McDD/Northrop/BAe ASTOVL/MRF/JAST/JSF studies

[Antonio]

[Moderator note - added in some older posts of earlier STOVL designs from Northrop, McDonnell-Douglas from the "US VTOL Projects" topic. I think these are interesting to consider in the light of the combined JAST design]



I want to add the Northrop-Grumman ALF. Pictures from Air&Cosmos Nº1482 August 1994. In this article, the aircraft is called X-32 and the program was Affordable Lightweight Fighter. Other X-32 candidates came from McDonnell Douglas, Boeing and Lockheed.

The STOVL version was to be designed around a concept similar to that of the Yak-141. The engine selected was the P&W F119. Empty weight was estimated at 10,9 t. Dimensions similar to F-18. Demonstrator first flight was scheduled for 1996. At that stage, the ALF was to be melted with the JAST (Joint Advanced Strike Technology).

 

[flateric]

Sundog - perfect posting! Third picture in series is not so generic, and indentified as one of Northrop's 1990 MRF proposal.

[Moderator's note - added Sundog's pic to this post]

 

[flateric]

Sixth picture is one of MDC MRF myriad iterations (to be correct, -011) ca 1991 - now with V-tails, but obviously the same planform.

[Sundog's pic added to post - Moderator]

 

[flateric]

MDC 1992 MRF study

 

[CammNut]

The X-36 was based on an early iteration of McDonnell Douglas's JSF design, produced under its precursor the Joint Advanced Strike Technology (JAST) research programme. While the design continued to evolve, MDC spun off its JAST 1 configuration and built the subscale X-36 as an unmanned tailless-fighter demonstrator.

These diagrams show the early evolution of the eventual MDC/BAe JSF design.

 

[overscan (PaulMM)]

The McDonnell-Douglas/Northrop-Grumman/BAe JAST submission.

 

[overscan (PaulMM)]

All pics from jsf.mil

 

[flateric]

Try these as starting point...Last pic is 9C.2 four post tail configuration very close to final V-tailed one. Note one of unique McDD/Northrop/BAe JAST design know-hows that team so hoped would help them to win - 'variable' internal weapons bay adoptable for carrying various AA/AG load depending on mission.

To my sorrow, I can't post some images from my collection due to promises I've made.

 

[overscan (PaulMM)]

Yes, the idea was to sacrifice a little stealth but get internal carriage of bulkier items. The enlarged bays were interchangable with the standard ones. There were also four external hardpoints under the wings.

 

[flateric]

There were a hell lot of tail configuration studied...

 

[amsci99]

What was the proposed VTOL solution for VSTOL version? Boeing was going to use direct lift and of course Lockheed went off with their lift fan and swivelling nozzle.

 

[Sentinel Chicken]

I take it that the McDD/Northrop/BAe candidate had the Pelikan tail? What I'm wondering as well is how the Pelikan tail is different from the v-tail like on the F-117.......

 

[overscan (PaulMM)]

Vectored main engine plus lift jet.

 

[Archibald]

Which killed the project, as JAST rule was clearly A SINGLE engine for all flight phases...

 

[flateric]

This is bottom views - something rarely seen of McDD/Northrop/BAe JAST concept, that can provide some insights for modelling effort plus side view showing rather complicated open doors pattern orchestra and triple team final VTOL solution.

 

[overscan (PaulMM)]

A little easier to see on this edited version

 

[CFE]

The McDD design was the most aesthetically-pleasing of all the JAST/JSF designs, IMHO. Was the name "Voodoo II" ever considered? I doubt that the F-101 was inspiration for the lambda wing, but it still conjures up images of that sleek McDonnell jet from days of old.

 

[SteveO]

Was there any truth to the rumour that it would be able to fly back on it's lift jet if the main engine failed?

 

[Matej]

I don't think so. If you take a look to the internal arrangement, there is not the connection between the lift engine and the aft nozzle. And inject the hot gases to the main nozzle is in my opinion the only possible way to achieve the controlable (forward) flight. Correct me if I am wrong.

 

[flateric]

GEA-FXL lift engine nozzle had in fact a special thrust-vectoring grid that allowed fighter to fly with speeds up to 310 km/h back to base (in good hopes of designers) in case of main engine failure. WT tests of this feature were performed AFAIK.

 

[elmayerle]

What was the proposed VTOL solution for VSTOL version? Boeing was going to use direct lift and of course Lockheed went off with their lift fan and swivelling nozzle.

The original concept was to use a gas-driven lift fan instead of the mechanically-driven one that Lockheed-Martin used. When that didn't work out, McDD went with a lift engine and that broke the terms of the competition and they were eliminatated. I'm told that the aero types in Fort Worth considered them a much more worthy and dangerous competitor than Boeing.

 

[elider]

Don't know if this belongs in this thread. It is the MDD MRF model 1006 from Bill Sweetman's article in JDW about 15 years ago. It was a part of the design evolution to JAST, and is one of my favorite design concepts.

 

[CFE]

What was the proposed VTOL solution for VSTOL version? Boeing was going to use direct lift and of course Lockheed went off with their lift fan and swivelling nozzle.

The original concept was to use a gas-driven lift fan instead of the mechanically-driven one that Lockheed-Martin used. When that didn't work out, McDD went with a lift engine and that broke the terms of the competition and they were eliminatated. I'm told that the aero types in Fort Worth considered them a much more worthy and dangerous competitor than Boeing.

What specific ground rule of the competition ruled out the use of lift engines? IIRC, the reason why McDD didn't survive the downselect is because Boeing's concept was more conservative and represented a a much different approach from LockMart.

In the end, LockMart's investment in shaft-driven lift fan technology paid off in spades and justified the risk and cost associated with the effort. The Boeing direct lift concept appeared weak, even when the tests were unrealistically stacked to improve the X-32B's performance.

 

[Mike Pryce]

What specific ground rule of the competition ruled out the use of lift engines?

As I understand it, none formally, but in reality the US Marine Corps did! They did not want to have to support two different types of engine, which would increase the logistic footprint of a deployed squadron etc. In addition, I think there were latent worries about lift jet reliability - requiring a whole other bit of turbomachinery to fire up once or twice on each sortie, in addition to the main engine, multiplied the chances of one engine failing to many people's minds.

Although MDC worked to overcome these fears, I would not be surprised if they were factored into some pretty adverse life cycle costings by DoD - more maintenance plus less reliability = $ (and £), which the lower weight that the lift jet promised (so less manufacturing/fuel costs etc.) and use of standard F119 on the MDC design failed to offset.

Interesting though that it had a very hot front jet - many think it may be possible to live with one, if you know how. But best avoided if possible!

 

[CFE]

Weren't there problems with runway erosion on the Yak-141 due to the use of lift jets?

 

[elmayerle]

Weren't there problems with runway erosion on the Yak-141 due to the use of lift jets?

And, I believe, with the Yak-38 as well as in testing done with the VAK-191B.

 

[LowObservable]

The Yak-141 hovered at Farnborough but did not land vertically...

There was no formal rule in JSF against LPLC. Bill Scheuren - who was forcefully opposed to LPLC - was no longer the PM at source selection for the X-plane stage. NorthGrum had decided early that LPLC was actually the best approach, and the gas-driven concept (the basis of Macs' CALF) proved a dud, this was adopted by the MDC team. LPLC did play a part in the selection, but I think it was more a question of evaluating the cheaper and simpler direct-lift solution alongside LMT's fan-boosted concept.

I have never been convinced that a lift jet would be much more complex, more risky or heavier than the shaft-driven setup.

 

[SteveO]

GEA-FXL lift engine nozzle had in fact a special thrust-vectoring grid that allowed fighter to fly with speeds up to 310 km/h back to base (in good hopes of designers) in case of main engine failure. WT tests of this feature were performed AFAIK.

Thanks flateric, I thought I had read it somewhere and wasn't imagining it ;D

I never understood the 'two types of engine not allowed' argument. The complexity of the F-35B's lift fan is surely going to be as big a burden as a hot front end.

The disadvantages of the lift jet could have been tackled by STOL operations on land and wind over deck at sea.

 

[LowObservable]

Yes, the "no lift engines" thing was mostly prejudice.

 

[Sundog]

First, in response to SC

I take it that the McDD/Northrop/BAe candidate had the Pelikan tail? What I'm wondering as well is how the Pelikan tail is different from the v-tail like on the F-117.......

The tail on the F-117 is just a rudder. It's for yaw only. They took a single tail and split it for L.O. performance. Aerodynamically, think of the F-117 as a subsonic delta with an all moving vertical tail and apply first generation stealth technology to it.

The tail on the NG/McD design most likely is a derivative of the tail used on the YF-23, in which case they would be called "tailerons" because they are control surfaces that operate for stability and control in all three axes.

Second, IIRC, originally the two STOVL methods originally studied by L-M and N-G were just as a research program where L-M would study the shaft driven concept and N-G the bleed air equivalent. Then somewhere down the road, it got turned into a demonstrator/production contract, which kind of screwed N-G. If I was them, I would have screamed bloody murder and asked for the data for the drive shaft research performed, since it was government sponsored.

In fact, it was when it went from a demonstration of technologies program to a production contract that N-G scrambled to find a "workable" solution, since they already knew the bleed air design was a dud. That's why they went to the lift engine design.

 

[LowObservable]

Not exactly - it was Macs who were doing the gas-driven fan work. They and Lockheed (Skunk Works) were the leaders in the ASTOVL work for the Navy/Marines and US-UK and were most heavily involved in STOVL Strike Fighter and CALF.
Boeing was following its own independent track with a direct-lift design, based on the premise that the next fighter had to be tri-service to be affordable.
Northrop Grumman pitched in as CALF was absorbed into JAST, proposing from the outset an LPLC solution which (at first) had the hammerhead LERX shape.

 

[Sundog]

I forgot about Calf. When you talk about the hammerhead LERX shape, are referring to their plane that I call the American Draken, where it had the small canards on the LERX and the low aspect ratio wing in the back with the lift engine behind the cockpit and the two lift nozzles in the wing roots? BTW, I call it the American Draken due to the shape and location of the vertical tail, mainly, because it reminds me of the Draken in that regard.

 

[LowObservable]

Yes, but the CALF submission did not have wing root fans... in fact those may only have appeared in unofficial ;D concepts. NG went LPLC for CALF.
I can't off the top of my head recall why gas-driven was kaput, but it had to have some horrible safety/combat damage issues. The only way you'd know that you had a fragment hole in the duct was when 1000K gas started blowing into the jet's vitals.

 

[flateric]

Yes, battle damage was a main issue as stated in most publications from JPO's 'JSF Clips' that I've read.

 

[CFE]

The tail on the NG/McD design most likely is a derivative of the tail used on the YF-23, in which case they would be called "tailerons" because they are control surfaces that operate for stability and control in all three axes.

My understanding of the McDD-NG JAST design is that yaw control was provided by a combination of the "Pelikan Tail" and decelerons on the outboard wings. X-36 was supposed to perform risk reduction for the final JAST, but it was felt the Pelikan Tail was necessary because JAST would need the extra stability of a vertical control surface when the plane went supersonic.

It's funny how the NOVA documentary on the JSF flyoff brought the term "Pelikan Tail" into common usage, replacing terms like "ruddervators." Did Ralph Pelikan play a role in the selection and design of ruddervators on the YF-23? Due to the proprietary nature of that program, we may never know.

 

[Sundog]

You also have to consider that the X-36 had thrust vectoring in yaw, I believe through fluidic controls, which I don't think JAST had, but it's obviously design specific.

I've also heard as well that the YF-23 did use differential drag on the wing trailing edges to aid in yaw. It's like I've said to many people, with the advanced control systems available now, all of the flight control surfaces work together in such a way that to call them ailerons, elevators, stabilators, rudders, or flaps misses the point. You would have to ask the flight control group which surface is performing which role in what part of the envelope to have an idea.

As for the Pelikan tail, though, isn't it different from the YF-23's, which was a butterfly, in that the Pelikan tail has an inboard horizontal component to it?

 

[LowObservable]

Right - that was the difference in the Pelikan tail vs the classic V-tail on the YF-23. The result is that the moving surface has a crank in it, but the hinge is also different in that it is where the horizontal section meets the body, at a spanwise line. This eliminates the highly loaded pin and trunnion and makes room for actuators.

 

[CFE]

Thanks for clearing up the precise definition of a "Pelikan Tail" for me.

 

[flateric]

1993 MDC/BAe GCLF (Gas Coupled Lift Fan) configuration of ASTOVL/JAST. Note cool CGI of this era and - at the last pic - Achilles' tubes of this concept.

 

[CFE]

The layout of the McDD design looks very similar to the early work being done by Lockheed on the ASTOVL program. In the 1996 PC game "Jane's ATF," there's an aircraft called the "X-32 Ghost Hawk" based on Lockheed's concept artwork.