FTW95FA181

While on a local training flight, preparing the private pilot student for his commercial certificate check flight, the helicopter descended into a clearing. During departure from this site, the helicopter struck the static line of a power transmission array which crossed the area. The helicopter impacted in a vertical descent approximately 600 feet beyond the transmission line.

History of flight

On April 25, 1995, at 1050 central daylight time, a Bell 47D1 helicopter, N2202C, impacted the ground approximately one half mile southeast of Ardmore Executive Airport (1F0), Ardmore Oklahoma. The flight instructor and private pilot occupants received fatal injuries and the aircraft was destroyed. Visual meteorological conditions prevailed for this local area instructional flight and no flight plan was filed. The operator was Versatile Aviation.

According to the chief pilot, the flight was a pre-check for the student who was working on his commercial helicopter certificate. Witnesses located approximately one quarter mile from the accident site at Lake Murray State Park said they first saw the helicopter in a climb coming from behind some trees and heading generally towards the airport. The witnesses said the helicopter appeared and sounded normal at first and then they heard engine surge type noises and yaw became erratic. The witnesses did not see the impact, but from the sound, they said they were aware the helicopter had crashed and proceeded to the site.

Examination of the area by the investigator-in-charge (IIC) provided information that 90 foot high power lines crossed the area where the helicopter first appeared from behind the trees. Witnesses provided information that the helicopter was below the level of the lines when it first came into view. The accident site was approximately 600 feet beyond the power lines in the direction of the airport.

Personnel information

The flight instructor was a graduate of Versatile Aviation flight training through their 14 CFR Part 141 program. He received his flight instructor rating on September 9, 1994, and was familiar with the local flying area. For details of flight experience refer to page 3 of this document.

The student was also a graduate of the school and received his private pilot certificate on March 24, 1995, with ratings in airplane single engine land and helicopter. He also held an airplane instrument rating. He was working towards his commercial helicopter certificate at the time of the accident. His certificate number was pending. For details of flight experience refer to the Second Pilot Supplement of this report.

Aircraft information

The helicopter, serial number M-1, was remanufactured from parts by Timothy Moriarty. The helicopter was certified July 16, 1991, and conformed with type certificate specifications of the original Bell 47D1 manufactured July 14, 1953.

Wreckage and impact information

Impact occurred in a field with the wreckage oriented on a heading of 335 degrees. There were no skid marks and the impact crater under the helicopter was approximately 24 inches in depth and contained portions of the sump and tachometer generator. The helicopter was intact except for the aft portion of the tail boom and the cabin doors all of which were located in the impact area.

A fence ran through the impact area on a heading of 360 degrees and witness marks provided evidence that a portion of this wire fence was struck by the helicopter during the impact sequence. In addition, a clump of trees approximately 15 feet in height was located at the left rear of impact site and witness marks provided information that the helicopter struck these trees during the impact sequence.

Medical and pathological information

According to officials of the state of Oklahoma, autopsies were not performed due to excessive workload caused by the bombing of the Federal building in Oklahoma City. Death was attributed to trauma associated with impact forces.

Toxicological tests were conducted by the Civil Aeromedical Institute, Oklahoma City, Oklahoma. The results of the tests were negative for substances of abuse and alcohol.

Tests and research

An examination of the engine, drive train, flight control system and airframe was conducted at the facilities of Versatile Aviation. Persons present for the examination were representatives from Versatile Aviation, FAA, and the IIC. No evidence of preimpact failure or malfunction was found during the course of the examination.

One tail rotor blade had leading edge damage consisting of compression of the leading edge approximately two inches in depth and about four inches inboard from the blade tip. The compression was rounded and contained transfer of a gray metallic material with the appearance and properties of zinc which is used as a coating on transmission array static lines. The depression was compared to the static line of the power line which crossed the area in the vicinity of the accident site. The tail rotor blade depression and static line matched in shape and size.

Examination of the tail boom, tail rotor drive shaft and tail rotor gear box, provided evidence of separation from their mountings and the tail boom had fractured. Both the main rotor blades and tail boom contained transfer witness marks.

The power line was not marked and a review of applicable regulations provided information that this line did not meet the minimum height and span requirements to require marking.

Additional information

The wreckage was released to the Director of Training, Versatile Aviation, Inc., on April 27, 1995. No parts were retained.