Fly-By-Wire Flight Controls

Benjamin Gawert wrote:
Eunometic schrieb:

Eunometic schrieb:
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...


I didn't think Tornado was fully FBW?

The PA200 Tornado is fully FBW with a mechanical linkage backup system...

Benjamin

Then why does it need a thermal backup battery to remain airborn?

Eunometic schrieb:

The PA200 Tornado is fully FBW with a mechanical linkage backup system...

Benjamin


Then why does it need a thermal backup battery to remain airborn?

Because besides power for certain important instruments and the radio
the EPS battery also powers an electric motor that powers a hydraulic pump.

"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). When in
so-called "mech mode" the stick is connected to several hydraulic valves
that control the hydraulic actuators. So you need hydraulics pressure,
and in cases of double engine out this hydraulic pressure comes from an
electric pump that powered by the EPS battery.

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. The mechanical linkage is inactive (in
emergencies the stick gets linked to the mechanical controls through a
honeycomb block which gets squeezed by the stick movement applied by the
panicing pilot ;-)

This applies to the GR versions (bomber), I don't know if the F versions
are somewhat different.

Benjamin

Benjamin Gawert wrote:
Eunometic schrieb:

The PA200 Tornado is fully FBW with a mechanical linkage backup system...

Benjamin


Then why does it need a thermal backup battery to remain airborn?

Because besides power for certain important instruments and the radio
the EPS battery also powers an electric motor that powers a hydraulic pump.

"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). Given the need for power it doesn't seem to make
much sense to bother to use a mechanical system at all. 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. I believe F-16 uses fiber optics.

When in
so-called "mech mode" the stick is connected to several hydraulic valves
that control the hydraulic actuators. So you need hydraulics pressure,
and in cases of double engine out this hydraulic pressure comes from an
electric pump that powered by the EPS battery.

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.

The mechanical linkage is inactive (in
emergencies the stick gets linked to the mechanical controls through a
honeycomb block which gets squeezed by the stick movement applied by the
panicing pilot ;-)

This applies to the GR versions (bomber), I don't know if the F versions
are somewhat different.

Benjamin

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

"Eunometic" wrote in message
oups.com...

Benjamin Gawert wrote:
Eunometic schrieb:

Eunometic schrieb:
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...


I didn't think Tornado was fully FBW?

The PA200 Tornado is fully FBW with a mechanical linkage backup
system...

Benjamin

Then why does it need a thermal backup battery to remain airborn?

The One Shot Battery is there to provide electrical power to a Fuel pump (or
in combination with a Hyd pump). The engines also need electrical power to
keep their systems running - without electrics, the engines will "run
away" - Very bad thing if you're not near a nice big bit of tarmac......

Ian wrote:
"Eunometic" wrote in message
oups.com...

Benjamin Gawert wrote:

Eunometic schrieb:


Eunometic schrieb:
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...


I didn't think Tornado was fully FBW?

The PA200 Tornado is fully FBW with a mechanical linkage backup

system...

Benjamin

Then why does it need a thermal backup battery to remain airborn?


The One Shot Battery is there to provide electrical power to a Fuel pump (or
in combination with a Hyd pump). The engines also need electrical power to
keep their systems running - without electrics, the engines will "run
away" - Very bad thing if you're not near a nice big bit of tarmac......


Or, more importantly, a runway. They tend to be made of concrete not
asphalt.

Dan, U.S. Air Force, retired

Benjamin Gawert wrote:
Eunometic schrieb:

Eunometic schrieb:
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...


I didn't think Tornado was fully FBW?

The PA200 Tornado is fully FBW with a mechanical linkage backup system...

Benjamin

Then why does it need a thermal backup battery to remain airborn?