# NTSB DEN84LA128: Cessna 421C, N6205X, Farmington, NM, April 15, 1984

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: April 14, 1984, 23:50 local (Apr 15, 1984, 06:50 UTC)
- Place: Farmington, NM
- Coordinates: 36.750221, -108.179275 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=36.7502&lon=-108.1793&mi=10
- Phase of flight: [Taxi](https://openairdocs.org/ntsb-phases/250) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 16363
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN84LA128
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/16363/pdf
- Page: https://openairdocs.org/ntsb/DEN84LA128

## Sequence of events

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

- Main gear collapsed, taxi - from landing
  - hydraulic system - contamination (cause)
  - landing gear,gear locking mechanism - movement restricted (cause)
  - landing gear,gear locking mechanism - unlocked

## Analysis

WHILE TAXIING AFTER LANDING, THE ACFT WAS IN A LEFT TURN WHEN THE RIGHT MAIN GEAR COLLAPSED. THE PLT REPORTED THAT ALL 3 GEAR INDICATED DOWN & LOCK, BOTH BEFORE & AFTER THE MISHAP. AN EXAM OF THE RIGHT MAIN GEAR ACTUATOR, PN 9910136-4, REVEALED THAT CONTAMINATION HAD COLLECTED ON THE INNER CYLINDER WALL & PREVENTED THE KEYS FROM PROPERLY EXTENDING TO THE LOCKED POSITION. ALSO, THE GEAR SYS WAS DESIGNED TO MAINTAIN HYDRAULIC PRESSURE ON THE DOWN SIDE OF THE ACTUATOR WHEN IT WAS EXTENDED. HOWEVER, THE CONTAMINANT ALSO PREVENTED THE SWITCH (IN THE ACTUATOR) FROM OPERATING PROPERLY.

## Aircraft

- Registration: N6205X (not matched to a registry record)
- Reported make and model: CESSNA 421C
- Category: Airplane
- Serial number: 421C0901
- Airframe hours: 1380
- Engines: CONTINENTAL GTSIO-520-N 375 horsepower reciprocating
- Damage: Substantial damage
- Flight: Executive/Corporate, Part 91
- Registered owner: Aztec Well Servicing Co.
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, September 15, 1983, 8 hours before
- Departed: EO2, ODESSA, TX
- Flight plan: IFR
- Airport: FMN, Farmington Muni

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 37; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: valid medical--w/ waivers/lim; seat: left; flight hours: 7,369 total, 1,450 in this make and model, 7,163 as pilot in command, 118 in the last 90 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Night/dark
- Wind: 330° at 4 knots
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 41 °F, dew point 1 °F
- Altimeter: 30.00 inHg
- Observed at: FMN

## 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 19840414013619A](https://openairdocs.org/incident/19840414013619A), Apr 14, 1984: Cessna 421C, Farmington, NM, Substantial damage. Landing gear collapsed during taxi. Contaminant in actuator prevented downlock keys from locking in place.

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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