On May 6, 2015 at 1426 central daylight time, an Enstrom F-28F, N8011Q, impacted trees while maneuvering over a field near Argyle, Texas. The helicopter sustained substantial damage. The private pilot and flight instructor sustained serious injuries. The helicopter was registered to US Aviation Group LLC and operated by Longhorn Helicopters under Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed the time of the accident. The local flight originated from DTO about 1330.
According to a Federal Aviation Administration (FAA) inspector from the North Texas Flight Standards District Office, the pilot stated he and the flight instructor had flown for approximately 30 minutes prior to the accident. The pilot stated that the helicopter engine seemed to be functioning normally, and he did not recall any unusual power fluctuations or noises. The pilot and flight instructor were practicing confined area takeoffs and had accomplished two confined area takeoffs just preceding the accident with no abnormal issues. During the third confined area takeoff, the helicopter developed power up to 32 inches of manifold pressure and they began the vertical climb to just above tree top level. At that time he stated that they began transition to forward motion and the helicopter began to "settle with power". The pilot stated that as the helicopter began to descend, the flight instructor announced that she "had the controls" and began to attempt increasing power and immediately turned the aircraft around intending to return to the departure point, away from the trees. The helicopter continued to descend and impacted the trees in a slight nose down attitude.
According to the FAA inspector, on-scene examination of the helicopter revealed that it made contact with a group of trees, approximately 10 feet from the pasture in which the confined area takeoff maneuver was initiated. The trees were estimated to be 30 feet in height. Debris was confined to the location in which the aircraft impacted. Fire/rescue personnel removed approximately 30 gallons of fuel from the helicopter, which had a fuel capacity of 40 gallons.
The right side of the cockpit impacted a tree which penetrated up to the right side collective. The bottom of the cockpit area on both sides near the rudder pedals sustained major damage from impact with the ground. The tail boom and engine area sustained minor damage due to impact with trees and the helicopter remained intact although it was resting in approximately a 30 degree angle with the tail boom suspended in a tree to the rear of the crash site. The main rotors were in a high pitch setting and intact. One main rotor had substantial damage from impact with a tree the other two main rotors did have some bending suggesting a largely vertical descent.
The flight instructor stated that she believed that the engine turbocharger waste gate malfunctioned, which prevented them from receiving the extra power required.
No mechanical anomalies that would have precluded normal aircraft operation were noted during the examination.
The required National Transportation Safety Board Pilot/Operator Accident/Incident Report, form 6120, was not received from the private pilot.