# NTSB DCA10IA082: Boeing 767-322, N644UA, Chicago, IL, August 4, 2010 - Type: NTSB incident investigation - Classification: Incident · Minor injuries · Incident investigation · Final report - Date: August 4, 2010, 15:47 local (20:47 UTC) - Place: Chicago, IL - Coordinates: 41.585277, -87.542503 - Nearby events: https://openairdocs.org/map.md?lat=41.5853&lon=-87.5425&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) - Highest injury: Minor injuries - Injuries: 6 minor, 184 uninjured - Status: Completed, report March 30, 2020 - Report: Approved by Office Director - NTSB office: Major Investigations Division - NTSB case key (mKey): 76871 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA10IA082 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/76871/pdf - Page: https://openairdocs.org/ntsb/DCA10IA082 ## Probable cause the brake fire after landing was caused by hydraulic fluid leaking on to hot brakes. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Environmental issues](https://openairdocs.org/ntsb-findings/03040000): Environmental issues › Task environment · Effect on equipment (probable cause); cases with it: [Boeing 767-322, 1 case](https://openairdocs.org/ntsb-findings/03040000/cases.md?model=1385200), [All aircraft, 7 cases](https://openairdocs.org/ntsb-findings/03040000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-landing roll: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) (defining event); cases with it: [Boeing 767-322, 3 cases](https://openairdocs.org/ntsb-events/150/sequence.md?model=1385200), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md) - [Other: Evacuation](https://openairdocs.org/ntsb-events/460); cases with it: [Boeing 767-322, 1 case](https://openairdocs.org/ntsb-events/460/sequence.md?model=1385200), [All aircraft, 103 cases](https://openairdocs.org/ntsb-events/460/sequence.md) - [Other: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330); cases with it: [Boeing 767-322, 2 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=1385200), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) ## Analysis Flight 949 conducted a normal landing under maximum landing weight and the crew did not receive any warnings or cautions. There were no system anomalies found except for the damaged left-hand brake assembly. Examination of the left brake assembly found that it caught fire due to catalytic oxidation, most likely as a result of the carbon disk being exposed to deicing fluid. The catalytic oxidation allowed the pistons from the brake housing to punch through the softened pressure plate and contact the rotor resulting in piston displacement, possible piston bushing damage and hydraulic fluid leakage. When the 2R slide was unpacked at the manufacturer to determine why it did not fully inflate during the evacuation, the aspirator was found unattached. This was likely removed when the slide was packed for shipping because the slide would not have even partially inflated if it was not installed during the evacuation. When the slide was laid out, the two missing portions of the aspirator spider arms were found within the slide. Analysis of the fracture surfaces on both spider arms found that each had preexisting cracks. These preexisting cracks were stress risers that reduced the strength of the arms. Since the fracture faces contained no evidence of fatigue, the two arms fractured during slide inflation sequence which caused the slide to not properly inflate during the evacuation. The preexisting cracks most likely occurred during the manufacturing process. ## Factual narrative On August 4, 2010, at about 1547 central daylight time, the flight crew of United flight 949, a Boeing B767-322, N644UA, initiated an evacuation after being informed by air traffic control (ATC) that the airplane's left main landing gear was on fire after landing at Chicago O'Hare International Airport (KORD), Chicago, Illinois. Twelve crew and 178 passengers were on board, and 6 minor injuries occurred during the evacuation. The flight was operating under 14 Code of Federal Regulations Part 121 as a scheduled international passenger flight from Heathrow International Airport (LHR), London, United Kingdom. Post incident inspection revealed that the left main landing gear brake piston housing had ruptured, and the 2R (right aft) emergency evacuation slide did not fully inflate. The brake assembly and slide were both removed and shipped to their respective manufacturers for examination. Brake assembly The examination of the brake assembly revealed evidence of catalytic oxidation, which occurs when premature oxidation of the carbon disks are exposed to contaminants which can accelerate the oxidation process. According to Honeywell, runway deicer fluid has been known to cause catalytic oxidation on carbon disks. Oxidation occurs in localized regions and can lead to softening and loss of disk strength. Catalytic oxidation is a known phenomenon and is addressed by Boeing service letter 767-SL-32-106, dated January 2009, a Honeywell service bulletin 2612412-32-006, dated February 12, 2010, and FAA SAIB NM 08-27. After the event, United inspected all of their 767-300 installed brakes for evidence of catalytic oxidation. None of the 35 aircraft inspected had evidence of catalytic oxidation. United AMM767-32-41-08 Main gear wheel brakes inspection/check dated June 6, 2009 did not contain any inspection criteria for carbon brake oxidation. Although Boeing AMM dated April 2009 did contain carbon brake oxidation criteria in addition to sketches showing areas and examples of oxidation damage. United revised their AMM to include Boeing AMM content on carbon brake oxidation. United also updated component maintenance manual (CO-65-32-43-06-JD) with the requirements of servicing 767 brakes in accordance with Honeywell SB 2612412-32-006. In addition, installing a backing plate during overhaul as called out in the SB. Slide examination The failed slide was sent to the manufacturer for examination. When the slide was unpacked, the upper chamber aspirator was not installed on the slide and that the "spider" in the aspirator was damaged with two pieces missing. During slide inflation and examination, the two missing pieces of the spider were recovered from within the slide. The upper aspirator assembly and two fractured arm portions of the spider were sent to the NTSB materials laboratory for further examination. Examination of the two fractured arms of the spider portion of the aspirator found that both contained a preexisting crack. Further examination revealed thefracture face contained ductile dimple features typical of overstress separation. The fracture face contained no evidence of crack arrest marks (fatigue cracking). ## Aircraft - Registration: [N644UA](https://openairdocs.org/aircraft/N644UA), registered now, S/N 25094, built 1991 (OpenAirDocs) - Reported make and model: BOEING 767-322 - Registry model: [Boeing 767-322](https://openairdocs.org/model/boeing-767-322) (registry code 1385200) (OpenAirDocs) - Registry engine: [Pratt & Whitney PW4000 series](https://openairdocs.org/engine/pratt-whitney-pw4000-series) (registry code 52119, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 25094 - Airframe hours: 82012 - Engines: P&W PW4000 SER 60000 lbs thrust turbo fan; P&W PW4000 SER 60000 lbs thrust turbo fan - Damage: Minor damage - Fire: On-Ground - Flight: Part 121 - Operator: United - Registered owner: Wells Fargo Bank Northwest Na Trustee - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, May 28, 2010 - Departed: LHR, London - Destination: ORD, Chicago, IL - Flight plan: IFR - Airport: ORD, Chicago O'Hare Intl, runway 27L, 7,967 × 150 ft, concrete - Equipment: Stall warning system, Data recorder ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; injuries: none; commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, unknown; last flight review March 1, 2009; seat: left; restraint: 4-point; flight hours: 8,962 total, 8,962 in this make and model - Co-pilot; age 47; injuries: none; airline transport, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, unknown; last flight review February 1, 2009; seat: right; restraint: 4-point; flight hours: 5,985 total, 5,985 in this make and model ## Weather - Conditions: Visual (VMC), Day ## 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 20100804040569I](https://openairdocs.org/incident/20100804040569I), Aug 4, 2010: Boeing 767-322, Chicago, IL, Minor damage. During landing rollout rwy 27R the number two (2) front brake caught fire. Aircraft exited rwy onto rwy 22R where they initiated a passenger (pax) evacuation.… ## Other investigations on N644UA (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 DCA15WA024](https://openairdocs.org/ntsb/DCA15WA024), Nov 4, 2014: Boeing 767 322 (N644UA), Lima, Peru, incident, no damage 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.