Piper PA-31-310 accident near La Verne, California, April 15, 1999
On April 15, 1999 at about 10:30 pm local time, a Piper PA-31-310, registered N57AS, was substantially damaged in an accident near La Verne, California. It was a flight of an unrecorded kind under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The in-flight separation of the right engine cowling due to the operator's inadequate maintenance quality control procedures and the pilot's inadequate preflight inspection.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 15, 1999 · about 10:30 pm local time
- Place
- La Verne, California · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Piper PA-31-310 · all PA-31-310s on the register
- Registration
- N57AS · registry record · serial 31-113
- Damage
- Substantial damage
- Flight
- Flight of an unrecorded kind · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The aircraft had been in maintenance for an adjustment to the right engine manifold pressure differential controller. The procedure required the uncowling of the engine. A certificated airframe and powerplant mechanic removed the cowling and made the required adjustments, then left for the day. A noncertificated mechanic replaced the cowling and the pilot then proceeded to perform the postmaintenance test flight. During climbout, the right engine upper cowling separated and wrapped around the right horizontal stabilizer. The pilot experienced difficulty in controlling the aircraft until the airspeed was reduced, then he returned to the airport and landed. Inspection of the cowling disclosed that the inboard latches on the upper cowling were not damaged. In his written statement, the pilot notes that his failure to detect the unlatched inboard cowling fasteners resulted from 'poor preflight inspection habits and a failure to follow the checklist.'
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: commercial pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 1,455 hours in all; 88 in this make and model; 40 in the last 90 days; 10 in the last 30 days; 1,347 as pilot in command; 568 on instruments
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 7,259 hours
- Last inspection: 100-hour inspection, March 21, 1999; 79 hours since
- Maximum gross weight: 6,500 lb
- Seats: 2
- Landing gear: retractable
- Engine: Lycoming TSIO-540-A2B (piston); 0 hours total
The flight
- Departed from: POC at 10:30 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 64°F (18°C), dew point 0°F (-18°C)
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.