# NTSB CHI86FA119: Boeing 737-222, N9054U, Chicago, IL, April 8, 1986

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Field investigation · Final report
- Date: April 8, 1986, 13:19 local (19:19 UTC)
- Place: Chicago, IL
- Location: 41.9769° N, 87.9081° W: Placed by OpenAirDocs at CHICAGO O'HARE INTL (ORD), within about a mile (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=41.9769&lon=-87.9081&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor, 113 uninjured
- Status: Completed, report January 25, 1988
- Report: Approved by Office Director
- NTSB case key (mKey): 13252
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI86FA119
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/13252/pdf
- Page: https://openairdocs.org/ntsb/CHI86FA119

## Sequence of events

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

- Main gear collapsed, landing - roll
  - landing gear,main gear - fatigue (cause)
  - procedures/directives - not followed, company maintenance personnel (cause)

## Analysis

THE LEFT MAIN LANDING GEAR COLLAPSED MOMENTS AFTER TOUCHDOWN. WINDS AS REPORTED BY THE TWR WERE FROM 350 DEGS AT 19 KTS GUSTING TO 29 KTS. THE CAPTAIN AND COPILOT REPORTED THE TOUCHDOWN WAS NORMAL. THE 3 FLIGHT ATTENDANTS SAID THE AIRCRAFT LANDED HARD AND STARTED SHAKING VERY BADLY. THE FLIGHT ATTENDANTS ALSO REPORTED THAT THE PREVIOUS 2 LANDINGS HAD BROUGHT A GREAT DEAL OF VIBRATING/SHAKING TO THE AIRCRAFT. THE LEFT MAIN LANDING GEAR TEE BOLT WAS FOUND SEPARATED. METALLURGICAL EXAMINATION OF THE TEE BOLT SHOWED THE FRACTURE EMANATED FROM A SHALLOW PREEXISTING CRACK IN THE DRAG BRACE BEARING SURFACE RADIUS THAT THE METALLURGIST FOUND TO BE SHARPER THAN DESIRED. THE COLLAPSE OF THE LANDING GEAR IS CONSIDERED RELATED TO THE FRACTURED TEE BOLT. THE SAFETY BOARD IS UNABLE TO DETERMINE WHETHER OTHER EVENTS, CIRCUMSTANCES OR CONDITIONS WERE PRESENT THAT CONTRIBUTED TO THE TEE BOLT FAILURE IN THIS INSTANCE. THE OPERATOR HAS AMENDED THEIR REPAIR SPECIFICATIONS FOR THE TEE BOLTS.

## Aircraft

- Registration: [N9054U](https://openairdocs.org/deregistered/N9054U-1999-07-16), registration cancelled 1999-07-16, S/N 19935 (OpenAirDocs)
- Reported make and model: BOEING 737-222
- Registry model: [Boeing 737-222](https://openairdocs.org/model/boeing-737-222) (registry code 1384473) (OpenAirDocs)
- Category: Airplane
- Serial number: 19935
- Airframe hours: 32714
- Engines: P&W JT8D-9 14500 lbs thrust turbo jet
- Damage: Substantial damage
- Fire: On-Ground
- Flight: Part 121
- Operator: United Airlines
- Registered owner: United Airlines
- Airworthiness certificate: Standard, Transport
- Departed: OMA, OMAHA, NE
- Flight plan: IFR
- Airport: ORD, Chicago-O'Hare Int'L, runway 27R, 7,416 × 150 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 53; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 11,400 total

## Weather

- Conditions: Visual (VMC), Day
- Wind: 300° at 15 knots
- Visibility: 15 statute miles
- Lowest ceiling: 3,500 ft broken
- Temperature: 54 °F, dew point 28 °F
- Altimeter: 29.00 inHg
- Observed at: ORD

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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