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immediate entry into autorotation to prevent a yaw and
the subsequent roll. Corrections to this rolling moment
can exceed rotor limits and cause mast bumping or
droop stop pounding.
Helicopters equipped with skids-on-floats are limited
in ground operations. Minimize horizontal movement
during takeoffs and landings from hard surfaces to
avoid scuffing or causing other damage to the floats.
Perform approaches, in which hover power may not be
available, by flaring through hovering altitude in a
slightly nose-high attitude to reduce forward motion.
Just prior to the aft portion of the floats touching down,
add sufficient collective pitch to slow the descent and
stop forward motion. Rotate the cyclic forward to level
the helicopter, and allow the helicopter to settle to the
ground, then reduce collective pitch to the full down
position. In helicopters with low inertia rotor systems,
an autorotation to a hard surface requires a more
aggressive flare to a near-zero groundspeed to ensure
minimal movement upon landing. A running takeoff or
landing on a hard surface is not recommended in
helicopters equipped with skids-on-floats.
Helicopters equipped with floats-on-skids are capable
of performing running takeoffs and landings, and
autorotations to hard surfaces require the same
procedures as non-float equipped helicopters. The
surfaces should be flat and clear of objects that may
puncture, rip, or cause other damage to the floats. Do
not attempt to land on the heels of floats-on-skids as
they may cause the tail boom to kick up and be struck
by the rotor.
Helicopters equipped with stored emergency pop-out
floats are operated with the same procedures as a
helicopter without floats. When emergency floats are
deployed, the helicopter may have similar characteristics
to a helicopter with fixed floats and should be
flown accordingly. If emergency floats are deployed
during autorotation, the increased surface increases
parasite drag with a resulting reduction in airspeed. To
regain the recommended autorotation airspeed, the
nose must be lowered.
Effects on aircraft performance must also be considered
during water operations. Air is often cooler near
bodies of water, thus decreasing the density altitude but
also increasing humidity. Although the higher humidity
of the air has little effect on aerodynamic performance,
it can reduce piston engine output by more then 10
percent. Properly leaning the mixture might possibly
return some of this lost power.
Turbine engines experience only a small, often negligible,
power loss in high humidity conditions.
Right
Roll
Yaw
Left
Intended Flightpath
Figure 9-4. Float instability.
Ch 09.qxd 8/25/04 11:32 AM Page 9-2
9-3
STARTING
A helicopter on a hard surface has the friction of the
skids or floats to counter the torque produced when
the rotor is engaged. Therefore, you have more control
over the helicopter if you can engage the rotors while
it is sitting on a hard surface. On water, little or no antitorque
control is present until the rotor system has
accelerated to approximately 50 percent of its normal
operating r.p.m. A heavily loaded helicopter’s floats
sit deeper in the water and create more resistance to
the turning force than a lightly loaded helicopter. Thus
a helicopter turns less when heavily loaded and more
when lightly loaded.
To overcome the spinning and to prevent drifting, tie
the helicopter securely to a dock or to the shore using
the fore and aft cross tubes if not otherwise indicated
in the POH or RFM. If help is not available for casting
off, it may be necessary to paddle to a clear location
well away from the shoreline for a safe start. Wind
and water currents may cause the helicopter to turn or
drift a considerable distance before control is obtained.
To compensate, use a starting position upwind and
upcurrent of a clear area.
Illusions of movement or non-movement can make it
difficult to maintain a fixed position during rotor
engagement and runup. Techniques to overcome these
illusions are discussed later.
TAXIING AND HOVERING
Where possible, it is usually more convenient and
safer to hover taxi to the destination. However, due to
power limits, local restrictions, noise, water spray, or
creating a hazard to other vessels or people, it may be
necessary to water taxi the helicopter. To taxi in water,
maintain full rotor r.p.m. and use sufficient up collective
to provide responsive cyclic control to move the
helicopter. Never bottom the collective pitch while the
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