Your 'What If' TFX design and profile?

[MAD]

Gents I say with great pride that the General Dynamics F-111 would have to be my favorite Strike/Interdiction.
What with its range, payload, and low-altitude speed and performance, there are few designs out there that come close to its capability, even after almost 30-years since it was designed.
(Although I have always thought that the Boeing Model 818 design would have been a better choice! )
Being in the ADF have been privileged over the years to have seen the mighty Pig in action – from high speed tree top passes, terrain following and dropping bombs!!!!
And I must say that I think I would prefer to have pins in my eyes than see it's phased out of service!

Now with the advent of the very promising and capable Russian Sukhoi Su-34 'Fullback', I can not help but reflect on the fact that if the Su-34 was to go into full scale production and service, it would have achieved what the USAF had tried all those decades back in the 1960's in developing a common airframe/aircraft that could carry out a myriad of roles and missions – at a great cost saving.
This was called the 'Tactical Fighter Experimental' TFX program.
Apart from the political interference of the then Secretary of Defence – Robert McNamara , who forced the United States Air Force and United States Navy too work jointly to develop a common airframe which would maximize commonality to serve both services roles and missions of fighter-bomber, tactical nuclear strike/interdiction tactical reconnaissance, and Fleet Air Defence (FAD).
This would become the General Dynamics F-111.
But the culmination of cutting edge technology such as - terrain following radar (TFR), variable-geometry (VG) wing design, avionics etc.....), plus the grueling needs for aircraft carrier compatibility, and the variations in the needs of types and numbers of various weapons to be carried, and possibly one of the greatest factor that would effect the size and weight of the design – the range and endurance requirements of opposing services!

We all know of the problems that plagued the TFX/F-111 design and development and in some case its in-service history.

I would like to ask you all out there – what with the skills and knowledge on military aircraft and aerospace technology we have out there in the world of this great web site – Given the chance, how would you have designed the TFX/F-111?

There are some rules and constraints that still apply to this Request for Proposal (RfP)

1.   Robert McNamara and his Ford Motor Company management mentality still reigns – The USAF & USN are forced to joint develop this aircraft
2.   variable-geometry (VG) wing design must be used in the design
3.   The Pratt & Whitney TF 30 augmented turbofan has to be used (although a future growth / replacement engine would be a wise move to incorporate into your design.
4.   The navy's need to be capable of carrying six AIM-54 Phoenix air-to-air missiles, and the powerful and advanced Hughes AN/AWG-9 pulse-doppler radar.              The Navy had requested a maximum takeoff weight of 50,000 lb (22,686 kg).        loiter on station for long periods
5.   The Air Force needs of a low-level speed of Mach 1.2, a high-altitude speed of Mach 2.5, a combat radius of 890 mi (1,430 km), good short-field performance, and a ferry range long enough to reach Europe without refuelling.


What layout would you have adopted?
What seating/cockpit arrangement will you opt for – tandem or side-by-side?
Will the majority of weapons be wing or under fuselage mounted?
Will you retain the small weapons bay or go for something larger/more volume?
Would you have a different landing gear arrangement?
Single or twin tail fin arrangement?

Looking forward to seeing your efforts and ideas of your TFX profiles

M.A.D  

[tinlail]

Question can the Su-34 meet those spec?

Honestly the best idea I can come up with to meet those specs, is some thing along the lines of take the F-14 design the back half between the engines, so that it can be constructed two ways.
One like the the f-14, the other more like the A-5 (flat bottom, lots of space for fuel, not the linear bomb bay however)

The need for a internal bomb bay probably means that you can't really do it with a conformal belly tank between the engines. So you have to design to different fuselages that are enough similar, that enough cost savings could be had to keep the SoD happy.

So thoughts about how this plane would look compared to the F-14.

• Wider and longer noise, up front to hold the TFR avionics.
• Bomb bay behind the cockpit
• Fuel behind the bomb bay, as far back as CG and area rule allows.

[GTX]

I'll have to think about this one for a little while.

Mind you, I don't see what you see in the F-111 - they annoy me on a daily basis.  Can you even imagine how difficult it is for me having to work at RAAF Base Amberley and try to talk to people when a pair of F-111s decide to take off or do low level passes???  Even worse when they taxi past my office about 100m away???

Regards,

Greg

[Weaver]

Many year ago, a mate of mine found himself driving past a US base (can't recall which one - Bentwaters maybe?) and decided to stop and press his nose to the fence for a bit. As he watched, an F-111 taxied out towards the runway. Just as it was making a fairly sharp turn onto the runway, it stopped dead, so hard and suddenly that it completely compressed the nosewheel strut and he swears the radome actually hit the tarmac. The crew then leapt out (and that's a big drop without ladders) and one of them immediately legged it, but the other one took time out to give the nosewheel an almighty kicking before joining him.....

They were met by the airfield emergency vehicles coming the other way at top speed. At that point, my mate started to reflect on what it might be carrying, and decided to get back in his car and drive off really quickly.......

Looking at MAD's list of requirements, I can see the genesis of the problems right in there. A couple of things strike me (I know these things were specified for real, but they're the ones I'd query for real...):

Point 2. Is it really appropriate to specify that it have VG wings? Surely it's for the services to specify the Vmax, landing speed, ceiling and maneuverability, and for the designers to come up with the appropriate technical solution? In other words, if a designer thinks he can meet the spec with (for instance) a variable incidence, heavily-blown wing, why should it be arbitarily excluded?

Point 5. Okay, the airforce are entitled to ask for these speeds, but I'd query the wisdom of it. Every study has shown that an aircraft is no safer at Mach 1.2 at low level than it is at Mach 0.9, but the former imposes an enormous fuel and structural penalty. Likewise, Mach 2.5 at altitude (for any length of time) imposes kinetic heating penalties that Mach 2.2 doesn't, yet has no operational advantage over the lower figure.

A better approach might be to say that the fighter/fighter-bomber mission and the deep strike mission are incompatible, and develop a joint-service successor to the F-4 (F-14ish, but maybe fixed wing with a single seat option) and a joint service strike aircraft that combines the best attributes of the A-6 and F-105 but has no pretensions to being a fighter.

If I had to meet the requirement as stated then, as tinlail has said, the end result would probably end up looking much like an F-14, since the Navy's fighter and deck landing requirements HAVE to dominate the design.

Question: is a full internal bomb bay an Airforce requirement, or is conformal carriage acceptable?

[MAD]

I'll have to think about this one for a little while.

Mind you, I don't see what you see in the F-111 - they annoy me on a daily basis.  Can you even imagine how difficult it is for me having to work at RAAF Base Amberley and try to talk to people when a pair of F-111s decide to take off or do low level passes???  Even worse when they taxi past my office about 100m away???

Regards,

Greg

How inconsiderate of those flight crews!!!!
I think it will be a case that although their TF-30's annoy you on a daily basis, will only be truly appreciated when they are taken out of service!
Sad days indeed!

What I would find interesting, is to put my 'What If' question too the likes of these 'Pig' crews (both flight and maintenance crews) and with their personall and operation experience find out what they come up with. 

M.A.D

[Archibald]

Now with the advent of the very promising and capable Russian Sukhoi Su-34 'Fullback', I can not help but reflect on the fact that if the Su-34 was to go into full scale production and service, it would have achieved what the USAF had tried all those decades back in the 1960's in developing a common airframe/aircraft that could carry out a myriad of roles and missions – at a great cost saving.
This was called the 'Tactical Fighter Experimental' TFX program.

Ah, so I'm not the only one thinking that the Su-27 family is the true TFX incarnation ?
http://www.whatifmodelers.com/index.php/topic,16601.0/highlight,su-27.html

[MAD]

Now with the advent of the very promising and capable Russian Sukhoi Su-34 'Fullback', I can not help but reflect on the fact that if the Su-34 was to go into full scale production and service, it would have achieved what the USAF had tried all those decades back in the 1960's in developing a common airframe/aircraft that could carry out a myriad of roles and missions – at a great cost saving.
This was called the 'Tactical Fighter Experimental' TFX program.

Ah, so I'm not the only one thinking that the Su-27 family is the true TFX incarnation ?
http://www.whatifmodelers.com/index.php/topic,16601.0/highlight,su-27.html

Sorry mate!
I had not seen your post!

Added to this is the fact that the Su-35 is truely self escorting - with a great air-to-air capability and armament!

M.A.D

[MAD]

Looking at MAD's list of requirements, I can see the genesis of the problems right in there. A couple of things strike me (I know these things were specified for real, but they're the ones I'd query for real...):

Point 2. Is it really appropriate to specify that it have VG wings? Surely it's for the services to specify the Vmax, landing speed, ceiling and maneuverability, and for the designers to come up with the appropriate technical solution? In other words, if a designer thinks he can meet the spec with (for instance) a variable incidence, heavily-blown wing, why should it be arbitarily excluded?

Weaver - I hear what you are saying 'loud and clear'
And I completely agree with your points!
I think the push for variable-geometry (VG) wing design was due to western technological prestige and the aeronautical advances this exciting new technology offered.
Saying this I do not really think they took into consideration both the weight and maintenance penalties that come with VG wing designs.
These factors would only come with in-service experience and newer technologies.
Hence why we have seen a clear steering away from VG wings, after many nations and air forces had had a play at them.
A good example of this is the Soviets obsession with VG technology after the arrival and publicity of the American F-111, was their Sukhoi T-6 strike/interdiction project.
The T-6 was more along the lines of the British TSR.2 project in terms of layout and wings, and yet with the advent of the TFX program, the Soviets had to be part of this – hence they redesigned the T-6 layout to the VG wing Su-24 'Fencer' we know today.
Then there was the Su-7 transition to the semi-VG wing Su-17/22, and then came the Tupolev Tu-22M 'Backfire'
Then the Europeans had too be part of this aerospace revolutionary process as well, with the French G.8 VG wing design (it should be noted that the French were probably the first nation to see the cost and weight constraints of the VG-wing design, opting too revert back to fixed wing designs on the grounds of cost!!)
Finally we had the joint European Tornado program that went for VG-wings as the basis of their design.

In defence of the VG wing design though, must be the known and unquestionable ability to contribute to high-speed, low-altitude
(terrain following) performance, crew comfort, and weapons platform stability, which can not be matched even by latter designed fixed-wing designs like the Su-27/30/32/33 'Flanker' series, or the F-15E Strike Eagle!

Point 5. Okay, the airforce are entitled to ask for these speeds, but I'd query the wisdom of it. Every study has shown that an aircraft is no safer at Mach 1.2 at low level than it is at Mach 0.9, but the former imposes an enormous fuel and structural penalty. Likewise, Mach 2.5 at altitude (for any length of time) imposes kinetic heating penalties that Mach 2.2 doesn't, yet has no operational advantage over the lower figure.

Your fact about high speed survivability was a hang over of the era, when speed was everything, the military the world over!
It would only be after the costly experiences gained in the air war over Vietnam that the USAF would reevaluate the importance and viability of bigger and faster is best mind set.
This wake up call would be the birth of the LWF (YF-16/YF-17) and AX (YA-10/YA-9) programs, which were so controversial with many of the ranks of the USAF, as these programs were some of the first to sacrifice for the needs of cost saving, simplicity, maneuverability, target identification and ordinance delivery accuracy, at the cost and obsession for the need of speed.

In the form of strike / bomber aircraft, this factor would come later with the resurgence of the Rockwell B-1B program, which clearly identified that the original B-1A's design parameters for high supersonic speed was no longer relevant, and hence deleted in the B-1B model.

A better approach might be to say that the fighter/fighter-bomber mission and the deep strike mission are incompatible, and develop a joint-service successor to the F-4 (F-14ish, but maybe fixed wing with a single seat option) and a joint service strike aircraft that combines the best attributes of the A-6 and F-105 but has no pretensions to being a fighter.

No arguments here my friend!
But neither the USAF or USN was able to convince Robert McNamara!


If I had to meet the requirement as stated then, as tinlail has said, the end result would probably end up looking much like an F-14, since the Navy's fighter and deck landing requirements HAVE to dominate the design.

is a full internal bomb bay an Airforce requirement, or is conformal carriage acceptable?

Question:

For many years the USAF had been aware of the advantages and disadvantages of weapons bays in its tactical aircraft – with the likes of the Convair F-102, F-106, McDonnell Douglas F-101, Martin/EE B-57 and the aircraft the TFX was to replace – the Republic F-105.
It was also with the F-105 taking the brunt of the offensive air war against North Vietnam (crazy), that the Air Force learned the hard way the disadvantages imposed on the carriage of external ordanance over a long distance.
I would say with the advent of the likes of the Paveway PGB, and its successful performance in Vietnam, the need too carry large numbers of conventional bombs would possibly have been viewed very early by the USAF to be a possible thing of the past.
What with the ability to carry say only 4 x Paveway's in place of 24 x 500lb GP bombs to attack/destroy the same given targets, the internal weapons bay would have been very much considered and desired.
Added to this is the first hand experience the USAF, USN and USMC had experienced with some of the most advanced and deadly air defence radar directed gun and missile air defence any one country had experienced in history.
Low 'Radar Cross Section' (RCS) had been reiterated to the US military.
With the lessons of Vietnam still in the minds of those who flew, designed the aircraft of the USAF, the internal carriage of weapons would clearly equal:
-Lower aerodynamic drag (= better range performance)
-Lower RCS

Saying this the semi-recessed / conformal carriage arrangement would be far better than that of the conventional pylon/hardpoint carriage configuration!


I personally believe that the likes of a re-visited and redesigned North American A-5C Vigilante airframe (using North American Aviation's original NAGPAW (North American General Purpose Attack Weapon) design could have meet the TFX requirements of both the USAF and USN.

It would have had the following advantages:
-It was already carrier compatible and a proven performer in the US Navy.
-   Already designed for high speed performance and all-weather capability
-   Already designed, serving and equipped to perform the roles of long-range nuclear strike, reconnaissance
-   North American Aviation was already skilled and jigged for production of the basic aircraft
-   Research and development had already been done, and paid for.
-   The USAF had already gone through the humiliation of being forced too use a US Navy designed, built and operated naval aircraft in the form of the McDonnell Douglas F-4 Phantom and Vought (LTV) A-7 Corsair II.
-   It already had a two seat (Tandem) arrangement.
-   Its carrier designed capability would have met the USAF requirements for rough-field performance (for if you can survive a controlled crash aboard an aircraft carrier, you can land and take off a rough airfield!!).

Modification of the NA A-5C Vigilante to meet TFX requirements:

-   Replacement of the linear bomb bay, with either a Martin rotary bomb bay/fuel tank type arrangement (as used on the Martin XB-51, B-57 and Blackburn Buccaneer) or even a conventional bomb bay.
                                    Or
    Completely remove linner bomb bay arrangement altogether
    replacing it with fuel, avionics, ECM/EW systems                                                                                       In turn the lower fuselage would be strengthened to take either pylons/hard points or conformal carriage arrangement for weapons carriage.
-   The rear fuselage would be modified to accommodate the Pratt & Whitney TF-30 turbofans in place of the General Electric J79 turbojets (this use of the TF-30's would have the advantage of being lighter and of less fuel consumption = a better range and endurance performance)
-   The Air Force model could have a smaller area wing (as the original NAGPAW was designed with!), which will be strengthened, allowing for the stress of low altitude, high-speed flight. (note the Air Force wing will not have the hinged out wing of the navy carrier variant!).
-   The Navy FAD variant will have a larger area wing of the A-5 Vigilante, to maximize high altitude flight and endurance.
-   The large single folding tail fin will be replaced by the original North American NAGPAW intended twin tail fin arrangement.
-   A specific designed forward fuselage would be built for both the Air Force and Navy.                                                                                                                                                   The Navy variants forward fuselages will be shorten after the rear cockpit to the centre fuselage to reduce overall length and carrier lift compatability                  
The Air Force having its forward fuselage designed to house the AN/APQ-113 attack radar AN/APQ-110 terrain-following radar.
The Navy having its forward fuselage designed to house their AN/AWG-9 pulse-Doppler radar.




M.A.D

[tinlail]

The only real comment I have is that the TF-30 is bigger , so the fuselage will have to change. This might push the plane designs in directions that might the assumption that it will work for a carrier, no longer valid.

source: http://www.aviationnow.com/media/pdf/spec_04_gas_turbines.pdf
TF30
Diameter: 49
Length:   242

J79
Diameter: 39
Length:    208

Of course the other thing to do is see what putting the pancake on a A-5 would make it look like ...

[Weaver]

-   Its carrier designed capability would have met the USAF requirements for rough-field performance (for if you can survive a controlled crash aboard an aircraft carrier, you can land and take off a rough airfield!!)

Not so: a carrier landing is a hard landing, but a rough field landing is a soft landing. Try landing an A-5 in a field, and what you'll end up with is a belly-landed aircraft at the end of three long trenches where the u/c has gone straight into the surface......

The carrier landing is dominated by high sink-rate, which requires very strong gear and very strong shock absorbtion, but on the other hand, the perfectly hard deck means that you can get away with tiny, high-pressure tires which save space and weight. The soft-field landing is dominated by peak ground pressure and taxiing safety, which require big, low-pressure tires and long-travel, softly-sprung legs.

So, very roughly, you can say that carrier aircraft require heavy undercarriage, whilst rough-field aircraft require big undercarriage, imposing very different constraints on the designer. That isn't to say you can't reconcile the differences within one design, but the compromises will impose a penalty of their own.

For an example, compare and contrast the u/c of, say, an A-7 and a Jaguar.....

[Zen]

50,000lb? Is that a hard figure?

Thats awfuly similar to the OR346, save for the range in strike being less. Its a point to make most of the decent submissions to OR.346 bust that weight limit AND the TO and L speeds.

At least the USN's large CV's can handle higher landing energies, but its still going to be hard to meet this.
BUT VG answers that problem.

Drop speed, mach2.35 is the limit for aluminium-lithium alloy, beyond that your headed into expensive and difficult to fabricate materails (steel maybe cheaper but not as easy to construct an aircraft out of). Frankly mach2 is high enough, and from personal testimony of a ex-USN pilot, F4's where rarely taken over mach 1.9 due to the effect it had on the canopy and windscreen.

Side-by-side cockpits are good for cooperation between pilot and RIO/WSO but makes for a larger cross sectional area at that point along the fusilage. Tandem seating produced less cross sectional area.

[Orne M]

This info and other photos/drawings popped up on Secret Projects a few days ago: variations of A-5 Vigilante with VG wings, etc.
http://www.secretprojects.co.uk/forum/index.php/topic,5272.0.html

[KJ_Lesnick]

Variable-Geometry was a requirement in the original TFX design?


KJ Lesnick

[ysi_maniac]

Hi MAD:
TFX or not, I like your Bomber Vigilante

[elmayerle]

Ironically, from what I've been given to understand from an engineer who was there "in the day", the biggest resistance to putting larger engines in the Vigilante was NAA-Columbus' management, since that would require changing out the frame with the tail surface spindles and that was a massive machined forging.  This reluctance inhibited re-engining studies with both J93s and J58s that my friend (and former co-worker) did mention.