# NTSB LAX91LA129: Cessna 421B, N924MD, Tucson, AZ, March 12, 1991

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: March 11, 1991, 18:58 local (Mar 12, 1991, 01:58 UTC)
- Place: Tucson, AZ
- Coordinates: 32.150413, -110.930671 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=32.1504&lon=-110.9307&mi=10
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 3 serious, 3 minor
- Status: Completed, report March 24, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27137
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX91LA129
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27137/pdf
- Page: https://openairdocs.org/ntsb/LAX91LA129

## Probable cause

THE FATIGUE FAILURE OF THE RIGHT ENGINE TURBO EXHAUST CLAMP, AND, THE FAILURE OF THE FLYING PILOT TO COMPLETE THE SINGLE ENGINE EMERGENCY PROCEDURES IN A TIMELY MANNER.  A FACTOR IN THE ACCIDENT WAS THE FAILURE OF THE PILOT IN COMMAND TO ADEQUATELY SUPERVISE THE CONDUCT OF THE FLIGHT.

## Sequence of events

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

- Loss of engine power(partial) - mech failure/malf, takeoff - initial climb
  - 1 engine
  - exhaust system,clamp - fatigue (cause)
  - exhaust system,clamp - failure,total (cause)
- In flight collision with object, descent
  - object - wire,transmission
  - descent - inadvertent
  - emergency procedure - delayed, copilot/second pilot (cause)
  - propeller feathering - delayed, copilot/second pilot (cause)
  - remedial action - delayed, pilot in command (cause)
  - supervision - inadequate, pilot in command (contributing factor)
- In flight collision with terrain/water, maneuvering - turn to landing area (emergency)

## Analysis

THE PLT (PIC) WAS A PART 135 CHECK AIRMAN & WAS OCCUPYING THE RGT SEAT. A 2ND COMPANY PLT WAS IN THE L SEAT TO GET SOME TIME IN THE CESSNA 421. THE 2ND PLT MADE THE TAKEOFF & THE ACFT WAS 10 TO 15 SEC INTO THE INITIAL CLIMB, WHEN A LOSS OF PWR WAS DETECTED IN THE RGT ENG. A 3RD PLT (SITTING IN THE BACK) CALLED OUT THAT HE SAW FIRE COMING FM THE RGT ENG NACELLE. THE PIC STATED THAT THE 2ND PLT 'APPREHENSIVELY ATTEMPT(ED) THE EMERGENCY PROCEDURES & GAVE THE AIRPLANE TO ME AS (THE) AIRSPEED RAPIDLY DECLINED.'  THE PIC SAID SOME PWR LINES WERE DRCTLY AHD & HE ELECTED TO GO UNDER THE WIRES TOWARD A VACANT FLD. THE ACFT COLLIDED WITH THE PWR LINES, THEN IMPACTED THE GND IN THE FLD. AN ON SITE EXAM OF THE ACFT REVEALED THE RGT ENG TURBOCHARGER EXHAUST CLAMP HAD FAILED, ALLOWING EXHAUST GASSES TO FLOW THRU LOUVERS IN THE RGT NACELLE.  NO EVIDENCE OF AN ACTUAL FIRE WAS FND. A METALLURGICAL EXAM OF THE RGT ENG TURBO EXHAUST CLAMP REVEALED IT HAD FAILED FM FATIGUE.

## Aircraft

- Registration: [N924MD](https://openairdocs.org/deregistered/N924MD-2012-10-09), registration cancelled 2012-10-09, S/N 421B0427, built 1973 (OpenAirDocs)
- Reported make and model: CESSNA 421B
- Registry model: [Cessna 421B](https://openairdocs.org/model/cessna-421b) (registry code 2076014) (OpenAirDocs)
- Registry engine: [Continental GTSIO-520-C](https://openairdocs.org/engine/continental-gtsio-520-c) (registry code 17035, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 421B0427
- Engines: CONTINENTAL GTSIO-520-H 375 horsepower reciprocating
- Damage: Substantial damage
- Flight: Positioning, Part 91
- Operator: Deer Valley Aviation, Inc
- Registered owner: Golden Eagle Aviation, Inc
- Destination: SDL, SCOTTSDALE, AZ
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 37; 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: 4,800 total, 400 in this make and model, 4,200 as pilot in command, 180 in the last 90 days, 50 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Dusk
- Wind: 310° at 15 knots
- Visibility: 30 statute miles
- Lowest ceiling: none
- Temperature: -0 °F, dew point -0 °F
- Observed at: TUS, 1 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 19910311005209A](https://openairdocs.org/incident/19910311005209A), Mar 11, 1991: Cessna 421B, Tucson, AZ, Substantial damage. Turbocharger rear clamp broke on takeoff. Lost tailpipe and power right engine,began turn back. Feathered . Hit wire

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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