# NTSB LAX99LA181: Piper PA-31-310, N57AS, La Verne, CA, April 15, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: April 15, 1999, 15:30 local (22:30 UTC) - Place: La Verne, CA - Coordinates: 34.149276, -117.760986 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.1493&lon=-117.7610&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report November 22, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 46317 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX99LA181 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46317/pdf - Page: https://openairdocs.org/ntsb/LAX99LA181 ## 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. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Miscellaneous/other, climb - cooling system,cowling - not secured (cause) - maintenance,installation - inadequate, company maintenance personnel (cause) - aircraft preflight - inadequate, pilot in command (cause) - cooling system,cowling - separation ## Analysis 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.' ## Factual narrative On April 15, 1999, at 1530 hours Pacific daylight time, a Piper PA-31-310, N57AS, sustained substantial damage to the horizontal stabilizer when the right engine upper cowling separated in flight near La Verne, California. The aircraft was owned and operated by Air Desert Pacific Corporation of La Verne, and was on a postmaintenance test flight under 14 CFR Part 91 of the Federal Aviation Regulations. Visual meteorological conditions prevailed and no flight plan was filed for the local area flight. The commercial pilot, the sole occupant, was not injured. The flight originated from the Bracket Airport in La Verne at 1525. The operator did not report the accident to either the Safety Board or the Federal Aviation Administration (FAA). FAA inspectors from the Los Angeles Flight Standards District Office discovered the damaged aircraft during an airport visit. The inspectors interviewed the pilot and the operator's maintenance personnel. According to the FAA inspector's report, 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." ## Aircraft - Registration: [N57AS](https://openairdocs.org/deregistered/N57AS-2013-11-07), registration cancelled 2013-11-07, S/N 31-113, built 1967 (OpenAirDocs) - Reported make and model: Piper PA-31-310 - Registry model: [Piper PA-31-310](https://openairdocs.org/model/piper-pa-31-310) (registry code 7103102) (OpenAirDocs) - Registry engine: [Lycoming TI0-541 series](https://openairdocs.org/engine/lycoming-ti0-541-series) (registry code 41536, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 31-113 - Airframe hours: 7259 - Engines: Lycoming TSIO-540-A2B 310 horsepower reciprocating - Damage: Substantial damage - Flight: Part 91 - Registered owner: Air Desert Pacific Corp - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, March 21, 1999, 79 hours before - Departed: POC ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 38; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 1,455 total, 88 in this make and model, 1,347 as pilot in command, 40 in the last 90 days, 10 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 64 °F ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19990415042149A](https://openairdocs.org/incident/19990415042149A), Apr 15, 1999: Piper PA31310, La Verne, CA, Substantial damage. (-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… 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. --- 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.