Why a Swept-Wing?

This is taken from Aerospace web
http://www.aerospaceweb.org/aircraft/fighter/s37/

"The advantages of forward sweep have long been known as such wings offer
lower wave drag, reduced bending moments, and delayed stall when compared to
more traditional wing shapes. Unfortunately, forward sweep also induces
twisting strong enough to rip the wings off an aircraft built of
conventional materials. To solve this problem, the Su-47 makes use of
composite materials carefully tailored to resist twisting while still
allowing the wing to bend for improved aerodynamic behavior. "

"However, Sukhoi has apparently decided to abandon the forward-swept wings
of the S-37, and the future production model will return to a more
conventional wing layout. If true, Sukhoi may have reached the same
conclusion as NASA did following testing of the X-29--the benefits of
forward-swept wings are just not worth the extra cost and complexity
associated with their design and manufacture."

Curt

"James Dandy" wrote in message
m...
Pardon my ignorance on all matters concerning modern aviation but just
why the hell would you want to sweep a wing forward?

Doesn't that make any aircraft unstable? If so, why would any pilot
feel safe in it?

Has anyone ever made one work?

James Dandy

"C Knowles" wrote in message
m...
This is taken from Aerospace web
http://www.aerospaceweb.org/aircraft/fighter/s37/

"The advantages of forward sweep have long been known as such wings offer
lower wave drag, reduced bending moments, and delayed stall when compared
to
more traditional wing shapes. Unfortunately, forward sweep also induces
twisting strong enough to rip the wings off an aircraft built of
conventional materials. To solve this problem, the Su-47 makes use of
composite materials carefully tailored to resist twisting while still
allowing the wing to bend for improved aerodynamic behavior. "

"However, Sukhoi has apparently decided to abandon the forward-swept wings
of the S-37, and the future production model will return to a more
conventional wing layout. If true, Sukhoi may have reached the same
conclusion as NASA did following testing of the X-29--the benefits of
forward-swept wings are just not worth the extra cost and complexity
associated with their design and manufacture."

Actually, once the notch filter was adjusted such that the wing did not
delaminate, there was no benifit to forward swept wings. The program
falsified X-29 flight test data and USAF was quite punative in blackballing
the whole group. Perhaps Mary would like to speak to that issue, as she was
very close.

"James Dandy" wrote in message
m...
Pardon my ignorance on all matters concerning modern aviation but just
why the hell would you want to sweep a wing forward?

Doesn't that make any aircraft unstable? If so, why would any pilot
feel safe in it?

Has anyone ever made one work?

James Dandy

On Sun, 11 Jan 2004 09:57:12 -0800, "Tarver Engineering"
wrote:

Actually, once the notch filter was adjusted such that the wing did not
delaminate, there was no benifit to forward swept wings.

Uh... excuse me, but what's a "notch filter" in this context?

--
__________ ____---____ Marco Antonio Checa Funcke
\_________D /-/---_----' Santiago de Surco, Lima, Peru
_H__/_/ http://machf.tripod.com
'-_____|(

remove the "no_me_j." and "sons.of." parts before replying

"machf" wrote in message
news
On Sun, 11 Jan 2004 09:57:12 -0800, "Tarver Engineering"
wrote:

Actually, once the notch filter was adjusted such that the wing did not
delaminate, there was no benifit to forward swept wings.

Uh... excuse me, but what's a "notch filter" in this context?

In the feedback control system of the X-29 was a z-transform type filter at
3.2 Hz. This was a simple third order filter in the original airframe.
Once the filter was altered to eliminate the flutter problem on the second
airframe, there was no manuverability advantage. The first airframe having
a delaminated wing by that time.

On Mon, 12 Jan 2004 08:04:07 -0800, "Tarver Engineering"
wrote:


"machf" wrote in message
news
On Sun, 11 Jan 2004 09:57:12 -0800, "Tarver Engineering"
wrote:

Actually, once the notch filter was adjusted such that the wing did not
delaminate, there was no benifit to forward swept wings.

Uh... excuse me, but what's a "notch filter" in this context?

In the feedback control system of the X-29 was a z-transform type filter at
3.2 Hz. This was a simple third order filter in the original airframe.
Once the filter was altered to eliminate the flutter problem on the second
airframe, there was no manuverability advantage. The first airframe having
a delaminated wing by that time.

Oh, I see... I forgot that the X-29 had to rely heavily on electronics, and
thought maybe it was some mechanical equivalent or something. Thanks for
clearing that up.
Ah, z-transforms... It's been quite a while, but I used to be pretty good at
that stuff.

--
__________ ____---____ Marco Antonio Checa Funcke
\_________D /-/---_----' Santiago de Surco, Lima, Peru
_H__/_/ http://machf.tripod.com
'-_____|(

remove the "no_me_j." and "sons.of." parts before replying

"machf" wrote in message
...
On Mon, 12 Jan 2004 08:04:07 -0800, "Tarver Engineering"
wrote:


"machf" wrote in message
news
On Sun, 11 Jan 2004 09:57:12 -0800, "Tarver Engineering"

wrote:

Actually, once the notch filter was adjusted such that the wing did
not
delaminate, there was no benifit to forward swept wings.

Uh... excuse me, but what's a "notch filter" in this context?

In the feedback control system of the X-29 was a z-transform type filter
at
3.2 Hz. This was a simple third order filter in the original airframe.
Once the filter was altered to eliminate the flutter problem on the
second
airframe, there was no manuverability advantage. The first airframe
having
a delaminated wing by that time.

Oh, I see... I forgot that the X-29 had to rely heavily on electronics,
and
thought maybe it was some mechanical equivalent or something. Thanks for
clearing that up.

It could have been done mechanically, as the Russians have proven.

Ah, z-transforms... It's been quite a while, but I used to be pretty good
at
that stuff.

One of the people that worked for me at NASA got tasked with commenting the
original FORTRAN and came to me for help understanding what Mr. Main had
written. He was completely dissatisfied with what a third order filter does
and was certain the software did nothing.