# NTSB SEA94LA218: Beech 99, N14MV, Helena, MT, August 20, 1994

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: August 20, 1994, 02:10 local (08:10 UTC)
- Place: Helena, MT
- Coordinates: 46.530197, -112.210899 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=46.5302&lon=-112.2109&mi=10
- Phase of flight: [Taxi](https://openairdocs.org/ntsb-phases/250) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report May 16, 1995
- Report: Approved by Office Director
- NTSB case key (mKey): 42005
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA94LA218
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42005/pdf
- Page: https://openairdocs.org/ntsb/SEA94LA218

## Probable cause

LANDING GEAR LOCKING MECHANISM OVERLOAD AND IMPROPER RIGGING.

## Sequence of events

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

- Gear collapsed, taxi - from landing
  - landing gear,gear locking mechanism - overload (cause)
  - maintenance,adjustment - improper, other maintenance personnel (cause)

## Analysis

AFTER LANDING AND EXITING ON TO THE TAXIWAY, THE LEFT MAIN LANDING GEAR COLLAPSED. METALLURGICAL EXAMINATION OF THE BROKEN DOWN LOCK HOOK, LINK, FITTING, AND PIN REVEALED FRACTURES TYPICAL OF AN OVERSTRESS SEPARATION. THESE FAILURES WERE THE RESULT OF THE DOWN LOCK HOOK NOT PROPERLY ENGAGING THE LOCK PLATE ON THE DRAG LINK, EITHER FROM INADEQUATE RIGGING OR FROM EXCESSIVE BINDING OF THE FITTING.

## Factual narrative

On August 20, 1994, at 0210 mountain daylight time, a Beech 99, N14MV, collapsed the left main landing gear after turning off the runway at Helena, Montana.  Visual meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed.  The airplane was substantially damaged and the airline transport pilot and commercial pilot were not injured.  The flight had departed from Billings, Montana, on August 20, 1994, at 0115, as a cargo flight conducted under 14 CFR 135.

It was reported that after departing runway 27, via the high speed taxi way, the left main landing gear collapsed.  The airplane skidded another 52.5 feet before coming to rest on the taxi way.

The maintenance inspection and subsequent repairs were to the outboard rear spar, ribs and upper and lower skins on the left wing.  Other repairs or replacements were to the left main landing gear assembly, fuselage belly and left flap.

During the post crash inspection of the left main landing gear, it was found that the down lock hook, link, fitting and pin were broken.  A metallurgical examination of the broken parts revealed fractures typical of an overstress separation.  According to the metallurgist's discussions with the manager of the Air Safety group at Beech, the failure was most likely a result of the down lock hook not properly engaging the lock plate on the drag link, either from inadequate rigging or from excessive binding of the fitting.  The Beech manager reported that this condition could occur repeatedly and may not be easily detected unless this portion of the gear was inspected directly.  The collapse of the gear could then occur under certain loading conditions.

## Aircraft

- Registration: [N14MV](https://openairdocs.org/aircraft/N14MV), registered now, S/N U59, built 1969 (OpenAirDocs)
- Reported make and model: BEECH 99
- Registry model: [Beech 99](https://openairdocs.org/model/beech-99) (registry code 1154002) (OpenAirDocs)
- Registry engine: [Pratt & Whitney Canada PT6A-60A](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-60a) (registry code 52043, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: U59
- Engines: P&W PT6A-28 680 horsepower turbo prop
- Damage: Substantial damage
- Flight: Part 135
- Operator: Alpine Aviation
- Registered owner: Precision Airlease Inter.
- Airworthiness certificate: Standard, Normal
- Departed: BIL, BILLINGS, MT
- Destination: HLN
- Flight plan: IFR
- Airport: HLN, Helena Regional, runway 27, 9,000 × 150 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 49; commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 4,620 total, 100 in this make and model, 3,000 as pilot in command, 120 in the last 90 days

## Weather

- Conditions: Visual (VMC), Night/dark
- Wind: 70° at 5 knots
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 54 °F, dew point 37 °F
- Altimeter: 30.00 inHg
- Observed at: HLN

## 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 19940820022259A](https://openairdocs.org/incident/19940820022259A), Aug 20, 1994: Beech 99, Helena, MT, Substantial damage. Left main gear collapsed turning off runway on high speed taxiway. Down lock hook missed lockplate. Rigging suspect

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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