Tail Rotor Crosshead Drive Plate... Was Not Bolted To The Tail Rotor Crosshead

Location: Fairfield, NJ Accident Number: ERA22FA257
Date & Time: June 4, 2022, 12:01 Local Registration: N98ZA
Aircraft: Bell Helicopter Textron Canada 407 Injuries: 1 Serious
Flight Conducted Under: Part 91: General aviation - Positioning

On June 4, 2022, about 1201 eastern daylight time, a Bell 407 GXP helicopter, N98ZA, was substantially damaged when it was involved in an accident near Fairfield, New Jersey. The commercial pilot was seriously injured. The helicopter was operated by Zip Aviation as a Title 14 Code of Federal Regulations Part 91 positioning flight.

The helicopter departed Essex County Airport (CDW), Caldwell, New Jersey, about 1147 and was destined for John F. Kennedy International Airport (JFK), New York, New York. A review of archived automatic dependent surveillance broadcast (ADS-B) data showed the helicopter in a cruise profile on a southeasterly track about 500 ft mean sea level (msl). Preliminary air traffic control data and a review of the helicopter’s onboard video system revealed that about 2 miles south of Teterboro International Airport (TEB), Teterboro, New Jersey, the pilot requested to return to CDW. When asked by the TEB controller if he needed assistance, the pilot said no. The helicopter reversed course, and as it approached CDW, the pilot was cleared to land on runway 28. The helicopter crossed the runway threshold about 150 ft msl and 33 knots groundspeed. The helicopter generally maintained its altitude and groundspeed over the runway for about 10 seconds before it slowed, climbed, and turned to the right.

Airport surveillance video captured the helicopter’s approach, its alignment with the runway, and its slowing as the nose pitched upward. As the helicopter slowed, the nose yawed to the right, the helicopter became unstable, and started to descend vertically while rotating around the main rotor mast. Seconds into the vertical descent, the right yaw slowed, stopped, and the helicopter rotated to its left for the remainder of the vertical descent to ground contact. After ground contact, the main rotor continued to turn and the main rotor blades continued to strike the ground, ultimately shedding about 50 percent of the span of each blade. The helicopter sustained substantial damage to the fuselage and tail boom.

A postaccident examination revealed that the tail rotor crosshead drive plate, in place behind the pitch change rod attachment nut, was not bolted to the tail rotor crosshead as prescribed. The two attachment bolts were not present, and there were no remnants of any bolts in their threaded receptacles in the crosshead. Further, the threads were undamaged and showed no signs of corrosion, deformation, smearing, or cross-threading.

Main rotor flight control continuity was confirmed from the cockpit through several breaks to each respective rotor blade. Tail rotor control was confirmed from the pedals through breaks to the tail rotor gearbox to the pitch control rod. Movement of the pitch change push-pull tube resulted in smooth movement of the pitch change rod; the attached tail rotor crosshead drive plate moved with the pitch change rod, but independently of the crosshead to which it was no longer bolted.

According to the operator, the tail rotor was installed the day before the accident following the replacement of 4 “feathering bearings.” The director of maintenance (DOM) had performed the task and said that he prepared the tail rotor assembly for installation by laying the parts out on a maintenance cart. He then performed the installation and had one of his mechanics verify the mast nut torque. He then “finished” the installation and had another “verify” the work. A company pilot completed a preflight inspection of the helicopter and performed “ground functional checks” and three consecutive maintenance runs to affect balancing of the tail rotor.

According to the DOM, between the mast nut torque application and completion of the installation, he was “called out” to consult on two different aircraft repairs. He could not recall how much time elapsed before he returned to the installation of the tail rotor assembly.

Non-volatile memory was recovered from onboard avionics and the video recording system and retained for further analysis.

FMI: www.ntsb.gov