# Accident 19990415042149A: Piper PA31310, La Verne, CA, April 15, 1999

- Type: FAA accident report (Accident/Incident Data System), as reported
- Date: April 15, 1999, 15:30 local time
- Place: La Verne, CA
- Damage: Substantial damage
- Phase of flight: Normal Cruise
- Operating rules: General operating rules (Part 91)
- Location: 34.1493° N, 117.7610° W: From the FAA, an estimate near the named town, within about 3 miles
- Nearby events: https://openairdocs.org/map.md?lat=34.1493&lon=-117.7610&mi=10
- Aircraft: N57AS, a cancelled registration (https://openairdocs.org/deregistered/N57AS-2013-11-07) (OpenAirDocs)
- Registry model: Piper PA-31-310 (registry code 7103102, https://openairdocs.org/model/piper-pa-31-310) (OpenAirDocs)
- Registry engine: Lycoming TI0-541 series (registry code 41536, https://openairdocs.org/engine/lycoming-ti0-541-series) (OpenAirDocs)
- Reported make and model: PIPER PA31310
- Reported engine: LYC TIO540A2B
- People aboard: 1
- Fatal injuries: 0
- Pilot flight hours: 1,455 total, 88 in this make and model, 40 in the last 90 days
- NTSB investigation: [NTSB LAX99LA181](https://openairdocs.org/ntsb/LAX99LA181) (OpenAirDocs)
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/19990415042149A

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

(-23) ON 04/15/99 PIPER NAVAJO, N57AS, DEPARTED BRACKET AIRPORT ON A TEST FLIGHT FOLLOWING A RIGHT ENGINE MANIFOLD PRESSURE ADJUSTMENT. PRIOR TO DEPARTURE THE RIGHT ENGINE UPPER COWLING WAS REMOVED AND THE PRESSURE DIFFERENTIAL CONTROLLER WAS ADJUSTED BY A CERTIFICATED MECHANIC. THE CERTIFICATED MECHANIC WENT HOME AND LEFT THE COWLING INSTALLATION TO BE COMPLETED BY AN UNSUPERVISED, UNCERTIFICATED MECHANIC. THE UNSUPERVISED MECHANIC INSTALLED THE COWLING AND FAILED TO SECURE THE INBOARD LATCHES. THE AIRCRAFT COWLING DEPARTED THE AIRCRAFT AFTER LEVEL FLIGHT WAS ACCOMPLISHED. THE COWLING WRAPPED AROUND THE RIGHT HORIZONTAL STABILIZER. THE PILOT DECLARED A MAYDAY DUE TO CONROL PROBLEMS WITH THE AIRCRAFT. THE AIRCRAFT WAS BROUGHT UNDER CONTROL AND LANDED AT BRACKETT WITHOUT FURTHER INCIDENT. (.4) 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 POSTMA INTENANCE 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 NTSB's investigation of this event (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB LAX99LA181](https://openairdocs.org/ntsb/LAX99LA181), Apr 15, 1999: Piper PA-31-310 (N57AS), La Verne, CA, substantial damage. Probable cause: 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.

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.