CARE AND OPERATION OF ARTIFICIAL
HORIZONS
GENERAL OPERATION
All artificial horizons are precision instruments which need to be handled
carefully to achieve maximum life and operational reliability.
The instrument should ideally be mounted somewhere near the centre
of the instrument panel. When flying in cloud you need to be able to read
it easily, and be able to achieve a good scan between it and the other
instruments. Mounting it near the bottom of the panel where it is obscured
by the stick is not generally a good idea.
Switch on the instrument a couple of minutes before entering cloud.
The gyroscope in electrically driven instruments rotates at nearly 24000
rpm and takes a little while to get there. As soon as power is applied
the power fail flag should disappear. DO NOT USE
THE FAST ERECT MECHANISM AS SOON AS YOU SWITCH ON THE INSTRUMENT.
The gyroscope needs to be rotating at a reasonable speed before the fast
erect mechanism will work satisfactorily. If the beam bar bounces around
like crazy, or rolls continuously when using the fast erect the gyro is
not rotating fast enough. Release the switch and wait about 30 seconds
before trying again. Using the fast erect mechanism when the gyro is running
at low speed can damage the instrument. The fast erect mechanism should
only be used in level or near level flight. If fast erect is used in a
steep turn then the instrument can erect to a false horizon, and give erroneous
readings. When using fast erect hold the button in continuously until the
beam bar is level in both pitch and roll.
SOME GENERAL DO's AND DON'Ts
DO use the instrument on a regular basis. This will keep the bearings in
good condition. In general I normally run the horizon on every flight,
even if only for 20 minutes. In winter when the glider is not being used
for months, it is a good idea to run the instrument on the ground every
now and then. This also applies to Turn and Slip indicators.
DO keep your glider batteries in good condition. If your syndicate is
of the type which recharges the batteries every 10 flights then you will
be disappointed. I normally recharge the batteries after every flight.
Remember that sealed lead acid batteries DO NOT have to be fully discharged
before recharging unlike NiCads. Leaving lead acid batteries in a discharged
state seriously reduces their life. In addition the cables connecting the
batteries to the glider instrument panel should be as thick as possible
in order to minimise voltage drop.
DO NOT drop the instrument. This is definitely very bad for it. When
transporting the instrument in your car pack it carefully in a box. Very
heavy landings can damage ALL gyro instruments as well as your glider and
back so avoid them. Indulging in aerobatics such as loops is not recommended
with the horizon running.
DO NOT break the front glass. The central "pip" is actually the front
outer gimbal bearing. If the glass is broken then not only will air be
allowed into the sealed instrument, but the bearing may then be out of
true. If the glass is broken then the instrument is effectively useless.
Glass which has been broken due to carelessness or heavy landings is not
covered by the warranty.
Finally a word about backup systems. It seems that a number of you out
there venture into cloud with either a single turn and slip or a single
horizon or a single battery. This is definitely a BAD idea. If this single
item fails then you are in BIG trouble. My own recommendation is that your
instrument panel contains an artificial horizon and a turn and slip indicator,
with a double battery system, so that any battery can be connected to any
instrument.