Piper PA-24-180 accident near San Luis Obispo, California, July 10, 1999
On July 10, 1999 at about 7:30 pm local time, a Piper PA-24-180, registered N6597P, was substantially damaged in an accident near San Luis Obispo, California (San Luis Obispo airport). It was an instructional flight under general aviation rules (Part 91). No one was hurt; 2 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The failure/separation of the crankshaft idler gear and the fatigue failure and subsequent separation of the crankshaft dowel pin due to the improper static and dynamic balance of the propeller by maintenance personnel.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 10, 1999 · about 7:30 pm local time
- Place
- San Luis Obispo, California · San Luis Obispo · map
- Type
- Accident
- Injuries
- No one was hurt; 2 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Piper PA-24-180 · all PA-24-180s on the register
- Registration
- N6597P · no longer on the register · serial 24-1719
- Damage
- Substantial damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The instructor said that the power came up smoothly on the takeoff roll, but that the engine suddenly quit at 600 feet agl. The flight instructor took the controls, lined up on a major interstate highway, and touched down in the northbound lanes. The right wing struck a bush, which spun the airplane off the highway and down the embankment next to the highway. An engine teardown disclosed that the crankshaft idler gear (left magneto) was detached from the mounting pad at the back of the crankcase. The crankshaft gear was not secured to the crankshaft, and the locating dowel pin was fractured and separated. Further examination of the idler gear shaft and attaching parts revealed severe wear signatures on the attachment bolts and locking plate, and the bolts displayed signatures consistent with prolonged contact with the rotating idler gear. The bore at the idler gear shaft-mounting pad was also severely worn and elongated. The crankshaft counterbore and corresponding gear revealed fretting and corrosion signatures at the mating surfaces, and the dowel pin was separated in line with the parting surfaces of the gear and counterbore. The dowel pin fracture surface displayed fatigue. A propeller overhaul was completed 20 hours prior to the accident. The Hartzell propeller manual prohibits balance weights in excess of 0.9 ounces (25.51 grams) in any one location on the spinner. Weights totaling 36 grams were found on one location on the airplane spinner.
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: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane single-engine; instructor: instrument airplane; instrument: airplane
- Flight time: 2,790 hours in all; 45 in this make and model; 160 in the last 90 days; 63 in the last 30 days; 2,700 as pilot in command; 1,670 on instruments
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: rgt
The aircraft
- Airframe total time: 4,799 hours
- Last inspection: annual inspection, May 1, 1999; 20 hours since
- Maximum gross weight: 2,550 lb
- Seats: 4
- Landing gear: retractable
- Engine: Lycoming O-360-A1A (piston); 0 hours total
The flight
- Departed from: KWHP Pacoima CA at 5:30 pm
- Flight plan: VFR
- Runway 29, 4,799 ft by 150 ft
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 270° at 10 knots
- Visibility: 20 statute miles
- Sky: scat at 20,000 ft
- Temperature: 81°F (27°C), dew point 57°F (14°C)
- Altimeter: 30.00 inHg
- Observation at 7:30 pm from SBP, 3 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 2 |
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.