# NTSB SEA97LA152: Cessna 172A, N6844X, Ogden, UT, June 26, 1997 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: June 26, 1997, 09:15 local (15:15 UTC) - Place: Ogden, UT - Coordinates: 41.17942, -111.909317 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=41.1794&lon=-111.9093&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor, 1 uninjured - Status: Completed, report January 28, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 42642 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA97LA152 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42642/pdf - Page: https://openairdocs.org/ntsb/SEA97LA152 ## Probable cause The fracture of the no. 4 exhaust valve and subsequent loss of engine power. Factors contributing to the accident include a congested landing area, and rough terrain. ## 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,valve,exhaust - fractured (cause) - Forced landing, emergency descent/landing - On ground/water encounter with terrain/water, emergency descent/landing - terrain condition - congested/confined area (contributing factor) - terrain condition - rough/uneven (contributing factor) - weather condition - tailwind - Nose over, emergency landing ## Analysis About 30 minutes after takeoff, the engine began to run rough and lose power. The first pilot (pilot-in-command) attempted to regain full power and return to the departure airport. The airplane continued to descend and the first pilot attempted to land in a hayfield about four miles from the airport. During the forced landing, which occurred in a tailwind, the pilot noticed power lines ahead. He forced the airplane onto rough terrain beneath the power lines. The airplane nosed over on landing and was substantially damaged. An examination of the engine revealed that the exhaust valve stem on the no. 4 cylinder had separated from the valve head. The fracture surface was obliterated and the mode of failure could not be determined. After the failure of the valve, further damage to other cylinder components subsequently occurred as the engine continued to operate in a degraded condition. The no. 4 cylinder had been reworked about 108 flight hours prior to the accident. ## Factual narrative On June 26, 1997, at 0915 mountain daylight time, N6844X, a Cessna 172A, operated by the owner/pilot, nosed over during a forced landing and was substantially damaged near Ogden, Utah. The forced landing was precipitated by a loss of engine power during cruise flight. One private pilot (first pilot) received minor injuries, and the other private pilot (second pilot) was not injured. Visual meteorological conditions prevailed and no flight plan had been filed. The personal flight departed from the Ogden-Hinkley Airport on a local flight about 0845, and was en route back to the airport when the accident occurred. The flight was conducted under 14 CFR 91. In a written statement to the Safety Board, the first pilot (pilot-in-command seated in the left front seat) stated that he was flying at 4,400 feet about 15 miles north of Ogden when the engine "...started missing." Engine power began to decrease despite the pilot's efforts to regain full engine power. The airplane then began to descend under partial power. The pilot declared an emergency with the Air Traffic Control (ATC) tower at Ogden and attempted to return for an emergency landing there. The pilot further stated: Called Ogden Tower [and] told them I was having power problem and did not know if I would make it back to Ogden. Called Ogden [again and] told them I was going to land in a hay field in Slaterville. Attempted to land in hay field, but [the landing area] was obstructed by wires. Attempted to go under wires, but...ground was to close. According to a Federal Aviation Administration (FAA) aviation safety inspector from Salt Lake City, Utah, the second pilot stated that both pilots knew that they would not be able to make it to the Ogden-Hinkley Airport, so they decided to attempt a landing on a private grass airstrip located about four miles north of the airport. During the forced landing, which was performed during a prevailing tailwind, the airplane was forced downward by the first pilot onto a hayfield. It then nosed over during the landing roll. The inspector examined the accident site and reported that fuel was found on board the airplane. The wreckage was then moved to facilitate a detailed examination of the engine. During the examination, a fractured exhaust valve was found in the no. 4 cylinder assembly. The valve pieces and the entire cylinder assembly was removed from the engine and sent to the Safety Board's Materials Analysis Division in Washington, D.C. for further analysis. According to the Safety Board's Materials Laboratory Factual Report (attached), the fracture features of both valves were completely obliterated. One of the valves was missing its stem. One of the push rods "... revealed circumferential scratches below one of the ballends." The report also noted that "dissimilar wear patterns... were observed on the rocker to valve stem contact faces." Corrosion pits were found in several locations on the exterior of one of the rocker shafts. Damage was also found on the valve seat and valve spring seats. According to FAA records, the aircraft N6844X, was manufactured in 1960. It was acquired by the registered owner in July 1995. The airplane was powered by a single 145-horsepower Continental model O-300-C engine. The Safety Board recovered and examined the maintenance records (excerpts attached) of the airplane. The examination revealed that the engine and airframe had accumulated 2,566 hours of operating time at the time of the accident. The engine had accumulated 866 hours since its last major overhaul (SMOH), and 20 hours since its last 100-hour inspection on April 12, 1997. The records revealed the following recent entries: August 5, 1994 Engine Time SMOH = 711.3 hours No. 5 cylinder "impaired" / Compression test of cylinders indicate "all within manufacturers recommended limits." November 1, 1994 Engine Time SMOH = 758.09 hours No. 2 and no. 4 cylinders "removed due to low compression" and "reworked" February 6, 1995 Engine Time SMOH = 807.96 No. 2 cylinder removed "due to venting exhaust valve" December 3, 1995 Engine Time SMOH = 833.81 Engine receives annual inspection / All cylinders exhibit acceptable compression values during compression check. April 12, 1997 Engine Time SHOM = 846.33 Engine receives 100-hour inspection / All cylinders exhibit acceptable compression values during compression check except for no. 5 cylinder. No. 5 cylinder removed for "venting exhaust valve" / No. 5 cylinder reinstalled after rework / No metal found in oil screen. An examination of the maintenance records also revealed that all of the aforementioned cylinder repair work occurred at an FAA repair station in Salt Lake City, Utah, known as Precision Air-Power. According to FAA records, both pilots held Private Pilot certificates with a rating in airplane single engine land airplanes. Both pilots also held expired FAA Class III medical certificates and had not received any flight reviews during the two years prior to the accident. ## Aircraft - Registration: [N6844X](https://openairdocs.org/deregistered/N6844X-2004-04-27), registration cancelled 2004-04-27, S/N 47744, built 1960 (OpenAirDocs) - Reported make and model: Cessna 172A - Registry model: [Cessna 172A](https://openairdocs.org/model/cessna-172a) (registry code 2072404) (OpenAirDocs) - Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 47744 - Airframe hours: 2566 - Engines: Continental O-300-C 145 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Tipping, Burdell - Airworthiness certificate: Standard, Utility; Standard, Normal - Last inspection: 100 hour, April 12, 1997, 20 hours before - Departed: OGD, UT ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 64; private; airplane ratings: single-engine land; medical: class 3, expired; seat: left; flight hours: 400 total, 400 in this make and model, 360 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: 155° at 5 knots - Visibility: 30 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 41 °F - Altimeter: 30.00 inHg - Observed at: OGD, 4 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 19970626016049A](https://openairdocs.org/incident/19970626016049A), Jun 26, 1997: Cessna 172A, Ogden, UT, Substantial damage. Pilot reported a rough running engine and attempted to make it back to airport, made emergency landing. (.4)about 30 minutes after takeoff, the engine began to… ## Other investigations on N6844X (1) 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. - [NTSB DEN76DTM16](https://openairdocs.org/ntsb/DEN76DTM16), Jan 30, 1976: Cessna 172A (N6844X), Logan, UT, substantial damage 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.