Cessna 172D N2755U accident near Fairhope, Alabama

Probable cause

The pilot’s failure to maintain adequate separation from a helicopter during the approach to landing, which resulted in an encounter with the helicopter’s trailing vortices, a loss of airplane control, and impact with terrain.

NTSB analysis

The pilot reported that the airplane entered the downwind leg of the traffic pattern behind a large helicopter and that he followed the helicopter closely in the traffic pattern. While on short final approach, the airplane remained behind the helicopter as the helicopter was terminating its approach about three-quarters down the runway. When the airplane was about 30 ft above the approach end of the runway, it banked and pitched suddenly, and it then impacted the ground. The pilot reported no mechanical malfunctions or failures with the airplane that would have precluded normal operation nor were any found during a postaccident examination of the wreckage. A simulation modeling the helicopter's trailing vortex-generating tendencies showed that vortices of significant strength were likely present at the airplane's reported position at the time of the upset. If the pilot had maintained adequate separation from the large helicopter during the approach to landing, the airplane likely would not have encountered the trailing vortices that caused the loss of airplane control.

Text from the NTSB. Open the NTSB docket for ERA14LA147 for the full record.