On March 30, 2019, about 1215 eastern daylight time, a Bell 222 helicopter, N222ML, was substantially damaged when it was involved in an accident near Montgomery, New York. The private pilot and four passengers were not injured, and one passenger sustained minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The pilot stated he completed the preflight inspection by the checklist, boarded passengers, and started the engines. Prior to takeoff, all gauges were in the “normal range.” The pilot conducted the takeoff from a concrete pad on his property, and about 500 ft above ground level he noticed a “split” in the #1 (left) and #2 (right) engine rpm needle indications. The #1 engine rpm needle had decreased below normal operating rpm, and the #2 needle had “spiked” above the normal operating rpm.
The pilot believed there was a loss of engine power on the #1 engine, and he initiated a sharp left turn to return to his property to perform a run-on landing to a short asphalt surface in front of a utility building. According to the pilot, a strong wind pushed the helicopter left, and the left landing gear touched down in the grass that bordered a short strip of gravel, which pulled the helicopter onto uneven ground. The helicopter came to a stop, then tipped over onto its left side and the main rotor impacted the ground. After it came to rest there was a small fire underneath the helicopter. All the occupants exited the helicopter, and the fire was extinguished.
The helicopter was righted to prevent a fuel leak. A Federal Aviation Administration (FAA) inspector traveled to the site and examined the helicopter. The rotor and transmission were separated and resting next to the helicopter. There was substantial damage to the nose and transmission pylon area, and fire damage to the upper portion of the fuselage aft of the number one engine.
Postaccident examination found both of the throttles near the idle position. Continuity of the throttle was confirmed from the #2 engine twist grip to the respective fuel control. Continuity of the #1 throttle control could not be verified due to breaks in the linkages, though the twist grip and fuel control lever were both free to move.
The airframe examination revealed no pre-impact anomalies. Both engines were removed, examined, and placed in test cells, where each ran satisfactorily. No anomalies were noted on either engine that would have precluded normal operation. During the examination, the #2 engine P3 Ng speed sensor connector was found disconnected. According to the engine manufacturer, a disconnected P3 connector could have caused the cockpit indication of the speed for the #2 engine to indicate 0 rpm. Additionally, the power turbine governors were functionally tested and exhibited no anomalies that would have precluded normal operation.
The helicopter manufacturer performed one engine inoperative performance calculations based on the environmental and loading conditions of the helicopter at the time of the accident. Based on the calculations, the helicopter did not have the capability to hover in or out of ground effect, and that the flight manual advised pilots to perform a run-on landing under those conditions.
The helicopter manufacturer also provided an explanation of how the helicopter’s configuration could result in the instrument indications similar to those that the pilot reported. The explanation stated that, “When the throttle for one engine on the twin engine Bell 222 is not in the fully governed range, then the affected engine will tend to droop at a lower Ng (N1) setting and not provide full engine power to the helicopter drive system. The helicopter will then in affect be flying in or near an OEI condition (One Engine Inoperative). Therefore, the pilot will see a split on the triple tachometer with the affected engine Np (N2) speed drooping and the unaffected engine Np (N2) speed stable at 100% Np. Depending on the conditions of flight (hover, landing, approach, maneuvering, cruise), outside temperature, and gross weight of the helicopter, the Nr (rotor rpm) might also droop. The remedy of having a drooping Nr would be to put the affected throttle back to the full on fully governed throttle position to regain N2 speed on the affected engine. If the pilot did not recognize the throttle was out of the governed region, a running landing to a suitable area should be performed. The engine run up checklist states the throttles should be rotated to FULL OPEN and verify Np at 97 to 100% during the engine runup and remain in that position until takeoff.”