2440.8 - Engines: Continental Motors Inc. TSIO-360-LB1 210 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 15, 2018, 40 hours before - Departed: N07, Lincoln Park, NJ - Destination: POU, Poughkeepsie, NY - Equipment: Stall warning system, ADS-B, Auto-pilot, Handheld GPS, Onboard weather ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; injuries: minor; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review August 29, 2018; seat: left; restraint: 3-point; flight hours: 916 total, 114 in this make and model, 916 as pilot in command, 18 in the last 90 days, 10 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 34 °F, dew point 18 °F - Altimeter: 30.39 inHg - Observed at: TEB, 6 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20181209020659A](https://openairdocs.org/incident/20181209020659A), Dec 9, 2018: Mooney Aircraft Corp. M20K, Paramus, NJ, Substantial damage. On December 9, 2018 N5756W, a Mooney M20K, with four people on board departed lincoln park airport (N07)for a VFR 14 CFR part 91 flight at approximately 1200… ## Docket (9 files) The files NTSB released with the investigation on December 20, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=98746. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 5.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479312&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - JPI Factual Report (item 2, .PDF, 2 photos, 994 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479313&FileExtension=.PDF&FileName=JPI%20Factual%20Report-Master.PDF - JPI Factual Report - Attachment 1 (item 3, .CSV, 29 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479314&FileExtension=.csv&FileName=JPI%20Factual%20Report%20-%20Attachment%201-Master.csv - Maintenance Manual Excerpts (item 4, .PDF, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479315&FileExtension=.PDF&FileName=Maintenance%20Manual%20Excerpts-Master.PDF - Continental Motors Engine Examination Report w/photos (item 5, .PDF, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479316&FileExtension=.PDF&FileName=Continental%20Motors%20Engine%20Examination%20Report%20w%2Fphotos-Master.PDF - Continental Motors Maintenance Manual Excerpts (item 6, .PDF, 511 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479317&FileExtension=.PDF&FileName=Continental%20Motors%20Maintenance%20Manual%20Excerpts-Master.PDF - Continental Motors Service Information Letter - Sealants, Lubricants and Adhesives Authorized by CMI (item 7, .PDF): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479318&FileExtension=.PDF&FileName=Continental%20Motors%20Service%20Information%20Letter%20-%20Sealants,%20Lubricants%20and%20Adhesives%20Authorized%20by%20CMI-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 8, .PDF, 653 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479319&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF - Investigative Photographs (item 9, .PDF, 4 photos, 4.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479320&FileExtension=.PDF&FileName=Investigative%20Photographs-Master.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.