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zotbox
22nd Mar 2007, 09:48
After years of lurking, my first post on Pprune.

Is it possible to fully sweep (67 Degrees if I recall correctly) the wings on the F3 or Gr4 with the 2250 litre "hindenburger" tanks fitted or is there some configuration/ c of g issue that prevents this.


Question was from a scale modeller who would like to know.

thanks in advance.

Backwards PLT
22nd Mar 2007, 09:55
With the big fuel tanks (L fit) the max sweep is 63, iirc (on the F3 anyway).

tu chan go
22nd Mar 2007, 09:59
Backwards is correct. The max sweep is 63 degrees as the tailerons would hit the back end of the tank. The limit is achieved by a detent that can be placed on the wing sweep lever stopping the lever from moving all the way back. Unfortunately, this all that stops the wings from moving and it is possible to put them all the way to 67 degrees, even with the tanks fitted.

zotbox
22nd Mar 2007, 10:42
Thanks for the responses, 63 degrees it is then.

MostlyHarmless
22nd Mar 2007, 12:11
Unfortunately, this all that stops the wings from moving and it is possible to put them all the way to 67 degrees, even with the tanks fitted.

That could be entertaining - another military design classic.... :eek:

XV277
22nd Mar 2007, 12:19
So the F3 was never fitted with the planned Automatic Wing Sweep system then?:)

Jimmy Macintosh
22nd Mar 2007, 15:02
Slight aside, but with regards to the detent sytem to limit movement, if I recall correctly when Cottesmore was the TTTE back in the late 80's the tensions of the detent on one tornado were set incorrectly (I think not enough shim in place) and someone managed to sweep the wings while the flaps were down :eek:

Excuse the lack of possible correct terminology, I was on work experience there and was only 14! (It might have also been a tall tale told by a liney)

humbout
22nd Mar 2007, 15:12
Things are slightly more robust on the GR4, there is a covered switch in the front cockpit (which is set by the engineers when they load the fuel tanks). With 2250l tanks fitted, the switch is set to 63 degrees and it becomes impossible for the pilot to sweep the wings past this, no matter how strong he is, without uncovering and then changing the switch to 67 degrees.

formertonkaplum
22nd Mar 2007, 15:49
With Lima's (2250's) fitted to F3, it recognises they are present and limits wing sweep. If the wing sweep is incorrectly set to 67 before power is applied, the lever will move forward to 63 position and 67 sweep selection will no longer be available until the Lima's are removed.

Used to be a post Lima fit check for the Plumbers........

FTP

flipflopman RB199
22nd Mar 2007, 21:53
Agree with formertonkaplum.

IIRC, there is also a small indicator immediately to the rear of the throttles, similar to the RCOV INT/ENG indicators, which display 63 (Orange) and 67 (Green) respective to tank fit.


Flipflopman

TonkaEngO
22nd Mar 2007, 22:00
FTP is correct - still is a check c/o by A I'm an Arm.....for Big Jugs (still gets a giggle) and still pisses off the Rects Cont...

soddim
22nd Mar 2007, 23:29
To respond to XV277, yes, F3s were fitted with auto wing sweep but it was disabled on RAF delivery. The RSAF have it on all their F3s and it includes auto manoeuvres (slat & flap). It is a huge improvement and the RAF were very remiss to disable it. One could attribute at least one accident to lack of auto wing sweep.

threepointonefour
23rd Mar 2007, 00:23
One could attribute at least one accident to lack of auto wing sweep.
I think that's being a little too lenient - cognitive failures tend to account for this type of accident, not the presence of the 'technology' (I use the term loosely here) in question.
It's like saying that a recent Harrier crash was exacerbated by the presence of the nozzle lever.

People used to make too much of the WS on the Tornado (I'm sure they still do). It's just like a gear stick. One position to go fast and straight (63/67), one to go slow and be 'vaguely' manoeuverable (25) and one in the middle (45).

(And a hidden 4th one that reputedly gives better mpg!)

Ghostflyer
23rd Mar 2007, 04:34
It is a huge improvement and the RAF were very remiss to disable it

The reason the RAF got rid of the system was because crews would regularly beat the system. If you were hitting a merge with the wings back, as the speed started to decay you would move the wings forward so that they arrived in the right configuration as the speed was reached. Same with maneuvre devices. If you knew you were going to turn you would put the slats out in anticipation. The automatic system had to react and so it was felt you had perhaps lost a bit of 'edge'. The OEU did the trial to quantify the performance.

The promised improvement, WASPMD - 'The wingsweep and slat pilot's mindreader device' never came to fuition.

Ghost

maxburner
23rd Mar 2007, 09:16
The auto wing sweep was not the improvement you might have thought. Once you hit the speed at which a move was scheduled the wings would start to move and the whole transition from, say, 25 to 45 WS would be completed regardless of what the speed did in the interim. So, if you were turning with someone, did a quick unload to gain a little energy and hit the magic number, the wings would sweep to 45, regardless of the subsequent pull and re-commit you had performed. The trial referred to (can't remember the name) showed a loss of turning performance and a huge increase in wear in the flap motors and so on.

A nice idea, but the implementation was not great.

DownloadDog
23rd Mar 2007, 09:19
Where would be the fun with auto-wing sweep, for instance, you wouldn't be able to laugh at your oppo trying to tank in 45 wing because they forgot to sweep them forward on the pre-join checks. Or what about the opportunity to select 67 wing and pull to the limiting alpha in an attempt to use aerodynamic braking to slow down when you've overcooked it on a tanker join....

The 4th wing position has also been alluded to, certainly gives you something to do while transiting the NAGA..

FCWhippingBoy
23rd Mar 2007, 11:14
And the mystical 4th position is / does what .....?!
(just curious!)

threeputt
23rd Mar 2007, 11:22
From my GR1 days, IIRC, it was about 33 deg and about 6 alpha to give best fuel economy at height (obviously a bit of fettling required by the GIF to get it right).;)

3P

soddim
25th Mar 2007, 17:18
To respond to the various critics of my earlier post, yes, a pilot concentrating on wing sweep versus speed/mach could beat the automatics but a pilot concentrating on the fight and tactical situation as first priority frequently screws up the wingsweep setting and loses performance - even overstresses the wings. I know, I've flown both and I've watched pilots get it badly wrong.

The statement 'at least one accident' was quite correct - it was an unload at lowish altitude accompanied by an early selection of wings to 67 then a 'oh my God' pull to avoid the sea with the wings at 67 and the speed commensurate with 45/25 wing. The fact that the aircraft impacted the sea at a shallow angle low enough for the Nav to survive is a fair indication of the likelihood of recovery had the wings been at the best sweep angle. There are others I could quote from the bombers in Saudi where incorrect sweep angle was the cause of failure to recover from the dive once the error had been perceived.

For those aircrew who remain convinced of their ability to do better than automatic wing sweep - all they have to do to override it is to move the wing sweep lever. However, since the RAF did not accept it they do not have that option.

Phil_R
25th Mar 2007, 18:56
> laugh at your oppo trying to tank in 45 wing

Why is that a problem?

Phil

advocatusDIABOLI
25th Mar 2007, 19:41
FC,

The 'Magical' 4th position is 35 Wg, Basically the 'Bast@rd' ('Bast@rd') child of 45 Wing. It has the most stringent g and speed restrictions, but is very ecconomical in cruise. My spies tell me that the reason for the limitations are that it doesn't report fatigue values to the mother ship.......:ooh: Hmmmmm

Advo

threepointonefour
25th Mar 2007, 21:35
> laugh at your oppo trying to tank in 45 wing

Why is that a problem?

45 Wg tanking makes the jet adopt about a 20 deg attitude - dead funny to watch!

The best trick was to sit on the left hose and watch your wingman attempt tank in 45Wg on the right hose, then, just as he plugs in, tell him he's in 45Wg and hope that he panics and selects 25Wg, thus promptly dropping out!!

Oh, the fun we had. That, and JTIDS text messages !!

Touchin' Down
1st Apr 2007, 23:48
Indeed the fatigues are only recorded in 25/45 and 67 wings (hence the 3 banks on the fatigue meter). This is one reason why the g limits are much lower in other sweeps. In addition to 35 wing, 58 wing is good for high speed climbs as it is a high lift wing (compared to 67 at least), although it is subsonic.

Photoplanet
30th Sep 2013, 11:25
"Jimmy Macintosh "Slight aside, but with regards to the detent sytem to limit movement, if I recall correctly when Cottesmore was the TTTE back in the late 80's the tensions of the detent on one tornado were set incorrectly (I think not enough shim in place) and someone managed to sweep the wings while the flaps were down http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/eek.gif ""

The bit of kit that controls the interaction between wing sweep angle and flap/slat position is the "High Lift Wing Sweep Control Unit - HLWSCU" It's basically a mechanical computer with detent drums, driven by the position of the wings and flaps/ slats to either permit or block the selection of things. If the wings are back, and manoeuvre is selected on the throttle top, then the flaps/ slats should not deploy until after the wings have moved forward. Also, the throttle quadrant has mechanical interlocks, preventing the inadvertent selection of flaps with wings back, or wings back with flaps selected.

gr4techie
30th Sep 2013, 12:52
someone managed to sweep the wings while the flaps were down

This can happen when a feedback shaft has been physically removed from the airframe during maintenance and somebody then does a wingsweep (function test). Because the High Lift Wing Sweep Control Unit will not know when the wings have reached the selection made in the cockpit and the wings will keep on motoring back and back and back. Then the flaps go through the side of the airframe.

Photoplanet
30th Sep 2013, 13:25
Agreed...., Sometimes creative solutions are required, to overcome 'foolproof' systems....