CEN25LA132

A flight of three U.S. Army helicopters (two Boeing AH-64Es each with a maximum gross weight of 23,000 lbs and one Sikorsky UH-60M with a maximum gross weight of 22,000 lbs) had recently completed refueling operations at the uncontrolled civilian airport. A flight of three Taylorcraft BC-12D airplanes (each with a maximum gross weight of 1,200 lbs) were inbound to land. The pilot of the lead airplane performed radio communication on the common traffic advisory frequency (CTAF) for the flight, and the airport manager relayed to the airplanes that a flight of three helicopters was staged on a taxiway in front of a hangar. The first airplane landed and taxied to its hangar without incident. As the second airplane was turning short final, he observed the helicopters starting to move from their refueling position. The second airplane landed and as it was taxiing to its hangar, the third airplane announced that it was on short final for the runway. The flight of three helicopters, who had repositioned to a different taxiway in a trail formation about 40 meters apart from each other (a Boeing AH-64E helicopter in the lead chalk 1 position, a Boeing AH-64E helicopter in the middle chalk 2 position, and the Sikorsky UH-60M helicopter in the trail chalk 3 position), announced on CTAF that they were going to wait on the inbound third airplane to land before initiating their departure to the east, parallel to the runway. When the departure CTAF announcement was made, the flight of three helicopters reported that there was one airplane in the traffic pattern and another one or two airplanes about two miles away “making their way” to the runway. As the pilot of the second airplane was taxiing to his hangar, the lead helicopter started the takeoff from the taxiway and the second airplane encountered wake turbulence. The left wing was picked up and the airplane came to rest upright about 130° from its original direction. The second airplane did not sustain any damage, and the occupants were not injured. Shortly after, the two remaining helicopters departed from the taxiway. The pilot of the third airplane reported that the radio communication from the helicopters indicated that they planned to taxi to the runway for the takeoff. As the third airplane was on short final, the lead helicopter unexpectedly began the takeoff directly from the taxiway. The pilot reported this takeoff was initiated even though previous radio communications indicated they would wait for all the airplane arrivals to land before their departure. The pilot was concerned that if he executed a go-around this would place his airplane near the helicopters and encounter wake turbulence. The pilot decided to land, as he was also concerned about encountering wake turbulence during the landing. He classified the departure of the helicopters as “unexpected” and “distracting.” During the touchdown to the painted runway numbers, the airplane encountered “gusty wind” like conditions and the pilot haddifficulty maintaining directional control. The airplane departed the runway to left, nosed over, and came to rest inverted on a flat grass field between the runway and the taxiway that the helicopters departed from. The pilot was able to egress from the left door of the inverted airplane without further incident. The third airplane sustained substantial damage to the left wing, the right wing strut, and the empennage. The pilot reported there were no preimpact mechanical malfunctions or failures with the airframe or the engine that would have precluded normal operation. The pilot further reported that while the helicopters previously indicated they would wait until all airplanes had landed before departing, that their decision to depart early introduced a “sudden and unanticipated hazard during a critical phase of flight” and that increased coordination and clarification on the CTAF could have prevented the accident. A postaccident search did not reveal any security camera video footage or CTAF recordings of the accident sequence. According to Federal Aviation Regulation Part 91.113 Right-of-way rules: Except water operations, subpart (g) Landing states, in part; Aircraft, while on final approach to land or while landing, have the right-of-way over other aircraft in flight or operating on the surface, except that they shall not take advantage of this rule to force an aircraft off the runway surface which has already landed and is attempting to make way for an aircraft on final approach. A review of the current U.S. Army Training Circular 3-04.4 Fundamentals of Flight (the July 2022 edition) did not contain any wake turbulence guidance for larger and heavier U.S. Army helicopters operating in close vicinity near smaller and lighter general aviation aircraft at uncontrolled civilian airports.