Piper Cub Vs F-15

In article , Alan
Dicey wrote:

Alan Dicey wrote
The first production fly-by-wire aircraft was the F-16.

Eunometic wrote:

Concord actually. They even wanted to put sidearm controllers on it.

Ron wrote:

F-16 was the first with a DIGITAL FBW. I think Concorde, and
possibly F-111 too had analog systems.

Peter Stickney wrote:

F-111, actually. And, perhaps the A-5 Vigilante, depending on how you
want to define FBW.

A major problem here is that the term fly-by-wire was popularised as a
marketing soundbite by the GD team during the Lightweight Fighter
competition in the early seventies. As such it had no strict
engineering definition. Prompted by the original poster, I was using it
in the way that Harry Hillaker does: -

"'Fly-by-wire' is a totally electronic system that uses
computer-generated electrical impulses, or signals, to transmit the
pilot's commands to the flight control surfaces instead of a combination
of the push rods, bell cranks, linkages, and cables used with more
conventional hydromechanical systems."

(Harry J. Hillaker is retired vice president and deputy program director
for the F-16, General Dynamics Corporation)

- which does come down to a somewhat circular definition (fly-by-wire
is defined as what the F-16 has, so of course it is the first).
However, I think most people understand fly-by-wire to include elements
of electrical signaling and computer control, which leads us back to
Hillakers definition, which makes the defining characteristics:

* electrically signalled
* no manual connection
* pilot flies computer: computer flies plane.

The first two are what a fly-by-wire system is.
The third is one particular implementation of fly-by-wire.
And it doesn't matter whether it's analog or digital,
or whether the a/c is inherently unstable and the FBW
system keeps it in the air. Those are also just implementations of
fly-by-wire .
Claiming you're the first because of your particular implementation
is disingenuous.

--
Harry Andreas
Engineering raconteur

Harry Andreas wrote:
In article , Alan
Dicey wrote:

* electrically signalled
* no manual connection
* pilot flies computer: computer flies plane.


The first two are what a fly-by-wire system is.
The third is one particular implementation of fly-by-wire.
And it doesn't matter whether it's analog or digital,
or whether the a/c is inherently unstable and the FBW
system keeps it in the air. Those are also just implementations of
fly-by-wire .

If I understand you correctly, you hold to the view that any
electrically signalled flight control system is fly-by-wire? I think
that makes the Vulcan a pioneer, along with the Vigilante.

The point I was trying to make was that the term has only gained
currency recently, starting with the F-16. It has since been applied
retroactively to aircraft that lack the intermediate computer (be it
digital or analog), some of which have electromechanical equivalents
(mixer boxes) and/or control augmentation systems, autopilots or terrain
following systems. I don't think the term fly-by-wire was applied to
these aircraft when they were being designed or in service, but I would
be happy to be proved wrong, in the interests of illumination.

Claiming you're the first because of your particular implementation
is disingenuous.


Thats a bit harsh. I stated up front that circular reasoning was
involved in the definition I was using and also indicated that the line
wasn't clearcut. No dishonesty or insincerity involved.

And its not my claim, nor ever has been: it was GD's claim, and only in
the sense that they made a selling point out of it.

To me, fly-by-wire will always mean a system where the pilots inputs are
moderated by the flight control computers. As we have just
demonstrated, it has no clearly-agreed technical meaning, a fact which I
ascribe to its birth in the mind of a marketeer.

On Wed, 30 Jun 2004 09:49:39 -0700, "Darrell" wrote:

No single engine privileges
because I wasn't current in any single engine aircraft.

Seems to me the lesser airplane ought to be included in the greater,
just as the "lesser included offense" bit the sergeant who was found
innocent of rape, guilty of adultery.

all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! weblog www.vivabush.org

On Wed, 30 Jun 2004 11:18:16 -0400, "Mortimer Schnerd, RN"
wrote:

People put dope on the cork?

Keeps them from getting gas-logged. Or water-logged. Or sumpin.

I pay no attention to the float, since you can't rely on it in flight.
After two hours, I look for a place to refuel.

all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! weblog www.vivabush.org

On Wed, 30 Jun 2004 19:48:28 +0100, Alan Dicey
wrote:

I think this is also the kind of system the original poster was thinking
of, where the aircraft is kept from departing from controlled flight by
the flight control computer overriding the pilot inputs and keeping the
aircraft right on the edge of its flight envelope.

And would crash without the computer? As I understand it, a human
pilot can't control the B-2 unaided. Is that correct, and would that
be a fair definition of fly-by-wire?


all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! weblog www.vivabush.org

In article , Alan
Dicey wrote:

Harry Andreas wrote:
In article , Alan
Dicey wrote:

* electrically signalled
* no manual connection
* pilot flies computer: computer flies plane.


The first two are what a fly-by-wire system is.
The third is one particular implementation of fly-by-wire.
And it doesn't matter whether it's analog or digital,
or whether the a/c is inherently unstable and the FBW
system keeps it in the air. Those are also just implementations of
fly-by-wire .

If I understand you correctly, you hold to the view that any
electrically signalled flight control system is fly-by-wire? I think
that makes the Vulcan a pioneer, along with the Vigilante.

As long as we're talking about the primary flight controls.
I'm not familiar enough with the Vulcan to say.


The point I was trying to make was that the term has only gained
currency recently, starting with the F-16. It has since been applied
retroactively to aircraft that lack the intermediate computer (be it
digital or analog), some of which have electromechanical equivalents
(mixer boxes) and/or control augmentation systems, autopilots or terrain
following systems. I don't think the term fly-by-wire was applied to
these aircraft when they were being designed or in service, but I would
be happy to be proved wrong, in the interests of illumination.

Lots of things fall under a later definition, say, supercruise...


Claiming you're the first because of your particular implementation
is disingenuous.


Thats a bit harsh. I stated up front that circular reasoning was
involved in the definition I was using and also indicated that the line
wasn't clearcut. No dishonesty or insincerity involved.

I wasn't criticizing you....


And its not my claim, nor ever has been: it was GD's claim, and only in
the sense that they made a selling point out of it.

....I was commenting on GD's re-definition of the term. Sorry if that
wasn't clear.


To me, fly-by-wire will always mean a system where the pilots inputs are
moderated by the flight control computers. As we have just
demonstrated, it has no clearly-agreed technical meaning, a fact which I
ascribe to its birth in the mind of a marketeer.

Can't argue with that.
ciao.

--
Harry Andreas
Engineering raconteur

Harry Andreas wrote:
In article , Alan
Dicey wrote:
If I understand you correctly, you hold to the view that any
electrically signalled flight control system is fly-by-wire? I think
that makes the Vulcan a pioneer, along with the Vigilante.


As long as we're talking about the primary flight controls.
I'm not familiar enough with the Vulcan to say.


One reference below, look about 3/4 down the article for a paragraph
entitled Vulcan: A Revolutionary Forebear.

http://www.defensedaily.com/cgi/av/s...e=1001a380.htm

Anybody know if the B-52 was electrically signalled?

How about Victor or Valiant?

Cub Driver wrote:

On Wed, 30 Jun 2004 19:48:28 +0100, Alan Dicey
wrote:

I think this is also the kind of system the original poster was thinking
of, where the aircraft is kept from departing from controlled flight by
the flight control computer overriding the pilot inputs and keeping the
aircraft right on the edge of its flight envelope.

And would crash without the computer? As I understand it, a human
pilot can't control the B-2 unaided. Is that correct, and would that
be a fair definition of fly-by-wire?


That is my understanding of it. Some modern aircraft are designed to be
aerodynamically unstable (center of pressure in front of center of
gravity) in part or all of the flight envelope, for reasons associated
with stealth, variable geometry or vectored thrust.

Here's a couple of links with some basic descriptions of the B-2 FCS:

http://www.edwards.af.mil/articles98...er/page_5.html

http://www.globalsecurity.org/wmd/sy...-2-history.htm

recompose them to one line if they break in your newsreader.

Here's another discussion of flight control systems in general, with a
definition of fly-by-wire that seems to agree with mine in that it
specifies computer signal processing;

http://www.aero.polimi.it/~l050263/b...6-FligCont.pdf


From what I can find, it looks as if the B-2 is designed for
fly-by-wire control, probably to keep it stealthy as much as anything.
The flying wing shape by itself does not demand FBW, as the XB-35 and
YB-49 designs of the 40's were controllable without computer assistance.

Alan Dicey wrote in message ...
Alan Dicey wrote
The first production fly-by-wire aircraft was the F-16.

Eunometic wrote:

Concord actually. They even wanted to put sidearm controllers on it.

Ron wrote:

F-16 was the first with a DIGITAL FBW. I think Concorde, and
possibly F-111 too had analog systems.

Peter Stickney wrote:

F-111, actually. And, perhaps the A-5 Vigilante, depending on how you
want to define FBW.

A major problem here is that the term fly-by-wire was popularised as a
marketing soundbite by the GD team during the Lightweight Fighter
competition in the early seventies. As such it had no strict
engineering definition. Prompted by the original poster, I was using it
in the way that Harry Hillaker does: -

"'Fly-by-wire' is a totally electronic system that uses
computer-generated electrical impulses, or signals, to transmit the
pilot's commands to the flight control surfaces instead of a combination
of the push rods, bell cranks, linkages, and cables used with more
conventional hydromechanical systems."

(Harry J. Hillaker is retired vice president and deputy program director
for the F-16, General Dynamics Corporation)

- which does come down to a somewhat circular definition (fly-by-wire
is defined as what the F-16 has, so of course it is the first).
However, I think most people understand fly-by-wire to include elements
of electrical signaling and computer control, which leads us back to
Hillakers definition, which makes the defining characteristics:

* electrically signalled
* no manual connection
* pilot flies computer: computer flies plane.

I think this is also the kind of system the original poster was thinking
of, where the aircraft is kept from departing from controlled flight by
the flight control computer overriding the pilot inputs and keeping the
aircraft right on the edge of its flight envelope. My original point
was that the F-15 does not have this kind of fly-by-wire :-)

Probably because the F15 doesn't need it. However perhaps the F15
does have some sort of 'stability augmentation system' that opperates
through the fly by wire system. Even 707 I am told had am
accelerometer in the talifin to slap the rudder to stop phugoid type
snaking.

There inherently isn't anything a digital system can do that analog
system can't except that complexity and non linear rules are much
easier to implement.


The F-16 system, manufactured by Lear Seigler, was initially an analog
system, by the way. The first digital-from-scratch FBW aircraft was the
F-18 Hornet.

If you broaden the definition of fly-by-wire to include all
electrically-signalled FCS, there are many aircraft prior to the F-16
that qualify, among them being:

The Avro Vulcan: Tim Laming's The Vulcan Story includes the aircrew
manual which describes the system as electro-hydraulic, and including
artificial feel, autostabilisation and mach trimmers.

The A-5 Vigilante:
http://www.airtoaircombat.com/backgr...p?id=87&bg=305
The aircraft had a primitive fly-by-wire flight control system in which
stick movements of the stick were converted into electrical signals
which fed into actuators that controlled lateral and l longitudinal
movements. The actuators then mechanically positioned the control
valves, the horizontal stabilizer, and the spoiler activators. There was
a mechanical backup system in case this system failed.

Concorde
http://www.concordesst.com/autopilot.html
Concorde has an Automatic Flight Control System (AFCS) installed, that
for the 1970s was state of the art. The system is designed to allow
"hands off" control of the aircraft from climb out to landing. There are
2 mains parts to the system; the Autothrottles and Autopilot, and a
number of associated systems, such as the warning displays and test systems


One aspect of the Concord was that its 6 elevons (ie combined
elevators and aelerons) also provided the aircraft with 'variable
camber'. The elevons are adjusted to provide the aerodynamically
optimal wing camber for the particular flight regime. This changes
the trim of the aricraft but this is compensated by pumping fuel
between for and aft tanks.

These sorts of things are much easier to do in a fly by wire system
alalog or digital.

The trim changes associated with variable wing sweep would also make
fly by wirse attractive. Furthermore the slab tail of aircaft such as
the F111 needs to provide both roll and pitch correction: again
something that must be hard to do mechanically.





http://www.concordesst.com/flightsys.html
Although it is described as fly-by-wire, it is not computer-controlled
and there is manual reversion. Shades of meaning, I know.

Autopilot plus autothrottle is not fly-by-wire, by the "F-16"
definitions :-)

I don't know offhand and can't find on the web a good enough description
of the F-111 FCS to tell; but I suspect that it too falls short of the
definition I am using.

Tornado is fly-by-wire, but comes after the F-16. It is also
aerodynamically stable and has a manual reversion mode.

I'm sure there are better qualified people than me on this newsgroup who
can give a more authorative opinion: I only used to work for Marconi
Avionics, so what do I know :-)

Cub Driver wrote:


[ much snippage...]

As I understand it, a human
pilot can't control the B-2 unaided. Is that correct, and would that
be a fair definition of fly-by-wire?

I assume the B-2 would be tough to fly unaided -
but you've got a fight on your hands with almost
every gray-haired avionics guy if you insist that
FBW automatically includes a computer element.

FBW replaces mechanical links with wire; nothing more.
(Though of course, there may be a lot more attached
to a FBW system...)