Eunometic schrieb:

"Mechanical linkage" does not mean that the stick is connected to
pushrods and levers that move the control surfaces (which would be silly
on a fighter/bomber aircraft with up to ~55000 pounds weight).


Which means that PA200 Tornado when using 'mechanical' backup is
actually fully power opperated as opposed to power assisted (power
assisted can be designed to connect into a fully manual system with
limited movement).

correct.

Given the need for power it doesn't seem to make
much sense to bother to use a mechanical system at all.

The mechanical linkage backup is there if the 2x redundant fly-by-wire
system fails or gets damaged. When in "mech mode" (FBW dead but engines
are running) the aircraft is fully controllable (but of course reacts
more sensible due to the lack of CSAS and also lacks things like spin
prevention and AOA limiter etc). Loosing the FBW does not mean the
aircraft can't return safely...

An additional
layer of redundancy and an 'analog' backup would be better use of the
weight. Perhaps Panavia was worried about Electromagnetic Pulse or
Weapons.

Correct. Thanks to the mechanical linkage the aircraft is still operable
even when suffering from an EMP or with a damaged electronics system.
Even 4x redundant FBW wouldn't provide this safety, and the weight
penalty isn't really big.

I believe F-16 uses fiber optics.

The Eurofighter Typhoon uses fiber optics. The F-16 used a wire harness
(don't know if that has been changed in a later block but I doubt that).

In normal operation the potentiometers connected to the stick submit
stick position data to the flight control system (CSAS and SPILS) which
calculate the necessary control surface deflection and control the
corresponding actuators.


They use potentiometers? I though LVDT were normally used.

No, it's some sort of potentiometer, but of course a bit more
sophisticated than what you can find in consumer electronics ;-)

Benjamin