Accident Briefs: March 2019

SCHWEIZER 269C
Medford, New Jersey/ Injuries: 2 Fatal

The purpose of the flight was to provide an orientation/pleasure flight to the passenger, who was scheduled to perform in a concert on the airport later that evening. Several minutes after takeoff, the pilot reported over the airport UNICOM frequency that he was unable to control engine rpm with throttle inputs. He reported that he could "roll" the twist-grip; however, there was no corresponding change in engine power when he did so.

Three helicopter flight instructors, one a Federal Aviation Administration (FAA) inspector, one an FAA designated examiner, and a company flight instructor, joined the conversation on the radio to discuss with the pilot remedial actions and landing options. These options included a shallow, power-on approach to a run-on landing, or a power-off, autorotational descent to landing. The instructors encouraged the pilot to perform the run-on landing, but the pilot reported that a previous run-on landing attempt was unsuccessful. He then announced that he would shut down the engine and perform an autorotation, which he said was a familiar procedure that he had performed numerous times in the past. The instructors stressed to the pilot multiple times that he should delay the engine shutdown and autorotation entry until the helicopter was over the runway surface.

Video footage from a vantage point nearly abeam the approach end of the runway showed the helicopter about 1/4 to 1/2 mile south of the runway as it entered a descent profile consistent with an autorotation. Toward the end of the video, the descent profile steepened and the rate of descent increased before the helicopter descended out of view. Witnesses reported seeing individual rotor blades as the main rotor turned during the latter portion of the descent.

The increased angle and rate of descent and slowing of the rotor blades is consistent with a loss of rotor rpm during the autorotation. Despite multiple suggestions from other helicopter instructors that he initiate the autorotation above the runway, the pilot shut down the engine and entered the autorotation from an altitude about 950 ft above ground level between 1/4 and 1/2 mile from the end of the runway. Upon realizing that the helicopter would not reach the runway, the pilot could have landed straight ahead and touched down prior to the runway or performed a 180° turn to a field directly behind the helicopter; however, he continued the approach to the runway and attempted to extend the helicopter's glide by increasing collective pitch, an action that resulted in a decay of rotor rpm and an uncontrolled descent.

Examination of the wreckage revealed evidence consistent with the two-piece throttle control tie rod assembly having disconnected in flight. The internally threaded rod attached to the bellcrank and an externally threaded rod-end bearing attached to the throttle control arm displayed damage to the three end-threads of each. The damage was consistent with an incorrectly adjusted throttle control tie rod assembly with reduced thread engagement, which led to separation of the rod end bearing from the tie rod and resulted in loss of control of engine rpm via the throttle twist grip control.

Probable Cause(s): The pilot's early entry into and failure to maintain rotor rpm during a forced landing autorotation after performing an engine shutdown in flight, which resulted in an uncontrolled descent. Contributing to the accident was the failure of maintenance personnel to properly rig the throttle control tie-rod assembly, which resulted in an in-flight separation of the assembly and rendered control of engine rpm impossible.

AIR TRACTOR INC AT-602
Stirum, North Dakota/Injuries: 1 Fatal

An employee of the operator reported that the planned aerial application flight was delayed about 2 hours while the pilot waited for the weather conditions to improve. The pilot had spoken with individuals by phone before the flight in an attempt to assess the local conditions. The visibility at the airport was about 1-1/2 miles when the pilot departed.

A witness reported that she was sitting on her patio when she heard the airplane. The sound of the engine was normal, "not anything unusual at all." She observed the airplane emerge from the fog and "within seconds" impact the ground. The airplane was level or descending slightly and did not appear to change its flight path before impacting gradually rising terrain. She noted that the airplane did not appear to be out of control, nor did it seem that anything was wrong mechanically. She recalled that it was "very, very foggy" at the time, with about 200 yards visibility. There was no precipitation and little or no wind at the time.

A postaccident examination did not reveal any anomalies consistent with a preimpact failure or malfunction.

It is likely that the pilot encountered instrument meteorological conditions while operating at a low level and inadvertently impacted the terrain.

Probable cause(s): The pilot's decision to attempt flight with low-level fog in the area, which resulted in an encounter with instrument meteorological conditions and impact with terrain.