Bell
206 Jet Ranger C-GBXK
10
October 2001
Namao, AB
On 10 October 2001 a civilian registered
Bell 206 Jet Ranger (C-GBXK), operated by 408 Squadron
crashed while practicing an extended range autorotation.
The pilots received minor injuries and the aircraft
sustained "A" category damage.
The flight was a proficiency trip for two squadron pilots.
The Aircraft Commander (AC) was a Qualified Flying Instructor
(QFI), and the co-pilot was a 408 Sqn Regular Force
rotary-wing pilot awaiting the CH-146 conversion course.
The flight began with a navigation route and culminated
in a series of autorotations to a grass strip adjacent
to an abandoned runway at CFB Edmonton. On the fifth
and final autorotation, the QFI attempted an extended
range autorotation to the grass strip.
The 'Extended Range' autorotation is an emergency procedure
designed to maximize the distance travelled during autorotative
flight. Crews practice this manoeuvre for the express
purpose of extending the gliding distance in order to
reach a suitable landing area. The pilot will enter
the manoeuvre by rolling the throttle to idle and lowering
collective. The aircraft attitude is adjusted to achieve
69 knots and the collective set to maintain 90-107%
Rotor RPM (RRPM). In practice, the collective is raised
to reduce the RRPM as close as possible to the 90% end
of the RRPM range, as this maximises the distance covered
during the autorotation. Once the pilot judges that
the landing spot will be made, the speed and RRPM are
adjusted to meet the requirements of the 100 foot check:
area made, RRPM in the green (90-107%), airspeed minimum
50 knots (60 kts desirable) and bank, drift and crab
are eliminated. If any of these parameters is not met,
an overshoot must be initiated. The normal descent rate
for an autorotative glide in the Jet Ranger is 1500
feet per minute or 25 feet per second. The time from
the '100 Foot Check' to touchdown is thus only 4 seconds.
The purpose of the '100 Foot Check' cannot be overstated;
it allows sufficient time and altitude to safely recover
if the aircraft is not in a position to land.
The QFI made a late decision to overshoot and did not
effectively execute either the overshoot or an autorotative
flare and landing. The aircraft hit the ground very
hard, in a near level attitude with at least 69 knots
of speed. It slid along the ground for approximately
60 feet then became airborne again due to flight control
inputs. As the aircaft came off the ground the QFI applied
aft cyclic to reduce speed and coupled with the low
rotor RPM caused the main rotor blades to sever the
tail boom. The helicopter lost tail rotor thrust, rotated
about its vertical axis through 720 degrees, hit the
ground a second time and then came to rest on its left-hand
side.
Although the fire trucks were on scene within 3 minutes,
the medical response was delayed due to communication
problems within the base. The crash bells were not functioning
in the hospital and the ambulance had difficulty getting
clearance to enter the airfield. Had the crew been more
seriously injured this could have proved fatal. The
Squadron and Base have since rectified these deficiencies.
The co-pilot had been assessed as too tall to fly the
Jet Ranger and was required to use a modified (thinner)
seat cushion when flying the helicopter. The investigation
revealed shortfalls in the tracking of aircrew anthropometric
restrictions and the standardisation of seat configuration
in Jet Ranger aircraft. 1 CAD is pursuing a more efficient
means of achieving this.
Pilots tread a fine line between success and failure
when practicing autorotations to touchdown, but rigid
adherence to meeting the parameters of the 100 foot
check will tip the balance significantly in their favour.
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