Eunometic schrieb:

These EPS (Emergency Power System) Batteries are usually known as
"Thermal Batteries". They have an eutectic electrolyte of salts that
are melted by a pyrotechnical charge. Because the electrolyte is inert
and sold untill melted shelf lives of 20+ years are possible. Because
of the high opperating temperature very high power densities are
possible.

The original PA200 EPS battery used liquid acid which when activated
flowed in precharged battery chambers. Due to several hazards that these
batteries incorporate they have been replaced by thermal batteries.

20 years would not be full life for an airliner and a ram air turbine I
suggest would require less maintenance. (ie it doesn't ever need
replacement)

Nope. A RAM air turbine _does_ indeed need maintenance, not only because
of aging seals and other items that have to be replaced from time to
time but also because it's a quite complicated mechanical part that has
to be checked in certain intervals to make sure it is in working condition.

RAM air turbines are certainly not a put-it-in-and-forget-it thing...

The Panavia Tornado also has Nickel Cadmium Secondary rechargeable
batteries (perhaps upgraded to NiMH now?) for APU starting and other
power. I suspect that these could keep the system up for a few minutes
on their own if in good condition.

Nope, the master battery (which is indeed NiMH now) only feeds certain
busbars that are required for start and is not suitable for emergency
operation...

I a lot of airplanes the APUs (resp. their intakes and exhausts) are
mounted in a way that they can't be used inflight.


This would hardly apply to the Tornado.

It does apply for the PA200 Tornado. The APU is not operable in-flight,
if you loose both engines and the one-shot battery is down you have to
get out of that thing...

Tornado however uses its
entire slab sided botton fueselage for weapons: there is little room
for ram air turbine.

Nope. It would be possible to integrate a RAM air turbine into the PA200
Tornado by relocating and re-arranging equipment in the lower
electronics bays. However, the efforts and also the cost are not
justifyable because a RAM air turbine would bring no real safety
imrpovement on the Tornado which already has a really very good safety
record, not to forget that it's old now and most airforces are planning
and/or already working on replacing it.

Benjamin