# NTSB ANC94LA097: Cessna 206, N5200X, Mosquito Flats, AK, August 5, 1994 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 5, 1994, 14:50 local (22:50 UTC) - Place: Mosquito Flats, AK - Coordinates: 63.17995, -143.10028 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=63.1799&lon=-143.1003&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report May 9, 1995 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - NTSB case key (mKey): 2534 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC94LA097 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/2534/pdf - Page: https://openairdocs.org/ntsb/ANC94LA097 ## Probable cause THE MISSING NUMBER 6 CYLINDER PISTON PIN CAP AND THE SUBSEQUENT FAILURE OF THE NUMBER 6 CYLINDER CONNECTING ROD CAP. ALSO, THE LACK OF SUITABLE LANDING AREA FOR THE FORCED LANDING. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, cruise - normal - engine assembly,other - missing (cause) - engine assembly,connecting rod cap - failure,total (cause) - Forced landing, descent - emergency - Nose over, landing - roll - terrain condition - none suitable (cause) ## Analysis THE ENGINE OIL PRESSURE BEGAN TO DROP AND THE TEMPERATURE BEGAN TO RISE. BEFORE THE PILOT COULD RETURN TO TOK, ALASKA, THE ENGINE STOPPED PRODUCING POWER AND WOULD NOT WINDMILL. THE ENGINE DISASSEMBLY SHOWED THAT THE NUMBER 6 CYLINDER PISTON PIN CAP WAS MISSING AND THAT THE NUMBER 6 CYLINDER CONNECTING ROD CAP WAS FRACTURED INTO THREE MAJOR PIECES. ALL BEARING SURFACES SHOWED SIGNS OF HEAT DAMAGE. THE AIRPLANE WAS FORCED TO LAND ON MUSKEG AND NOSED OVER DURING THE LANDING ROLL. ## Factual narrative On August 5, 1994 at 1450 Alaska daylight time, a wheel equipped Cessna 206 airplane, N5200X, registered to and operated by 40 Mile Air LTD, of Tok, Alaska, experienced a rise in oil temperature, a drop in oil pressure, and a subsequent engine stoppage during cruise flight. The flight was forced to land on Mosquito Flats and nosed over during the landing roll. The air taxi flight, operating under 14 CFR Part 135, departed Tok for a local flight. Visual meteorological conditions prevailed and a company flight plan was in effect. The pilot and the passenger were not injured and the airplane received substantial damage. According to the pilot, he saw a rise in oil temperature and a drop in oil pressure. He immediately reversed course to return to Tok. The engine stopped producing power before reaching the airport and he was forced to land on the muskeg. Examination of the engine showed that the number 6 cylinder piston pin cap was missing. The number 6 connecting rod cap was found broken in three major pieces and numerous smaller pieces. According to John Lauer, Customer Service Representative for Superior Air Parts, the number on the piston pin identifies the pin as a German manufactured piston pin and the Service Bulletin, which recalls the Superior Air Parts Piston Pin number SA520046, does not apply to that installed piston pin. Mr. Lauer stated that in the past, and as a result of his experiences, the reasons for piston pin failures could be misalignment, rod fit/pin fit in small end of rod bushing, a bent or twisted connecting rod, too much endplay (thrust washer), infrequent oil changes which would allow the pin to bind up, and wear in the bushing in the rod. The examination of the engine could not show which of these situations applied. Mr. Lauer stated that this event occurred in a relatively brief period of time, and that the metal introduced into the engine resulted in oil starvation. ## Aircraft - Registration: [N5200X](https://openairdocs.org/aircraft/N5200X), registered now, S/N U20605591, built 1980 (OpenAirDocs) - Reported make and model: CESSNA 206 - Registry model: [Cessna U206G](https://openairdocs.org/model/cessna-u206g) (registry code 2073356) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 206005591 - Airframe hours: 7597 - Engines: CONTINENTAL IO-520-F 300 horsepower reciprocating - Damage: Substantial damage - Flight: Part 135 - Registered owner: 40 Mile Air Ltd - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, July 24, 1994, 32 hours before - Departed: TKJ, TOK, AK - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 28; commercial, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 1,400 total, 210 in this make and model, 1,030 as pilot in command, 210 in the last 90 days, 80 in the last 30 days, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 40 statute miles - Lowest ceiling: none - Temperature: 84 °F, dew point 50 °F - Altimeter: 29.00 inHg ## 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 19940805020419A](https://openairdocs.org/incident/19940805020419A), Aug 5, 1994: Cessna U206G, Tok, AK, Substantial damage. Lost power on local flight. Nosed over on forced landing on muskeg. Poston pin failure. Metal blocked oil screen. 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.