Fatal Loss of Tail Rotor Effectiveness, Collision

On September 25, 2015, about 10:40 eastern daylight time, a Hughes 269B, N9567F, collided with terrain following a loss of control during an approach to a private landing area near Eustis, Florida. The commercial pilot and a passenger, who was also a student pilot, were seriously injured, and the helicopter was substantially damaged. The helicopter was owned and operated by the student pilot.

The student pilot reported that he was in the right cockpit seat and the pilot was in the left seat. The pilot was flying and was approaching the residence of a friend, at an altitude of 600 feet above the ground and a speed of 60-70 mph. The pilot then began descending and slowing down the helicopter as they approached the residence. At some point the helicopter then began "spinning slowly to the left a few times then violently spinning to the right." He then recalled waking up on a medical air ambulance helicopter after the accident.

An inspector with the Federal Aviation Administration responded to the accident site and examined the wreckage. The helicopter came to rest on its right side. The main rotor blades received structural damage and remained attached to their hub. The tail rotor drive shaft was sheared in two locations. The tail rotor blades remained attached to their hub. Control continuity was established from the cockpit to the main rotor and tail rotor system except for impact damage. There was sufficient fuel on board and there was oil in the engine. An external examination of the engine revealed no anomalies. His overall assessment of the wreckage did not reveal any evidence of a mechanical malfunction or anomaly.

The FAA issued Advisory Circular ("AC") 90-95, Unanticipated Right Yaw in Helicopters, in February 1995. The AC stated that the loss of tail rotor effectiveness (LTE) was a critical, low-speed aerodynamic flight characteristic which could result in an uncommanded rapid yaw which does not subside of its own accord and, if not corrected, could result in the loss of aircraft control. It also stated, "LTE is not related to a maintenance malfunction and may occur in varying degrees in all single main rotor helicopters at airspeeds less than 30 knots."

The full text of the advisory circular can be found at tiny.cc/ac95.

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