Magazine Helicopter Industry #101

HELICOPTER INDUSTRY I FLIGHTEST I
THE STARTING PHASE
Although our helicopter is in the middle of its scheduled daily
flight program, some adjustments and checks are required.
Eight levels of adjustment allow to select the right distance
between the seat cushion and the pedals, so pilots of
different sizes will easily find the most comfortable position.
The engine and rotor are still running, which eliminates the
need for a full start-up procedure, which however deserves
to be described here.
The pilot in command, once the pre-flight visit has been
made, puts the battery on, checks that all the indicator lights
are working, confirms that the fuel level indicated on board
is the same as that which had been previously checked with
a manual gauge during the outdoor pre-flight. If the engine
is started for the first time of the day, the engine must heat
until the oil temperature reach its nominal operating level of
200°F. But if the engine, at the time of starting, is already
hot, the pilot plays on the booster, avoiding admitting too
much fuel by rotating the gas throttle located at the top of
the collective lever.
If the engine is cold, it will overfill it by opening the full
throttle. The fuel pump is turned on and the mixture control
on full rich for eight seconds. Then, the pump is switched off
and the mixture reduced to «lean».
The start sequence is activated by pressing a master switch.
Finally, the starter is actuated using another button located
on the collective lever. Two or three seconds are enough to
launch the four cylinders of the 225 shp Lycoming HIO-360
turbocharged.
Maintained at 1,500 rpm, the engine begins to heat. While
waiting for the nominal 200°F, the clutch is made using a
lever to synchronize the rotation of the rotor and that of the
engine. Then, the engine set at 2,300 rpm, the oil temperature
rises quickly to 80°F.
CHECKS AND PRESETS
At this temperature, the pilot set the engine to its nominal
speed of 3,050 rpm. He then checks the two magnetos
the cylinders are powered by two spark plugs each. The
magnetos are cut one after the other. At each cut, a loss
of 100 to 125 rpm is tolerated. With the two magnetos in
operation again, the pilot tests the response of the freewheel
by cutting off abruptly the power. The main rotor must
continue to rotate normally, when the engine revolutions have
dropped. The desynchronization of the engine revolution and
rotor revolution indicators having been checked, the engine
is set back to the initial speed of 3050 rpm. The turbocharger
requires to adjust the mixture, in order to prevent the exhaust
gases from reaching a too high temperature. On the flight
deck, a dial indicates the fuel mixture. We therefore reduce
a little the mixture, adjusting the consumption to 65 or 70
pounds/hour so as to limit the temperature of the exhaust
gases (TIT)to 1500 ° F.
Take-off is now imminent. Belts fastened, doors closed, all
nominal parameters checked and no obstacles around. A
pull on the collective allows us to hover at one meter from
the ground. The amplitude on the pedals is normal, without
exaggeration. The movement of the foot alone (and not of
the leg) is enough to steer the nose of the aircraft in the right
direction. A glance at the exhaust temperature confirms
that the preset is correct. The balance of the helicopter is
good. We are now moving slowly towards the take-off area.
On a piston engine, the power indicator corresponds to the
manifold pressure applied to the engine. When hovering, the
pressure gauge on the Enstrom is 26 to 27 inches. But with
the turbocharger, during the takeoff phase, we will be able to
increase the manifold pressure up to 39 inches.
We are ready and lined-up for takeoff. A tiny pressure on
the cyclic, forward, triggers our longitudinal movement and
quickly brings us to the hanging speed - the one where the
helicopter flies outside the ground effect. n
HI I 70