# NTSB SEA93LA120: Cessna 185A, N4080Y, Lowell, ID, May 23, 1993 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: May 23, 1993, 11:15 local (18:15 UTC) - Place: Lowell, ID - Coordinates: 46.079906, -115.860298 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=46.0799&lon=-115.8603&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report August 1, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 41712 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA93LA120 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41712/pdf - Page: https://openairdocs.org/ntsb/SEA93LA120 ## Probable cause FATIGUE OF THE ROCKER ARM AND UNSUITABLE TERRAIN WHICH WAS ENCOUNTERED DURING THE PRECAUTIONARY LANDING. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(partial) - mech failure/malf, cruise - normal - engine assembly,rocker arm/tappet - fatigue (cause) - Nose over, landing - roll - precautionary landing - performed, pilot in command - unsuitable terrain or takeoff/landing/taxi area - encountered, pilot in command (cause) ## Analysis WHILE FLYING AT 8000 FEET MSL A PARTIAL POWER LOSS DEVELOPED. WHEN THE PILOT OBSERVED OIL ON THE LEFT WING STRUT HE CHOSE TO EXECUTE A PRECAUTIONARY LANDING IN A FIELD TO PREVENT ENGINE SEIZURE. DURING THE LANDING ROLL, IN SOFT TERRAIN, THE AIRCRAFT NOSED OVER. POST CRASH EXAMINATION REVEALED THE NUMBER TWO CYLINDER EXHAUST ROCKER ARM BROKEN IN HALF. METALLURGICAL EXAMINATION REVEALED THAT THE ROCKER ARM SEPARATED IN FATIGUE. THE ROCKER ARM(S), WHICH WERE NOT UNDER AN APPROVED STC, HAD BEEN INSTALLED APPROXIMATELY 11 HOURS PREVIOUS TO THE ACCIDENT. ## Factual narrative On May 23, 1993, at approximately 1115 hours Pacific daylight time (PDT), a Cessna C-185A, N4080Y, registered to and operated by Clarence R. Forbes, and being flown by Howard S. Hash, a certificated commercial pilot, was substantially damaged when the aircraft nosed over during a precautionary landing in a boggy field following an emergency descent due to a partial loss of power. The landing took place on the Idaho side of Lolo Pass at the Idaho/Montana border and approximately 50 nautical miles northeast of Lowell, Idaho. The pilot was uninjured. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal in nature, was to have been operated in accordance with the requirements set forth in 14CFR91 and departed from Stevensville, Montana, earlier in the morning intending to return to the same airport. The pilot reported in a telephonic interview with the investigator, that he was cruising at 8000 feet above mean sea level (MSL) when a partial power loss occurred. He stated that he was familiar with the terrain and, upon seeing oil on the left wing strut, became concerned that the engine might seize. He then executed a precautionary landing in a meadow. The pilot reported that the meadow was boggy and the aircraft nosed over during the rollout. Post crash examination of the engine by the pilot revealed a hole in the number two cylinder rocker box cover (refer to photograph 1). Post crash disassembly of the engine revealed that the number two cylinder exhaust rocker arm was broken in half through the center pivot bearing area (refer to photograph 2). The rocker arm halves and rocker box cover were shipped to the Safety Board's Materials Laboratory for metallurgical examination. The examination revealed three areas of fatigue progression on the surfaces of the rocker arm halves, two of which originated in the drilled oiling hole (refer to attached Metallurgist's Factual Report). The number two cylinder exhaust rocker arm, one of 12 such rocker arms, was provided by Clyde G. Ritter, for installation on N4080Y. The rocker arms were installed approximately 11 hours previous to the accident, during a major overhaul of the engine. A new camshaft provided by Mr. Ritter was installed at the same time, however, the Supplemental type Certificate for the camshaft (STC# SE5784NM) was not applicable for any IO-470 series engines. Additionally, no STC has been issued for the rocker arms. N4080Y did not have an experimental certification at the time of the accident. ## Aircraft - Registration: [N4080Y](https://openairdocs.org/aircraft/N4080Y), registered now, S/N 1850280, built 1961 (OpenAirDocs) - Reported make and model: CESSNA 185A - Registry model: [Cessna 185A](https://openairdocs.org/model/cessna-185a) (registry code 2072804) (OpenAirDocs) - Registry engine: [Continental I0-470 series](https://openairdocs.org/engine/continental-i0-470-series) (registry code 17027, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 1850280 - Engines: CONTINENTAL IO-470F 260 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Forbes, Clarence, R. - Registered owner: Forbes, Clarence R. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 15, 1993, 11 hours before - Departed: 32S, STEVENSVILLE, MT - Destination: 32S ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 51; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, expired; seat: left; flight hours: 6,000 total, 3,000 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 50° at 8 knots - Visibility: 15 statute miles - Lowest ceiling: none - Temperature: 61 °F, dew point 37 °F - Altimeter: 30.00 inHg - Observed at: MSO, 27 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 19930523015049A](https://openairdocs.org/incident/19930523015049A), May 23, 1993: Cessna 185A, Lowell, ID, Substantial damage. Lost partial power. Landed in boggy meadow. Nosed over. Rocker arm broke. Bogus camshaft used in engine overhall. 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.