Yes and no. Of course one needs a big fuse (mine is 7 Amps) on the battery
to protect the cable running to the instrument panel.
Individual fuses on simple instruments like a T/S do protect the main fuse
to blow off. On more sophisticated intrumentation like a radio or a flight
computer, the protect the instrument in the case you connect the battery
with the instrument switched on. That usually produces a spike which some of
the instruments (the LX160s is a good example) absolutely don't like.
Fuses which protect an instrument need to be fast fuses, fuses protecting
the main fuse or cables are slow fuses.

--
Bert Willing

ASW20 "TW"


"John Giddy" a écrit dans le message de news:
...
On Fri, 11 Mar 2005 09:24:23 +0100, Bert Willing wrote:

There are components which are not fused internally (i.e. T/S indicators,
Colibri etc).

Bimetal breakers are disastreous in this case as they are very slow and
will
ultimately less pass about 10 times the nominal value before cutting off.
This winter I was loocking into replacing my fuses by breakers, and I
decided that I didn't want to have this crap in my gliders. The breakers
to
use are magnetic ones which are pretty fast - but the price tag is very
different... so finally I kept going with fuses.

Fuses for individual instruments don't protect those instruments, but
do stop the larger battery fuse from blowing if the instrument fails
in a way which draws a high current from the battery.
This only works if the individual instrument fuses have a current
rating smaller than the common battery fuse.
If the common battery fuse blows, you lose ALL the instruments. If a
single instrument fuse blows, you lose that instrument, but you were
going to lose it anyway, as it is the failure of the instrument which
blows that fuse.
Cheers, John G.