Piper Cub Vs F-15

FBW replaces mechanical links with wire;

Have to be careful how you phrase that, or the Cub will qualify!

Also the brakes on a 1936 Ford! (Has anyone else here lay beneath a
Ford on a dark night on a lonesome highway, tightening up the brake
cables because the thang didn't stop at the last stop sign?)

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

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.


The B-2 has FBW controls and a 6000 psi hydraulic system to move the control
surfaces for a number of reasons, mainly stability and weight reduction. I
have several friends who have flown it and they generally describe it's flying
qualities as F-111-like. The B-35 and B-49 designs were unsuitable as bombers
because of lack of directional stability expecially on a bomb run. If you
notice, the competition (B-36) has a large vertical fin.

Steve

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.

Not really. The 35 had those great engine pods, and the 49 had a bunch
of vertical fins, so in fact neither one was a true flying wing.
Nobody ever managed to fly the 35 enough to determine its utility (the
long shafts were the main problem), and the 49 was so afflicted by
dutch roll that the bombardier got sicksick. Plus there was the
question whether it (and a British flying wing design) wasn't prone to
spin around its lateral axis. The latter is disputed. For opposing
views see www.warbirdforum.com/cardenas.htm and
www.warbirdforum.com/tucker.htm

The Germans may have had more success with their nurflugels. It's hard
to tell; the most famous Horten design killed its test pilot in
disputed circumstances. I once corresponded with a Horten associate
who claimed that the problem with the Northrop designs had to do with
center of gravity, but I'm not enough of an engineer to follow these
arguments.


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

Cub Driver wrote:

Plus there was the question whether it (and a British flying wing
design) wasn't prone to spin around its lateral axis.

Having built and flown experimental flying wings since 1996 I can
attest that if you find yourself in a spin around the lateral axis
(i.e: a "tumble") better hope you have jam in your pockets cos'
your ass is toast...

http://www.motolotnie.rsi.pl/mpg/film1s.mpg

Cub Driver wrote:
Not really. The 35 had those great engine pods, and the 49 had a
bunch of vertical fins, so in fact neither one was a true flying
wing. Nobody ever managed to fly the 35 enough to determine its
utility (the long shafts were the main problem), and the 49 was so
afflicted by dutch roll that the bombardier got sicksick. Plus there
was the question whether it (and a British flying wing design)
wasn't prone to spin around its lateral axis. The latter is disputed.
For opposing views see www.warbirdforum.com/cardenas.htm and
www.warbirdforum.com/tucker.htm


I read that the YB-35 managed to do without vertical surfaces due to the
props providing enough longtitudinal stability; although I'm not
entirely clear as to how that would work. In any case, when it came to
the YB-49 it was found that the turbines did not provide the same effect
and the vertical fins had to be added.

The British design would be the Armstrong-Whitworth AW52. Barrie Hygate
in British Experimental Jet Aircraft relates that it had severe probelms
of pitch sensitivity leading to oscillations, at least partly due to the
short control arm provided by the modestly swept back wing. One
prototype was lost in 1949 after entering divergent pitch oscillations,
the pilot making the first British use of a Martin-Baker seat for real.

All three aircraft needed at some stability augmentation system to be
safe and usable platforms. The AW52 was only ever intended as an
experimental type, to test laminar flow.

From: Alan Dicey
Date: 7/4/2004 5:27 AM Central Daylight Time
Message-id:

Cub Driver wrote:
Not really. The 35 had those great engine pods, and the 49 had a
bunch of vertical fins, so in fact neither one was a true flying
wing. Nobody ever managed to fly the 35 enough to determine its
utility (the long shafts were the main problem),

The main reason the 35 flopped was the contraprop gearing system was unreliable
so they went with the single props which radically affected performance.

snip

I read that the YB-35 managed to do without vertical surfaces due to the
props providing enough longtitudinal stability; although I'm not
entirely clear as to how that would work.

It wasn't the props as much as the drive shaft fairings.

snip

Dan, U.S. Air Force, retired

I read that the YB-35 managed to do without vertical surfaces due to the
props providing enough longtitudinal stability; although I'm not
entirely clear as to how that would work.

It wasn't the props as much as the drive shaft fairings.

Right, the fairings were long and (by the time they reached the prop)
high above the trailing edge of the wing, rather like the wing of a
paper dart. They would have acted very much like a vertical
stabilizer. (And created, as was posted, no end of problems with the
XB-35's propeller shafts, which vibrated.)

The fairings (and later the vertical fins on the YB-49) also served as
air dams, perhaps inadvertently solving a problem with swept-wing
designs, where the airstream tends to move laterally toward the
wingtips rather than straight back in the line of flight.


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