Accident Boeing 717-231 N935AT,
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Date:Monday 26 October 2009
Time:12:02 LT
Type:Silhouette image of generic B712 model; specific model in this crash may look slightly different    
Boeing 717-231
Owner/operator:Air Tran Airways
Registration: N935AT
MSN: 55069/5019
Total airframe hrs:23031 hours
Engine model:BMW ROLLS BR-700-715C1
Fatalities:Fatalities: 0 / Occupants: 122
Aircraft damage: None
Category:Accident
Location:Pleasant Grove, NC -   United States of America
Phase: En route
Nature:Passenger - Scheduled
Departure airport:Orlando International Airport, FL (MCO/KMCO)
Destination airport:White Plains-Westchester County Airport, NY (HPN/KHPN)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
During cruise descent the captain of the scheduled airline flight handed over control of the airplane to the first officer to make a public address announcement regarding turbulence. He had just turned on the fasten seatbelt sign when they received a resolution advisory (RA) from the onboard traffic alert and collision avoidance system (TCAS). The captain then took back control of the airplane and initiated an avoidance maneuver. During the avoidance maneuver, a flight attendant sustained serious injuries and a child passenger sustained a minor injury.

Review of air traffic control radar data and data from the onboard flight data recorder revealed that 1.5 seconds after the TCAS RA occurred, the captain initiated a series of excessive control inputs which resulted in a positive vertical acceleration of approximately 1.6g. One second after the positive vertical acceleration the airplane sustained a maximum negative vertical acceleration of approximately .2g. A second after the negative vertical acceleration the airplane sustained another positive load of 1.4g after which the acceleration was dampened out. According to the TCAS manufacturer's published guidance, a flight crew should "promptly but smoothly" follow a TCAS RA and since the maneuvers are coordinated between aircraft, the crew should never maneuver in the opposite direction of the advisory. The advisories are always based on the "least amount of deviation from the flight path" while providing safe vertical separation. Typical RAs that would require a maneuver by a flightcrew only requires crew response within 5 seconds and g-forces of ±.25g. Review of the airline's training and guidance materials for the two different types of airplanes the airline operated revealed that this information was included in the training and guidance material for one of the airplane types in their fleet but was not included in the training and guidance materials for the accident airplane type.

Probable Cause: The captain's excessive maneuver in response to a traffic alert and collision avoidance system (TCAS) alert, which resulted in a serious injury to a flight attendant. Contributing to the accident was the operator's inadequate TCAS training and guidance.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: ERA10LA041
Status: Investigation completed
Duration: 1 year and 10 months
Download report: Final report

Sources:

NTSB ERA10LA041

Location

Revision history:

Date/timeContributorUpdates
25-Mar-2024 07:32 ASN Update Bot Added
25-Mar-2024 07:34 ASN Updated [Aircraft type, Nature, Narrative]

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