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VIFFing, Please Settle an argument...

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VIFFing, Please Settle an argument...

Old 1st Jul 2018, 15:13
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VIFFing, Please Settle an argument...

Was viffing used in the Falklands (Mogwi?)? Someone is boring the harse off me about it. For my part, once upon a det in Belize, I was chatting with a Harrier pilot, whose view was that viffing was more 'neat' than useful. Real gen gratefully accepted. Would Sharkey know?

CG

Last edited by charliegolf; 1st Jul 2018 at 17:36.
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Old 1st Jul 2018, 16:19
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While waiting for much more qualified respondants I would be very surprised if it was used. In general, viffing was used at fairly slow speeds to use bleed air (through reaction ducts) to give monentary enhanced nose authority. It came at the expense of instability and loss of overall energy. From all reports I have read of Falklands combat the engagements were all fairly high speed and I can’t see viffing being of any benefit. Not a SHar expert though so I standby to be corrected.
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Old 1st Jul 2018, 16:31
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Thanks Flaps, that fits with all the writing I've seen on it.

CG
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Old 1st Jul 2018, 16:38
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In general, viffing was used at fairly slow speeds to use bleed air (through reaction ducts) to give monentary enhanced nose authority
Not what I understand. Viffing is deflecting the nozzles so that you get, temporarily, a small increase in g in a turn. The improvement is brief because the airspeed reduces, thus reducing wing lift and turn performance.
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Old 1st Jul 2018, 16:40
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According to the informed sources I used to work with no Argentinian fast jet ever got into a rear-hemisphere position on a SHAR, so there would be no actual need to do so. Other informed sources I still work with suggest that VIFF was unlikely to be used in combat unless/until someone dreamed up a way of doing it without destroying the kinetic energy. They state categorically than no fast jet pilot would ever deliberately lose that much energy in close combat.
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Old 1st Jul 2018, 16:43
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Thatks again fellas.

CG
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Old 1st Jul 2018, 17:01
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kenparry,

My comment about slow speed is based on my GR5/7 experience where I cannot think of a time where I would have used it in the way you describe because the wing was so good that the small, very brief increase in instantaneous turn rate would be more that wiped out by the subsequent loss of energy. This loss is obviously much more marked in the high speed environment which is why it was only really used in the slow speed environment where the energy bleed is proportionately much less. In the slow speed fight it would allow increased nose authority and also allowed roll and yaw control at speeds well below what would be possible in truly conventional flight.

It’s rather a moot point as a) you were very unlikely to get any air defender to venture into that slow speed environment and b) the jet can become so unstable that, unless very closely monitored, a subsequent departure would make the outcome of the combat rather one sided!
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Old 1st Jul 2018, 18:24
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Originally Posted by PDR1 View Post
According to the informed sources I used to work with no Argentinian fast jet ever got into a rear-hemisphere position on a SHAR, so there would be no actual need to do so.
Sharkey Ward did admit that an Argentine Dagger nearly got him with cannon. He was completely unaware that the Dagger was behind him.

I checked Steve’s tail was clear but he was far too busy to think of checking my own 6 o’clock. Otherwise he would have seen the third Mirage closing fast on my tail...... Later I was to discover that the third Mirage Dagger had entered the fight from the north and found me in his sights. As he turned towards the west and home he had been firing his guns at me in the turn, but had missed. It was the closest shave that I was to experience.
https://weaponsandwarfare.com/2015/0...the-falklands/
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Old 1st Jul 2018, 19:35
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I just tried to post a rant about Ward’s self aggrandising link above but thankfully the ether swallowed it up. God that man is utterly insufferable.
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Old 2nd Jul 2018, 04:23
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Didn't the US Marines use it on their Harriers to quite a good effect in trials, suddenly forcing the rear-guy to overshoot and enter the firing area?
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Old 2nd Jul 2018, 09:05
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The USMC were always more focussed on air combat than the RAF and so perhaps practiced using the nozzles a bit more but the old “quick viff and he’ll fly right by” is really a non starter. The fighter would just use the vertical and the harrier would now be low and slow with nowhere to go. It was considered as a last ditch option if someone was closing for guns as, by that stage, you’re pretty much out of options anyway. Seem to remember that RAF release to service only allowed viffing in clean jets and you tended to only fly those on dedicated air combat practice phases so the chances of using the nozzles in any sort of real world combat are very very small indeed.
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Old 2nd Jul 2018, 10:34
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Were the ducts and nozzles permanently linked?

I have a vague understanding on the way the nozzles and ducts interlocked, ie more down nozzle more bleed air to the ducts.

Was this proportional or was some other mixing involved?

And my main question - was is possible to de couple so the nozzles so they remained fully aft but you could still have duct authority slower or have I got it wrong?

Thanks
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Old 2nd Jul 2018, 10:35
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The old metal Harrier could use the nozzles rather more freely. It was even part of the air test to fly straight and level at speed, pull the nozzle lever back, then note the speeds at which the lever reached the braking stop, and when the nozzles followed, their motion being delayed by air load. Jerry Pook flew the RAF VIFF trials, looking at both ACM and ground attack. He describes the results in chapter 13 of his book Flying Freestyle.

The USMC did indeed go further with the jet. I recall an exchange pilot snagging a GR3 because he couldn’t get full rudder deflection in air combat. Engineers found no fault, but on questioning, he revealed that his airspeed at the time was 400 kts! Years later, in the AV-8B, they found what happens to the big Pegasus when you apply maximum power and maximum G at the same time. Titanium friction is not good.
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Old 2nd Jul 2018, 10:39
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Originally Posted by Shaft109 View Post
I have a vague understanding on the way the nozzles and ducts interlocked, ie more down nozzle more bleed air to the ducts.

Was this proportional or was some other mixing involved?

And my main question - was is possible to de couple so the nozzles so they remained fully aft but you could still have duct authority slower or have I got it wrong?

Thanks
It was pretty much all or nothing as the butterfly valve opened. With less than about 20 degrees nozzle, no reaction controls, more than 20, full reaction control. It was a direct mechanical link, not separable.
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Old 2nd Jul 2018, 12:39
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Never set foot in a Harrier but got to test guns tracking vs VIFF. As I recall the VIFF required only needed to be very brief to disturb a close-in pipper chase with a shorter-range gun (eg Aden 30) - but, as said, you are still giving away some energy and timing was everything. When the opponent had a somewhat better radar and gun combination (eg Mauser 27mm) the increased distance at typical 'open' range made the effect of the vectoring pretty much unnoticeable, at least from my perspective. About the only noticeable improvement during this DACT for the Harrier's perspective was that it was much harder to spot or maintain tally when it is flown with clean wings. Or it could be just my eyes...

A more dramatic change in a guns picture could be achieved by the venerable mud-moving Tornado. With the sight picture looking otherwise rosey it can be amazing how quickly a turning GR1 can slow down when the wings are suddenly pulled all the way back. I also remember a USAF Spangdahlem F-16 dude managing to over-stress his stores whilst trying to get out of the way of the GR1 he had just chased down when it did the wings & boards thing. Given the rather pedestrian G envelope of the Tornado that didn't go down too well and the bubble-bust did look a little worrying on the HUD tape.
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Old 2nd Jul 2018, 13:46
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No idea about the actual question - however:

Ascend Charlie - not that I’ve read anything with which I violently disagree but in the case you’re talking about: (NB throughout - this was 15-30 years ago).

If you noticed that your opponent might be about to suffer the indignation of a flight path fly through with the usual tell tales of high crossing rate (behind you), plan view (high angle off) and low separation - you could tighten up as others describe to help him along. Unload a fraction pull in 40 nozzle, watch the spectacle unfold. This had all the effects you’ve already had described. The trick was to be ready for what happened next.
Assuming you forced the fly through you’d probably be initially (split second) be faced with a fleeting shot opportunity as the hostile exited the AIM-9 Rmin, or perhaps get a snapshot guns if lucky. To make this play out in your favour a neat trick was to barrel roll (back towards the opponent) with the nozzles in full braking stop to force nose to tail separation. This needed practice and as back seat Captain/ Instructor was the bit you really had to watch when teaching the new guys. (The first time I tried resulted in being beaten up by a machine as Somerset and the sky changed places a few times - good times).
Against a high wing loader the combined two manoeuvres were very effective - if timed correctly with a decent chance of getting that timing right. Against something modern (at the time) for example the Mirage 2000 which had a staggering instantaneous turn they could lag a bit then back stick and would end up smack in your control zone with all their problems solved - not great for the home team - but the braking stop barrel did then cause them problems.
In all my time in the Sea Jet I used the above only a handful of times and it worked well against things like Alpha Jet which didn’t seem to slow down - the two other occasions when I successfully used VIFF were both falling out of a low speed flight into a ‘rate to base’ scenario where full braking stop and full power allowed me to sit at 70-80 degrees nose low and point my lift vector in lead using roll whilst my opponent was doing the standard 30 or so to gain energy. (Him going down a helterscelter me sat in the middle watching).
As per previous comments if a shot hadn’t followed quickly then I’d have been poorly placed but the Blue Vixen had great off boresight combat modes and the 9M was quite capable so it went my way. (Opponents in these cases Portuguese F-16 and Malaysian Hawk 208).
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Old 2nd Jul 2018, 20:04
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Sorry, been on my hols!

Yes, all good stuff above. High G barrel roll would fool 90% of conventional Jets the first time and 5% the second time they saw it. 450kts to 150 in about 4secs was hard to beat unless you knew what was about to occur. The counter was to pull high and watch the Bean wallowing around at 150kts until the time was right! We just hoped that we would splash enough guys on the first encounter to dissuade the others.

To the original question; no, VIFF was not used darn sarf. There was never a time when a Harrier was in the "last ditch" scenario and needed to pull the nozzles to frustrate an aiming solution. It was, however very useful when landing back on board!!

Actually, I have just remembered something that might count (must have more gin!). I did use it when trying to splash a Pucara over Stanley Harbour on 25th May. I saw him in a survival hold based roughly on the Upland Goose at low level, as I returned from CAP over the sound. I left Lems at FL250, selected the braking stop and full power, entered a steep low-speed dive and tried to bore sight the missile. First time, no joy. Second time, got a growl but he was heading directly for the cathedral. Third time, intermittent lock and pressed my luck too far, bottoming out below 14k. Loud shout of "missile launch, missile launch" from Lems, followed by holy sh*te pull up, trip the limiters and haul skywards to avoid 2 Rolands. They fell away about 500' below me in the climb.

So I guess the answer is actually - yes VIFF was used in air-to-air combat in the Falklands - but as an aggressive manoeuvre not a defensive one.

Mog
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Old 3rd Jul 2018, 05:50
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Many years ago an old, very bold RAF fighter pilot was sent to the ME to teach pilots from the emerging nations fighter tactics.
Starting with basic aerobatics he commenced the training.
Mid course a senior QFI flew a couple of stan checks.
During a debrief the QFI said to the OAB "They fly well but I'm curious after every aerobatic manouvre to a man they rolled out and flew straight and level for thirty seconds".
OAB replied " Yep I told them that after the maneuver you must do that to relax the a/c. We will be fighting these bastards one day and that's when we'll get them".
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Old 3rd Jul 2018, 07:26
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Slight drift but was there any sort of speed interlock that prevented guns and weapon release below a certain A/S or G/S?
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Old 3rd Jul 2018, 07:54
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Not on anything I can recall. Lots of limits of course from poor weapon performance (eg slow-speed AIM9 shots), seekers freezing, fusing of bombs, self-damage criteria, stores capture limits et al.
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