Piper Cub Vs F-15

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...)

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 :-)

Subject: Piper Cub Vs F-15
From: "Emilio"
Date: 6/29/2004 11:13 AM Central Daylight Time
Message-id:

It is hard to believe that F-15 can fly formation with Piper Cub.

http://www.pipercubforum.com/intercep.htm

Do F-15 fly by wire system prevent the aircraft from stalling at that low
speed? Last time I saw an aircraft with fly by wire system did such a
stunt, Airbus plowed right in to the forest at the end of the forest!

Emilio.

The article is from ANN which automatically makes the details automatically
suspect. If it was written my Jim "Capt Zoom" Campbell it is near fiction even
based on an actual event. For a little overview see:
http://mywebpages.comcast.net/ousterj/zoom.html

What tripped my BS alarm was the C-172's pilot's first hint he wasn't alone was
the "smell of burning paint." Unless the guy was stone deaf would he not have
heard the F-15 if it were close enough to smell? I'm am not saying the event
didn't occur, just not the way it was written.

Dan, U.S. Air Force, retired

On 29 Jun 2004 19:45:36 GMT, (B2431) wrote:

What tripped my BS alarm was the C-172's pilot's first hint he wasn't alone was
the "smell of burning paint." Unless the guy was stone deaf would he not have
heard the F-15 if it were close enough to smell? I'm am not saying the event
didn't occur, just not the way it was written.

That's the pilot talking, not the reporter.

Personally, I read the Aero-News Propwash every morning and find it at
least as informative as this newsgroup, and the opinions probably less
biased.

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

Your comment about Airbus is quite out... The fact you are speaking
about is coming from a direct mistake of a pilot stupid enough to
execute a non planned demo, with passengers on board, over an un
prepared field...
And this aircraft is not a fighter...

That particular case was a 172.

F-16s were evidently dispatched to intercept me while I was bring a
Cub home on 9/11. Happily I was on the ground before they located me.
www.pipercubforum.com/defcon.htm

Which is what sparked my interest in the matter. I hope you hear from
an F-15/F-16 driver who has been obliged to make such an interception.

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 Tue, 29 Jun 2004 11:13:15 -0500, "Emilio"
wrote:

It is hard to believe that F-15 can fly formation with Piper Cub.

http://www.pipercubforum.com/intercep.htm

I've seen thirty F/A-18s and six "Ducks" fly in formation, too. It
didn't last very long, though. Ditto the F-15 and the A-37. They
only have to be in the proper relative position long enough for the
photographer to get the photo.

Do F-15 fly by wire system prevent the aircraft from stalling at that low
speed? Last time I saw an aircraft with fly by wire system did such a
stunt, Airbus plowed right in to the forest at the end of the forest!

The F-15 isn't fly-by-wire. It's augmented, but not fly-by-wire.

Mary

--
Mary Shafer Retired aerospace research engineer