NTSB Identification: CEN14TA126
14 CFR Part 91: General Aviation
Accident occurred Wednesday, January 29, 2014 in Fort Carson, CO
Probable Cause Approval Date: 09/24/2014
Aircraft: DIAMOND AIRCRAFT IND INC DA20-C1, registration: N959DA
Injuries: 2 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this public aircraft accident report.
According to air traffic control (ATC) audio recordings, a tower controller cleared an airplane for takeoff about 23 seconds after a UH-60 helicopter was cleared for takeoff from a midfield location. The tower controller ensured that a runway separation standard of 3,000 feet was present and did not give a wake turbulence advisory. The flight instructor reported that she was aware of the helicopter’s takeoff and that she perceived adequate separation from the helicopter. The flight instructor incorrectly identified the helicopter as a Bell UH-1, which weighs less than the UH-60. Shortly after takeoff, the airplane encountered the wake vortex of the helicopter and entered a steep left bank. The flight instructor attempted to counteract the left roll with full right aileron inputs, but she was unable to maintain control. The airplane impacted terrain near midfield and came to rest inverted. A review of ATC audio recordings and airplane performance data revealed that the airplane trailed the helicopter by about 48 to 63 seconds at the midfield location and was about 150 to 200 feet above ground level when it encountered the helicopter’s wake vortex.
Current Federal Aviation Administration (FAA) ATC guidance does not require specific wake turbulence separation criteria for a small airplane following a helicopter nor does it require a controller to give a wake turbulence advisory for a small airplane following a helicopter. Current FAA pilot guidance, including the Airman’s Information Manual and an advisory circular on aircraft wake turbulence, also do not recommend separation criteria for a small airplane following a helicopter. After the accident, the FAA issued amended guidance for wake turbulence hazards to pilots and air traffic controllers, including specific wake turbulence separation criteria between small airplanes and helicopters.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The flight instructor’s loss of control after takeoff following a wake turbulence encounter from a preceding helicopter. Contributing to the accident were the flight instructor’s misidentification of the helicopter type and a lack of Federal Aviation Administration wake turbulence separation criteria for a small airplane following a helicopter.
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