# NTSB DEN92LA012: Piper PA-31-350, N354AC, Denver, CO, November 29, 1991

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: November 29, 1991, 03:05 local (10:05 UTC)
- Place: Denver, CO
- Location: 39.8617° N, 104.6732° W: Placed by OpenAirDocs at DENVER INTL (DEN), within about a mile (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=39.8617&lon=-104.6732&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report May 27, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 18183
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN92LA012
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/18183/pdf
- Page: https://openairdocs.org/ntsb/DEN92LA012

## Probable cause

A FALSE UNSAFE LANDING GEAR INDICATION DUE TO A FROZEN DOWN LOCK SWITCH. FACTORS WERE:  ICING CONDITIONS AND LOW CEILINGS.

## Sequence of events

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

- Gear not extended, approach
  - landing gear,gear indicating system - false indication (cause)
  - remedial action - attempted, pilot in command
  - landing gear,gear switch - frozen (cause)
  - weather condition - icing conditions (contributing factor)
  - weather condition - low ceiling (contributing factor)
- In flight collision with terrain/water, landing - flare/touchdown
  - wheels up landing - intentional, pilot in command

## Analysis

DURING THE APPROACH, THE PILOT COULD NOT OBTAIN A GEAR DOWN AND LOCKED INDICATION ON THE LEFT MAIN LANDING GEAR.  HE ELECTED TO LAND GEAR UP WHICH CAUSED SUBSTANTIAL DAMAGE TO THE BOTTOM OF THE FUSELAGE. POSTACCIDENT TESTS REVEALED THAT THE LEFT MAIN LANDING GEAR DOWN LOCK SWITCH HAD FROZEN FROM AN ACCUMULATION OF ICE.  WEATHER CONDITIONS AT THE TIME INCLUDED ICING, LOW CEILINGS AND LOW VISIBILITY.  PRIOR TO THE ACCIDENT, THE PILOT REPORTED ACCUMULATIONS OF MODERATE ICE.  FOLLOWING THE ACCIDENT, ICE ACCUMULATION OF UP TO 3 INCHES WAS FOUND ON THE AIRCRAFT.

## Aircraft

- Registration: [N354AC](https://openairdocs.org/deregistered/N354AC-1992-12-28), registration cancelled 1992-12-28, S/N 317752049 (OpenAirDocs)
- Reported make and model: PIPER PA-31-350
- Registry model: [Piper PA-31-350](https://openairdocs.org/model/piper-pa-31-350) (registry code 7103110) (OpenAirDocs)
- Category: Airplane
- Serial number: 31-7752049
- Engines: LYCOMING LTSID-540-J2B 350 horsepower reciprocating
- Damage: Substantial damage
- Flight: Part 135
- Operator: Alpine Air, Inc.
- Departed: SLC, SALT LAKE CITY, UT
- Flight plan: IFR
- Airport: DEN, Stapleton International, runway 26, 10,004 × 150 ft, concrete

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 30; airline transport, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; flight hours: 3,179 total, 490 in this make and model, 2,876 as pilot in command, 282 in the last 90 days, 94 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Instrument (IMC), Night/dark
- Visibility: 1 statute miles
- Lowest ceiling: 400 ft overcast
- Temperature: 28 °F, dew point 28 °F
- Altimeter: 29.00 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).

- [Incident 19911129058729I](https://openairdocs.org/incident/19911129058729I), Nov 29, 1991: Piper PA31350, Denver, CO, Minor damage. Unable to lower landing gear. Landed gear up. Found a malfunctioning down-locked switch on left main gear.

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.