Bethlehem, GA, USA
N8180H
Hiller UH-12A
The commercial pilot attempted a downwind departure at or about maximum gross weight in a very tight landing zone with high obstacles, forcing the pilot to use rotor energy to gain altitude which would have slowed rotor RPM below safe operating limits. With a tailwind the engine had insufficient power for the helicopter to reach transitional lift. Once the pilot determined that he could not regain rotor speed, he would have selected an area in the woods to try and descend. Rotor RPM would have continued to decay and the pilot would have initiated an Auto-Rotation. The pilot closed the throttle as noted by the crushed throttle linkage. The tail-rotor descended into the trees as evidenced by impact marks to the leading edge of the tail-rotor blades. The engine was still developing power to the rotor system as observed in the twisting of the tail-rotor drive shaft aft of the tail-rotor universal joint. The helicopter descended through the trees vertically and nosed down when the main rotor blades exited the helicopter. The metal strip on the main rotor blades contacted the tail boom at the rear universal joint of the tail rotor drive shaft. The helicopter impacted the ground. The transmission and rotor system crushed the flight deck. Examination of the helicopter found no preimpact mechanical failure or malfunctions that would have prevented the helicopter from operating properly.
On February 24, 2007, about 1508 eastern standard time, a Hiller UH-12A helicopter, N8180H, collided with the ground during takeoff from a private enclosed landing site, in Bethlehem, Georgia. The two pilots on board the helicopter, a commercial helicopter pilot, and a passenger, who was a certificated private helicopter pilot, were killed. The helicopter sustained substantial damage by impact forces. The flight was operated as an instructional flight under the provisions of Title 14 Code of Federal Regulations Part 91 with no flight plan filed. Visual Meteorological conditions prevailed at the time of the accident. According to one witness, the helicopter was on its sixth takeoff. The witness stated that during the accident takeoff "the rotor sound which was normally loud seemed to subside. The engine did not sound as though it was turning as high a revolution per minute (RPM) as it usually did when you heard the helicopter after he cleared the trees. A brief moment later it sounded as though the engine stopped running and at the same time you could hear what sounded like tree limbs breaking and then a heavy thud." Another witness in the local area and a friend of the private pilot, who also owns a UH-12 helicopter, stated that he had advised the private pilot not to attempt a takeoff without clearing woods several hundred more feet from his landing site. He stated that about a week before the accident the private pilot had topped several trees, which would allow the helicopter to clear the first two hundred feet. However, the witness stated that this still presented an extreme danger due to it being the only way in or out of the landing zone. The witness further stated that the load capacity for this helicopter was around 500 pounds. This did not include the extra fuel tank that was recently installed by the owner. With full fuel and two people on board (the two pilots combined weight was 412 pounds) would have put the helicopter at its maximum gross weight of 2500 pounds. In the witness's experience, "if you do not at any time pay complete attention to the RPM running at 3100 under a load, you will loose power and have to descent if you are in a hover." "Because of this factor the helicopter can drop power on takeoff. It is not a difficult correction but the path of departure that" the private pilot had created made [it] impossible to recover," if this happened. According to the witness the commercial pilot had sold the helicopter to the private pilot and the purpose of the flight was for the commercial pilot to show the owner how to get the helicopter in and out of his enclosed landing site. Examination of the helicopter by an FAA Inspector found the engine and transmission separated from their mounts and resting in the cockpit, with the tail boom resting against a tree. The tail rotor blades and main rotor blades had separated during the impact sequence. The throttle was observed closed and the throttle linkage was crushed in that position. The tail rotor drive-shaft was observed twisted and bowed aft of the tail rotor drive-shaft u-joint. Main rotor blades contacted the tail boom at the rear u-joint of the rear drive-shaft. The helicopter impacted the ground nose down and slightly to the right side. Examination of the cockpit found that the flight controls could be manipulated from either the center seat position or the left seat position. The flight controls could not be manipulated from the right seat. According to the FAA Inspector, the private pilot rated passenger was removed from the right side of the helicopter by rescue personal after cutting his restraint system.
The pilot's failure to maintain adequate rotor rpm, which resulted in an attempted autorotation and in-flight collision with trees. Contributing to the severity of the accident was the pilot exceeding the helicopters takeoff capability.
Source: NTSB Aviation Accident Database
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