Fly-By-Wire Flight Controls

Suppose a smaller airplane with it's fly-by-wire controls goes runs out
of fuel. All the engines quit. On a larger jet a ram air turbine
would drop into the airstream and power the controls. How does it work
on smaller planes like the Dassault Falcon or the F-16?

Alternatively, I've always wondered if one could not keep a special
reserve tank for the APU. When the engines quit, the APU
automatically starts to power the controls. Would such a system be
safe and would it be certifiable? Would it weigh less than the
existing system?

-Charles Talleyrand

"Charles Talleyrand" wrote in message
oups.com...
Suppose a smaller airplane with it's fly-by-wire controls goes runs out
of fuel. All the engines quit. On a larger jet a ram air turbine
would drop into the airstream and power the controls. How does it work
on smaller planes like the Dassault Falcon or the F-16?

Alternatively, I've always wondered if one could not keep a special
reserve tank for the APU. When the engines quit, the APU
automatically starts to power the controls. Would such a system be
safe and would it be certifiable? Would it weigh less than the
existing system?

-Charles Talleyrand


On the A-6E and EA-6B aircraft, the Emergency Ram Air Turbine (RAT) only
powers the Emergency DC Bus which in turn provides power to a small set of
essential instruments. It does not provide any hydraulic power for the
flight controls.

Charles Talleyrand wrote:
Suppose a smaller airplane with it's fly-by-wire controls goes runs out
of fuel. All the engines quit. On a larger jet a ram air turbine
would drop into the airstream and power the controls. How does it work
on smaller planes like the Dassault Falcon or the F-16?

The same way on a BAE Hawk.

Alternatively, I've always wondered if one could not keep a special
reserve tank for the APU. When the engines quit, the APU
automatically starts to power the controls. Would such a system be
safe and would it be certifiable? Would it weigh less than the
existing system?

Some years ago there was an Airbus A330 FBW fly by wire widebody that
ran out of fuel crossing the atlantic. It had to make an emergency
landing at (I thnk) the Azores I think from over 100km out without
fuel.

A leaking fuel delivery pipe in the engine pylon drained the aircrafts
fuel: the pilot didn't believe his instruments and thus kept
transfering fuel from the good side to the bad side rather than
shutdown the bad engine. He thus drained both wings.

When fuel cut out (I saw a dramatisation ogf the events) the ram air
turbine deployed and the pilots, after finally acknowledging their fuel
situation went through their checklist.

Lights and pressurisation was lost with the power.

Most pointedly they lost spoilers and flaps; they really only had a few
instruments, ailerons, tail surfaces and the undercarriage. As a
result of being without flaps the landing speed was very high and
becuase there were no spoilers they couldn't loose speed or altitude
and actually had to circle and zig zag to loose both speed an altitude.
This made the one chance of making the runway even harder as there
would be no go arounds.

To cap it all of the runway in the azores ends in a 300ft shear cliff.
They stopped a few dozen meters short with blown tyres.

Airbus changed their software and though the pilot was clearly not
making the best decisions that day it was easier to given him awards.

The ram air turbine provides very little power. I think the idea of
giving the APU its own reserve fuel supply is tempered by the fact that
it is perhaps better to keep the engine lit for a few seconds longer.

Perhaps a cartriedge or two of of rocket-gas generator turbine could be
used to provide pressure for flap and spoiler deployment

Perhaps a cartriedge or two of of rocket-gas generator turbine could be
used to provide pressure for flap and spoiler deployment

Why not just load more fuel. It would not weigh any more and would be
far less complicated. Also have sirens which screech at the pilot.

"Eunometic" wrote in message
ups.com...


Some years ago there was an Airbus A330 FBW fly by wire widebody that
ran out of fuel crossing the atlantic. It had to make an emergency
landing at (I thnk) the Azores I think from over 100km out without
fuel.


70nm at 34,500 ft

A leaking fuel delivery pipe in the engine pylon drained the aircrafts
fuel: the pilot didn't believe his instruments and thus kept
transfering fuel from the good side to the bad side rather than
shutdown the bad engine. He thus drained both wings.

When fuel cut out (I saw a dramatisation ogf the events) the ram air
turbine deployed and the pilots, after finally acknowledging their fuel
situation went through their checklist.

Lights and pressurisation was lost with the power.

Most pointedly they lost spoilers and flaps; they really only had a few
instruments, ailerons, tail surfaces and the undercarriage. As a
result of being without flaps the landing speed was very high and
becuase there were no spoilers they couldn't loose speed or altitude
and actually had to circle and zig zag to loose both speed an altitude.
This made the one chance of making the runway even harder as there
would be no go arounds.

To cap it all of the runway in the azores ends in a 300ft shear cliff.
They stopped a few dozen meters short with blown tyres.

Airbus changed their software and though the pilot was clearly not
making the best decisions that day it was easier to given him awards.


Airbus did not change their software which had behaved correctly, they
re-issued the flight manuals emphasizing the advice that was already
present to close the cross feed valves in the case of unexpectedly high
fuel consumption on one engine.

Transport Canada fined the airline C$250,000 (about US$165,000)
for maintenance infractions relating to an improper installation of a
hydraulic pump on an engine of the incident aircraft.


Keith



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Most pointedly they lost spoilers and flaps; they really only had a few
instruments, ailerons, tail surfaces and the undercarriage. As a
result of being without flaps the landing speed was very high and
becuase there were no spoilers they couldn't loose speed or altitude
and actually had to circle and zig zag to loose both speed an altitude.

What powered these controls?

I assume the insturments were powered by the ram air turbine, but
ailerons are BIG. What powered those?

-Thanks

Charles Talleyrand schrieb:

Suppose a smaller airplane with it's fly-by-wire controls goes runs out
of fuel. All the engines quit. On a larger jet a ram air turbine
would drop into the airstream and power the controls. How does it work
on smaller planes like the Dassault Falcon or the F-16?

The Panavia 200 Tornado has a EPS battery (one shot battery) that in
case of double engine out situations supplies a few instruments and an
electric pump to have some hydraulic pressure. This allows maintaining
control over the a/c for ~5-7 (max 10) minutes.

Alternatively, I've always wondered if one could not keep a special
reserve tank for the APU. When the engines quit, the APU
automatically starts to power the controls. Would such a system be
safe and would it be certifiable? Would it weigh less than the
existing system?

I a lot of airplanes the APUs (resp. their intakes and exhausts) are
mounted in a way that they can't be used inflight. Besides that, if
there still is fuel in the tanks it's better served for keeping the
engine alive than just the APU...

Benjamin

Benjamin Gawert wrote:
Charles Talleyrand schrieb:

Suppose a smaller airplane with it's fly-by-wire controls goes runs out
of fuel. All the engines quit. On a larger jet a ram air turbine
would drop into the airstream and power the controls. How does it work
on smaller planes like the Dassault Falcon or the F-16?

The Panavia 200 Tornado has a EPS battery (one shot battery) that in
case of double engine out situations supplies a few instruments and an
electric pump to have some hydraulic pressure. This allows maintaining
control over the a/c for ~5-7 (max 10) minutes.

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.

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)

Thermal batteries appear to be the battery of choice for missiles. I
did read though that the early MANPAD Stingers handed over to the
Mujahidine had thermal batteries that would now be failing and thus
(thankfully) rendering the missiles inopperational.

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.


Alternatively, I've always wondered if one could not keep a special
reserve tank for the APU. When the engines quit, the APU
automatically starts to power the controls. Would such a system be
safe and would it be certifiable? Would it weigh less than the
existing system?

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

Besides that, if
there still is fuel in the tanks it's better served for keeping the
engine alive than just the APU...

Benjamin

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

"Benjamin Gawert" wrote in message
...
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.

The F3 (ADV) has a RAT