# NTSB DCA11FA053: Airbus A319, N801UA, Chillicothe, MO, May 9, 2011 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Field investigation · Final report - Date: May 9, 2011, 04:06 local (09:06 UTC) - Place: Chillicothe, MO - Coordinates: 39.876667, -93.640556 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.8767&lon=-93.6406&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Turbulence encounter](https://openairdocs.org/ntsb-events/360) - Highest injury: Serious injuries - Injuries: 1 serious, 124 uninjured - Status: Completed, report May 28, 2013 - Report: Approved by Office Director - NTSB office: Major Investigations Division - Parties: Federal Aviation Administration - NTSB case key (mKey): 79072 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA11FA053 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/79072/pdf - Page: https://openairdocs.org/ntsb/DCA11FA053 ## Probable cause An inadvertent encounter with unforecast convective turbulence. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Turbulence: convective turbulence](https://openairdocs.org/ntsb-findings/03032020): Environmental issues › Conditions/weather/phenomena · Effect on personnel (probable cause); cases with it: [Airbus Industrie A319-131, 1 case](https://openairdocs.org/ntsb-findings/03032020/cases.md?model=3930317), [All aircraft, 145 cases](https://openairdocs.org/ntsb-findings/03032020/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Windshear or thunderstorm](https://openairdocs.org/ntsb-events/390); cases with it: [Airbus Industrie A319-131, 1 case](https://openairdocs.org/ntsb-events/390/sequence.md?model=3930317), [All aircraft, 224 cases](https://openairdocs.org/ntsb-events/390/sequence.md) - [Enroute-cruise: Turbulence encounter](https://openairdocs.org/ntsb-events/360) (defining event); cases with it: [Airbus Industrie A319-131, 1 case](https://openairdocs.org/ntsb-events/360/sequence.md?model=3930317), [All aircraft, 423 cases](https://openairdocs.org/ntsb-events/360/sequence.md) ## Analysis No adverse weather was forecast for the route. The seatbelt sign was turned off at FL320. The airplane leveled off at a final cruise altitude of 37,000' and the ride was smooth up until the turbulence encounter. Both the captain's and first officer's weather radar was in use before and during the turbulence event, and there was no adverse weather along the route visible on radar. The flight crew received no weather updates from Air Traffic Control, no pilot reports (PIREPS), and there was no traffic along the same route in front of this flight. Evaluation of the winds using FDR data revealed that the aircraft sustained strong and adverse wind fluctuations on all three axes during the turbulence encounter, which included an upwards vertical wind gradient was about 80 knots in a 10 second timeframe. Recorded ground weather radar information revealed that the flight was probably passing over or through the extreme top of a rapidly developing area of convective weather at the time of the turbulence encounter. Although ground based radar reflectivity data indicated that the precipitation rate within this rapidly developing cell at the time was light to moderate, detection of the cell would likely have required active adjustment of the aircraft's weather radar system. However, the flight crew was not actively manipulating the aircraft radar at the time of the event given the lack of severe weather indications. ## Factual narrative HISTORY OF FLIGHT: On May 9, at 0406 CDT, an Airbus A319-131, N801UA, flew through an area of convective turbulence. During the turbulence encounter one flight attendant was seriously injured. None of the other two flight attendants, two pilots, or 120 passengers were injured, and the airplane was undamaged. The airplane was registered to and operated by United Airlines under the provisions of 14 Code of Federal Regulations Part 121 and the flight was designated as a passenger-carrying flight. The flight was operating on an IFR flight rules flight plan. The flight originated at Phoenix Sky Harbor Airport (PHX), Phoenix, Arizona, and landed uneventfully at O'Hare International Airport (ORD), Chicago, Illinois. According to the operator and the pilots, the flight departed PHX for ORD at 23:51 PST on Sunday, May 8, 2011. The first officer was the pilot flying. Takeoff and climb were reported as normal and no adverse weather was forecast for the route. The seatbelt sign was turned off at FL320, approximately 20 minutes after takeoff. The airplane leveled off at a final cruise altitude of 37,000' and the ride was smooth up until the turbulence encounter. There was no adverse weather along the route visible on radar. The captain's navigation/radar display was set to a 40 nm range and the first officer's was set to 160 nm. The radar tilt was set to minus 0.5°. There were no weather updates from Air Traffic Control (ATC), no pilot reports (PIREPS), and there was no traffic along the same route in front of this flight. Approximately 30 minutes prior to initial decent, the captain left the cockpit for a bathroom break. At that time, a flight attendant entered the cockpit, in accordance with the operator's two-person policy. During the captain's break, when the aircraft was approximately about 7 nm north northwest of Chillicothe, MO, the airplane encountered turbulence which caused sudden altitude changes (both positive and negative), coupled with rolling moments. The first officer then disengaged the autothrottles and reduced thrust to slow the airplane down. He then disengaged the autopilot and countered the rolling moment. Shortly thereafter he applied forward yoke to counter the airplanes ascent. The altituded peaked at about 38,000 feet, and a recovery to 37,000 was accomplished. All passengers were seated at the time and there were no passenger injuries. The captain was able to secure himself in the forward cabin crew jumpseat. The flight attendant in the cockpit was thrown off his feet. A flight attendant in the forward galley secured herself under the galley counter. A flight attendant in the aft galley area hit her head on the ceiling and landed on the floor and was seriously injured. The pilots stated that the turbulence lasted approximately 30 seconds and then the ride returned to smooth conditions. The captain returned to the cockpit and the crew communicated with ATC, company dispatch and obtained updates on the injured flight attendant'scondition. A doctor and nurse practitioner attended to the injured flight attendant in the aft galley. The flight continued to Chicago for a normal approach and landing. INJURIES: The aft flight attendant suffered a compression fracture of the L1 vertebrae. METEOROLOGICAL INFORMATION: According to recorded weather radar data, at the time of the event a stationary weather front associated with a low pressure system to the west stretched eastward across central Missouri. The stationary front acted as a lifting mechanism to help thunderstorms to form in the area overnight. Also, cooler upper air temperatures existed in the area, which also helped thunderstorm formation. Recorded ground weather radar information revealed that the flight was probably passing over or through the extreme top of a rapidly developing area of convective weather at 0406 CDT, the time of the turbulence encounter. The first lightning discharge associated with this developing cell occurred 25 seconds after the airplane first encountered turbulence, approximately 6 nautical miles to the left of the flight's ground track. Radar reflectivity indicated that the precipitation rate at the time was light to moderate. FLIGHT RECORDERS: According to the flight data recorder, 0405:46, as the aircraft was cruising at an altitude of about 37,000 feet and 262 knots, there were perturbations recorded in various parameters which lasted around 30 seconds. During that time, the aircraft roll parameter began oscillating and measured a maximum +15 degrees of right roll followed by -10 degrees of left roll 2 seconds later and some slight pitch changes. The acceleration parameters fluctuated over the time period of the disturbance with the vertical acceleration parameter reaching a maximum value of 1.84g's and, 2 seconds later, a minimum vertical acceleration value of -.36g's as well as a minimum lateral acceleration value of .28 g's. The Autopilot 2 parameter transitions from engaged to disengaged at 0406:09. At 0406:33, the Autothrottle System (ATS) Active parameter becomes not active for 5 seconds and at 0407:01, both the ATS Active and ATS Engaged parameters show disengaged. At 0408:04, the autopilot and ATS parameters recorded engaged again. A wind reconstruction based upon the FDR data performed by Airbus revealed that the aircraft sustained strong and adverse wind fluctuations on all three axes during the turbulence encounter. A longitudinal tailwind with gusts up to 80 knots, and a right crosswind with gusts up to 40 knots existed. Also, the upwards vertical wind gradient was about 80 knots in a 10 second timeframe. The cockpit voice recorder was overwritten during the flight. ## Aircraft - Registration: [N801UA](https://openairdocs.org/aircraft/N801UA), registered now, S/N 686, built 1997 (OpenAirDocs) - Reported make and model: AIRBUS A319 (131) - Registry model: [Airbus Industrie A319-131](https://openairdocs.org/model/airbus-industrie-a319-131) (registry code 3930317) (OpenAirDocs) - Registry engine: [IAE V2500SERIES](https://openairdocs.org/engine/iae-v2500series) (registry code 34601, turbo-jet) (OpenAirDocs) - Category: Airplane - Serial number: 686 - Airframe hours: 47316 - Engines: IAE V2522 turbo fan; IAE V2522 turbo fan - Damage: No damage - Flight: Part 121 - Operator: United Airlines, Inc. - Registered owner: United Airlines, Inc. - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, May 6, 2011 - Departed: PHX, Phoenix, AZ - Destination: ORD, Chicago, IL - Flight plan: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, unknown; last flight review April 20, 2010; seat: left; flight hours: 9,000 total, 4,701 in this make and model ## Weather - Conditions: Visual (VMC), Night/dark - Lowest ceiling: none ## 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 20110509010859A](https://openairdocs.org/incident/20110509010859A), May 9, 2011: Airbus Industrie A319-131, Kirksville, MO, No damage. Flight crew was aware during preflight of possible turbulence for route of flight in southern Colorado and northern new Mexico. The aircraft weather radar was… 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.