Discussion: F-14, F-15 Hybrid Idea

[elmayerle]

Okay, I've been busy, but let me try and answer your questions.

The wing/LERX fences clearly added some drag, I don't have the info to say how significant it was and there are enough interactions there that'd I'd be leery of claiming anything without looking at the data.

The entraining wouldn't affect drag as much at supersonic speeds, but there would still be some effect.

I don't think that the critical technology for the flexible wing, flexible composite skins, was available during the time VFX could have adopted them.  I don't know that you'd necessarily see more stress in using flaps that way (though you might under maneuvering conditions) but there's also the wear factor to consider.  I imagine you can deal with it in the airframe design, but I've not got a "gut feel" for how much the weight penalty would be.

Contamination includes atmospheric particulates, bugs, and other things that can get mechanisms.  I suspect that it's a matter of designing around these things to deal with it.  Slats can have most, if not all, of their mechanism inside the wing while leading edge flaps will require linkages that'll be exposed, unless you're going to a level of enclosure required for other reasons (low observables, for one).  I'm not sure how many of these techniques were readily usable when the VFX was being designed.  Flaps are generally used primarily in the low speed regimes and thus don't necessarily see the same loads that they would if used in active maneuvering; again, their mechanism design tries to keep as much internal to the wing as possible, but you still have problems today.  There's nothing that can't be designed around, I'm just unsure of the costs/penalties involved (I do note that the F-14 uses slats and flaps solely in low-speed regimes, though that's as much a factor of the swing-wing as anything else - I'll also point out that the F-15, as built, does not use an leading edge devices and never has; I'm certain that a fixed wing VFX design could use such a wing, though it wouldn't be as adaptable as you're wanting).

Regarding the A3J/A-5, given the afterbody shape, I don't think that changing from a single vertical to twin verticals would have greatly altered the shape of the aerodynamic fairing; now, going to a conventional bomb bay instead of the linear one could well have changed things.  BTW, I understand the original NAA-Columbus NAGPAW (North American General Purpose Aerial Weapon) proposal, that the Vigilante developed from, was for an all-weather subsonic aircraft not that far off from the A2F/A-6.

[KJ_Lesnick]

El Mayerle,

The wing/LERX fences clearly added some drag, I don't have the info to say how significant it was and there are enough interactions there that'd I'd be leery of claiming anything without looking at the data.

Understood.

The entraining wouldn't affect drag as much at supersonic speeds, but there would still be some effect.

I kind of had a feeling (even with my limited knowledge of aerodynamics) it either was going to be non-existant at supersonic speeds or drastically reduced, but I had to make sure.

I don't think that the critical technology for the flexible wing, flexible composite skins, was available during the time VFX could have adopted them.

That's kind of what I was worried about...

I don't know that you'd necessarily see more stress in using flaps that way (though you might under maneuvering conditions) but there's also the wear factor to consider.  I imagine you can deal with it in the airframe design, but I've not got a "gut feel" for how much the weight penalty would be.

Don't some fighters use their flaps during maneuvering conditions?  If I recall correctly...
-The F-104s were modified with flaps that allowed them to extend them up to 550 kts airspeed to enhance maneuvering capabilities
-The F-14 could use it's flaps up to 10-degrees during maneuvering conditions (although this is only at low-speed, but the plane could maneuver quite tightly at low-speeds).
-I've heard mention that the F-16 does use it's flaps in addition to it's slats to increase lift for maneuvers.

I would assume the leading-edge devices aren't something to be all that worried about for maneuvering-conditions as many planes use slats for maneuvering purposes to enhance turns, correct?

Contamination includes atmospheric particulates, bugs, and other things that can get mechanisms.  I suspect that it's a matter of designing around these things to deal with it.  Slats can have most, if not all, of their mechanism inside the wing while leading edge flaps will require linkages that'll be exposed, unless you're going to a level of enclosure required for other reasons (low observables, for one).  I'm not sure how many of these techniques were readily usable when the VFX was being designed.

How did the F-18 manage to get around this problem?  Its flaps also were used for variable-camber as well (and were single slotted like the concept I'm proposing). 

While I'm at it, did the YF-17 have such a variable-camber system for it's flaps and leading-edge devices? 

Flaps are generally used primarily in the low speed regimes and thus don't necessarily see the same loads that they would if used in active maneuvering; again, their mechanism design tries to keep as much internal to the wing as possible, but you still have problems today.  There's nothing that can't be designed around, I'm just unsure of the costs/penalties involved (I do note that the F-14 uses slats and flaps solely in low-speed regimes, though that's as much a factor of the swing-wing as anything else - I'll also point out that the F-15, as built, does not use an leading edge devices and never has; I'm certain that a fixed wing VFX design could use such a wing, though it wouldn't be as adaptable as you're wanting).

I'm aware that the F-15 does not use any leading-edge devices.  I suppose it would be possible to design a VFX design without any leading-edge devices, but I don't think it would do so well in the higher-speed ranges, which is kind of important for an interceptor design.

Regarding the A3J/A-5, given the afterbody shape, I don't think that changing from a single vertical to twin verticals would have greatly altered the shape of the aerodynamic fairing; now, going to a conventional bomb bay instead of the linear one could well have changed things.

Thank you for your response.  I was really curious about that one. 


KJ Lesnick

[KJ_Lesnick]

I was thinking about what's been said about the F-14's pancake and I'm thinking that it might not be such a bad idea to at least think of incorporating into the what-if design.  It would allow more lift to be gained from the fuselage and could allow a wing that's not quite as obscenely large than would be required without a pancake.  Especially when you consider that (At least from what I remember reading) the F-14 did not have serious interference-effects problems with the pancake/tunnel (not sure if it was due to the insides of the inlet ducts being canted out or not) design-feature -- even when carrying the Phoenix-missiles (granted in a palletized set-up):  The predominant factor that produced reductions in range and speed were actually the weight of the missiles more than the drag they produced overall (at least for the ones carried under the pancake). 

I'm still not sure if the design could achieve speeds as fast as an F-15 with a flush-mounted Sparrow-loadout (the particular sparrow load out on an F-15 produces virtually no speed penalty), plus there are some problems with the pancake, such as a lower rate of roll -- and the F-14 doesn't have the roll-rate the F-15 does to the best of my knowledge. 

The idea I'm thinking of a engine-spacing/tunnel set-up somewhere between the F-14 (engines widely spaced all the way to the back, huge pancake) and F-15 (engines right next to each other, though inlet ducts at the front are spaced about as far apart as the F-14's and no pancake) seems best to me. 

Like the MiG-29. 


I don't know of any roll-rate problems with that aircraft.  Granted the MiG-29 has the bulk of the fuselage and nose above virtually the whole pancake, but I figure if the F-15 can have no pancake, and the F-14 can have a pancake, and considering both have their fuselages in between the engine intakes, I figure it could be done.  More blending might be needed though 


Opinions anybody?


KJ Lesnick,
BTW:  Considering the engine spacing would be about the same as the MiG-29, I don't know if a tail-fairing like the RA-5C, would be needed as the MiG-29 itself doesn't have one, however the fuselage being lower on this WHIF design might somehow make things different -- anyone got any info here?

[KJ_Lesnick]

will leave it to the experts but ı really liked the Mig .Does the picture come in a series so that we can see more ?

I don't think so.  There are other photos on airliners.net that look similar, but they are not by the same photographer though.


KJ Lesnick

[tinlail]

Couple of thoughts.
The Russian's consider the overall shape to be a pretty good one, all of their newer planes, seem to have it in one form or another.
The width of the pancake in the F-14 seems to have been driven by an attempt to get the pivot points of the wings out there, compared to the F-111, which apparently had them to close in. If your plane is fixed wing this issue goes away.
I believe that the F-14 had the fuselage, really the nose, lower down between the  engines to keep the nose gear shorter, if it wasn't a carrier plane it could of been more like the Russian designs.

[KJ_Lesnick]

tinlail,

Couple of thoughts.
The Russian's consider the overall shape to be a pretty good one, all of their newer planes, seem to have it in one form or another.
The width of the pancake in the F-14 seems to have been driven by an attempt to get the pivot points of the wings out there, compared to the F-111, which apparently had them to close in. If your plane is fixed wing this issue goes away.

Not true actually, if you look at the first Grumman concepts they were fixed wing, yet the designs had widely-spaced engines with the characteristic tunnel.

I believe that the F-14 had the fuselage, really the nose, lower down between the  engines to keep the nose gear shorter, if it wasn't a carrier plane it could of been more like the Russian designs.

Possibly true, but the design *IS* a carrier plane.


KJ Lesnick
BTW:  During the TFX program (The F-111B in particular), General-Dynamics and Grumman both were asked to submit design-proposals.  Grumman generally went with designs that departed more from the F-111B design, often abandoning swing-wings in lieu of fixed ones, where as General-Dynamics' designs kept going with swing wings.  If General-Dynamics submitted a fixed wing design (and a good one too), it would almost certainly have been taken as a slap in the face to McNamara among others -- would McNamara have reacted vindictively in such a situation?

[Sauragnmon]

You could actually get away with it, since you are fixed wing.  Narrow the engine section, but keep the intakes flared around the cockpit which keeps down to keep the nose gear short.  Wide shoulder, narrow waist.  Trim a few inches off that pancake, maybe give an option for a centerline CFT in the tunnel?  I don't know.  You also should consider your payload mountings with regards to the layout you have planned.

[Taiidantomcat]

Yup, considering that the man who told congress that "all the thrust in the world couldn't make that plane a fighter" in reference to F-111 had his career ended by Macnamara for killing his retarded brain child.

Also Sukhoi was the company that had the blended wing design first, MiG had considered something like it early on then decided against it, but ordered the change after seeing Sukhoi's design. MiG then also suggested (knowing that the Flanker would have more capabilities than his smaller Fulcrum, thus costing him the contract) that the Russians adopt a "Light" fighter to supplement the heavier Flanker much like the USAF F-15/F-16 combo. smart salesman.

[Taiidantomcat]

the admiral talking of trust in Christendom did not lose his job , the F-14 was coming and McNamara was one the first men to see it coming and he didn't really try to stop it .He was a good man at heart.

didn't say he got fired, said it ended his career. Promotions were hard to come by after that. Also he didn't see the F-14 coming considering that it didn't get started until AFTER the F-111 was canceled. MacNamara did some stupid things in the name of saving money and it killed people. Chrome Chambers for M-16s were deemed too expensive and caused jams that cost lives in Vietnam. the problem was so bad that Marines wrote their congressmen and the Corps temporarily switched back to the M-14. He also came up with the idea of making engine companies design Turbines for specific aircraft, thus stagnating engine tech growth to the availability of new airframes. He was a good accountant at heart.

[Sauragnmon]

Thrust alone does not make the airplane.  The F-4 wasn't exactly a stupendous fighter, it did a good job, in the right task, but it had a big glaring weakness in its pathetic wing loading.  The words Great Big Flying Brick come to mind.  The F-111 had potential, really it did, as a strike bomber.  Any other thoughts just don't work.  It's like a Diet B-1 Lancer.  Could have done well as the EF-111 as well.  The M-16 early models... weren't worth the paper they were designed on.  It was a design that needed a good smack upside the head with the KISS principle.  Not to mention whoever thought venting the gas back into the chamber was a good idea should have been smacked with an engineering text.

But I digress, and so does the rest of the thread.  Like I said, consider your weapons payload before deciding how to narrow out the pancake.  You could go with the big shoulder narrow waist concept, as demonstrated on newer aircraft.  That would help thin it out, but it might limit some of the payload.

[KJ_Lesnick]

Sauragnmon,

You could actually get away with it, since you are fixed wing.  Narrow the engine section, but keep the intakes flared around the cockpit which keeps down to keep the nose gear short.  Wide shoulder, narrow waist.  Trim a few inches off that pancake,

Like the MiG-29's afterbody area?

maybe give an option for a centerline CFT in the tunnel?

That sounds interesting, though I'm not sure exactly how they would affect interference effects.

You also should consider your payload mountings with regards to the layout you have planned.

I actually have no idea what the best set-up for mounting the Phoenix's are with or without a palletized weapons system.  I have a pretty good idea how to mount AIM-7's (flush mounted on the engine-box -- virtually no drag penalty at least on the F-15) and AIM-9's.


Taiidantomcat,

Yup, considering that the man who told congress that "all the thrust in the world couldn't make that plane a fighter" in reference to F-111 had his career ended by Macnamara for killing his retarded brain child.

What would happen to an aerospace company under the situations I speculated?

Also Sukhoi was the company that had the blended wing design first, MiG had considered something like it early on then decided against it, but ordered the change after seeing Sukhoi's design. MiG then also suggested (knowing that the Flanker would have more capabilities than his smaller Fulcrum, thus costing him the contract) that the Russians adopt a "Light" fighter to supplement the heavier Flanker much like the USAF F-15/F-16 combo. smart salesman.

I know the Su-27 came first.


r16,

a few snippets

the admiral talking of trust in Christendom did not lose his job , the F-14 was coming and McNamara was one the first men to see it coming and he didn't really try to stop it .He was a good man at heart.

VADM. Tom "Tomcat" Connolly was his name.  Regarding McNamara not doing anything to stop F-14:  I did wonder how the F-111B managed to get cancelled and the F-14 managed to get the green-light before McNamara resigned...  still I doubt I would consider him a good man at heart.

the gap between the engines form a useful drag reduction at some speeds and it is on the Tomcat to increase loiter time . I don't know exactly how though .

I'm guessing it was shaped in such a way that it increased pressure as air flowed through the tunnel on the underside of the plane.  At supersonic speed, the area where the fuselage meets the pancake seems to be shaped in such a way to form oblique shockwaves, so it would increase pressure through the duct at supersonic speeds -- I'm not sure how favorable the interference effects would be with the engine pods there though. 

the Russian version was first on the "back of an envelope" and the general charges of espionage actually depend on this as the engineers of the Russian equivalent of NASA did discuss the benefits in a private situation and they might have seen western original papers somewhere , sometime .

The Russians swiped the pancake from the F-14? 

thanks to KJ Lesnick for the picture source

Thank you.


Taiidantomcat,

didn't say he got fired, said it ended his career. Promotions were hard to come by after that.

I thought he resigned right afterwords...

Also he didn't see the F-14 coming considering that it didn't get started until AFTER the F-111 was canceled.

Who didn't see the F-14 coming?  VADM Connolly or SECDEF McNamara?  To the best of my knowledge, McNamara would have known (assuming he didn't resign yet -- he resigned sometime in 1968) as the F-14 was given the go-ahead in early to mid 1968.

MacNamara did some stupid things in the name of saving money and it killed people.

Yeah, a *LOT* of stupid things in the name of saving money, and stupid things for spiteful purposes (like trashing the F-12B because he wanted to make an USAF interceptor derivative of the F-111)

Chrome Chambers for M-16s were deemed too expensive and caused jams that cost lives in Vietnam.

That was a disaster...

the problem was so bad that Marines wrote their congressmen and the Corps temporarily switched back to the M-14.

I never knew that...

He also came up with the idea of making engine companies design Turbines for specific aircraft, thus stagnating engine tech growth to the availability of new airframes. He was a good accountant at heart.

When did he do that?  And why?  Wouldn't it be cheaper to design one engine that fits all?  No doubt though, he was a good accountant at heart! 


Sauragnmon,

Thrust alone does not make the airplane.

That's actually true, there's a lot more to an airplane than that such as wing-loading, roll, pitch, and yaw-rates, ease of handling among the first few...

The F-4 wasn't exactly a stupendous fighter, it did a good job, in the right task, but it had a big glaring weakness in its pathetic wing loading.  The words Great Big Flying Brick come to mind.

I knew it wasn't the most maneuverable airplane, and it didn't have the best wing-loading in the world, but I didn't think it would be that atrocious... those wings were quite big, and they were thick and cambered.  To the best of my knowledge the F-105 was worse, but I don't know how much of a statement that is... an AIM-9 Sidewinder probably has better wing-loading than an F-105 (j/k -- unless I'm right )

The F-111 had potential, really it did, as a strike bomber.  Any other thoughts just don't work.  It's like a Diet B-1 Lancer.

I'd say attack/bomber.  It could perform both missions, it had the range enough to be strategic (barely) and a payload that could class it as a medium bomber (it's range isn't enough for what SAC would have liked in a medium-bomber though). 

I'd say calling it a Diet-B-1 Lancer is a little overkill.  The B-1A had substantial range over the F-111 (as it was designed as a totally strategic aircraft), in addition to the obvious bomb-load (75,000 lbs internal, 40,000 lbs external)...

The M-16 early models... weren't worth the paper they were designed on.

The only thing I really like about the M-16 (and that was more current models) was the fact that it was very stable and very accurate to aim at full-auto compared to the M-14, the M-14 was more accurate when firing semi-auto though (better sights, though both M-14 and M-16 have very good sights)


KJ Lesnick

[Sauragnmon]

I'm not a hundred percent sure with regards to the MiG-29's afterbody thought.  The YF-23's Y-style to its engine ducts was more to what I was thinking about, when I suggested the wide shoulder narrow waist.

The Centerline CFT would, with enough shaping, work smooth with the aerodynamics.  You could smooth it down off the nose, branch it towards the intakes, you can smooth it around into the intakes.

The Phoenix you could also run a payload bay along the centerline, potentially.  Carry two up front, one down the backside, Maybe have an internally mounted extension fuel tank on the inside.

Additionally, yeah.  Pitch and yaw rates, climb rates, wing loading, those definately make a good note on the plane.  Also does the payload capacity.

The F-4 was just the first aircraft that was big thrust, poor maneuverability that came to mind.

The F-111 was a diet Lancer.  Similar airframe, but performance like an anorexic beside a trained swimmer.  Lower stamina, lower lifting capability, yeah that's a diet Lancer.

Yeah, the M-16's controllability and recoil compensation are about its ONLY redeeming benefits.  You can hold it stable in full auto, right up until it jams.  Then you have a problem, and cursing insues.  The M-14 had better range, semi-auto accuracy, kinetic energy... It's the kind of rifle you want when you absolutely need to make sure the target is fracking dead, without needing a muzzle brake, bipod, and big budget rifle.

[KJ_Lesnick]

I'm not a hundred percent sure with regards to the MiG-29's afterbody thought.  The YF-23's Y-style to its engine ducts was more to what I was thinking about, when I suggested the wide shoulder narrow waist.

Fascinating idea actually.  However, I checked the spacings... the F-14/F-15's spacing at the inboard portion of where the inlet wall is about the same as the YF-23 (the outboard area might be a little bit further out), and the spacing between the left and right engine is also about the same as the MiG-29 -- somewhere between the F-14 and F-15.

The Centerline CFT would, with enough shaping, work smooth with the aerodynamics.  You could smooth it down off the nose, branch it towards the intakes, you can smooth it around into the intakes.

Why not just employ more significant blending between the lifting surface and the inboard engine-duct (outer) walls?  Possibly fiddling with the height of the pancake in the middle to avoid excessive thickness in the middle. 

The Phoenix you could also run a payload bay along the centerline, potentially.

I like the concept of internally carried weapons, but it's overly complicated and takes up more internal volume than necessary, unless you need absolutely insane speed, stealth, or both.  I think External mounting is obviously the way to go, especially in this case. 

Additionally, yeah.  Pitch and yaw rates, climb rates, wing loading, those definately make a good note on the plane.  Also does the payload capacity.

Correct

The F-4 was just the first aircraft that was big thrust, poor maneuverability that came to mind.

Okay, I know what you mean.

The F-111 was a diet Lancer.  Similar airframe, but performance like an anorexic beside a trained swimmer.  Lower stamina, lower lifting capability, yeah that's a diet Lancer.

I'd say more like a diet Midget-Lancer :p


KJ Lesnick

[Sauragnmon]

The angled intake ducts was an idea to size down the airframe for you, it might pan out well.  I don't know.  It came out with the something of a necessity you had for the wide shoulder on the wingspan, and your desire to shrink that pancake.

Your tactic is equally sound, I was just considering blending the whole airframe along the low end of the engine duct to keep down the below-wing space and maintain ground clearance.  Running it right down to the pancake might be an idea, though you could also do something else with that space, see next point.

The payload bay concept would require a lot of tinkering.  It would lighten up airframe drag, reduce your cross section, and if you had it set up for a quick enough rail actuator, you could bring the missile down in time with bay opening, lock, fire, retract in a decent time.  Electromechanical actuators over any other form would likely be the best solution.  They've been proven to be more efficient for speed over hydraulics.  It would also allow you to do something like carrying an extra avionics package in the aft section, smoothing the blend over to the pancake, though you'd still have to consider your arrrestor hook mounting as well in that section.  You were muddling over a non-pallet stowage for the Phoenix missiles, there's your prime concept, and it would give you a multirole mounting in the centerline.  Perhaps, instead of making it a purebred bay, you could have bay doors as an option when carrying bomb payloads, but for weapon systems like the Phoenix, have them semi-recessed over a mounted internalized fuel tank.  Not as much capacity as the full blown tank, but it would optimize the aircraft in the interceptor role, allowing for longer range intercept.  True reach-out and intercept-someone capacity.  You wouldn't have to model the bay that way, you could just have the recessed phoenix mountings over the smoothed out section.  It's just a thought, by no means a must.

I'll opt not to continue the other points, as we've reached a mutual understanding in those sections, I should think.

[Sauragnmon]

I'm not sure I like MacNamara much in general.  He doesn't seem entirely like the brightest bulb in the box, from a strategic perspective... cutting costs is good, but there's going too far...  But then, I'm a bit more of a mad scientist, I would have embraced more interesting, forward thinking projects.

The M-16 only started getting good after it'd seen a few revisions to fix its glaring problems.  It still is far too unreliable for a service rifle, in my opinion.  But then, I'm an AK man.  I like a weapon designed to survive seven shades of hell and keep working.  What can I say.  That, or a FAL.

If you're slash and burning, yes, thrust is all you need worry about, but it's never so simple, there is a need to consider that no matter how much drilling you go through, a pilot will always vary from the norm when it's in the fan.

Naval F-111 would have been at best a questionable affair, where the merit would exist in such a bird would leave me wondering.  EF-111, Navalized, that might have been something, anything else, I would dare to wonder what in the nine circles of hell it was doing with a hook and carrier mods.