Cessna 172L accident near Prescott, Arizona, October 10, 2007
On October 10, 2007 at about 5:14 pm local time, a Cessna 172L, registered N9897G, was substantially damaged in an accident near Prescott, Arizona. It was a personal flight under general aviation rules (Part 91). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The failure of maintenance personnel to detect fatigue cracks in the number 3 exhaust rocker arm, which lead to a partial loss of engine power.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 10, 2007 · about 5:14 pm local time
- Place
- Prescott, Arizona · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 172L · all 172Ls on the register
- Registration
- N9897G · no longer on the register · serial 17259797
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
While in cruise flight, the engine had a sudden partial loss of power and made "clanging" noises. Although the engine continued to operate at a maximum of 900-1,100 revolutions per minute (rpm), insufficient power was available to maintain altitude. The pilot contacted the tower of a nearby airport, but determined that he would not be able to reach the runway. Due to power lines and a blind curve on a paved road, the pilot opted to land adjacent to the road. The airplane impacted a ditch and came to rest inverted. The engine had been overhauled 2.0 flight hours before the accident. A field overhaul had been performed on the engine due to a bent pushrod, stuck valve, and broken lifter for the number 3 cylinder. During the field overhaul, all four of the rocker arms had been magnetic particle inspected. Examination of the engine revealed that the number 3 cylinder exhaust rocker arm had separated into two pieces. A metallurgical examination was performed on the rocker arms by a Safety Board metallurgist. The number 3 exhaust rocker arm had fractured around the central pivot hole due to fatigue. The fatigue originated at the outer surface of the oil hole. The corners of the hole were sharp and had not been deburred, which increases the likelihood of fatigue cracking. The outer surface of the fatigued area was 0.31 inches long on the left side of the oil hole, and 0.21 inches long on the right side. The fractured exhaust rocker arm had been magnetic particle inspected for cracks during the field overhaul. The Safety Board metallurgist also noted staining on the cracks from the solution used during the magnetic particle inspection. Based on the staining, the cracks would have been detectable in size (about 0.2 inches) at the time of the inspection.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: private
- Ratings: single-engine land; instrument: airplane
- Flight time: 398 hours in all; 106 in this make and model; 33 in the last 90 days; 9 in the last 30 days; 345 as pilot in command
- Last flight review: May 1, 2007
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: minor injuries
The aircraft
- Airframe total time: 3,670 hours
- Last inspection: annual inspection, October 1, 2007; 2 hours since
- Maximum gross weight: 2,300 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming O-320-E2D (piston); 0 hours total
The flight
- Departed from: DVT Deer Valley AZ at 4:00 pm
- Destination: PRC Prescott AZ
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 140° at 6 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 73°F (23°C), dew point 21°F (-6°C)
- Altimeter: 30.15 inHg
- Observation at 4:53 pm from PRC, 9 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.