Question of Lavi(LO-33)

These days I read artical which told me information of Lavi can fixed Conformal Fuel Tank UNDER airframe side. I think again and again, in terms of such small aircraft how can it carry CFT? There is no picture accompany with the narrate so I have no idea also hard to imagine. Who can help me?

Emile,

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These days I read an article which told me information of Lavi can fixed Conformal Fuel Tank UNDER airframe side. I think again and again, in terms of such small aircraft how can it carry CFT? There is no picture accompany with the narrate so I have no idea also hard to imagine. Who can help me?
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Posting the article in question would likely provide a more contextually interpretable understanding of the original writer's intended meaning if not your exact answer.

Assuming you are referring to the IAI Lavi lightweight fighter, with only 5-6,000lbs of internal fuel (almost 1,200lbs/15% less than even the F-16) I have long wondered at the claims for upwards of 1,150km/625nm worth of interdiction radius with an X8 M117 (6,300lbs) bombload.

The obvious answer of course is that 'the Israeli's being Israeli's', lied through their teeth when they said that they were after an A-4 Skyhawk class (replacement ground attack jet) airframe and the fudging the spec was only a part of the coverup to generate an export fighter to compete with the F-16.

As the sleek lines, afterburning engine and period compareable AMX-1 Centauro all highlight as differences in wasted weight and performance for a mere CAS/INT jet.

OTOH, if you look at the belly of the Lavi-

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Unlike that of the F-16 which has a distinct separation between the engine nacelle and the side sponsons onto which the tails and wings are mounted, the Lavi has a blended wing:body structur resulting from what is effectively a low-wing monoplane format 'over' a modified nose/inlet system (like a Su-27). As you can see, despite having a short wheelbase, there is also considerable CG freedom inherent to the long centerline tank.

Looked at in front elevation and planview-

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It also becomes obvious that the principle wing pylons are mounted well outboard (presumably to clear the canard arc) and the ground track is quite 'tight'.

From these, one can surmise two possible options.

The first is a cross between the Northrop scabbed ALQ-171 jammer system tested for the Swiss F-5E force in the early 1980's. By integrating cutouts with the tight landing gear inner-door clearances, they managed to fit a fairly hefty sized pallet system to the bottom of a rather narrow fuselage.

The other option that comes to mind is something along the lines of the F-4E 'Super Phantom 2000' conformal tank which again was more along the lines of a bathtub enclosure that fitted over the belly. In this case, the Lavi would probably use twin installations under the wide wingroots and possibly mount freefall stores to them (as indeed MacDac experimented with).

If you then put 600 gallon (IAI F-16 mod) tanks underwing and ARM or AAM outboard, along with using the cheek pylons for a targeting/nav pod, you could probably get on the order of 18,300lbs of fuel split between 5,000lbs in the conformals, 5,500lbs internally and 7,800lbs in the wing bubbles. Assuming the poor beast could get off the ground (probable topoff via IDFAF tankers), with that load, with the improved TSFC of the PW1120, it would likely give a Lavi strike package the 600nm radius claimed.

15,500lbs empty + 26,300lbs consumeables and warload = 41,800lbs. With a 42,500lbs max gross, you wouldn't quite pull the wings off.

But your maneuver limits until you burned down or dropped some of that weight would be extreme, probably under 5.5G and 430 knots. Certainly unable to 'self escort' through anything like a high threat area.


KPl.

I just feel hard to imagine that there are any pylon under Lavi's airframe, but thank s for your reply.

Emile, you don't need to imagine it, KPI showed you pictures, how come you can't believe it

When you are talking external stores weight is only one consideration and usually not the main one. Drag and loss of lift have to be taken into consideration as well. A conformal fuel tank is designed to compliment the aerodynamics of the aircraft that it is attached to. This means that there is less of a penalty in performance compaired to the advantage of the extra fuel.

JIMC5499,

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When you are talking external stores weight is only one consideration and usually not the main one.
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I would say that the structural limiters are indeed weight vs. stress imposed. And a jet which cannot maneuver is a jet which is eminently killable, either by mission ordnance dumping or by 'oh well, there goes one third the inventory on a Yamamoto Mission gone ugly'.

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Drag and loss of lift have to be taken into consideration as well. A conformal fuel tank is designed to compliment the aerodynamics of the aircraft that it is attached to. This means that there is less of a penalty in performance compaired to the advantage of the extra fuel.
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Drag and balance issues on the F-15 (even the 'fighter' C) with CFT is still enough to turn it into a bus.

And while tangential carriage helps in relation to say conventional multiracks (F-15C with TC configured Type-2 CFT vs. F-15B DRF) it's still significantly additive unless you submerge the weapon within an 'aerodam' equivalent (contiguous flow) envelope described by the tank.

Indeed, the Dual Role Demonstrator with ONE (2,000lb) class munition on the primary stub had less drag than TWO AIM-7F on the mini-stubs. And either of those configurations has less than the amount that a Type-4 HRL with the same load (X1 GBU-31 on the center station) plus empty ministubs above it does.

The real question here is why you would want to put X8 of _any_ dumb weapon onboard when the combination of burner fuel to reach penetration speed and expendables loss on the popup would restrict you to one target pass at those kinds of radial depths anyway.

If you put an IVER (again, the BRU-55 is copied in or from an IMI design) on the center wing pylon, and a 1,000lb Delilah optical-configured, up-warheaded, mini-cruise under each rack attachment, that's _four_ individual targets hit without ever having to come closer than 80nm to any given target.

Give me lower throttle settings and standoff non-contestment over 'low drag carriage' anyday. Especially in a tub where I'm trading up to a gator for about 1,500lbs of fuel (most of the IDFAF Lavi would have been twincabs IIRR).


KPl.

Ch1466 even though at times i dislike your long posts they can be helpful so in case you have taken anything from me overly negative I apoligize. So my question to you is if the F-15c is turned into a "bus" with CFT's what is the benifit of them in the first place.

[edit on 15-6-2006 by Canada_EH]

Originally posted by waynos
Emile, you don't need to imagine it, KPI showed you pictures, how come you can't believe it

No, All of pix showed there is no pylons under Lavi's airframe

Then what do you suppose that rather large fuel tank is attached to in the first two pictures?

Picture request !!!

Can anyone help me out with a picture of a Lavi with the open speed-brake ???? ... a friend of mine is modeling one in 1/32 and is looking for details !

Thanks, Deino :-)

Canada_EH,

If The Bear had gone over another Mountain and we had ended up going to war in the PG with the RDF in the 1980's, the F-15C's assigned to CENTCOM would have been dropping bombs while the rest of TAC got their act together and tried to remember there were places /other than/ NATO they needed to get to. To move those Langley 'first responders' to Saudi without CFT would have required prolonged pre-staging of tankers across ascension and thru Egypt or Akrotiri.

To get them across the Gulf with two MERs worth of dumb iron and a centerline tank (assuming you had a working ICMS which, at the time, most F-15's did not, requiring an ALQ pod on the centerline for certain band coverages) plus combat reserves would have been well nigh impossible unless the Iranians let us in and the Russians were just plain stupid.

CFT don't compete for three functoning pylons on an Eagle and hence all 1st TFW jets had them assigned, early on.

Similarly, if you were a Black Knight out of Keflavik or one of the 3rd Wingers doing work over the Aleutians or across the Bering Sea, you often couldn't count on landing at the same airfield you took off from with the nearest divert being in Scotland or 'over the hills' in Anchorage or King Salmon. Which is a good long ways in overwater terms and a real hairy eyeball situation whn you've already spent a couple hours running out and sidling up to a Bear determined to test your ADIZ responsiveness.

Lastly, to put things in real-war perspective: The IDFAF put CFT on their F-15A/B from the outset. Thus, when they _really needed to_ they could fly that monster wing through all the bumpies of a 2hr trip through the turbulence under 500ft, for 550nm. Make a burner zoom to cover four separate IRAF airfields and then gather up their F-16 bombers and run 'high cover' _into a headwind_ at 35-40,000ft. All the way back home. Whereupon they dropped off their charges at Etzion AB (IIRC) in Southern Israel and returned to Tel Nof all the way at the other end of the country. With 6,000lbs remaining on average. The F-16s landed, every single one in a fullon fuel-emergency, with between 800 and 1,200lbs. One was supposedly so low 'it was off the E on the dial' with something like 400lbs left in the jet. Every jet was also broken with some kind of full-down problem that prevented them from further immediate fight participation as well.

This after having dropped everything but their centerlines (which was a recent delivery 'just for that raid' and had clearance issues) and tip weapons. The F-15's took two 610s, 4 AIM-9D, 4 AIM-7 and a centerline Elta jammer pod in addition to the CFT gas. And brought IT ALL back. Landed and took off again to help put up an intimidation 'ready when you are for round 2' effort along the Syrian borders where every radar could see a horde of IDFAF airpower just waiting.

Since the first requisite of maintaining dominance so that you _don't have to fight_ is in fact 'being there', patrolling the parapets wherever a potential enemy thinks he can get away with something sight-unseen, PRESENCE is the first prerequisite of who wins and who loses.

Coming back with a warload to finish the job if need be is the second.

Having the spear-in-throat performance to win and come home is the third.

CFT gets Rodan to almost any engagement. Whether you win once you're there is going to depend an awful lot on how much your missiles and tactics push their noses in while letting you rotate from threat to threat and keeping everyone sorted with mixed BVR shotlines. As well as how tight and smooth your coordination lets you stick it to the other team /just long enough/ to get the mission tasking completed so that you can all fade together.

The Israelis are past masters of this kind of thing but it must be said that they played a REALLY long hand to an inside draw on 14 jets and a potential declaration of war.

If the Iraqi AF had come up in serious numbers all 'round the compass, the F-16s would have run out of gas unless met by an extraction force over Jordan and the F-15's would have been slaughtered trying to give them even that much of a running-start chance (can't ditch conformals and hence the 'bus like' vulnerabilities). If the jets had been engaged by King Hussein's Finest, it would have been a running fight at best (F-5E and Mirage F-1 IIRR, none with BVR capabilities but Jordan's drivers aren't too shabby compared to other ME nations...).


KPl.

Originally posted by Deino
Picture request !!!

Can anyone help me out with a picture of a Lavi with the open speed-brake ???? ... a friend of mine is modeling one in 1/32 and is looking for details !

Thanks, Deino :-)

Deino,

Tell your friend that it's a lot easier in 48th or 72nd. Two Words- Donor Kits.

Second, the data I have shows that, as of late 1986, after IAI refused to provide accurate labor data for their cost estimate, the entire yearly commitment for the Lavi (some 69 million dollars) was withheld and among those items that were on a 'past due' payment list was a final optimized Lear Siegler card for the FLCS computer. And a 'Pneu Draulics' actuator for the speed brake. Clearly, the TDs finally flew but a check of all the online photos I can find plus my own collection shows only ONE open speed brake shot and that is from the front with the panel so hyperextende in an assembly shot that there is clearly no ram inside.

You might check the AvLeak site for PIREPs. I'm pretty sure that Dave Fulghum or one of the other high chief flunky's got a ride. And if so, they would likely have a mention of airbrake effectiveness in their acceleration/deceleration data.

Emile,

From page 54 of the June 1 1987 edition of AW&ST 'Lavi A New Israeli Multirole Aircraft' (Special advertising section).

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The wing has three-dimensional twist and camber to minimaliz high speed cruise drag, as well as multiple hardpoints (including two wingtip missile stations), and conformal carriage hardpoints in low drag arrangement on the fuselage.
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Here-

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You see a J-10 equipped for similar carriage of fuselage stubmounted stores.

Yet 'at a glance'-

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You would never suspect it to be anything but a wing-store carriage A2A machine.

Since I consider the J-10 to be nothing but a cheap thievery of Lavi technology that the U.S. designed and paid for and Israel 'sold on' in a fit of pique over not being able to rape the export market with for their own gain, I believe that it's likely the Lavi TDs (= _Technology Demonstrators_, the first three of six intended being only intended for aeros work and not even equipped with a full set of avionics) were either not equipped with activated weapons stations or had them stripped before being sent to the IAF Museum and the PRC respectively.


KPl.