NTSB Factual Report

History of Flight

On May 31, 1997, at 0705 hours mountain standard time, a homebuilt experimental Rotorway 162F helicopter, N176BT, collided with the ground following an emergency descent at the Deer Valley Airport, Phoenix, Arizona. The aircraft was destroyed by the impact and postcrash fire. The pilot sustained fatal injuries. The aircraft was operated by the owner/builder as a local flight under 14 CFR Part 91 when the accident occurred. Visual meteorological conditions prevailed and a VFR flight plan was not filed. The flight originated at Deer Valley Airport at 0620.

According to the communications transcripts from the Federal Aviation Administration (FAA) Air Traffic Control Tower, the pilot declared an emergency while inbound to the airport by transmitting "mayday" twice. The nature of the emergency was not made clear.

There were several witnesses to the emergency descent and crash sequence. The first eyewitness interviewed stated that he was situated directly across the field from the accident site. He said he was watching the helicopter during the initial descent and noted that approximately 300 feet above ground level, the helicopter began to spin around. He estimated that it made about "four to five revolutions." He said it stopped spinning and then it began to fall. He stated he could hear the helicopter hit the ground "pretty hard." He contacted Westwind Aviation on the field to notify them of the accident. They reported that the crash had already been reported to the appropriate authorities. This eyewitness stated that he thought the pilot would "be able to save it." He further stated that the helicopter was approximately 150 feet above ground level when it stopped "corkscrewing and fell straight to the ground." He said that it seemed like the pilot was "goosing" the motor when it started spinning.

The second eyewitness was interviewed at the scene by an FAA operations inspector from the Scottsdale, Arizona, Flight Standards District Office, who conducted the initial on-scene investigation at the request of the Safety Board. The eyewitness reportedly told the FAA inspector that the aircraft "pitched way up and then down at least thirty degrees." She noted that the engine was sputtering. She also observed that the rotors had stopped turning prior to impact with the ground.

The same FAA inspector contacted the Designated Pilot Examiner (DPE) who gave this pilot his Private Pilot rotorcraft checkride. The DPE told the FAA inspector that initially, he wanted to flunk this pilot during his checkride due to "the pilot's lack of judgment." He stated that the pilot had been "abusing" the engine of the helicopter by hooking a turbocharger up to the engine. He further stated that the pilot had gotten himself into the height velocity curve while flying the aircraft and had been known to fly under power lines.

The aircraft was removed from the accident site and taken to a secure location for further examination. The FAA Operations Inspector and a Principle Maintenance Inspector (PMI) examined the wreckage with the assistance of the president of Rotorway International. According to the report received from the PMI, the inspection revealed that the pivot bolts and brackets for the tail rotor drive assemblies had been overtorqued. Additionally, it was revealed that the pivot belts had no lubrication on the bolts or the surfaces that rub together. The tail rotor drive belt was found frayed and shredded.

The Safety Board obtained copies of RotorWay Advisory Bulletin A-20 which discusses the tail rotor drive belts. This document states, "Test results showed that the failure of a belt could only be induced by incorrect tension."

Tail rotor drive belt Advisory Bulletin A-21 stressed the importance of checking the condition and tension of the belts before every flight. Additionally, the bulletin advises the operator to install temperature strips on the two tail rotor idler pulleys and the drive pulley on the tail rotor shaft. The bulletin further states, "The heat sensitive 'dots' will darken if the indicated temperature is exceeded." It further instructs the operator to: "Examine the temperature strips before and after each flight. . .If the 170-degree dot darkens, it is an indication that a belt may be slipping or some other problem may exist. The problem should be identified and corrected before continuing flight. If the 180-degree (or higher) dot darkens, the belts have been damaged from heat and MUST be replaced."

The tail rotor drive check is a preflight item as outlined in the RotorWay Exec 162F Flight Manual, Section Three, Normal Procedures. During preflight the pilot is instructed to check the travel of the idler pulley swing arm, condition of the drive belts, tension of the drive belts, condition of the pulleys, and bearings and temperature strips on the idler pulleys and drive pulleys. In the postcrash FAA inspection report, the FAA inspectors noted that all of the "heat dots" were popped from the belt friction. The president of RotorWay told the Safety Board that the temperature on the tail rotor pulleys would have had to exceed 200 degrees Fahrenheit for all of the dots to have popped. Additionally, visual inspection of the tail boom assembly revealed that the inspection door on the bottom revealed no evidence of ever having been opened as outlined in the pre/post flight checklist.

The president of RotorWay stated that after he examined the two idler pulleys and their associated mountings, he determined that they were not constructed or installed correctly. He stated that, "The side plates were sawed out leaving sharp pieces of metal extending out to the side of both pulleys mounting scissors, the pivot belts were tightened too tight with no lubrication on the bolts or the surfaces that rub together and that there was evidence that the sharp extending metal from the mounting scissors cut into the bulkheads thus restricting the travel of the swing arm."

Pilot Information

The pilot was a citizen of Canada and held a Canadian Private Pilot's License No. VRP-168260 with an airplane single engine land rating. Additionally, he held a United States private pilot certificate with a rotorcraft/helicopter rating, which was issued March 6, 1997. He held an experimental aircraft repairman certificate with the limitation for the RotorWay Model 162F, Serial Number 6144. This certificate was issued on July 11, 1996. According to the Airman Medical Records, the pilot reported a total time of 250 hours as of his last third-class medical certificate.

NTSB Probable Cause

the owner/builder incorrectly installed the tail rotor drive pulley mounting scissors, overtorqued the pivot belts, did not perform the required maintenance lubrication of the pivot belts, and failed to perform adequate visual maintenance checks of these areas during the pre/postflight checks; the resultant overtemperature on the pulley idlers; eventual catastrophic failure of the drive belts; and the pilot's failure to maintain rotor rpm during autorotation, which resulted in loss of aircraft control and subsequent collision with the terrain.