# NTSB CHI88FA110: Boeing 747-136, Chicago, IL, May 9, 1988

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Field investigation · Final report
- Date: May 9, 1988, 16:35 local (21:35 UTC)
- Place: Chicago, IL
- Location: 41.9807° N, 87.8109° W: Placed by OpenAirDocs from NTSB’s distance and direction from CHICAGO O'HARE INTL (ORD), within about a mile (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=41.9807&lon=-87.8109&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 304 uninjured
- Status: Completed, report June 25, 1990
- Report: Approved by Office Director
- Safety recommendations: Yes
- NTSB case key (mKey): 13943
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI88FA110
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/13943/pdf
- Page: https://openairdocs.org/ntsb/CHI88FA110

## Probable cause

FAILURE OF THE NUMBER THREE FLAP TRACK DUE TO STRESS CORROSION CRACKING. FACTORS CONTRIBUTING TO THIS FAILURE ARE INSUFFICIENT DESIGN OF THE MEMBER AND INADEQUATE INSPECTION AND MAINTENANCE PROCEDURES TO DETECT CRACKS BEFORE THEY PROPAGATE TO A CRITICAL LENGTH.

## Sequence of events

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

- Airframe/component/system failure/malfunction, approach - faf/outer marker to threshold (ifr)
  - flight control,flap attachment - failure,total (cause)
  - maintenance,aaip/progressive program - inadequate, manufacturer (contributing factor)
  - acft/equip,inadequate design, manufacturer (cause)
  - flight control,flap attachment - stress corrosion (cause)
  - maintenance,service bulletin/letter - inadequate, manufacturer (contributing factor)
  - maintenance,compliance with ad - inadequate, faa(other/organization) (contributing factor)

## Analysis

THE ACFT WAS ON FINAL APPROACH TO CHICAGO O'HARE INTER'L AIRPORT WHEN A STRUCTURAL FAILURE OF THE NUMBER THREE FLAP TRACK OCCURRED. THE ACFT SUSTAINED SUBSTANTIAL DAMAGE TO THE LEFT WING, LEFT INBOARD FLAP ASSEMBLY, LEFT INBOARD SPOILERS AND SPOILER SUPPORT BEAM. THE PILOT EXPERIENCED SIGNIFICANT UNCOMMANDED ROLL AND YAW, BUT REGAINED CONTROL OF THE ACFT AND EXECUTED AN UNEVENTFUL LANDING. THE INVESTIGATION HAS REVEALED A HISTORY OF FLAP TRACK CRACKING PROBLEMS ASSOCIATED WITH STRESS CORROSION AND DESIGN INADEQUACY. A DESIGN CHANGE OF THE MEMBER WAS ACCOMPLISHED IN 1971 BY THE MANUFACTURER, BUT FLAP TRACKS OF THE EARLIER DESIGN WERE ALLOWED TO REMAIN IN SERVICE ON 239 AIRCRAFT. THE AIRWORTHINESS DIRECTIVES AND SERVICE BULLETINS APPLICABLE TO THIS PARTICULAR STRUCTURAL MEMBER ARE NOT ADEQUATE IN METHODOLOGY AND PERIODICITY TO ENSURE CRACK DETECTION, AND DO NOT REQUIRE INSPECTION FOR THE CAUSE OF THE CRACK-CORROSION PITS.

## Aircraft

- Registration: GAWND (not matched to a registry record)
- Reported make and model: BOEING 747-136
- Category: Airplane
- Serial number: 19764
- Airframe hours: 1868
- Engines: P&W JT9D-7 40000 lbs thrust turbo fan
- Damage: Substantial damage
- Flight: Part 129
- Operator: British Airways, doing business as British Airways
- Registered owner: British Airways
- Airworthiness certificate: Standard, Transport
- Last inspection: Continuous airworthiness, March 9, 1988
- Departed: EGLL, LONDON, OF
- Destination: ORD
- Flight plan: IFR
- Airport: ORD, Chicago O'Hare, runway 27L, 10,140 × 150 ft, concrete

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 41; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 6,978 total, 1,815 in this make and model, 2,584 as pilot in command, 196 in the last 90 days, 70 in the last 30 days, 8 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 220° at 16 knots, gusting 26
- Visibility: 3 statute miles
- Lowest ceiling: 1,000 ft broken
- Temperature: 55 °F, dew point 55 °F
- Altimeter: 29.00 inHg
- Observed at: ORD, 5 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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