# NTSB LAX87LA275: Piper PA-28-161, N91338, Milpitas, CA, July 20, 1987

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: July 20, 1987, 12:30 local (19:30 UTC)
- Place: Milpitas, CA
- Coordinates: 37.439712, -121.86972 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.4397&lon=-121.8697&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report August 13, 1988
- Report: Approved by Office Director
- Safety recommendations: Yes
- ADs cited in the narratives: [AD 87-10-06 R1](https://openairdocs.org/ad/87-10-06-R1) (OpenAirDocs)
- NTSB case key (mKey): 25644
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX87LA275
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/25644/pdf
- Page: https://openairdocs.org/ntsb/LAX87LA275

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Loss of engine power(partial) - mech failure/malf, climb - to cruise
  - engine assembly,rocker arm/tappet - fractured (cause)
  - maintenance,compliance with ad - improper, other maintenance personnel (cause)
  - maintenance,service bulletin/letter - inadequate, manufacturer (cause)
- Forced landing, descent - emergency
- On ground/water encounter with terrain/water, landing - roll
  - terrain condition - rough/uneven (contributing factor)

## Analysis

WHILE CLIMBING TO CRUISE PLT HEARD A LOUD KNOCKING NOISE FOLLOWED BY 'VIOLENT VIBRATIONS' & A LOSS OF POWER. PLT MADE A FRCD LNDING IN A NEWLY EXCAVATED CONSTRUCTION SITE & WENT OVER AN EMBANKMENT. INVES REVEALED DEFORMATION OF THE #4 CYLINDER VALVE COVER. #4 EXHAUST VALVE ROCKER ARM WAS FOUND TO BE BROKEN. REVIEW OF ACFT MAINTENANCE RECORDS REVEALED THAT AD 87-10-06 WHICH INCORPORATES LYCOMING SERVICE BULLETIN (SB) 477A WAS ACCOMP 78.7 HRS PRIOR TO THE ACCIDENT. THE SB REQUIRES ROCKER ARMS THAT DO NOT HAVE A WALL THICKNESS OF.075 BE REPLACED. IF THE ROCKER ARM PASSES THE THICKNESS EXAM THE ROCKER ARM OIL DRIP HOLE OUTER EDGE MUST BE 'BURRED' TO THE APPROX .030 RADIUS PRIOR TO REASSEMBLY. THE ROCKER ARM WAS MEASURED USING A ROUND ANVIL MICROMETER. THE MEASUREMENT MET THE MIN DIMENSION OF .075. AFTER THE ACCIDENT, MET LAB EXAM REVEALED FRACTURE FEATURES OF HIGH CYCLE FATIGUE & OVERSTRESS. THE ORIGIN OF THE FATIGUE WAS TRACED TO THE REWORKED OIL DRIP HOLE WHICH DID NOT MEET .030 RADIUS. THE WALL THICKNESS MEASURED .055 USING A MEASURING MICROSCOPE.

## Aircraft

- Registration: [N91338](https://openairdocs.org/aircraft/N91338), registered now, S/N 28-8616008, built 1985 (OpenAirDocs)
- Reported make and model: PIPER PA-28-161
- Registry model: [Piper PA-28-161](https://openairdocs.org/model/piper-pa-28-161) (registry code 7102803) (OpenAirDocs)
- Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 288616008
- Airframe hours: 368
- Engines: LYCOMING O-320-D3G 160 horsepower reciprocating
- Damage: Substantial damage
- Flight: Instructional, Part 91
- Operator: Flying Country Club, Inc.
- Registered owner: R.F. Buttler
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, June 17, 1987, 79 hours before
- Departed: RHV, SAN JOSE, CA
- Destination: CCR, CONCORD, CA
- Flight plan: VFR
- Airport: RHV, Reid Hillview

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 50; student; medical: class 3, valid medical--w/ waivers/lim; seat: left; toxicology performed; flight hours: 101 total, 101 in this make and model, 28 as pilot in command, 49 in the last 90 days, 16 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 270° at 8 knots
- Visibility: 50 statute miles
- Lowest ceiling: none
- Altimeter: 29.00 inHg
- Observed at: RHV, 8 nm away

## 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 19870720035569A](https://openairdocs.org/incident/19870720035569A), Jul 20, 1987: Piper PA28161, Milpitas, CA, Substantial damage. Engine vibration and power loss. Crash landed. Rocker arm failure. Wall thickness not per AD on rocker arm assembly

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.