FTW98LA198 · Cessna 172N
Aspen Air Cessna 172N · Accident: partial loss of engine power (mechanical failure) on approach
From Centennial Airport (APA) to an unrecorded destination
Event
- NTSB case
- FTW98LA198
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Cessna 172N
- Aircraft type
- Cessna 172
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N6356D
- Operator
- Aspen Air
- Onboard fatalities
- Unknown
- Route
- From Centennial Airport (APA), Englewood, COTo not recorded
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Approach
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Partial loss of engine power (mechanical failure)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Engine assembly, rocker arm/tappet › Fractured
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
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.
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record FTW98LA198
- Event ID
- 20001211X09870
- Case number
- FTW98LA198
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: fef84e48fac4f95ebdadf93026ee71e0dbc269512f913bfdd58910522dbffb2d; retrieved 2026-09-22T17:51:25.733Z.