GRAUPNER JetCat 6810, Руководство пользователя

Страница: 94 / 210

Helicopter mechanics
with model turbine engine
24
6.7 Additional measures
As a fundamental rule it is essential that all parts, including cables and connectors, are
securely fixed, and that there are no loose parts in the fuselage which the turbine could
ingest when running.
Additional measures can be taken in an effort to achieve an enhanced level of safety, i.e. to
minimise the risk of fire inside the fuselage, and even if a fire should occur, to maintain control
of the model and limit the damage.
•
The gas hoses can be sleeved in spiral silicone tubing which you can make yourself from
suitable fuel tubing or exhaust hose. If a flame should occur momentarily in the fuselage,
this could prevent it burning through the hose and igniting the gas.
•
As far as possible, all cables should be deployed along the bottom of the fuselage, and
should also be protected with spiral silicone tubing to guard against catching fire.
•
All essential servo leads (swashplate) should be bundled together to form a loom, which
can then be protected from fire with spiral silicone hose.
•
All non-essential servo leads (retracts, lighting system etc.) can be bundled together to
form looms, again protected with spiral silicone hose. It is also worthwhile fitting a fuse
(approx. 3...6A) in the power supply; this will prevent a short-circuit caused by a cable fire
disabling the entire receiving system.
•
Especially in Summer you must ensure that inflammable gases do not collect inside the fu-
selage when the model is in storage. Regularly vent the fuselage to prevent this happening.
•
Check the liquid gas system regularly for leaks; even after several days a filled gas tank
should still be full.
•
Lubricate the gas filler valve occasionally with a little silicone oil. The rubber gasket tends to
turn brittle after contact with liquid gas, and it will then leak. We recommend installing the
valve externally, so that gas will not collect inside the fuselage (the gas used is heavier than
air) even if the filler valve should develop a leak.
7. Main rotor blades
The main rotor head is of the link-less type, i.e. it has no flapping links, and this means that the
main rotor blades must flex in order to absorb the flapping motion. The rotor blades designed for
this mechanical system are therefore capable of bending, but are extremely stiff in torsion; this
is necessary for smooth, efficient running.
The hot turbine exhaust gas inevitably flows through the main rotor to a greater or lesser extent,
depending on the design of the helicopter. This causes no problems when the rotor is spinning,
even if the exhaust is blown out directly upwards as is the case with the NH 90. However, it is
essential to ensure that no rotor blade is located above the exhaust outlet when the rotor is
stationary, because the heat will damage it. This applies in particular when starting the turbine,
but also when stopping in the middle of a series of short flights, for example when checking
blade tracking. You can avoid this problem after a flight by stopping the turbine before the main
rotor is allowed to come to rest.
If you wish to use rotor blades other than those recommended, you must ensure that
they exhibit the same bending characteristics and the same torsional stiffness, otherwise
there is a serious risk of overloading the mechanical system, possibly leading to failure
of parts of the rotor head.
You must not use main or tail rotor blades made of metal.
8. Installing the mechanics in the fuselage
The mechanical system is designed to be installed in a fuselage which must be obtained sepa-
rately; the method of installation is described in the building instructions supplied with the fuse-
lage.