# NTSB CHI91IA223: Beech B200, N770M, Greenbay, WI, July 22, 1991

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: July 22, 1991, 09:05 local (14:05 UTC)
- Place: Greenbay, WI
- Coordinates: 44.589401, -88.120361 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.5894&lon=-88.1204&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 8 uninjured
- Status: Completed, report January 27, 1993
- Report: Approved by Office Director
- ADs cited in the narratives: AD 91-18-11 (OpenAirDocs)
- NTSB case key (mKey): 14931
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI91IA223
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14931/pdf
- Page: https://openairdocs.org/ntsb/CHI91IA223

## Probable cause

INADEQUATE AIRFRAME DESIGN, WHICH RESULTED IN THE IN-FLIGHT SEPARATION OF THE LEFT ENGINE'S OUTBOARD AFT UPPER COWL DOOR.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise - normal
  - door,inspection - separation (cause)
  - acft/equip,inadequate airframe, manufacturer (cause)
  - precautionary landing - performed, pilot in command

## Analysis

THE TWIN-ENGINE TURBO PROP AIRPLANE WAS CRUISING AT 8000' MSL, WHEN THE LEFT ENGINE'S OUTBOARD AFT UPPER ACCESSORY CASE COWL DOOR SEPARTED FROM ITS MOUNT.  THE COWL DOOR STRUCK THE TOP SURFACE OF THE LEFT WING (OUTBOARD OF THE ENGINE NACELLE) & PENETRATED THE WING'S FUEL CELL.  THIS RESULTED IN FUEL SIPHONING & PROMPTED THE PILOT TO PERFORM A PRECAUTIONARY ENGINE SHUTDOWN.  THE AIRPLANE WAS LANDED WITHOUT FURTHER INCIDENT.  AIRWORTHINESS DIRECTIVE (AD) 91-18-11 (EFFECTIVE 9/3/91) REQUIRED STRUCTURAL MODIFICATION OF THE AFT UPPER COWL ASSEMBLY DOORS TO PREVENT INFLIGHT SEPARATION.

## Aircraft

- Registration: N770M (not matched to a registry record)
- Reported make and model: BEECH B200
- Category: Airplane
- Serial number: BB1330
- Engines: P&W PT6A-42 840 horsepower turbo prop
- Damage: Minor damage
- Flight: Business, Part 91
- Registered owner: Marshall & Isley Bank
- Departed: MKE, MILWAUKEE, WI
- Destination: GRB, GREENBAY, WI
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 52; airline transport, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; flight hours: 6,800 total, 1,800 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 240° at 7 knots
- Visibility: 3 statute miles
- Lowest ceiling: 8,000 ft broken
- Temperature: -0 °F, dew point -0 °F
- Observed at: GRB, 35 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).

- [Incident 19910722035799I](https://openairdocs.org/incident/19910722035799I), Jul 22, 1991: Beech B200, Green Bay, WI, Minor damage. Aft upper cowl door separated in flight. Shut engine down and landed at destination safely.

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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