Operation Manual

Switching to Autorotation
(access via Set-Up Menu)
76 Helicopter
AUTOROTATION
Autorotation is a helicopter flight condition, in which
the main rotor is no longer powered by the engine
but by the air flow trough the rotor in descending
flight. So that sufficient main rotor RPM remains, the
rotor blades must be brought, with the collective
pitch control stick, to a suitably small angle of
incidence. The ground approach angle lies depends
on the wind strength and is between 45° (zero wind)
and 80° (strong wind). Landing from this descending
flight is achieved by increasing the blade angle,
using the energy stored in the rotor to create lift.
Using autorotation both a full-size as well as model
helicopters able to safely land without power, e.g.
with engine breakdown.
Also in case of a loss of the tail rotor, immediate
shutdown of the engine and the landing using
autorotation is the only possibility, otherwise an
uncontrollable spin develops around the vertical axis
and the model will crash.
A requirement to be able to do this is a suitably
trained pilot, who is familiar with the aircraft and in
this flight condition. Fast reactions and a good
judgement by eye are also needed, since the
rotational energy stored in the rotor is available only
for a very limited time at the point of landing as rotor
speed decreases rapidly when producing lift.
With autorotation as task in competitions, the engine
is required to be turned off. However, during training
autorotation landings it is favourable to keep the
engine at idle so if necessary the autorotation can be
aborted and the model is able to resume normal
powered flight.
The mc-16/20 transmitter offers the ability to switch
the use of autorotation, using an external switch
attached to socket 3 of the transmitter board.
The throttle function is separated from the control
stick, which still controls the collective pitch; the
throttle servo takes a position set in the "ATR"
program.
Additionally the activation of the autorotation switch
causes the following:
• The mixers "ST..." for the static and "DYN" for
dynamic torque compensation are switched off.
The announcements "STH", "STL" or "DYN"
flash in the display.
• The set values of the throttle curves are no
longer effective, which is indicated by "TL0",
"TL1" or "TL2" flashing in the display.
• The autorotation pitch curve setting become
effective as set using "PLA", "PMA" and "PHA"
(see page 73).
Set-Up
After selection the display initially shows "ATR OF" -
The autorotation program is switched off. The
program is switched on by the INC or DEC key and
the position of the throttle servo for autorotation can
now be adjusted over the range of 0 to +125.
In order to prevent inadvertent switching on
autorotation, and turning the engine off, the
autorotation option can be deactivated using the
CLEAR button (announcement "ATR OF").