- Date
- July 24, 1993, 22:20 local (Jul 25, 1993, 03:20 UTC)
- Place
- Purcell, OK
- Injuries
- 2 uninjured
- Damage
- Substantial damage
- Phase of flight
- Enroute
- Aircraft
- N4884GCessna 172N
- Weather
- Visual (VMC) · Night/bright
- Status
- Completed · report September 26, 1994
- Report
- Approved by Office Director
- FAA report
- 19930724025399A
- Case key
- 18796
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Probable cause
The lack of suitable terrain onto which to execute the forced landing which was neccesitated by the partial power loss. The power loss was a result of the fatigue failure of the exhaust valve rocker arm attachment stud. A factor was the night conditions.
Sequence of events
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Analysis
The airplane collided with rough terrain during a night forced landing following a partial power loss. The accident occurred during a night dual instructional flight and the instructor made the forced landing. Investigation revealed that the #3 exhaust valve rocker arm attachment stud had failed in fatigue. The separated stud subsequently lodged under the #3 intake valve mechanism and the corresponding push rod was bent. The engine and subject parts had accumulated a total of 2,903.5 hours.
Factual narrative
On July 24, 1993, at approximately 2220 central daylight time, a Cessna 172N, N4884G, was substantially damaged when it collided with rough terrain during a forced landing near Purcell, Oklahoma. The forced landing was executed following a partial loss of engine power. The airplane was on a night cross country dual instructional flight. A VFR flight plan was filed and visual meteorological conditions prevailed throughout the area. Neither the instructor pilot nor the rated student pilot were injured.
According to the instructor, the engine lost power down to 1,500 RPM while in cruise flight, about twenty minutes after takeoff from the Westheimer Airport in Norman, Oklahoma. The instructor stated that his efforts to regain power were unsuccessful and the airplane would not sustain level flight at the reduced power. He subsequently executed a forced landing to what appeared to be an open field. The airplane impacted rough terrain during the landing roll.
The number 3 cylinder exhaust rocker arm attachment stud had separated at the face of the cylinder head. The separated stud was found lodged under the number 3 intake valve mechanism. The number 3 intake valve push rod was bent. The operator stated that the stud was examined by a metallurgy lab at the University of Oklahoma and the failure mechanism was determined to be fatigue. The engine and subject parts had accumulated a total of 2,903.5 hours.
Neither the instructor nor the student submitted a pilot/operator accident report. Both subsequently left the country.
Aircraft
- Registration
- N4884G
- Reported as
- Cessna 172N
- Category
- Airplane
- Serial number
- 17273431
- Airframe hours
- 2,904
- Engine
- Lycoming O-320-H2AD, 160 horsepower, reciprocating
- Damage
- Substantial damage
- Flight
- Instructional · Part 91
- Registered owner
- Airman'S Flight School, Inc.
- Airworthiness certificate
- Standard, Normal
- Departed
- OUN · Norman, OK
- Destination
- GLE · Gainesville, TX
- Flight plan
- VFR
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 21
- Certificate
- Commercial
- Airplane ratings
- Single-engine land
- Instrument ratings
- Airplane
- Medical
- Class 1, Valid Medical--no waivers/lim.
- Seat
- Right
- Flight hours
- 1,300 total · 200 in the last 90 days · 1 in the last 24 hours
Weather
- Conditions
- Visual (VMC) · Night/bright
- Wind
- 160° at 14 knots
- Visibility
- 10 statute miles
- Lowest ceiling
- None
- Temperature
- 90 °F, dew point 64 °F
- Altimeter
- 29.00 inHg
- Observed at
- OKC, 20 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.