Accident Overview
On March 30, 2019, at approximately 1215 eastern daylight time, a Bell 222 helicopter, registration N222ML, sustained substantial damage in an accident near Montgomery, New York. The helicopter was being operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The private pilot and four passengers were not injured, and one passenger received minor injuries.
Pilot's Account
The pilot reported completing a preflight inspection using the checklist and starting the engines with all gauges within normal range. After takeoff from a concrete pad on his property, at about 500 feet above ground level, he observed a split in the engine rpm indications for the number one (left) and number two (right) engines. The number one engine rpm decreased below normal, while the number two engine rpm spiked above normal. Believing a loss of power on the number one engine, the pilot initiated a sharp left turn to return to his property for a run-on landing to a short asphalt surface in front of a utility building. Strong winds pushed the helicopter left, causing the left landing gear to touch down in grass bordering a gravel strip. The helicopter was pulled onto uneven ground, came to a stop, and then tipped onto its left side, with the main rotor impacting the ground. A small fire ignited under the helicopter, but all occupants evacuated safely, and the fire was extinguished. The helicopter was subsequently righted to prevent a fuel leak.
Examination Findings
A Federal Aviation Administration inspector examined the helicopter at the site. The rotor and transmission were separated and resting beside the helicopter. Substantial damage was noted to the nose and transmission pylon area, along with fire damage to the upper fuselage aft of the number one engine. Postaccident examination revealed both throttles near the idle position. Continuity from the number two engine twist grip to its fuel control was confirmed, but the number one throttle control continuity could not be verified due to broken linkages, although the twist grip and fuel control lever were free to move. The airframe showed no pre-impact anomalies.
Both engines were removed, examined, and tested in test cells, where they operated satisfactorily with no anomalies that would have precluded normal operation. During the examination, the number two engine P3 Ng speed sensor connector was found disconnected. According to the engine manufacturer, a disconnected P3 connector could have caused the cockpit indication for the number two engine speed to read zero rpm. The power turbine governors were functionally tested and exhibited no anomalies.
Manufacturer's Performance Calculations and Explanation
The helicopter manufacturer performed one-engine-inoperative (OEI) performance calculations based on the environmental and loading conditions at the time of the accident. The calculations indicated that the helicopter did not have the capability to hover in or out of ground effect, and the flight manual advised pilots to perform a run-on landing under such conditions.
The manufacturer also provided an explanation of how the helicopter's configuration could produce instrument indications similar to those reported by the pilot. When the throttle for one engine on a twin-engine Bell 222 is not in the fully governed range, that engine tends to droop at a lower Ng setting and does not provide full power to the drive system. The helicopter then operates in or near an OEI condition. The pilot would see a split on the triple tachometer with the affected engine's Np speed drooping and the unaffected engine's Np speed stable at 100%. Depending on flight conditions, rotor rpm might also droop. The remedy is to return the affected throttle to the full-on governed position. If not recognized, a running landing to a suitable area should be performed. The engine run-up checklist requires throttles to be rotated to FULL OPEN and Np verified at 97-100% during the runup, and the throttles should remain in that position until takeoff.