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.”