# NTSB CEN09FA094: Bombardier CL-600-2C10, N511MJ, Chicago, IL, December 16, 2008 - Type: NTSB incident investigation - Classification: Incident · No injuries · Field investigation · Final report - Date: December 15, 2008, 22:39 local (Dec 16, 2008, 04:39 UTC) - Place: Chicago, IL - Coordinates: 41.980834, -87.906387 - Nearby events: https://openairdocs.org/map.md?lat=41.9808&lon=-87.9064&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-IFR initial approach: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 32 uninjured - Status: Completed, report September 30, 2009 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Bombardier, FAA, Goodrich, Mesa Airlines, Inc - SAIBs cited in the narratives: [SAIB NM-09-06](https://openairdocs.org/saib/NM-09-06) (OpenAirDocs) - NTSB case key (mKey): 69580 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN09FA094 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/69580/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=69580 - Page: https://openairdocs.org/ntsb/CEN09FA094 ## Probable cause The failure of the left landing gear to extend due to improper maintenance when the landing gear door was replaced. Contributing to the incident was the manufacturer's inadequate maintenance manual instructions. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance/inspections: unscheduled maint checks](https://openairdocs.org/ntsb-findings/01010550): Aircraft › Aircraft handling/service · Incorrect service/maintenance (probable cause); cases with it: [All aircraft, 6 cases](https://openairdocs.org/ntsb-findings/01010550/cases.md) - [Doors: landing gear doors](https://openairdocs.org/ntsb-findings/01035280): Aircraft › Aircraft structures · Incorrect service/maintenance (probable cause); cases with it: [All aircraft, 1 case](https://openairdocs.org/ntsb-findings/01035280/cases.md) - [Doors: landing gear doors](https://openairdocs.org/ntsb-findings/01035280): Aircraft › Aircraft structures · Related maintenance info (probable cause); cases with it: [All aircraft, 1 case](https://openairdocs.org/ntsb-findings/01035280/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) - [Manufacture/production: document/info production](https://openairdocs.org/ntsb-findings/04013020): Organizational issues › Development · Manufacturer (probable cause); cases with it: [All aircraft, 15 cases](https://openairdocs.org/ntsb-findings/04013020/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-IFR initial approach: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing: Landing gear not configured](https://openairdocs.org/ntsb-events/095); cases with it: [All aircraft, 584 cases](https://openairdocs.org/ntsb-events/095/sequence.md) ## Analysis During the landing approach, the landing gear "Gear Disagree" warning message appeared. The flight crew performed the appropriate emergency checklists without success. An emergency landing was conducted with a fully extended nose and right main landing gear, but the left main landing gear was not extended. The pilot reported that he was able to keep the left wing up for only a few seconds before it contacted the runway. The airplane skidded to a stop with the left wing supported by the wing flaps and the outboard leading edge slats. The inspection of the airplane revealed that the landing gear belly fairing was fractured. The inspection further indicated that the left main landing gear door had intruded over the belly fairing and weather seal at the fracture area, and had become "hung up" and was not able to extend to the down position. The clearance between the left landing gear door and the belly fairing was measured while the landing gear was in the stowed position. The investigation revealed that the manufacturer’s Aircraft Maintenance Manual (AMM) did not specify the clearance measurement for zone “E”, which was the zone that corresponded to the fractured belly fairing. A review of the airplane’s maintenance records indicated that the left main landing gear door had been replaced at the manufacturer's heavy maintenance facility in September 2007. A maintenance review revealed that the door was rigged and checked with the use of the aircraft hydraulic pumps instead of the external hydraulic power unit as required by the AMM. As a result of the investigation findings, the following safety actions were taken: 1. On December 23, 2008, Bombardier issued Service Letter CRJ700/900-SL-32-039, “Body Fairing Seal Inspection Common to MLG Inboard Door” to provide operators with guidelines for inspecting the body fairing seal common to the main landing gear inboard doors at the next convenient maintenance opportunity (i.e., 72 hour or 100 flight hours). 2. On December 24, 2008, Bombardier issued Reference Instruction Letter (RIL) No. 1583, "Clarification of clearance for MLG door installation." It stated that it was permissable to use the clearances shown in AMM 32-12-01-220-801-A02 Fig 502 during utilization of AMM 32-12-01-220-801-A01 Figure 501. 3. On January 28, 2009, the Federal Aviation Administration (FAA) issued a Special Airworthiness Information Bulletin (SAIB) No. NM-09-06. The SAIB stated that the FAA “strongly recommends that the affected operators comply with Bombardier Service Letter CRJ700/900-SL-32-039 at the earliest opportunity.” 4. Mesa Airlines conducted a fleetwide inspection of their aircraft and found no other door seal anomalies. Bombardier plans to issue a revised AMM procedure to indicate the proper clearances for zone E. The FAA plans to issue an AD once Bombardier makes the revision to the AMM. ## Factual narrative HISTORY OF FLIGHT On December 15, 2008, at 2239 central standard time (all times cst), a Bombardier CL-600-2C10 (CRJ-700), N511MJ, operated by Mesa Airlines, Inc, dba Air Shuttle Flight 7164, sustained minor damage during a landing gear emergency at Chicago O'Hare International Airport (ORD). The Title 14 Code of Federal Regulations Part 121 passenger flight had departed ORD about 2130 en route to South Bend Regional Airport (SBN), South Bend, Indiana. During the landing approach to SBN, the landing gear "Gear Disagree" warning message appeared. The flight crew performed the appropriate emergency checklists without success. The flight returned to ORD where an emergency landing was conducted on runway 28 (13,000 feet by 150 feet, asphalt). The airplane landed on a fully extended nose and right main landing gear, but the left main landing gear was not extended. The airplane skidded to a stop with the left wing supported by the wing flaps and the outboard leading edge slats. The 2 pilots, 2 flight attendants, and 28 passengers were not injured, and they departed the airplane through the main cabin door. Night visual meteorological conditions prevailed at the time of the incident. An instrument flight rules (IFR) flight plan was filed. The pilot reported that he was able to keep the left wing up for only a few seconds before it contacted the runway. He maintained runway centerline during the landing and brought the airplane to a complete stop on the runway. The pilot reported that the flight attendants evacuated the passengers, and the emergency responders were on the scene immediately to secure the airplane and evacuate the passengers. PERSONNEL INFORMATION The pilot was an airline transport pilot with single-engine, multi-engine, and instrument airplane ratings. He was a certified flight instructor in single-engine and multi-engine airplanes, and an airplane instrument instructor. He held a first-class medical certificate that was issued on June 23, 2008. He reported a total of 3,100 flight hours with 570 hours in the Bombardier CL-600-2C10. The co-pilot was a commercial pilot with single-engine, multi-engine, and instrument airplane ratings. He was a certified flight instructor in single-engine and multi-engine airplanes, and an airplane instrument instructor. He reported a total of 1,450 flight hours with 210 hours in the Bombardier CL-600-2C10. AIRCRAFT INFORMATION The airplane was a Bombardier CL-600-2C10, serial number 10104, equipped with two General Electric CF34 engines. The left engine was a CF34-8C1 and the right was a CF34-8C5B. The airplane seated 64 and had a maximum gross weight of 75,250 pounds. The last continuous airworthiness inspection was conducted on December 13, 2008. The airplane had a total time of 14,596 hours. METEOROLOGICAL CONDITION At 2253, the surface weather observation at ORD was: Wind 360 at 10 knots, visibility 10 miles, few clouds at 2,100 feet, sky broken at 20,000 feet, temperature -12 degrees Celsius (C), dewpoint -17 degrees C, altimeter 30.59 inches of Mercury. FLIGHT RECORDERS The cockpit voice recorder (CVR) was sent to the National Transportation Safety Board’s (NTSB) Vehicle Recorder Division Audio Laboratory for download. The CVR recorded 30 minutes of cockpit voice communications. A summary of key events recorded on the CVR follows: At 22:08:58 - Start of recording. At 22:09:18 - Captain declared an emergency. At 22:09:42 - Captain took the flight controls. At 22:13:37 - Captain briefed flight attendants. Aircrew discussed evacuation door and safest location for passengers during landing. At 22:16:25 - Lead flight attendant briefed passengers on emergency. Crew continued with emergency checklist and secured loose equipment in the cockpit. At 22:18:27 - First officer reviewed entire checklist for familiarity. At 22:20:16 - Captain directed first officer to double-check the completed checklist items. At 22:20:59 - Discussion of landing technique At 22:22:24, Discussion of completed manual extension procedure At 22:23:57 - First officer reviewed emergency items to be accomplished after landing. At 22:25:54 - Captain briefed flight attendants on unlocking the cockpit door, depressurization, the brace command, and evacuation signal. At 22:28:24 - Crew reviewed emergency checklist items for approach and landing. At 22:28:25 - Lead flight attendant briefed passengers in detail. At 22:28:54 – Aircraft cleared for the instrument approach. At 22:33:34 - First officer notified company operations of emergency. At 22:35:55 - Cleared to land and told equipment was standing by. At 22:38:26 - Captain disconnected the autopilot. At 22:38:35 - Flight attendant gave brace command. At 22:39:07 - Sound similar to aircraft touchdown. At 22:39:57 - Captain gave command to evacuate. At 22:40:02 - End of recording. The flight data recorder (FDR) was sent to the NTSB Vehicle Recorder Division for download. The data indicated that after takeoff, the weight-on-wheels (WOW) parameters for the left, right, and nose landing gear all transitioned from “ground” to “air”. Approximately 22 minutes later, while the aircraft was in a descent, the gear down and locked parameters for the right and nose gear transitioned to down and locked, but the left parameter did not. The Gear Disagree and master warning parameters also activated at this time. The data indicated that the gear cycled and 3 minutes later, the right and nose gear parameters again showed “down and locked” while the left gear parameter did not. There was an associated master warning and Gear Disagree indication. The down and locked states and the Gear Disagree indication stayed active for the next 38 minutes until landing. Upon touchdown, the WOW right and nose parameters transitioned from “air” to “ground”, but the left gear parameter did not change state. After the aircraft came to rest, the roll angle on the FDR measured –9 degrees to the left. WRECKAGE AND IMPACT INFORMATION An on-site inspection of theairplane was conducted at a hangar facility at ORD. The inspection revealed that the left main landing gear door had gouge marks on the door, and the corresponding area of the belly fairing was fractured. The left landing gear door to belly fairing interface examination revealed that the screws used to secure the weather seal retainer on the belly fairing matched the gouge marks found on the left main landing gear door. The fractured belly fairing was speed taped into its original contoured position. With the airplane on jacks, the landing gear were raised into the stowed position. The left main landing gear door was found to be intruding over the belly fairing. When the landing gear was selected down, the left landing gear door forward edge penetrated the belly fairing fracture (held in place by the speed tape) and the left landing gear momentarily hesitated before breaking through the speed tape and extending to its down and locked position. The left landing gear door was examined and no new gouge marks were noted. The screws holding the belly fairing seal passed over the same gouge marks when the gear door penetrated the fractured belly fairing. The examination of the left belly fairing weather seal at the fracture area revealed black marks parallel to the seal that were consistent with heavy rubbing with the gear door. The weather seal contained an embedded metal strip in the seal for rigidity. The clearance between the left landing gear door and the belly fairing was measured while the landing gear was in the stowed position. It was noted that the manufacturer’s Aircraft Maintenance Manual (AMM) task 32-12-01-220-801-A01 did not specify any rigging criteria for zone “E”, which was the zone that corresponded to the fractured belly fairing. TESTS AND RESEARCH The left main landing gear retraction actuator and the Proximity Sensor Electronic Unit (PSEU) were removed from the airplane and sent to their respective manufacturers for testing. The functional tests revealed that both components operated within specifications when functionally bench tested. ADDITIONAL INFORMATION A review of the airplane’s maintenance records indicated that the left main landing gear door had been replaced in September 2007 because the original door was lost in flight. The maintenance records indicated that the door was replaced at the manufacturer’s heavy maintenance facility. The manufacturer reviewed all maintenance records of the incident door and interviewed maintenance personnel involved in the replacement of the door. The maintenance review revealed that the door was rigged and checked with the use of the aircraft hydraulic pumps instead of the external hydraulic power unit as required by AMM Task 32-12-01-220-801 (Config A01). On December 23, 2008, the aircraft manufacturer issued Service Letter CRJ700/900-SL-32-039, “Body Fairing Seal Inspection Common to MLG Inboard Door” to provide operators with guidelines for inspecting the body fairing seal common tothe main landing gear inboard doors at the next convenient maintenance opportunity (i.e., 72 hour or 100 flight hours). On January 28, 2009, the Federal Aviation Administration (FAA) issued a Special Airworthiness Information Bulletin (SAIB) No. NM-09-06. The SAIB stated that the FAA “strongly recommends that the affected operators comply with Bombardier Service Letter CRJ700/900-SL-32-039 at the earliest opportunity.” ## Aircraft - Registration: N511MJ (not matched to a registry record) - Reported make and model: BOMBARDIER CL-600-2C10 - Category: Airplane - Serial number: 10104 - Airframe hours: 14596 - Engines: General Electric CF34-8C1 13790 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Operator: Mesa Airlines, Inc - Registered owner: First Union National Bank Trustee - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, December 13, 2008 - Departed: ORD, Chicago, IL - Destination: ORD, Chicago, IL - Flight plan: IFR - Airport: ORD, Chicago O'Hare International, runway 28, 13,000 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 27; injuries: none; airline transport, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review September 12, 2008; seat: left; flight hours: 3,100 total, 570 in this make and model, 1,750 as pilot in command, 150 in the last 90 days, 40 in the last 30 days, 5 in the last 24 hours - Co-pilot; age 48; injuries: none; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review July 18, 2008; seat: right; flight hours: 1,450 total, 210 in this make and model, 900 as pilot in command, 210 in the last 90 days, 10 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Night - Wind: 360° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: 20,000 ft broken - Temperature: 10 °F, dew point 1 °F - Altimeter: 30.59 inHg - Observed at: ORD ## 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 20081215852789I](https://openairdocs.org/incident/20081215852789I), Dec 15, 2008: Cndair CL6002C10, Chicago, IL, Minor damage. N511MJ, a Canadair crj CL-600-2C10 (CRJ700) operating as mesa airlines flight 7164 (dba untited express) departed Chicago O'Hare intn'l airport (ord) on a… ## Docket (25 files) The files NTSB released with the investigation on August 13, 2009, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=69580. 16.0 MB in all. - Flight Data Recorder 10 - Factual Report of Group Chairman (item 1, .PDF, 125 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40312957&FileExtension=.PDF&FileName=Flight%20Data%20Recorder%2010%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF - Flight Data Recorder 10 - Attachment 1 FDR Tabular Data (item 2, .CSV, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40312958&FileExtension=.csv&FileName=Flight%20Data%20Recorder%2010%20-%20Attachment%201%20FDR%20Tabular%20Data-Master.csv - Cockpit Voice Recorder 12 - Specialist's Factual Report (item 3, .PDF, 187 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315529&FileExtension=.PDF&FileName=Cockpit%20Voice%20Recorder%2012%20-%20Specialist%27s%20Factual%20Report-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 4, .PDF, 493 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315530&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Witness Statements (item 5, .PDF, 75 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315531&FileExtension=.PDF&FileName=Witness%20Statements-Master.PDF - FAA SAIB NM-09-06 (item 6, .PDF, 79 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315532&FileExtension=.PDF&FileName=FAA%20SAIB%20NM-09-06-Master.PDF - NTSB Memorandum Concerning PSEU Examination (item 7, .PDF, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315533&FileExtension=.PDF&FileName=NTSB%20Memorandum%20Concerning%20PSEU%20Examination-Master.PDF - Bombardier Service Letter SL-32-09 (item 8, .PDF, 121 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315534&FileExtension=.PDF&FileName=Bombardier%20Service%20Letter%20SL-32-09-Master.PDF - Bombardier Reference Instruction Letter - RIL #1583 (item 9, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315535&FileExtension=.PDF&FileName=Bombardier%20Reference%20Instruction%20Letter%20-%20RIL%20%231583-Master.PDF - Maintenance Manual Pages (item 10, .PDF, 180 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315538&FileExtension=.PDF&FileName=Maintenance%20Manual%20Pages-Master.PDF - Maintenance Records (item 11, .PDF, 153 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315539&FileExtension=.PDF&FileName=Maintenance%20Records-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 12, .PDF, 406 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315541&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 13, .PDF, 120 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315542&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Master.PDF - Photo 1. View of Aircraft on the Runway (item 14, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315544&FileExtension=.PDF&FileName=Photo%201.%20%20View%20of%20Aircraft%20on%20the%20Runway-Master.PDF - Photo 2. Left Side of Belly Fairing (item 15, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315546&FileExtension=.PDF&FileName=Photo%202.%20%20Left%20Side%20of%20Belly%20Fairing-Master.PDF - Photo 3. Broken Piece of Belly Fairing (item 16, .PDF, 993 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315547&FileExtension=.PDF&FileName=Photo%203.%20%20Broken%20Piece%20of%20Belly%20Fairing-Master.PDF - Photo 4. Left Landing Gear Door Being Raised (item 17, .PDF, 982 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315556&FileExtension=.PDF&FileName=Photo%204.%20%20Left%20Landing%20Gear%20Door%20Being%20Raised-Master.PDF - Photo 5. Overlap of Left Landing Gear Door and Fairing (item 18, .PDF, 992 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315557&FileExtension=.PDF&FileName=Photo%205.%20%20Overlap%20of%20Left%20Landing%20Gear%20Door%20and%20Fairing-Master.PDF - Photo 6. Speed Tape Over the Belly Fairing Tear (item 19, .PDF, 996 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315558&FileExtension=.PDF&FileName=Photo%206.%20%20Speed%20Tape%20Over%20the%20Belly%20Fairing%20Tear-Master.PDF - Photo 7. Landing Gear in Retracted Position (item 20, .PDF, 962 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315559&FileExtension=.PDF&FileName=Photo%207.%20%20Landing%20Gear%20in%20Retracted%20Position-Master.PDF - Photo 8. Landing Gear Door on the Right Side of Aircraft (item 21, .PDF, 992 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315560&FileExtension=.PDF&FileName=Photo%208.%20%20Landing%20Gear%20Door%20on%20the%20Right%20Side%20of%20Aircraft-Master.PDF - Photo 9. Landing Gear Door Clearance to Fairing (item 22, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315561&FileExtension=.PDF&FileName=Photo%209.%20%20Landing%20Gear%20Door%20Clearance%20to%20Fairing-Master.PDF - Photo 10. Landing Gear Door Clearance to Fairing (item 23, .PDF, 962 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315563&FileExtension=.PDF&FileName=Photo%2010.%20%20Landing%20Gear%20Door%20Clearance%20to%20Fairing-Master.PDF - Photo 11. Landing Gear Door Breaking Through the Speed Tape (item 24, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315564&FileExtension=.PDF&FileName=Photo%2011.%20%20Landing%20Gear%20Door%20Breaking%20Through%20the%20Speed%20Tape-Master.PDF - Photo 12. Piece of Torn Fairing Seal (item 25, .PDF, 993 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40315566&FileExtension=.PDF&FileName=Photo%2012.%20%20Piece%20of%20Torn%20Fairing%20Seal-Master.PDF From the NTSB's public API. 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