# NTSB CHI93IA312: British Aerospace 146-300A, N611AW, Chicago, IL, July 21, 1993 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: July 20, 1993, 19:54 local (Jul 21, 1993, 00:54 UTC) - Place: Chicago, IL - Location: 41.8500° N, 87.6501° W: Placed by OpenAirDocs: center of Chicago, IL, within about 9 miles (OpenAirDocs) - Nearby events: https://openairdocs.org/map.md?lat=41.8500&lon=-87.6501&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 8 uninjured - Status: Completed, report October 20, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 9196 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI93IA312 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/9196/pdf - Page: https://openairdocs.org/ntsb/CHI93IA312 ## Probable cause was a crack in the fuel system fuel flow distribution manifold which resulted from an inadequate design by the manufacturer. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, takeoff - initial climb - fuel system,fuel flow divider/distributor - cracked (cause) - acft/equip,inadequate design, manufacturer (cause) - Fire, takeoff - initial climb ## Analysis DURING THE INITIAL CLIMBOUT THE FLIGHT ATTENDANT OBSERVED THE TAILCONE OF THE AIRPLANE'S NUMBER FOUR ENGINE GLOWING. AS THE POWER WAS REDUCED THE GLOW CEASED. THE AIRPLANE RETURNED TO THE DEPARTURE AIRPORT. THE ENGINE WAS INSPECTED AND ITS FUEL MANIFOLD WAS FOUND CRACKED AT THE SCALLOP RADIUS. THE MANUFACTURER MODIFIED THE FUEL MANIFOLD SO THAT ITS WALL WOULD BE THICKER AT THE RADIUS. THE MODIFIED MANIFOLD WAS NOT INSTALLED ON THE INCIDENT AIRPLANE. ## Factual narrative On July 19, 1993, at 2242 central daylight time (cdt), a British Aerospace 146-300A, N611AW, operated by Air Wisconsin, Incorporated, of Appleton, Wisconsin, as flight number 5140, and piloted by an airline transport certificated crew, experienced a fire on the number four engine during initial climb following takeoff from O'Hare International Airport, Chicago, Illinois. Visual meteorological conditions prevailed at the time of the incident. The 14 CFR Part 121 air carrier flight was operating on an IFR flight plan. The pilots, two flight attendants, and 4 passengers reported no injuries. The flight originated from Chicago, Illinois, at 2239 cdt. The captain said that during initial climb following takeoff a flight attendant observed a glow near the end of number four engine jet pipe. He stated that a fire warning light was not observed in the cockpit when the glow was observed by the flight attendant. The glow was no longer observed when the takeoff power setting was reduced to the climb power setting. He stated the difference between takeoff power and climb power settings is a two percent rollback. The airplane continued to its destination. The jet pipe area is not part of the fire/overheat detection and warning system. The detection and warning system is associated with the engine's fan casing bay and core engine assembly. An examination of the number four engine revealed a crack in the right-hand fuel manifold assembly (manifold) and a small hole burned through the engine fairing reinforcement ribs. Damage, similar to flame damage, was observed on the engine fairing skin next to the jet pipe. The manifold has cutouts (scallops) between its mounting bolt holes. The crack was located next to the number nine fuel nozzle, on the radius of the scallop. The metal thickness between the inner wall of the manifold's fuel channel and scallop surface was .042 inch. Company maintenance records showed the manifold had a total time of 7,581 hours and 11,185 cycles on it. The last inspection on the manifold was conducted 1,742 hours and 2,597 cycles before the failure. The engine manufacturer redesigned the manifold with an approximate .085 inch thickness about one year before this incident. Installation of the revised manifold was optional. According to the engine's manufacturer, the fuel manifold was an older design that had thinner metal near the crack. ## Aircraft - Registration: [N611AW](https://openairdocs.org/deregistered/N611AW-2008-02-07), registration cancelled 2008-02-07, S/N E3120, built 1988 (OpenAirDocs) - Reported make and model: BRITISH AEROSPACE 146-300A - Registry model: [British Aerospace BAE 146 SERIES 300A](https://openairdocs.org/model/british-aerospace-bae-146-series-300a) (registry code 1500267) (OpenAirDocs) - Registry engine: [Lycoming ALF-502 SER. series](https://openairdocs.org/engine/lycoming-alf-502-ser-series) (registry code 41580, turbo-jet) (OpenAirDocs) - Category: Airplane - Serial number: E3120 - Airframe hours: 9468 - Engines: LYCOMING ALF 502R 6970 lbs thrust turbo fan - Damage: Minor damage - Fire: In-Flight - Flight: Part 121 - Operator: Air Wisconsin, Inc., doing business as United Express - Registered owner: Air Wisconsin, Inc. - Airworthiness certificate: Standard, Transport - Last inspection: Annual, July 15, 1993, 28 hours before - Destination: ATW, APPLETON, WI - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: unknown, unknown; seat: left ## Weather - Conditions: Visual (VMC), Dusk ## Other investigations on N611AW (1) 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. - [NTSB CHI95IA079](https://openairdocs.org/ntsb/CHI95IA079), Jan 27, 1995: British Aerospace BAE-146-300 (N611AW), Madison, WI, incident, no damage. Probable cause: A fuel leak in the no. 2 engine left fuel manifold segment due to a design defect which led to a fatigue crack. 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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.