# NTSB CHI85IA097: Boeing 727-51, N463US, St. Paul, MN, January 26, 1985

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: January 26, 1985, 14:29 local (20:29 UTC)
- Place: St. Paul, MN
- Coordinates: 44.879558, -93.199569 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.8796&lon=-93.1996&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 61 uninjured
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 12909
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI85IA097
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/12909/pdf
- Page: https://openairdocs.org/ntsb/CHI85IA097

## Sequence of events

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

- Loss of control - in flight, approach
  - compressor assembly - brittle fracture (contributing factor)
  - maintenance,modification - improper, other maintenance personnel (cause)
  - improper use of procedure, other maintenance personnel (cause)
- Loss of engine power(partial) - mech failure/malf, takeoff - initial climb
  - compressor assembly - foreign object
  - precautionary landing - performed, pilot in command
  - aircraft performance,landing capability - inoperative

## Analysis

SHORTLY AFTER TAKEOF, THE AIRCRAFT EXPERIENCED AN UNCONTAINED 7TH TO 8TH STAGE REMOVABLE SLEEVE COMPRESSOR SPACER FAILURE IN THE NUMBER 3 ENGINE. PIECES OF THE SPACER PASSED THROUGH THE NUMBER 2 ENGINES DUCT CAUSING COMPRESSOR STALLS IN THAT ENGINE. THE AIRCRAFT LANDED SUCESSFULLY 9 MINUTES AFTER TAKEOFF USING THE SINGLE GOOD ENGINE. METALLURGICAL ANALYSIS OF THE RECOVERED SPACER PIECES REVEALED THAT CADMIUM EMBRITTLEMENT HAD OCCURRED AROUND AT LEAST ONE TIEROD SLEEVE HOLE ON THE SPACER. THIS EMBRITTLEMENT OCCURRED BECAUSE THE SPACER WAS INCOMPLETELY PLATED WITH NICKLE DURING A SPACER MODIFICATION THAT TOOK PLACE IN 1975. THE INCOMPLETE NICKLE PLATING ALLOWED A SUBSEQUENT CADIUM LAYER TO COME IN CONTACT WITH THE STEEL SPACER, CAUSING THE EMBRITTLEMENT.

## Aircraft

- Registration: [N463US](https://openairdocs.org/deregistered/N463US-2013-09-24), registration cancelled 2013-09-24, S/N 18799, built 1964 (OpenAirDocs)
- Reported make and model: BOEING 727-51
- Registry model: [Boeing 727-51](https://openairdocs.org/model/boeing-727-51) (registry code 1384014) (OpenAirDocs)
- Registry engine: [Pratt & Whitney JT8D-1](https://openairdocs.org/engine/pratt-whitney-jt8d-1) (registry code 52044, turbo-jet) (OpenAirDocs)
- Category: Airplane
- Serial number: 18799
- Engines: P&W JT8D-7B 12600 lbs thrust turbo jet
- Damage: Minor damage
- Flight: Part 121
- Registered owner: Northwest Orient Airlines
- Airworthiness certificate: Standard, Normal
- Departed: MSP
- Destination: DFW, DALLAS, TX
- Flight plan: IFR
- Airport: MSP, Minneapolis/St. Paul Arpt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 47; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 8,452 total, 3,890 in this make and model, 103 in the last 90 days, 59 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Instrument (IMC), Day
- Wind: 240° at 11 knots
- Visibility: 7 statute miles
- Temperature: 18 °F, dew point 5 °F
- Altimeter: 29.00 inHg
- Observed at: MSP, 1 nm away

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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