N134VGBell 206B · 1974

On June 29, 2021, at 1347 eastern daylight time, a Bell 206B, N134VG, was substantially damaged when it was involved in an accident at Griffiss International Airport (RME), Rome, New York. The airline transport pilot and two pilot-rated passengers sustained minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.

The purpose of the flight was to conduct an initial Part 135 competency check ride for the pilot. On board were two Federal Aviation Administration (FAA) aviation safety inspectors, one seated in the left seat performing the check ride and another in the left rear seat providing oversight and on-the-job training to the other inspector.

According to the pilot, after performing maneuvers, the flight returned to the airport where he was to perform a straight-in autorotation with a powered recovery to runway 33. He briefed the inspectors on the maneuver, carried out clearing turns and landing checks, and entered the autorotation at an altitude of 1,500 ft mean sea level. He lowered the collective and reduced the throttle to idle and maintained a speed of 65 knots. Before the flare, he advanced the throttle to the full open position and noted the power turbine and rotor RPM needles were in the green arc. Both he and the FAA inspector confirmed that the throttle was full open. As he raised the collective for recovery, the low rotor warning light and low rotor warning horn both activated. The engine lost partial power and the helicopter landed hard on the runway and rolled over on to its left side.

According to the FAA inspector seated in the left front seat, as the pilot reduced the collective at the start of the maneuver, he noticed a needle split on the tachometer and concluded the throttle had been reduced. He did not observe any yawing motion of the helicopter at the time. The helicopter “floated” somewhat after the entry and the descent was smooth. As the airspeed was reduced at the beginning of the recovery, he noticed that the altitude was “slightly high” (he estimated slightly above 100 ft above ground level). He checked the throttle position by attempting to rotate it towards full, and it did not move. He did not recall if he checked the tachometer at that time. He noticed that the helicopter was “higher than usual at the completion of the power recovery,” and then felt the helicopter descend and thought the pilot was lowering the helicopter to a “more reasonable altitude.” As the low rotor RPM horn sounded, he glanced inside and attempted to locate the tachometer but was unable to readily see it. As he looked back outside, the helicopter impacted the ground. After the helicopter came to rest with the engine still running, he rotated the right-side throttle grip to idle, noting that it took several iterations of gripping the throttle and rotating it with his fingers to rotate it to the IDLE position. He then struggled to press the detent button before he was able to rotate the throttle further to the OFF position.

In retrospect, the FAA inspector in the left front seat considered, when he checked the throttle position just prior to recovery by attempting to rotate it, that it may have been held in position by the pilot, who had been gripping the controls somewhat tightly, and was not against the stop in the full position as he assumed. Or, if it had been, perhaps it was rotated away from full, as the collective was raised to arrest the descent at the end of the autorotation.

A statement provided by the FAA inspector seated in the rear left seat, stated in part:

[the pilot] initiated the maneuver by reducing the collective and simultaneous bringing the throttle to the idle position. The initiation was performed at a proper point to ensure we made our intended point of termination. During the auto, I could hear the pilot making proper call-outs (i.e. Airspeed, rotor, touchdown point.) The deceleration was begun too high and a little too aggressive. Because of this, it is not uncommon for the “low rotor” audio warning to come on. I knew there was a problem when the audio warning continued. I attempted to look at the rpm gauge, but before I could verify whether or not the throttle was returned to the “open” position, we impacted the ground.

Initial examination of the helicopter by a third FAA inspector revealed substantial damage to the fuselage above the windscreen and the left horizontal stabilizer.

A subsequent examination of the helicopter demonstrated drive continuity within the main transmission. The tail rotor drive system rotated by hand freely throughout the entire system, demonstrating tail rotor drive continuity, and the tail rotor hub and blades remained intact. Both main rotor blades exhibited detached tips, trim tab separations, chordwise fractures and fragmenting of the blade skins and internal foam core. The main rotor hub was intact and the main rotor pitch change links exhibited overload fractures. The throttle was manipulated by hand during the examination to the three positions—Off, Idle, Full On (Fly)—and the proper corresponding positions at the fuel control unit (FCU) pointer were observed. The fuel valve switch was found in the “On” position. The fuel shutoff valve was removed from the helicopter before battery power was engaged during the examination and the valve was observed to be in the Full Open position. The remaining fuel within the fuel cell appeared to be clear and the airframe fuel filter was not obstructed. The fuel boost pumps were activated and operated properly in the green pressure range. Control continuity was confirmed from the flight controls in the cockpit to the corresponding flight control surfaces.

All of the engine and transmission chip detectors, fuel, and oil filters were free of debris. Fuel was present up to the fuel spray nozzle. All engine control pneumatic B-nuts were tight and torque-striped. Control continuity from the cockpit to the engine was confirmed. A borescope examination of the engine revealed metal splatter in the combustion chamber consistent with combustion taking place when the compressor ingested metallic fragments. There were no anomalies with the engine that would have precluded normal operation prior to the accident.

A review of the maintenance records revealed that the most recent 100-hour inspection was performed on April 19, 2021, about 60 flight hours before the accident. At that time, the fuel nozzle and filter were disassembled and cleaned, the starter generator was removed and its brushes were inspected, an engine oil flow check was performed and the fuel system was bled. No other maintenance activity was logged in the engine logbook after this inspection. Entries made in the airframe logbook since that inspection included replacement of the turbine outlet temperature indicator, after a pilot report of an abnormal reading during engine starting, on May 14, 2021. On June 4, 2021, the fuel cell was replaced and the fuel cell/sump drain valve was disassembled and cleaned. After a report of leaking, the drain valve was replaced on June 11, 2021.

According to the FAA Helicopter Flying Handbook:

“This is one of the most difficult maneuvers to perform due to the concentration needed when transitioning from powered flight to autorotation and then back again to powered flight. For helicopters equipped with the power control on the collective, engine power must be brought from flight power to idle power and then back to a flight power setting. A delay during any of these transitions can seriously affect rotor rpm placing the helicopter in a situation that cannot be recovered.”

Furthermore, it stated under the section that listed common errors:

“Failure to coordinate throttle and collective pitch properly, which results in either an engine overspeed or loss of rotor rpm…Late engine power engagement causing excessive temperature or torque, or rpm drop…Failure to go around if not within limits and specified criteria for safe autorotation.”