# NTSB CHI97LA078: Boeing 757-2Q8, N755AT, Chicago, IL, March 2, 1997 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: March 2, 1997, 05:55 local (11:55 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: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 4 serious, 18 minor, 180 uninjured - Status: Completed, report December 8, 1999 - Report: Approved by Office Director - NTSB case key (mKey): 10523 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI97LA078 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/10523/pdf - Page: https://openairdocs.org/ntsb/CHI97LA078 ## Probable cause Clear air turbulence. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight encounter with weather, descent - weather condition - turbulence,clear air (cause) ## Analysis The flight crew had checked weather for the intended flight from Durango, Mexico, to Chicago, Illinois, including a briefing from an arriving pilot who warned of light to moderate turbulence. The airplane encountered clear air turbulence while descending from 26,000 feet to 20,000 feet which was described as severe. When the turbulence was encountered the flight crew and a flight attendant made an announcement for the passengers to return to their seats and shortly after that, the 'Fasten Seatbelt' sign was turned on. Two of the passengers sustaining serious injuries were occupying the lavatory at the time of the turbulence encounter. ## Factual narrative On March 2, 1997, at 0555 central standard time, a Boeing 757-2Q8, N755AT, operating as Mexicana Airlines Flight 199, experienced turbulence approximately 120 miles south of Chicago, Illinois. The international 14 CFR Part 129 flight was descending through 26,000 feet. The flight departed Durango, Mexico, at 0335 with the intended destination of Chicago, Illinois. The airplane sustained no damage; however, of the 202 persons aboard, 18 suffered minor injuries and 4 sustained serious injuries. Visual meteorological conditions prevailed at the destination at the time of the accident. The Captain stated in his written statement that the turbulence began when the airplane descended through 26,000 feet and continued until 20,000 feet. He said that when passing through 26,000 he made an announcement to the passengers to take their seats. He said that during the turbulence he told passengers to fasten their seatbelts. He said that after the turbulence encounter the "Fasten Seatbelt" sign remained on. The First Officer, who was at the controls at the time of the turbulence encounter, said in his written report that descending through 28,000 feet he felt a little turbulence and discussed reducing penetration speed with the Captain, who agreed. He said that from 26,000 to 20,000 feet the airplane encountered severe turbulence with rate of climb reaching a 5,000 foot per minute descent and climb respectively. He said the auto pilot was turned off, and the turbulence lasted about two minutes. He said that while this was happening he told the Captain to turn on the "Fasten Seatbelt" light. He indicated that after the turbulence encounter the Captain took control of the airplane. A flight attendant described the turbulence encounter in her written statement stating that when it started she made an announcement for passengers to return to their seats and fasten their seatbelts. This announcement was given in English and Spanish. She indicated that the two most seriously injured passengers were in the lavatory when the turbulence encounter occurred. The company debriefed the crew. The company stated that the encounter was in clear air and they characterized it as "clear air turbulence." The company reported that the pilots received no previous warning of turbulence while in-flight. They did say that the Captain obtained meteorological information in Durango and talked with an arriving Captain who briefed him on the route conditions stating that he had encountered light to moderate occasional turbulence. The accident occurred on Sunday (March 2nd). Notification was received by the NTSB at 1008 on March 3rd. Prior to receiving notification, the airplane had been inspected by company maintenance personnel while in Chicago on the date of the incident and no external damage was found. The airplane was then returned to service and had made a return trip to Mexico the afternoon of the same day. There was no attempt to isolate the cockpit voice recorder or the digital flight data recorder prior to further operation of the airplane. ## Aircraft - Registration: N755AT (not matched to a registry record) - Reported make and model: Boeing 757-2Q8 - Category: Airplane - Serial number: 24965 - Engines: P&W PW 2040 41300 lbs thrust turbo fan - Damage: No damage - Flight: Part 129 - Registered owner: Mexicana Airlines - Airworthiness certificate: Standard, Transport - Departed: DGO, DURANGO - Destination: ORD, IL - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 56; airline transport, flight instructor; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 19,500 total, 200 in this make and model, 13,500 as pilot in command, 150 in the last 90 days, 50 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Night/dark - Wind: 300° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: 2,500 ft overcast - Temperature: 30 °F, dew point 25 °F - Altimeter: 29.00 inHg - Observed at: ORD, 120 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19970302015999A](https://openairdocs.org/incident/19970302015999A), Mar 2, 1997: Boeing 7572Q8, Danville, IL, Minor damage. Encountered severe turbulence on descent or airport. Turbulence unavoidable(-23) mexicana airlines flight 199, mar 2, 1997, encountered severe turbulence… 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.