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Old 30th Mar 2011, 03:12   #1 (permalink)

 
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Weight of Variable Geometry Wings

How is it that the X-5's swing wing mechanism weighed only 370 pounds and yet later swing-wing designs weighed so much more?
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Old 30th Mar 2011, 20:59   #2 (permalink)
 
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How are components of a ‘swing wing’ design defined, thus what is considered in the weight?
I can only speculate that as a research aircraft the X5 was not stressed to such high g levels as subsequent combat aircraft. Also, that fatigue issues from a long service life and/or a severe operating environment, and with wing stores were not of great concern.
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Old 3rd Apr 2011, 05:22   #3 (permalink)

 
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PEI_3721

What g-load was the X-5 designed to?

BTW: Do most swing-wing designs use a centralized pivot as well as tracks for the wing to sweep along? The X-5 if I recall used curved tracks for the wing to travel along as it swung from front to back
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Old 6th Apr 2011, 04:50   #4 (permalink)
 
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I believe the X-5's wing was ground-settable to a given sweepback NOT a fully variable geometry unit with actuators etc. plus it had no external hardpoints for stores.
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Old 7th Apr 2011, 05:40   #5 (permalink)
 
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From the NASA Dryden Research Centre website:
Quote:
The X-5 was tested from 1951 until 1955 at the NACA High-Speed Research Station. Built by Bell Aircraft Company, the X-5's maiden flight was June 20, 1951. The X-5 was the first aircraft capable of sweeping its wings in flight and helped our understanding of wing-sweep angles of 20, 45, and 60 degrees at subsonic and transonic speeds.
Quote:
Results of the research program demonstrated that the variable-wing-sweep principle worked. With the wings fully extended the low-speed performance was improved for take-off and landing and when swept back the high speed performance was improved and drag reduced. The pilots found they could use the variable wing sweep as a tactical control to out-perform the
accompanying escort aircraft during research missions. The X-5 flight tests provided some of the design background for the
F-111 and the Navy F-14 tactical aircraft.
Also worth looking at is this link, the last paragraph probably answers the original question: the system used worked, but it wasn't very practical, I guess later systems/mechanisms were more robust but the aerodynamic data gathered was still very useful.

As regards pivot points F14, MiG23/27,Su17 types use pivot points some way from the fuselage, the French AVG, European Tornado had pivots close in to the fuselage.

Also Grumman's Jaguar used a similar mechanism to the X5, no idea if that was why the type failed to enter service.
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Old 8th Apr 2011, 17:57   #6 (permalink)

 
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I am by no means an expert, but I was wondering why we didn't have variable sweep wings in civilian aviation. So I took a look at some designs.

Turns out during some initial testing as the wings sweep back, center of pressure moves back as well, and they lost some planes that were 'nose heavy'.

Hence when you look at your variable sweep planes these days, they have that fixed wing portion that extrudes away from the fuselage. It creates lift at a fixed point, keeping center of pressure at a fixed point. Extended from that are the smaller variable sweep portions, that being out so far don't seem to affect center of pressure so much as that portion of the wing doesn't create as much lift(less camber/less lifting area/less induced drag)

I gather they worked on a variable sweep wing that as it swept back, the attachment point to the wing, moved forward, to keep the center of pressure in a flyable place.

Seems the moving wing thing might be for the history books for a couple of reasons.

New wing technology seems to have made the 'lower and higher limits' of the wing larger...basically more efficient.

I suspect also that the computer, training, hydraulics, weight, etc...might add up to being more of a pain, when the engines are getting more efficient to get the speed/range advantages.

In civilian world a variable sweep wing would be great to increase range and speed at altitude, but I don't see it happening right now. Considering the SJ30 is probably the most efficient corporate jet on the market and that company is pretty much sunk, it tells you that technology moves slow in the civilian world.
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Old 8th Apr 2011, 22:19   #7 (permalink)
 
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Variable geometry doesn't have to be variable wing sweep, some other concepts like for example variable wingspan or variable wing area were tested in civil aviation as well, granted, "only" glider planes, but still
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Old 9th Apr 2011, 03:15   #8 (permalink)

 
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ICT_SLB

Quote:
The P.1109 fit that description; it was a German research-plane which the X-5 was loosely based on

Kitbag

Quote:
the last paragraph probably answers the original question: the system used worked, but it wasn't very practical, I guess later systems/mechanisms were more robust but the aerodynamic data gathered was still very useful.
Okay, so the wing pivoted and what would now be called the glove, would slide forward a little over two feet in order to keep the center of pressure in place.


theficklefinger

Quote:
Turns out during some initial testing as the wings sweep back, center of pressure moves back as well, and they lost some planes that were 'nose heavy'.

Hence when you look at your variable sweep planes these days, they have that fixed wing portion that extrudes away from the fuselage.
I believe that structure is called a glove (at least it's called a glove on the F-14) -- it's a wing-body fairing that the wing fits into (like how a hand fits into a glove)

Quote:
It creates lift at a fixed point, keeping center of pressure at a fixed point. Extended from that are the smaller variable sweep portions, that being out so far don't seem to affect center of pressure so much as that portion of the wing doesn't create as much lift(less camber/less lifting area/less induced drag)
I'm not sure if that is accurate, as the X-5 had a glove too. As far as I understand, the center of pressure was retained by designing the wing so that as it pivots aft, some of leading-edge slides out of the glove (lengthening the leading edge, increasing lift up front); some of the trailing-edge ends up slides inside the glove (shortening the trailing-edge, reducing lift in the rear).

Quote:
I gather they worked on a variable sweep wing that as it swept back, the attachment point to the wing, moved forward, to keep the center of pressure in a flyable place.
On the X-5, the whole glove slides forward as the wings pivot back; on later wings it would appear that as the wing sweeps back, additional leading-edge would slide out of the glove, whereas the trailing edge would slide into the glove increasing lift up front, and decreasing lift in the back.
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Old 11th Apr 2011, 18:56   #9 (permalink)

 
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I can only go by what I have read, on where they put the levers, cams, bearings...etc.

Doesn't matter, the issue is dealing with a moving center of pressure...you either move the wing forward as the wings angle back, or you create a lifting surface(F14) that provides a stable center of pressure. Your 'Glove' as you call it creates a lot of lift, like most wings nearer the root...so the outside part of the wing can move back and not affect stability as much.

Either way, maybe it's moot. Just build a skinny wing that goes fast, and add slats and flaps to create more lift at slower speeds.
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Old 12th Apr 2011, 11:50   #10 (permalink)
 
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Wild Goose

Barnes Wallis designed an RPV called Wild Goose which was tested at Predannack in Cornwall just post war. This used its swing wings for pitch and roll control too. Here it is on its launch dolly.


Due to the huge loss of life on the Dambuster raid, Wallis insisted on testing with RPVs first, for fear of any further deaths of aircrew due to his designs.

Wild Goose led to the Swallow design which, needless to say, got cancelled:



Quote:
some other concepts like for example variable wingspan or variable wing area were tested in civil aviation
You could argue that when any modern airliner lands with its slats and flaps out, that it is making use of variable wing area.
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Old 12th Apr 2011, 21:55   #11 (permalink)

 
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Idle ponderings on aircraft design aside, I just can't stand to sit in a slow aircraft anymore...most aircraft just seem so inefficient...so much induced and parasite drag that could be eliminated, not mention better thrust efficiencies.

Not hard for me to sit there and ponder the wings gong back 40 degrees, the airspeed increases 40 knots, the FMS shows that my trip will be 3 hours instead of 4...that would be so nice.
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Old 13th Apr 2011, 16:12   #12 (permalink)
 
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@the fickle finger

Your wish for more speed ("40 kts more") would be getting you well into the "Sonic Cruiser" area - and Boeing found no takers, remember ?
There are lots of possible ways to reduce drag, as you will no doubt know, but all have weight, cost, maintenance and other disadvantages, so designers have to come up with the best average ....
Not that that makes long flights any less booooooringggg, I agree !
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Old 13th Apr 2011, 17:36   #13 (permalink)

 
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Sonic cruiser?

The only thing keeping an aircraft from going faster are the rules of no super sonic flight over land, and aircraft manufacturers pandering to what the airlines want, pilots that can't handle fast aircraft, cost issues related to ticket prices and such.

I have no doubt if the laws were changed and pilots were up to the task we would be up into the Mach speed levels.

The ONLY reason the Concorde program is dead is because the pilots were over gross and decided to fly an aircraft that they should have rolled out on the ground.

It was a great plane and could have led to better designed and more efficient super sonic aircraft.

Why is the SJ30 dead in the water? Why can't a Citation X bust the speed of sound? We know the Falcon 10 can and did. Put some real engines on it and scoot.

What's going on in aviation is just plain ignorance and backwards thinking.

Personally it's hard for me to believe anyone with real hours on a long trip, can't imagine how to make his plane go faster...sure at what cost, but even so, just sitting there all day long gets me to thinking there has to be a better way.
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Old 16th Apr 2011, 01:36   #14 (permalink)

 
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theficklefinger

Quote:
Doesn't matter, the issue is dealing with a moving center of pressure...you either move the wing forward as the wings angle back, or you create a lifting surface(F14) that provides a stable center of pressure. Your 'Glove' as you call it creates a lot of lift, like most wings nearer the root...so the outside part of the wing can move back and not affect stability as much.
So the gloves on later planes were indeed larger? I suppose you're right in that it does produce a steady source of lift in that area. Regardless, the fact that as the wing pivots, some of the leading edge comes out and some trailing edge goes in seems to reduce the effect of C of P shift in addition to the glove producing a stable C of P in the middle.

Quote:
The only thing keeping an aircraft from going faster are the rules of no super sonic flight over land
What I'm wondering is, would hypersonic planes be allowed to go over land (once they were fully hypersonic)? It sounds odd, but hypersonic planes have shockwaves so highly swept back to the extent that they usually don't reach the ground (atmospheric conditions tend to keep the wave from reaching the ground). You would have to get away from land to accelerate from supersonic to hypersonic, but once up to speed you could fly over land without booming anybody as far as I know so long as you don't slow down.

Quote:
pilots that can't handle fast aircraft
What would prohibit a pilot from handling a fast aircraft?

Quote:
cost issues related to ticket prices and such.
Probably the biggest obstacle
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Old 11th Aug 2011, 04:08   #15 (permalink)

 
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I just thought of something. What about the XF10F Jaguar. It had a wing-sweep system similar to the X-5 whereby the wing pivoted aft and the roots traveled forward to keep the C/L in the right space.

Why was the X-5 light in weight, yet the XF10F Jaguar enormously overweight?


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Old 11th Aug 2011, 10:41   #16 (permalink)
 
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Quote:
Why was the X-5 light in weight, yet the XF10F Jaguar enormously overweight?
Perhaps some of the answer is the difference in purpose of the 2 aircraft; X-5 was a research aircraft, XF10 was meant to be the prototype of a combat aircraft. I found this which explains a lot.
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Old 11th Aug 2011, 15:11   #17 (permalink)

 
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Harley Quinn

If it is not classified, what g-loads was the X-5 stressed to?
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Old 11th Aug 2011, 16:52   #18 (permalink)
 
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Alternative ...

Remember the TSR2, anyone ? (and I think, the F-104, as well as the Buccaneer).
Way back then, the problem of getting good-enough low speed handling combined with high-speed performance was solved by flap blowing. Seems simple enough, till you think of all that interlinked pipework and the engine-out case, which could well have needed max. thrust on approach from the "good" engine and would probably not have been all that comfortable for the driver.
Tornado, the TSR2's "replacement", took the swing-wing approach, which seems to have been the better answer, despite the mechanical complication. Whether one or 'tother was the "best" solution in service; I leave to those who have experience of both, in flight and maintenance ...

Just a side-bar for the main thread ...
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Old 11th Aug 2011, 22:33   #19 (permalink)
 
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No idea if it is classified or not, and tbh 50 years after its retirement I would suggest its limitations cannot be regarded as a secret.
According to this paper from 1953 the X-5 was designed with a load limit of 7.33g, which was I think, more or less industry standard at the time. Remember this aircraft was built to investigate the effects of variable sweep and as technology demonstrator to prove the concept of Bells sweep system, not as a prototype combat aircraft.
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Old 11th Aug 2011, 23:48   #20 (permalink)

 
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Jig Peter

Quote:
Remember the TSR2, anyone ? (and I think, the F-104, as well as the Buccaneer).
Way back then, the problem of getting good-enough low speed handling combined with high-speed performance was solved by flap blowing.
That's correct, and as I understand it the TSR-2's takeoff (or landing, I forgot which) speed was around 140 kts despite it's heavy wing-loading.

If I recall correctly, and I don't know why this is so, the increase in lift is substantial, but roll authority doesn't increase in proportion with the increase in lift -- at least that's why I've been told it wasn't used as liberally on USN carrier planes though that could be some bullschite I was told (which makes it even less comprehensible that the USN didn't make more liberal use of it -- the USN did use blown flaps).


Harley Quinn

Okay, if it could pull 7.33g's I don't understand why there was any issue with producing a lightweight swing-wing mechanism...

What g-load was the XF10F-1 stressed to?

Last edited by Jane-DoH; 12th Aug 2011 at 00:47.
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