# NTSB DEN84MA247: Cessna 421C, N6231G, Fort Lupton, CO, August 1, 1984

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Major investigation · Final report
- Date: August 1, 1984, 16:35 local (22:35 UTC)
- Place: Fort Lupton, CO
- Coordinates: 40.08086, -104.80091 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.0809&lon=-104.8009&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 3 fatal
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 16501
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN84MA247
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/16501/pdf
- Page: https://openairdocs.org/ntsb/DEN84MA247

## Sequence of events

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

- In flight encounter with weather, cruise - normal
  - flight into known adverse weather - continued, pilot in command (cause)
  - weather condition - clouds (contributing factor)
  - weather condition - thunderstorm (contributing factor)
  - weather condition - rain (contributing factor)
  - weather condition - icing conditions (contributing factor)
  - wing - ice (cause)
- Loss of control - in flight, cruise
  - in-flight planning/decision - improper, pilot in command (cause)
  - stall - inadvertent, pilot in command (cause)
- Airframe/component/system failure/malfunction, descent - uncontrolled
  - design stress limits of aircraft - exceeded, pilot in command (cause)
  - wing - overload
  - fuel system,tank - overload
- Fire/explosion, descent - uncontrolled
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

DURING A PREFLT WX BRIEFING, THE PLT WAS ADVISED OF THUNDERSTORMS & INTENSE RAIN SHOWERS ON THE ROUTE OF FLT. HOWEVER, HE FILED AN IFR FLT PLAN & TOOK OFF. DURING FLT, THE ATC CONTROLLER ADVISED THE PLT OF A LEVEL 6 CELL AHEAD & NOTED THAT HE HAD NO REPORT ON ITS TOP. THE PLT REPORTED THAT HE WAS 'NOT SHOWING ANYTHING' ON HIS RADAR. ATTEMPTS WERE MADE TO DEVIATE. APRX 20 MIN LATER, THE PLT REPORTED THE ACFT WAS ENCOUNTERING ICING CONDITIONS & WAS LOSING ALT. AFTER ANOTHER 1 MIN & 38 SEC, HE REPORTED 'WE'RE GOING IN.' SUBSEQUENTLY, AN IN-FLT BREAKUP OCCURRED. THE WRECKAGE WAS FOUND SCATTERED OVER A 1/2 MI AREA. AN EXAM REVEALED THAT THE OUTBOARD WING PANELS HAD FAILED IN FLT. WITNESSES REPORTED SEEING EITHER SMOKE OR FIRE IN FLT BEFORE THE ACFT CRASHED. EVIDENCE OF AN ELECTRICAL DISCHARGE WAS FOUND ON THE OUTBOARD PORTION OF THE RIGHT WING. HOWEVER, THE PLT HAD NOT MENTIONED ANY ENCOUNTER WITH LIGHTNING ON THIS FLT. NO EVIDENCE OF METAL FATIGUE WAS FOUND.

## Aircraft

- Registration: [N6231G](https://openairdocs.org/deregistered/N6231G-1991-08-15), registration cancelled 1991-08-15, S/N 421C0262 (OpenAirDocs)
- Reported make and model: CESSNA 421C
- Registry model: [Cessna 421C](https://openairdocs.org/model/cessna-421c) (registry code 2076016) (OpenAirDocs)
- Category: Airplane
- Serial number: 421C0262
- Airframe hours: 23799
- Engines: CONTINENTAL GTSIO-520-L 375 horsepower reciprocating
- Damage: Destroyed
- Fire: Both
- Flight: Executive/Corporate, Part 91
- Registered owner: Brister, Inc.
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, December 13, 1983, 2,099 hours before
- Departed: AMA, AMARILLO, TX
- Destination: CPR, CASPER, WY
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 63; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; toxicology performed; flight hours: 4,000 total

## Weather

- Conditions: Visual (VMC), Day
- Wind: 160° at 8 knots
- Visibility: 8 statute miles
- Lowest ceiling: 4,000 ft broken
- Temperature: 72 °F, dew point 61 °F
- Altimeter: 30.00 inHg
- Observed at: DEN, 28 nm away

## 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 19840801036589A](https://openairdocs.org/incident/19840801036589A), Aug 1, 1984: Cessna 421C, Fort Lupton, CO, Destroyed, 2 fatal. Explosion, fire and airframe failure in flight in area of thunderstorms. Radar attenuation due to ice on radome.

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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