A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Military Aviation
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Why a Swept-Wing?



 
 
Thread Tools Display Modes
  #1  
Old January 11th 04, 01:39 PM
James Dandy
external usenet poster
 
Posts: n/a
Default Why a Swept-Wing?

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
Ads
  #2  
Old January 11th 04, 01:56 PM
Simon Robbins
external usenet poster
 
Posts: n/a
Default

"James Dandy" wrote in message
m...
Doesn't that make any aircraft unstable? If so, why would any pilot
feel safe in it?


I imagine it would move the centre of lift forward of the centre of gravity,
which might help to increase lift at slow speed or high angle of attack. (I
think..)

Si


  #4  
Old January 11th 04, 02:47 PM
C Knowles
external usenet poster
 
Posts: n/a
Default

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



  #6  
Old January 11th 04, 05:16 PM
patrick mitchel
external usenet poster
 
Posts: n/a
Default

The Hansa jet had forward sweep- the one pilot that had flown said type
stated no unkind words on the plane. Pat


  #7  
Old January 11th 04, 05:57 PM
Tarver Engineering
external usenet poster
 
Posts: n/a
Default


"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





  #8  
Old January 11th 04, 06:10 PM
Tarver Engineering
external usenet poster
 
Posts: n/a
Default


"Air Force Jayhawk" wrote in message
...
On 11 Jan 2004 05:39:04 -0800, (James Dandy)
wrote:

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


An aircraft is only unstable if the aerodynamic center is forward of
the center of gravity. If the wing root is sufficiently aft and the
AC stays aft of the CG, stability remains.

Why? Well it was tried with the X-29 but I never have read why no one
has pursued it since. The advantage was supposed to be that the
boundary layer (the thick air right next to the surface caused by
friction and very annoying) builds up as the air moves aftward along
the wing. With a FSW, the thickest part of the BL is at the root
rather than near the control surfaces, enhancing control while at high
angles of attack. There are other advantages but it's been a while so
I can't recall them off the top of my head.

I knew the USAF pilot on the X-29 project...he said it flew fine and
had no issues with it.


USAF got shafted on the X-29 and would have never built the second airframe,
had they known about the flutter problem. NASA falsified the flight test
reports such that they indicated the wing flutter sensor was within limits,
when in fact, the data went full scale and drew a straight line.

What would a pilot know about a vehicle? You've been there Rosco, how could
they possibly know?


  #9  
Old January 11th 04, 06:20 PM
Ed Rasimus
external usenet poster
 
Posts: n/a
Default

On Sun, 11 Jan 2004 09:55:02 -0500, Air Force Jayhawk
wrote:

An aircraft is only unstable if the aerodynamic center is forward of
the center of gravity. If the wing root is sufficiently aft and the
AC stays aft of the CG, stability remains.

Why? Well it was tried with the X-29 but I never have read why no one
has pursued it since. The advantage was supposed to be that the
boundary layer (the thick air right next to the surface caused by
friction and very annoying) builds up as the air moves aftward along
the wing. With a FSW, the thickest part of the BL is at the root
rather than near the control surfaces, enhancing control while at high
angles of attack. There are other advantages but it's been a while so
I can't recall them off the top of my head.

I knew the USAF pilot on the X-29 project...he said it flew fine and
had no issues with it.


As I recall the X-29 project, one of the objectives was evaluation of
the instability as a means of gaining agility for future highly
maneuverable aircraft. The "urban legend" was that the aircraft
required minimum of triple redundant FBW augmentation as loss of the
augmentation would result in immediate excursions from stable flight
and structural failure within seconds. The ultimate in "JC maneuvers".

Always thought it made for an extremely ugly airplane.

Wasn't the basic structure from an F-16A?



Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
Smithsonian Institution Press
ISBN #1-58834-103-8
  #10  
Old January 11th 04, 06:24 PM
Ed Rasimus
external usenet poster
 
Posts: n/a
Default

On Sun, 11 Jan 2004 09:55:02 -0500, Air Force Jayhawk
wrote:

An aircraft is only unstable if the aerodynamic center is forward of
the center of gravity. If the wing root is sufficiently aft and the
AC stays aft of the CG, stability remains.

Why? Well it was tried with the X-29 but I never have read why no one
has pursued it since. The advantage was supposed to be that the
boundary layer (the thick air right next to the surface caused by
friction and very annoying) builds up as the air moves aftward along
the wing. With a FSW, the thickest part of the BL is at the root
rather than near the control surfaces, enhancing control while at high
angles of attack. There are other advantages but it's been a while so
I can't recall them off the top of my head.

I knew the USAF pilot on the X-29 project...he said it flew fine and
had no issues with it.


As I recall the X-29 project, one of the objectives was evaluation of
the instability as a means of gaining agility for future highly
maneuverable aircraft. The "urban legend" was that the aircraft
required minimum of triple redundant FBW augmentation as loss of the
augmentation would result in immediate excursions from stable flight
and structural failure within seconds. The ultimate in "JC maneuvers".

Always thought it made for an extremely ugly airplane.

Wasn't the basic structure from an F-16A?



Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
Smithsonian Institution Press
ISBN #1-58834-103-8
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
German forward swept wing WWII fighter projects. Charles Gray Military Aviation 4 January 11th 04 01:49 PM
Canard planes swept wing outer VG's? Paul Lee Home Built 8 January 4th 04 08:10 PM
Props and Wing Warping... was soaring vs. flaping Wright1902Glider Home Built 0 September 29th 03 03:40 PM
Can someone explain wing loading? Frederick Wilson Home Built 4 September 10th 03 02:33 AM
Wing Extensions Jay Home Built 22 July 27th 03 12:23 PM


All times are GMT +1. The time now is 06:35 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 2004-2017 AviationBanter.
The comments are property of their posters.