# NTSB FTW98LA198: Cessna 172N, N6356D, Parker, CO, April 25, 1998 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: April 25, 1998, 13:30 local (19:30 UTC) - Place: Parker, CO - Coordinates: 39.500358, -104.759643 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.5004&lon=-104.7596&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report October 30, 1998 - Report: Approved by Office Director - NTSB case key (mKey): 20588 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW98LA198 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/20588/pdf - Page: https://openairdocs.org/ntsb/FTW98LA198 ## Probable cause a fractured #1 exhaust valve rocker arm stud, which subsequently resulted in loss of engine power and a forced landing. The lack of suitable terrain in the forced landing area was a related factor. ## 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, approach - engine assembly,rocker arm/tappet - fractured (cause) - engine assembly,push rod - bent - engine assembly,valve,exhaust - closed - Forced landing, emergency descent/landing - Nose over, emergency landing - terrain condition - none suitable (contributing factor) - terrain condition - rough/uneven (contributing factor) ## Analysis The instructor pilot (CFI) said that after completing a local instructional flight, he and his student entered an extended right base for runway 35R, about 5 miles southeast of the airport. He 'suddenly heard the engine lose a major portion of power.' While performing an emergency check of the instruments, the instructor noted that the engine power had dropped to 1,800 rpm. Realizing they would be unable to glide to the airport due to the loss of engine power, the CFI executed an emergency landing on a field near a golf course. The ground was muddy due to an accumulation of rain and snow from the previous night. After the airplane traveled a short distance, the nose wheel struck a rut, and the airplane nosed over. Examination of the aircraft engine revealed that the #1 (right front) cylinder intake pushrod was bent. After removing the valve cover, a stud that anchored the #1 exhaust valve rocker arm was found to be fractured, and the #1 exhaust valve was in the closed position. There was no damage to the valve lifters or camshaft. ## Factual narrative On April 25, 1998, approximately 1330 mountain daylight time, a Cessna 172N, N6356D, operated by Aspen Air Corporation, was substantially damaged during a forced landing near Parker, Colorado. The flight instructor and his student were not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The instructional flight was operated under Title 14 CFR Part 91 and originated at Englewood, Colorado, approximately one hour before the mishap. According to the flight instructor, he and his student were returning to the airport after an instructional flight. The instructor reported that while on an extended right base for runway 35R approximately 5 miles southeast of the airport, he "suddenly heard the engine lose a major portion of power." While performing an emergency check of the instruments, the instructor noted that the engine power had dropped to 1,800 rpm. Realizing they would be unable to glide to the airport due to the loss of engine power, the instructor executed an emergency landing in a field near a golf course. The ground was muddy due to an accumulation of rain and snow from the previous night. Upon touchdown, the airplane traveled a short distance before the nose wheel struck a rut left by a tractor, and the aircraft nosed over. This investigator examined the engine at the facilities of Beegles Aircraft Service, Greeley, Colorado, on May 18, 1998, and again on June 17, 1998. The no. 1 (right front) cylinder intake pushrod was bent. After removing the valve cover, it was discovered that the stud that anchors the exhaust valve rocker arm had fractured. The exhaust valve was in the closed position. There was no damage to the valve lifters and camshaft. ## Aircraft - Registration: [N6356D](https://openairdocs.org/deregistered/N6356D-2012-08-03), registration cancelled 2012-08-03, S/N 17272742, built 1979 (OpenAirDocs) - Reported make and model: Cessna 172N - Registry model: [Cessna 172N](https://openairdocs.org/model/cessna-172n) (registry code 2072434) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17272742 - Airframe hours: 2121 - Engines: Lycoming O-320-H2AD 160 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Aspen Air Corp. - Registered owner: 757gc Corporation - Airworthiness certificate: Standard, Normal; Standard, Utility - Departed: APA, ENGLEWOOD, CO ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 61; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 7,300 total, 5,000 in this make and model, 1,795 as pilot in command, 79 in the last 90 days, 29 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 360° at 10 knots - Visibility: 50 statute miles - Lowest ceiling: 16,000 ft broken - Temperature: 59 °F, dew point 30 °F - Altimeter: 29.00 inHg - Observed at: APA, 5 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 19980425013299A](https://openairdocs.org/incident/19980425013299A), Apr 25, 1998: Cessna 172N, Parker, CO, Substantial damage. Engine lost power on dual flight. Landed in muddy field. Nosed over. (.4)the instructor pilot (CFI) said that after completing a local instructional flight, he… ## Other investigations on N6356D (2) 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 DEN90LA101](https://openairdocs.org/ntsb/DEN90LA101), Apr 27, 1990: Cessna 172 (N6356D), Englewood, CO, substantial damage. Probable cause: THE PILOT LANDED WITH A TAILWIND, AND COST CONTROL OF THE AIRPLANE DURING ROLLOUT. - [NTSB DEN89LA040](https://openairdocs.org/ntsb/DEN89LA040), Dec 6, 1988: Cessna 172 (N6356D), Englewood, CO, 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.