# NTSB LAX92LA276: Cessna 421B, N11BU, Hayward, CA, July 3, 1992

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: July 2, 1992, 17:45 local (Jul 3, 1992, 00:45 UTC)
- Place: Hayward, CA
- Coordinates: 37.669845, -122.07933 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.6698&lon=-122.0793&mi=10
- Phase of flight: [Standing](https://openairdocs.org/ntsb-phases/150) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report May 26, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27672
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX92LA276
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27672/pdf
- Page: https://openairdocs.org/ntsb/LAX92LA276

## Probable cause

THE EXPLOSION OF FUEL VAPORS IN THE RIGHT WING DUE TO THE PILOT'S OVERPRIMING OF THE RIGHT ENGINE DURING A START ATTEMPT AND AN UNCORRECTED PREEXISTING FUEL SYSTEM LEAK.  A FACTOR IN THE ACCIDENT WAS INADEQUATE MAINTENANCE PERFORMED ON THE AIRCRAFT.

## Sequence of events

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

- Explosion, standing - starting engine(s)
  - fuel system - leak (cause)
  - maintenance - inadequate, company maintenance personnel (contributing factor)
  - starting procedure - improper use of, pilot in command (cause)
  - mixture - excessive, pilot in command (cause)
  - wing - exploded
- Fire, standing - starting engine(s)
  - fluid,fuel - fire

## Analysis

THE PILOT REPORTED THAT HE OVERPRIMED THE RIGHT ENGINE WHEN HE ATTEMPTED TO START IT.  DURING THE START OPERATION, AN ACCUMULATION OF FUEL VAPOR LOCATED OUTBOARD OF THE RIGHT ENGINE EXPLODED AND RIPPED OPEN A YARD LONG PORTION OF THE RIGHT WING'S UPPER SKIN PANELS.  EVIDENCE WAS OBSERVED OF AN UNCORRECTED  PREEXISTING FUEL LEAK IN THE VICINITY OF THE RIGHT ENGINE'S AUXILIARY FUEL PUMP.  THE PILOT REPORTED THAT HE WAS AN A & P MECHANIC, AND HE OWNED, OPERATED AND MAINTAINED THE AIRPLANE.

## Aircraft

- Registration: N11BU (not matched to a registry record)
- Reported make and model: CESSNA 421B
- Category: Airplane
- Serial number: 421B0912
- Engines: CONTINENTAL GTSIO-520H 375 horsepower reciprocating
- Damage: Substantial damage
- Fire: On-Ground
- Flight: Positioning, Part 91
- Operator: Professional Pilot Associates
- Registered owner: Peter J. Danto
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, April 8, 1992, 90 hours before
- Departed: HWD
- Destination: OAK, OAKLAND, CA
- Airport: HWD, Hayward

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 34; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 7,900 total, 900 in this make and model, 7,800 as pilot in command, 80 in the last 90 days, 22 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 270° at 5 knots
- Lowest ceiling: none
- Temperature: 70 °F
- Altimeter: 30.00 inHg

## 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 19920702023659A](https://openairdocs.org/incident/19920702023659A), Jul 2, 1992: Cessna 421B, Hayward, CA, Substantial damage. Explosion in right wing auxiliary tank. Leak in line to aux pump. Pilot believes he overprimed engine on start up.

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.

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