NTSB Notes No Mechanical Defect, And Pilot Was Denied Medical Certificate

The family of a man killed when his Robinson 44 helicopter lost power and went down on October 8th, 2006 in 20 feet of water in Lake Tapps near Tacoma, Washington is suing Robinson Helicopter for manufacturing a defective product, and seeking unspecified damages. His only passenger, a woman, survived the impact and was able to free herself from the wreckage and swim to the lake's surface. She suffered severe injuries in the accident.

An NTSB report shows Pilot Russel Lee Tom, and the passenger were looking at some land for potential development. Tom had originally intended to land at the home of a friend on the lake, but the passenger had said she was not comfortable with the landing zone. They were proceeding back to a landing pad at his home when the accident occurred.

The NTSB report states "According to the passenger, as they continued the descent toward the landing site, the pilot suddenly made a rapid movement of the stick (cyclic) toward the left. This was followed almost immediately by the helicopter "jerking violently" to the right (clockwise rotation). The helicopter then seemed to her to stabilize for one to two seconds, during which time she asked the pilot what was wrong, and he responded with, "I don't know." The helicopter then started spinning to the right and descending. The passenger believes that the helicopter spun around two full times, and then impacted the water "very hard." At the moment of impact, she felt something "snap or break" in her back, and then the aircraft almost immediately filled with water and sank rapidly to the bottom. After it came to rest on the bottom of the lake, the passenger looked and felt for the pilot, but could not determine where he was, so she unlatched her seatbelt, pushed up through an opening, and swam to the surface.

In a post-accident interview, the passenger said that just about the time the helicopter started to spin, she saw a number of "warning lights" come on, but she did not remember hearing any aural warnings. She further stated that she was not aware of any changes in engine rpm, nor did she remember hearing anything unusual from the engine. She did report during the interview that she was later told by her daughter and another person who were standing near the landing site watching them approach, that the engine had made a couple of loud "pops" just before the helicopter began spinning."

Several witnesses on the ground said they heard several loud mechanicals pops or backfires as the aircraft began spinning. They also noted rapid changes in engine RPM. One said he saw the rotor blades "dramatically slow or stop" during the aircraft's descent. Witnesses who went to the scene to try to assist after the aircraft went down noted a strong smell of gasoline at the impact site.

According to the NTSB report "This aircraft was factory-equipped with a carburetor heat assist device system. This system automatically changes the amount of carburetor heat application after the pilot has made the initial application, and acts inversely to the amount of collective input applied. Once the pilot applies carburetor heat to keep the carburetor air temperature (CAT) in the carburetor throat out of the yellow arc on the carburetor air temperature gage, the system provides for an automatic increase in carburetor heat when the collective is lowered, and automatically decreases the amount of carburetor heat as the collective is raised. The objective of the system is to decrease pilot workload, and to make more power available (carburetor heat reduction) when the collective is raised.

At the time of the recovery from the lake, the collective was found in the full-up position, and the carburetor heat control knob was found to be in an intermediate position between the OFF and FULL ON positions. An on-scene measurement determined that seven-eights of an inch of the control knob shaft was protruding from the panel.

As part of the investigation, the NTSB IIC asked Robinson Helicopter to estimate what position the carburetor heat knob would have been in during the cruise portion of the accident flight if the full-up collective at impact were responsible for repositioning the carburetor heat control knob to the seven-eights inch extended position. This determination was made using an estimated 1,850 pound gross weight for the aircraft, and a speed of approximately 90 knots, resulting in a collective position of about 55 percent application. According to Robinson, these parameters would result in the knob being extended about two inches during cruise flight. Two inches of extension is approximately 60 percent of the knob's allowable travel."

Robinson R44 File Photo

The report also indicates that the drive system appeared to be normal in the post crash inspection, though when drained, the tail rotor gearbox contained mostly water, with numerous small droplets of blue lubricating oil..

The NTSB did note that the pilot had been denied a medical certificate due to his use of the prescription anti-depressant Zoloft, and he was advised that it was unlawful for him to exercise airman privileges without holding the appropriate medical certificate.

The final probable cause report indicates "the helicopter experienced a total loss of engine power while approximately 100 feet above the surface of a lake. The pilot did not apply the proper flight control inputs to maintain a controlled autorotation to the surface of the lake, and therefore the aircraft spun multiple times around its vertical axis while descending to an uncontrolled impact with the water. Immediately after impacting the surface of the lake, the helicopter sank in about 20
feet of water. There was no indication of any mechanical failure or malfunction.  The National Transportation Safety Board determines the probable cause(s) of this accident as follows. The complete loss of engine power, for undetermined reasons, while on final approach, and the pilot's loss of control of the helicopter after the power loss. Factors include a lake below the final approach to the private landing pad."

The Tacoma, Washington News Tribune reports that in the lawsuit filed last week, the family contends that Robinson manufactured an aircraft that was "defective and unsafe." They are seeking unspecified damages for wrongful death, loss of future earnings, and “emotional distress arising out of the awareness of impending doom and injuries suffered by Russell Tom.”

FMI: www.ntsb.gov