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-   -   Viggen - plain intakes yet mach 2 (https://www.pprune.org/military-aviation/627072-viggen-plain-intakes-yet-mach-2-a.html)

nzhills 9th Nov 2019 04:43

Viggen - plain intakes yet mach 2
 
Hi, if you were American and from the 1970's, to do mach 2 required variable geometry intakes. Does anyone know how the Viggen could do it with plain intakes, did it just have so much thrust? Regards Mark

Asturias56 9th Nov 2019 08:48

Bill Gunston's "Jet Bombers" section on the Viggen said:-

" Extreme Mach numbers were relatively unimportant. The decision was taken to follow the formula adopted by the Type 35 (Draken) and use two lateral inlets of simple fixed-geometry form, but to make them appreciably larger and withe major axis vertical, standing well away from the fuselage with a gap for boundary layer air".

The Draken also had fixed inlets and in the "D" model these were extended forward until they were right next to the cockpit.

Possibly the long in (and quite large inlets) positioned well forward negated the need for fancy inlets - presumably there were some drawbacks but overall the balance worked very well.

57mm 9th Nov 2019 10:00

From Wikipedia, looks like they just used the biggest donk they could modify (JT-8D). And, despite fixed intakes, it worked.

treadigraph 9th Nov 2019 10:12

Brute force and ignorance then! :)

RedhillPhil 9th Nov 2019 12:28

Sounds like the Lightning's triumph of thrust over aerodynamics.

F-16GUY 9th Nov 2019 16:29


Originally Posted by nzhills (Post 10614379)
Hi, if you were American and from the 1970's, to do mach 2 required variable geometry intakes. Does anyone know how the Viggen could do it with plain intakes, did it just have so much thrust? Regards Mark

The F-16 from 1974 uses the same simple intake with great succes. Top speed is mach 2.05. It's all about making compromises....

ivor toolbox 9th Nov 2019 20:08

One purpose of variable intakes is to create a shock wave ahead of them so that only subsonic (relative) air reaches the engine... however if you put something else in way of intake that also causes same shockwave at speed, then you don't need variable intakes. Take a closer look at the Viggen, it has a prominent fixed splitter ramp between intake and fuselage.

Ttfn

nzhills 9th Nov 2019 20:40

Hi Ivor
Thanks for your message. I had considered the inside 'lip' to small to make a difference.
As F16_guy points out, the Viggen has F16 intakes rotated 90 degrees to the sides of the fuselage, (and a big motor).
So, do the variable ramps, in a Vigilante or Eagle, perform better off design point than fixed geometry and hence the Viggen intake was designed to function best at 2 speeds?
Regards
Mark

ORAC 9th Nov 2019 20:54

Saab pointed out during the test programme that variable intakes only make a major difference in performance above M1.4. Seeing as how little time the aircraft was expected to be in that regime it was decided the weight and complexity wasn’t worth the expense and time. Subsequent history would seem to have proven their case.

It should be pointed out the fixed Lightning bullet also served perfectly adequately during the same era.

Found in browsing....

https://eprints.soton.ac.uk/46202/1/AIAA-26830-529.pdf

ASRAAMTOO 9th Nov 2019 22:49

I'm not sure what percentage of Tornado GR4 ramps were serviceaable by the time the aircraft left service!

Easy Street 9th Nov 2019 23:08


Originally Posted by ASRAAMTOO (Post 10614961)
I'm not sure what percentage of Tornado GR4 ramps were serviceaable by the time the aircraft left service!

If memory serves correctly they were all inhibited well before the upgrade to GR4, at which point the published Mach limit came down to 1.3M. Saved a lot of maintenance effort that had been wasted on hydraulic leaks and rigging of ramps that the GR variant barely ever needed; addition of the laser rangefinder had scuppered higher Mach numbers anyway.

typerated 10th Nov 2019 07:38

Amazing this was built as a ground attack aircraft.(intercept variant followed)

And we bought Jags after this was in service and Harriers too.

Does a Jag out perform the Viggen at anything? apart from runway length used?

And after seeing an early Viggen do a down wind STOL take off and landing - was it worth all the extra compromises to make Harriers?



vascodegama 10th Nov 2019 08:30

typerated

According to google the Harrier was in service 4 years before Viggen. Not only that but it was our only option for FJ ops in the Falklands conflict for example.

I do however take your line on Jaguar. Maybe what we could have done is buy Viggen instead of Jaguar and have replaced some of the Lightings with the same basic ac.

Standing by for flak.

typerated 10th Nov 2019 08:49

Two years I'd say 69 for the Harrier - 71 for the Viggen.
And i think we were finding new and inspired ways of getting Harriers to fall out of the sky for much of that time.

No Falklands fast jets?
You can answer this a few ways.

1) Keep the Buccs and Phantoms and the Ark Royal going on the cost it took to develop the Harrier!!

2) Build Sea Viggens!

3) So what - no task force.. Maybe a submarine only blockage of Argentine would have been worked with time.

Asturias56 10th Nov 2019 09:55

The Swedes originally were planning to use Rolls Royce Medways as they'd used Avons on the Lansen and the Draken.

Unfortunately these were replaced in UK production by the Spey which was too small for the job so they went to P&Wh for the JT8D.

This was reworked extensively into the RM-8 and they developed their own afterburner and thrust reverser (which was a quite a thing in it's own right I believe).

When you think it was designed in 1957- 1963 it is a remarkable aircraft design.

BEagle 10th Nov 2019 22:41

I was at the 1969 Paris Air Show at which, amongst other aircraft, Viggen and Jaguar both appeared.

Viggen was astonishing. It thundered off in a very short distance, roared around the sky, did a short landing - then reversed back before blasting airborne again. Outstanding.

3 x Jaguars appeared in formation and did a couple of twinkle rolls. That was about the limit of their achievement. But it was quite a hot day, so no doubt they were thrust limited....

Quite an air show though - both Concorde prototypes flew at the same time and the 747 turned up from Seattle - it looked huge. Bob Hoover's Shrike Commander display was unbelievable - aerobatics in a twin prop executive aeroplane, culminating in an 8-point engines-off barrel roll and deadstick landing.

One of the weirdest was the Do 31 VTOL transport - which was very noisy when all 10 engines were operating!

HarryMann 10th Nov 2019 23:28

Bit of cynicism and thrust envy creeping in here, no?

Range & endurance of Jaguar Vs Viggen ?

Cost of Harrier development over egged as well.

treadigraph 11th Nov 2019 07:54


Bob Hoover's Shrike Commander display was unbelievable - aerobatics in a twin prop executive aeroplane, culminating in an 8-point engines-off barrel roll and deadstick landing.
I saw him fly the Shrike routine aged 77, shortly before he grounded himself the following spring. Quite remarkable.

Asturias56 11th Nov 2019 08:46

Dusting off some old copies of "Jane's" I see that the 1980-81 edition gave:-

Viggen -

Tactical radius with external armament

Hi-Lo-Lo +1000 nm
Lo-Lo-Lo + 270 nm

Jaguar

Attack radius internal fuel only -

Hi-Lo-Hi 460 nm
Lo-Lo-Lo 290 nm

Attack radius external internal fuel

Hi-Lo-Hi 760 nm
Lo-Lo-Lo 495 nm

Ferry Range -external fuel 1902 nm,

Looking at the numbers I think the Viggen could fly further and faster and had better field performance but the Jaguar could carry a much wider and heavier weapons load. Not surprising as the British & French had "proper" interceptors as well whereas the Swedes had to have only one type to do everything.

Looking around I guess the nearest US equivalent would have been the A-7 Corsair?

sandozer 11th Nov 2019 09:00


Originally Posted by Asturias56 (Post 10615250)
The Swedes originally were planning to use Rolls Royce Medways as they'd used Avons on the Lansen and the Draken.

Unfortunately these were replaced in UK production by the Spey which was too small for the job so they went to P&Wh for the JT8D.

This was reworked extensively into the RM-8 and they developed their own afterburner and thrust reverser (which was a quite a thing in it's own right I believe).

When you think it was designed in 1957- 1963 it is a remarkable aircraft design.

https://cimg9.ibsrv.net/gimg/pprune....48dd913652.jpg
Afterburner looked pretty! Taken Leu 2013


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