# NTSB DEN87IA032: Swearingen SA226TC, N124AV, Billings, MT, December 20, 1986

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: December 19, 1986, 21:10 local (Dec 20, 1986, 04:10 UTC)
- Place: Billings, MT
- Coordinates: 45.869285, -108.470596 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=45.8693&lon=-108.4706&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 13 uninjured
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 17134
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN87IA032
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/17134/pdf
- Page: https://openairdocs.org/ntsb/DEN87IA032

## Analysis

N124AV WAS OPERATING AS BIG SKY AIRLINES FLT 3857, SCHEDULED SERVICE FROM HELENA TO BILLINGS. THE FLT PROCEEDED UNEVENTFULLY UNTIL THE APCH INTO BILLINGS. THE FLT CREW STATED AFTER THE INCIDENT THAT WHEN THE LANDING GEAR WAS EXTENDED, THE LEFT MAIN GEAR LIGHTS DID NOT ILLUMINATE, VERIFYING THE 'DOWN AND LOCKED POSITION..' AFTER NUMEROUS ATTEMPTS TO ILLUMINATE THE LIGHTS AND CONFIRM THE POSITION OF THE LANDING GEAR, THE CREW EXECUTED AN INTENTIONAL GEAR UP LANDING. POST INCIDENT INSPECTION OF THE LANDING GEAR SYSTEM REVEALED IT WAS CAPABLE OF NORMAL OPERATION. THE MALFUNCTIONING COCKPIT INDICATOR LIGHT WAS TRACED BACK TO AN INOPERATIVE OUTBOARD DOWNLOCK MICROSWITCH.

## Sequence of events

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

- Airframe/component/system failure/malfunction, approach
  - landing gear,gear indicating system - failure,partial (contributing factor)
  - remedial action - improper, pilot in command (cause)
- In flight collision with terrain/water, landing - flare/touchdown
  - airport facilities,runway/landing area condition - runway
  - wheels up landing - intentional, pilot in command (cause)

## Aircraft

- Registration: [N124AV](https://openairdocs.org/deregistered/N124AV-1993-07-22), registration cancelled 1993-07-22, S/N TC364 (OpenAirDocs)
- Reported make and model: SWEARINGEN SA226TC
- Registry model: [Swearingen SA226TC](https://openairdocs.org/model/swearingen-sa226tc) (registry code 8780404) (OpenAirDocs)
- Category: Airplane
- Serial number: TC 364
- Airframe hours: 11273
- Engines: GARRETT TPE331-3U303G 904 horsepower turbo prop
- Damage: Minor damage
- Flight: Part 135
- Operator: Big Sky Airlines
- Registered owner: Itt Industrial Credit Company
- Airworthiness certificate: Standard, Normal
- Last inspection: Continuous airworthiness, December 19, 1986, 36 hours before
- Departed: HLN, HELENA, MT
- Destination: BIL, BILLINGS, MT
- Flight plan: IFR
- Airport: BIL, Billings Logan Int'L., runway 27R, 10,500 × 150 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 45; airline transport, commercial; airplane ratings: single-engine sea, multi-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 7,000 total

## Weather

- Conditions: Visual (VMC), Night/dark
- Wind: 230° at 11 knots
- Visibility: 20 statute miles
- Lowest ceiling: 20,000 ft overcast
- Temperature: 30 °F, dew point 10 °F
- Altimeter: 30.00 inHg
- Observed at: BIL

## 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 19861219076049I](https://openairdocs.org/incident/19861219076049I), Dec 19, 1986: Swrngn SA226TC, Billings, MT, Minor damage. Unable to obtain a safe gear indication on left main. Landed gear up. Microswitch was defective.

## Other investigations on N124AV (1)

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

- [NTSB DEN87LA067](https://openairdocs.org/ntsb/DEN87LA067), Mar 19, 1987: Swearingen SA-226TC (N124AV), Missoula, MT, substantial damage

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

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