CEN19LA016

The student pilot reported that, about 10 minutes into the flight, he observed the main rotor rpm indicating unit drop to zero. The student confirmed that the engine rpm indications were "still normal" and then decided to execute an autorotation to an open field and lowered the collective. He stated that the helicopter was in a "steady glide" when he realized that it might impact a fence at his intended landing area in the field. The student applied aft cyclic to avoid the fence, which changed the helicopter’s glidepath; he then flared the helicopter and applied collective for the landing. During the landing, the right skid’s rear portion impacted terrain. The helicopter bounced, the student lost helicopter control, and the helicopter came to rest on its right side resulting in substantial damage. Postaccident examination of the helicopter revealed an electrical short had occurred in the main rotor rpm indicating unit. Given the student reported that the engine rpm indications were “still normal," it is likely the helicopter was still functioning normally despite the loss of cockpit main rotor rpm indications.

On October 27, 2018, about 1800 central daylight time, a RotorWay International Exec 162F, N162RF, sustained substantial damage when it was involved in an accident near Passaic, Missouri. The student pilot sustained no injury. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The student pilot reported that fuel was added to the helicopter to full capacity, the preflight checks were completed, and he departed from the airport to the east. The helicopter climbed to about 500 ft above ground level (AGL) at about 80 mph. While flying easterly for about 10 minutes, the student pilot observed the main rotor rpm indicating unit in the cockpit drop to zero. The student pilot confirmed that the engine rpm indications were "still normal." The student pilot decided to execute an autorotation to an open corn field and lowered the collective. He was in a "steady glide" when he realized that he was going to potentially impact a fence at his intended landing area in the field. The student pilot applied aft cyclic to avoid the fence, which he reported changed his "glide path." The student pilot flared and then applied collective for the landing. During the landing, the rear portion of the right skid impacted terrain. The student pilot reported that this caused the helicopter to bounce, he lost control, and the helicopter came to rest on its right side. The student pilot executed an emergency shutdown and egressed from the helicopter without further incident. After egressing from the helicopter, the student pilot was in an area with adequate cellular phone reception and he contacted a friend for assistance. The helicopter sustained substantial damage to the main rotor system, the fuselage, the tailboom, and the tail rotor system. A postaccident examination of the helicopter was conducted by the Federal Aviation Administration (FAA). During the examination of the airframe, an electrical short in the main rotor rpm indicating unit was discovered. The short was located inside of the case between pins 5 and 9, which corresponded to a black wire (pin 5) and a dark blue wire (pin 9). The short was observed to travel through the circuit. The connector was removed from the indicator's circuit board and the short remained. When the black and dark blue wires were removed from the connecter, the short was no longer present. No other anomalies were noted with the airframe. The RotorWay International Exec 162 Pilot Operating Handbook (POH) provides engine failure indications and states in part: A change in noise level, a right yaw, and low oil pressure may be the first indication of an engine failure. The POH states, "during flight, check all instruments for anomalies." The POH further lists the procedures for an autorotation and states in part: 1. Lower collective FULL DOWN, apply left pedal to maintain trim, adjust cyclic to maintain level attitude. 2. Adjust collective to maintain rotor RPM within the green (100%). 3. Adjustairspeed to 65 MPH (60-70 MPH limit). According to the information provided in the student pilot's statement, the helicopter was operating outside of the shaded area of the height velocity envelope published in the POH during the initiation of the autorotation. The student pilot wore a Gentex SPH-4B helicopter flight helmet during the accident flight, even though he was not required to by the manufacturer or the FAA. The pilot had removed the visor assembly for flight operations. He reported that various scratches and impact marks from the accident sequence were sustained to the top of the flight helmet shell. He further reported that he "would have been cut up pretty bad" if it were not for his utilization of the flight helmet. The U.S. Army Aeromedical Research Laboratory Report 93-2 Flight Helmets: How They Work and Why You Should Wear One, discusses the multiple benefits of flight helmet utilization, and states in part: Throughout history, man has worn head protection in response to the threat of head injury. Such armor has limitations and drawbacks, but in helicopter aviation it is effective and worthwhile. All personnel regularly participating in helicopter flight (civilian or military) should be equipped with protective headgear. Although requested, the student pilot did not submit the National Transportation Safety Board Pilot/Operator Aircraft Accident/Incident Report Form 6120.1.