Author Topic: The Joint Strike Fighter Program  (Read 6818 times)

Offline taiidantomcat

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The Joint Strike Fighter Program
« on: May 06, 2016, 05:39:22 AM »
The Joint Strike Fighter Program from a design and engineering perspective.

Why do we need another F-35 thread? First off this is not just an F-35 thread. Obviously with the X-35 winning the "Battle of the X planes" means we will have more information on the F-35 than any other JSF proposal, as its the "lone survivor" but this is also about the X-32, and other proposals that did not even make it that far.

The goal is to compile information about the JSF program-- candidates, history, requirements etc. And basically create a "just the facts" resource on this program, the F-35 is going to be around for a while, and sometimes you have to memorize the script before you can ad lib the lines. This would be less about whimsical F-35 ideas (which we have a thread for see here: http://beyondthesprues.com/Forum/index.php?topic=273.0 ) and more of a resource for more realistic whifs. For example Evan had a great post about how an F-35 two seater would look and how it would fit with the center section in order to have it work. Speaking of Evan, we have 2 people on this very forum who work/worked on the F-35 that we know of, great resources should they choose to share. This is more about the construction and composition of the aircraft themselves, rather than debates about how it should or should not be employed tactically, and how the concepts evolved or changed throughout the program including the aircraft that lead to JSF. this is about the airplanes, not the politics. If you want to argue about X vs Y vs Z there are plenty of places to do that online, and we even have one here: http://beyondthesprues.com/Forum/index.php?topic=349.0

The F-35 is obviously controversial, its become about as civil as politics during an election year in the middle of a riot. I would really like to avoid that kind of ugliness here and generally know that we "can have nice things" again. Critism is welcome, but its uninformed, or inflammatory it will be moved. Saying things like "I think the X-32B didn't get a fair shot because X, Y, Z," thats great. If the comment is "STOVL should have never been added to the JSF" well that is not only outside the requirements of JSF-- but ignoring the history we are trying to highlight and the  basic fact that the STOVL Variant was technically the start of the JSF, and hardly "added" at the end as most people think. And it far more interesting to work within the requirements rather than dismiss the requirements that one felt should have been omitted (if only life worked that way!)

So something like this:



and not this:



The F-35 cost in cupcakes... more baking than engineering.





I'm going to try and start from the start, but there i nothing wrong with jumping and skipping around through the timeline. Without further ado:

Origins:
Quote
Advanced Short Take-Off/Vertical Landing (ASTOVL) 1983-1994
The Defense Advanced Research Projects Agency (DARPA) began a program in 1983 to begin looking at the technologies available to design and manufacture a follow-on supersonic replace for the AV-8 Harrier. The program, known as ASTOVL, would eventually lead become a joint U.S.-U.K. collaboration. In 1987 the results of the ASTOVL program made clear that the technologies available were not yet advanced enough to generate a replacement that the U.S. and U.K. would have been satisfied with. At this time, DARPA secretly approached the Lockheed Skunk Works in the hopes that they would be able to develop an aircraft like they had hoped would have appeared from the first phase of ASTOVL. Lockheed told DARPA that they had some ideas that could be matured and that, if they were successful would meet the goals that DARPA was trying to achieve. At the same time, DARPA continued with ASTOVL Phase II as a cover for the covert work being done at the Skunk Works.


i. STOVL Strike Fighter (SSF) 1987-1994
In the late 1980s the Lockheed Skunk Works was involved in a classified, non-acknowledged program with NASA Ames that looked into the feasibility of designing a stealthy supersonic STOVL fighter. This was a cooperative program that utilized the assets of NASA (wind tunnels, personnel, super-computers, etc.) along with the expertise of the Lockheed Skunk Works in designing stealthy air vehicles. The results from this highly classified program proved that a SSF could be successfully flown. Management at the Lockheed Skunk Works was convinced that the SSF design could be sold to both the U.S. Air Force and the U.S. Navy. (The U.S. Navy (NAVAIR) is the procuring office for Marine Corps aircraft.) The Skunk Works proposed a teaming between the USAF and the USN. The services agreed, a Memorandum of Understanding (MOU) was signed between the services and the SSF program began to come out of the black.



ii. Common Affordable Lightweight Fighter (CALF) 1993-1994
The ASTOVL/SSF concepts were originally seen as developing a replacement for the U.S. and U.K. Harrier jump-jet. As the ASTOVL/SSF concepts became multi-service with the suggestion of multiple variants, the program was re-christened as the Common Affordable Lightweight Fighter (CALF).

The management of the CALF program was handed by DARPA due to the experimental nature of the concept. DARPA was also managing the ASTOVL program, which was used by the SSF program as their unclassified, white-world cover story.

The CALF program's aim was to develop the technologies and concepts to support the ASTOVL aircraft for the USMC and Royal Navy (RN) and a highly-common conventional flight variant for the U.S. Air Force.

Although the CALF program was organized upon a suggestion from Lockheed, the government still wanted multiple contractors involved in the program. Initially, the only two contractors involved were Lockheed and McDonnell Douglas. Boeing later approached DARPA and offered to meet DARPA's financial contribution if they were allowed onto the program.

Under the auspices of the CALF program,
The CALF program has also been called the Joint Attack Fighter (JAF).



Multi-Role Fighter (MRF) 1990-1993
The U.S. Air Force’s MRF program began in 1991 as a relatively low-cost F-16 replacement. Similar in size to the F-16, the MRF was to have been a single-seat / single-engine aircraft, with a unit flyaway cost in the range of $35 to $50 million.

The MRF Program was managed by the Aeronautical Systems Center (ASC) at Wright-Patterson Air Force Base, Ohio. ASC hosted a planning meeting with industry in October 1991, and issued a Request For Information (RFI) with responses due in January 1992. The major U.S. aircraft manufacturers began to conduct concept and design studies for the MRF at their own expense.

A formal program start was expected around 1994. The MRF was expected to replace a large number of F-16s reaching the end of service life. The MRF might also have replaced Air Force A-10s and Navy F/A-18C/Ds. Therefore, providing large numbers of aircraft affordably was a higher priority for the MRF Program than any specific capability enhancements.

However, the post-Cold War defense drawdown made the F-16 service life situation considerably less critical. A reduction in the total number of U.S. Air Force fighter wings meant that the existing aircraft would not be replaced one-for-one. Furthermore, F-16 aircraft flying hours were reduced, allowing F-16s to remain in service longer than originally projected.

In August 1992, the MRF program was effectively put on hold. Due to budget pressures and the Air Force’s commitment to the F/A-22 program, sufficient funding for a new program start did not appear likely until around 2000. Until then, it was expected that MRF activity would proceed at a low level. Meanwhile, the Air Force intended to continue production of Block 50 F-16s. By early 1993, however, the MRF’s projected IOC had slipped to 2015. Shortly thereafter, the BUR canceled the MRF Program.



Advanced Tactical Aircraft (ATA) 1983-1991
The U.S. Navy Advanced Tactical Aircraft (ATA) program began in 1983 as a proposed long range, very low observable, high payload medium-attack aircraft to replace the Grumman A-6 in the carrier-based, medium-attack role.

On January 13, 1988 the McDonnell Douglas and General Dynamics team was selected over a Northrop team to develop the ATA. Designated the A-12 Avenger II, the unique flying wing design was to be a long-range, subsonic aircraft with a large internal weapons load including air-to-surface and air-to-air weapons.

Following the disclosure of severe cost and schedule overruns and technical problems in late 1990, the A-12 program was canceled on 7 January 1991.


Naval Advanced Tactical Fighter (NATF) 1990-1991
Due to Congressional intervention, the U.S. Navy agreed to evaluate a navalized version of the U.S. Air Force's Advanced Tactical Fighter (now the F/A-22) as a possible replacement for their F-14s. In return, the U.S. Air Force would evaluate a derivative of the ATA as a replacement for their F-111s.

In late 1988, a Naval ATF (NATF) program office was set up at Wright-Patterson Air Force Base and the existing ATF Dem/Val contracts were modified to include studies of potential NATF variants.

The Major Aircraft Review reduced the peak production rates of both the ATF and NATF. This had the effect of substantially increasing the program cost. In August 1990, Admiral Richard Dunleavy, who was in charge of Navy aircraft requirements, stated that he did not see how the NATF could fit into any affordable plan for naval aviation. In early 1991, before the final contractor for the ATF was even selected, the consideration of the NATF was dropped. This was mainly due to the fact that the Navy realized that a series of upgrades to their existing F-14's could meet the Navy's air superiority needs through 2015.


Advanced-Attack/Advanced/Fighter-Attack (A-X/A/F-X) 1992-1993
In January 1991, with the cancellation of the ATA and the NATF, the Secretary of the Navy directed that planning commence for a new A-6 replacement program. This new program became the known as the A-X, an advanced, “high-end,” carrier-based multi-mission aircraft with day/night/all-weather capability, low observables, long range, two engines, two-crew, and advanced, integrated avionics and countermeasures. The Air Force participated in this new program from its initiation, still seeking a replacement for the F-111 and, in the longer term, the F-15E and F-117A.

Contracts of $20M each were awarded to five contractor teams on 30 December 1991 (prime contractor listed first):

Grumman/Lockheed/Boeing
Lockheed/Boeing/General Dynamics
McDonnell Douglas/Vought
Rockwell/Lockheed
General Dynamics/McDonnell Douglas/Northrop
The original A-X / A/F-X CE/D work was due to be completed in September 1992. A solicitation for Demonstration/Validation (Dem/Val) proposals was expected in late 1992, leading to a Dem/Val start in 1994 and EMD in 1996. Under the Navy’s original plan, the short Dem/Val phase would consist of design refinements and other risk reduction activities, but would not include flying prototypes. However, in late 1992 Congress directed that the A-X Dem/Val phase also include competitive prototyping. This increased the projected duration of the Dem/Val phase from two to five years. Concurrently, as a result of the termination of the NATF in 1991, increased air-to-air requirements were added to the A-X, prompting a change in the name of the Program from Advanced Attack (A-X) to Advanced Attack/Fighter (A/F-X).

The existing A-X CE/D contracts were extended to reflect a revised Dem/Val strategy to accommodate flying prototypes. The expected IOC date of the A/F-X slipped from 2006 to 2008. A Defense Acquisition Board (DAB) Milestone I Review of the A/F-X Program was expected in Spring 1993; however, the BUR placed the A/F-X program on hold pending the outcome of the report. An Milestone I DAB for the A/F-X never took place.

On 1 September 1993, the release of the BUR announced the cancellation of the A/F-X as well as the MRF. As a result of the BUR, A/F-X efforts during the latter half of 1993 were directed toward closing out the program and transitioning applicable experience and results to the upcoming JAST program.

A core of A/F-X personnel performed a large portion of the working-level planning and definition of the emerging JAST Program. The A/F-X CE/D contracts were extended a second time, through 17 December 1993, to allow the contractors sufficient time to bring their activities to a logical conclusion. All A/F-X program operations ended on 31 December 1993.


http://www.jsf.mil/history/his_prejast.htm






https://www.youtube.com/watch?v=u-cfy-k_8ew

This is an hour and a half, but does a wonderful job explaining the JSF origins and the Battle of the X-planes. I would consider it a must listen (and luckily it works well in the background at the work bench) has tons of explanation and inside info and funny/interesting anecdotes from a Skunk Works Engineer and designer of the the Shaft Driven Lift Fan featured on the X-35/F-35, Paul Bevilaqua.

article from the Baltimore Sun:

Quote

3 approaches to the Joint Strike Fighter Lockheed Martin, Boeing, McDonnell Douglas have various ideas on warplane
October 20, 1996|BY A SUN STAFF WRITER



Three aerospace giants are competing to build the Joint Strike Fighter, a next-generation warplane that not only could be used by the Air Force but could fly from aircraft carriers for the Navy and land and take off vertically for the Marines and the British Royal Navy. Lockheed Martin Corp. of Bethesda, McDonnell Douglas Corp. of St. Louis and Boeing Co. of Seattle have all fielded entries in the competition, and sometime in the middle of next month the government will tell two of them to build prototypes. The final winner should be selected in 2000. Each company took a different approach.

Lockheed conservatism

Lockheed Martin created its Joint Strike Fighter by borrowing from its design for the F-22, which is a stealthy air superiority fighter that will replace the F-15.

Though experts have labeled the resulting Joint Strike Fighter proposal as "middle of the road," Lockheed Martin defends it as a conservative entry in a program that mandated low risk and conservatism.



David Wheaton, corporate vice president and Joint Strike Fighter program manager, said the design team did not set out to stick with what worked on the F-22. It went through hundreds of possibilities, he said, before finally agreeing that an F-22-type approach worked best. "We could have made a much more exotic-looking airplane," he said, "but it wouldn't have been nearly as balanced."

Its performance, the company claims, matches or exceeds that of Lockheed Martin's biggest project -- the F-16. Its sloping sides, canted vertical tails, sawtoothed bay doors and serpentine inlet duct contribute to the plane's stealthiness.

For the vertical takeoff and landing component, Lockheed Martin is proposing a big lift fan in the center of the plane that would be driven by a shaft and clutch from the main engine.

The fan puts out cool air, which solves the common vertical takeoff problem of hot exhaust being drawn back into the engine and causing it to overheat.

On Air Force versions of the plane, the fan would be replaced by a fuel tank.

Lockheed Martin has tested the lift fan extensively, and built a scale prototype of the plane that has undergone thousands of hours of wind tunnel work.

McDonnell Douglas approach

McDonnell Douglas is leading an all-star team with Northrop Grumman and British Aerospace, but the three were slow to settle on a design for their Joint Strike Fighter.

After quibbling over propulsion for a while, they settled on a configuration in the middle of last year -- long after the other two teams had begun testing their designs.

And it is not a risk-free proposal. McDonnell Douglas has taken two gutsy steps: First, it proposes a design that does not have a vertical tail. That makes the plane much more stealthy, but less stable than a traditional plane. The pilot would use vectored thrust to make up for the lack of a tail.

Second, McDonnell Douglas' team proposes using a separate engine for vertical lift. Designers point out that if the main engine somehow failed or were shot out, a pilot could theoretically limp home on the secondary engine.

But for a vertical landing, that secondary engine would have to start up reliably after sitting idle and cold during the plane's flight. The Marines rejected such a configuration during an earlier research project.

The McDonnell Douglas entry is probably the stealthiest of the three, most analysts agree. And, according to trade writer Bill Sweetman, the more controversial aspects of the plane are "not inherently any more risky" than the other teams' planes. It's more a matter of selling the military on a different way of doing things.

Boeing's aggressive method

Boeing took an aggressive approach to what otherwise could have been a stately competition between a pair of stalwarts, Lockheed Martin and McDonnell Douglas.


Drawing on its vast experience building commercial planes, Boeing fielded a design that looks radically different.

The plane has four basic components, the most noticeable being a big, single-piece delta wing. The dual canted tail, the cockpit and the fuselage underneath complete what is by far the simplest overall configuration in the contest.

Boeing claims almost 90 percent commonality for its design, meaning that only 10 percent of the plane must be modified to satisfy the various military services.

For vertical takeoff and landing, Boeing again took a simpler approach, eschewing any kind of secondary engine or fan and relying on the main propulsion system. Ducts and nozzles direct main engine thrust under the plane to lift it.

There has been some difficulty getting enough thrust out of the engine to lift the plane this way, but company officials say they can lick the problem.

It is the smallest and lightest of the three planes -- so small that it would not have to fold its wing to fit in the cramped space of a British aircraft carrier. The other two planes would.

Like Lockheed Martin, Boeing has subjected its design to extensive testing.


« Last Edit: May 06, 2016, 09:49:23 PM by taiidantomcat »
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Offline GTX_Admin

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Re: The Joint Strike Fighter Program
« Reply #1 on: May 07, 2016, 02:13:07 AM »
Something to assist people understand how an F-35 is made (if you click on the image, it expands):



You can also see a lot of interesting photos if you do a google Image search on "F-35 production"
« Last Edit: May 07, 2016, 02:24:06 AM by GTX_Admin »
All hail the God of Frustration!!!

Offline GTX_Admin

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Re: The Joint Strike Fighter Program
« Reply #2 on: May 07, 2016, 02:53:30 AM »
All hail the God of Frustration!!!

Offline Weaver

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Re: The Joint Strike Fighter Program
« Reply #3 on: May 07, 2016, 03:18:44 AM »
THE F-35 IS RUBBISH!!!

Sorry, just kidding... >:D

That Baltimore Sun article has a curious analysis. I would have said the Boeing approach was the most conservative, since diverting the fan thrust of a linear engine is conceptually similar to the Harrier. McDonnell Douglas's initial approach, with the gas-driven fan, was the most radical, since I don't know of anything like that ever being proposed before, while their final lift+lift/cruise proposal was almost as conservative as Boeing's in that such a configuration has been flown in service by the Russians, proposed many times in the past and therefore extensively studied and well understood. Lockheed Martin's shaft-driven fan was somewhere in the middle (literally and conceptually... ;) )

With hindsight, do you think it was a mistake to merge the F-16 replacement, A-6 replacement and Harrier replacement into the same program? Would it have been easier to build two or three different aircraft for the four different customers (USAF, USN, US Marines and RN), or would the reduced orders and market for the STOVL version have made it too vulnerable to cancellation?
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Offline jcf

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Re: The Joint Strike Fighter Program
« Reply #4 on: May 07, 2016, 04:40:04 AM »
The Ryan XV-5 used gas-driven lift-fans, and the Avrocar lift/flight fan was also gas-driven.

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Offline elmayerle

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Re: The Joint Strike Fighter Program
« Reply #5 on: May 07, 2016, 11:19:37 AM »
The Ryan XV-5 used gas-driven lift-fans, and the Avrocar lift/flight fan was also gas-driven.
And neither was particularly successful.  I wish McDD had gone to shaft-driven fan when gas-driven didn't pan out; their aerodynamics are/were better than Boeing's (I know the aero folk at Fort Worth considered them the far more dangerous competitors); too, separate lift+lift/cruise engines violated the terms of the competition and cost them a chance.
« Last Edit: May 07, 2016, 11:28:58 AM by elmayerle »

Offline Volkodav

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Re: The Joint Strike Fighter Program
« Reply #6 on: May 07, 2016, 08:04:36 PM »
THE F-35 IS RUBBISH!!!

Sorry, just kidding... >:D

That Baltimore Sun article has a curious analysis. I would have said the Boeing approach was the most conservative, since diverting the fan thrust of a linear engine is conceptually similar to the Harrier. McDonnell Douglas's initial approach, with the gas-driven fan, was the most radical, since I don't know of anything like that ever being proposed before, while their final lift+lift/cruise proposal was almost as conservative as Boeing's in that such a configuration has been flown in service by the Russians, proposed many times in the past and therefore extensively studied and well understood. Lockheed Martin's shaft-driven fan was somewhere in the middle (literally and conceptually... ;) )

With hindsight, do you think it was a mistake to merge the F-16 replacement, A-6 replacement and Harrier replacement into the same program? Would it have been easier to build two or three different aircraft for the four different customers (USAF, USN, US Marines and RN), or would the reduced orders and market for the STOVL version have made it too vulnerable to cancellation?

Well technically the F/A-18F has panned out as the A-6 replacement and in Australia the F-111 replacement while the F-35C will replace the USNs and some Marine Classic Hornets while the B will replace the remaining USMC Classics as well as their AV-8B and B+ fleets. 

Offline Weaver

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Re: The Joint Strike Fighter Program
« Reply #7 on: May 07, 2016, 08:33:51 PM »
The Ryan XV-5 used gas-driven lift-fans, and the Avrocar lift/flight fan was also gas-driven.
And neither was particularly successful.  I wish McDD had gone to shaft-driven fan when gas-driven didn't pan out; their aerodynamics are/were better than Boeing's (I know the aero folk at Fort Worth considered them the far more dangerous competitors); too, separate lift+lift/cruise engines violated the terms of the competition and cost them a chance.

Why didn't gas-driven pan out? On the face of it, I find the idea of diverting lightweight gas through fixed pipes much more attractive than driving 40,000hp through a clutch, a shaft and a 90 deg gearbox.
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Offline Weaver

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Re: The Joint Strike Fighter Program
« Reply #8 on: May 07, 2016, 08:41:23 PM »
THE F-35 IS RUBBISH!!!

Sorry, just kidding... >:D

That Baltimore Sun article has a curious analysis. I would have said the Boeing approach was the most conservative, since diverting the fan thrust of a linear engine is conceptually similar to the Harrier. McDonnell Douglas's initial approach, with the gas-driven fan, was the most radical, since I don't know of anything like that ever being proposed before, while their final lift+lift/cruise proposal was almost as conservative as Boeing's in that such a configuration has been flown in service by the Russians, proposed many times in the past and therefore extensively studied and well understood. Lockheed Martin's shaft-driven fan was somewhere in the middle (literally and conceptually... ;) )

With hindsight, do you think it was a mistake to merge the F-16 replacement, A-6 replacement and Harrier replacement into the same program? Would it have been easier to build two or three different aircraft for the four different customers (USAF, USN, US Marines and RN), or would the reduced orders and market for the STOVL version have made it too vulnerable to cancellation?

Well technically the F/A-18F has panned out as the A-6 replacement and in Australia the F-111 replacement while the F-35C will replace the USNs and some Marine Classic Hornets while the B will replace the remaining USMC Classics as well as their AV-8B and B+ fleets.

Okay, but what replaces what is not quite what I'm getting at. Let me put it another way: The F-35A is land-based CTOL, the F-35B is STOVL and the F-35C is carrier-based CTOL, but they're all based on the same airframe. To what extent is each type compromised in it's role by the need to build the other types from the same basic airframe, and to what extent are the capabilities of the whole programme compromised by the need to repalce so many different types?

In other words, would the F-35 be a better F-16/F-18 replacement if it wasn't also trying to be an AV-8B replacement and an A-10 replacement all in the same basic airframe, and vice-versa?
"I have described nothing but what I saw myself, or learned from others" - Thucydides

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Offline kitnut617

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Re: The Joint Strike Fighter Program
« Reply #9 on: May 07, 2016, 09:29:03 PM »
The Ryan XV-5 used gas-driven lift-fans, and the Avrocar lift/flight fan was also gas-driven.
And neither was particularly successful.  I wish McDD had gone to shaft-driven fan when gas-driven didn't pan out; their aerodynamics are/were better than Boeing's (I know the aero folk at Fort Worth considered them the far more dangerous competitors); too, separate lift+lift/cruise engines violated the terms of the competition and cost them a chance.

Why didn't gas-driven pan out? On the face of it, I find the idea of diverting lightweight gas through fixed pipes much more attractive than driving 40,000hp through a clutch, a shaft and a 90 deg gearbox.

Not wanting to be a JMN, but I thought that when the engine is driving the fan, it is never in after-burner mode ---- happy to be corrected of course --

Offline elmayerle

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Re: The Joint Strike Fighter Program
« Reply #10 on: May 07, 2016, 11:13:20 PM »
The Ryan XV-5 used gas-driven lift-fans, and the Avrocar lift/flight fan was also gas-driven.
And neither was particularly successful.  I wish McDD had gone to shaft-driven fan when gas-driven didn't pan out; their aerodynamics are/were better than Boeing's (I know the aero folk at Fort Worth considered them the far more dangerous competitors); too, separate lift+lift/cruise engines violated the terms of the competition and cost them a chance.

Why didn't gas-driven pan out? On the face of it, I find the idea of diverting lightweight gas through fixed pipes much more attractive than driving 40,000hp through a clutch, a shaft and a 90 deg gearbox.
Primarily the inefficiencies of the system, especially when scaled up from test rigs (same thing happened with the augmented wing on the XFV-12A).  Between duct losses and inefficiencies of the drive turbines, you lose way too much energy.

Offline taiidantomcat

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Re: The Joint Strike Fighter Program
« Reply #11 on: May 07, 2016, 11:28:39 PM »
Not wanting to be a JMN, but I thought that when the engine is driving the fan, it is never in after-burner mode ---- happy to be corrected of course --


Quote
Extra thrust for hovering

But, for hovering, the F-35B can rely on 40,000 pounds of thrust without having to use reheat. The F135's full-authority digital engine control (FADEC) software runs the engine at a higher temperature for hover flight than it does during conventional flight, producing more "dry" thrust than the engine normally develops without activating its afterburner.

"We de-rate for CTOL (conventional take-off and landing)" operations, explained Dan Tennant, Pratt & Whitney's F135 system demonstration and development program manager.

When the F-35B is hovering, all 40,000 pounds of thrust is directed downwards, not backwards. It also can be directed anywhere in between, and even slightly forwards, said Tennant.


- See more at: http://www.space.com/4778-supersonic-hover-35-flies.html#sthash.lxxO3a44.dpuf

 :)
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Offline taiidantomcat

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Re: The Joint Strike Fighter Program
« Reply #12 on: May 08, 2016, 12:29:32 AM »

That Baltimore Sun article has a curious analysis. I would have said the Boeing approach was the most conservative, since diverting the fan thrust of a linear engine is conceptually similar to the Harrier. McDonnell Douglas's initial approach, with the gas-driven fan, was the most radical, since I don't know of anything like that ever being proposed before, while their final lift+lift/cruise proposal was almost as conservative as Boeing's in that such a configuration has been flown in service by the Russians, proposed many times in the past and therefore extensively studied and well understood. Lockheed Martin's shaft-driven fan was somewhere in the middle (literally and conceptually... ;) )



I'm going to keep trying to find articles from way back when, because they are certainly interesting. You are right though.  Bevilaqua points out that the Boeing approach to STOVL Direct lift, got them selected basically because they pointed out the Harrier is the most successful (at the time only, I'm including the V-22 now) STOVL aircraft and it used direct lift. Very funny anecdote here actually:

https://youtu.be/u-cfy-k_8ew?t=47m22s


  McAir basically gambled that the STOVL design wouldn't be weighed as heavily as it was, even though I think they were warned the government would not accept it.


Let me put it another way: The F-35A is land-based CTOL, the F-35B is STOVL and the F-35C is carrier-based CTOL, but they're all based on the same airframe. To what extent is each type compromised in it's role by the need to build the other types from the same basic airframe, and to what extent are the capabilities of the whole programme compromised by the need to repalce so many different types?

In other words, would the F-35 be a better F-16/F-18 replacement if it wasn't also trying to be an AV-8B replacement and an A-10 replacement all in the same basic airframe, and vice-versa?


I think this thread is going to explore that. The JSF and compromised seem to go hand and hand but is there anything to it? and can we look at other programs as examples? First stand by for a "Stream of consciousnesses" post that hopefully doesn't get too muddled. I am looking at this first from an engineering perspective, I will save the political decisions and needs for another time.

An extreme example: is the F-22 compromised by its inability to carry paratroops? We would probably say no since that was not one of its goals, and early on we knew that this would not be a cargo aircraft, so the inability to carry cargo does not compromise its mission. So how "compromised" something is IMHO has a lot to do with the goals/requirements of the weapon systems. TFX struggle because the mission sets simply differed too much.

When the original F/A-18 came out it was widely panned because it couldn't carry the bomb load the distance that the A-7 it was replacing in the attack role could, Nor could it fly as fast as the F-4 it was replacing in the fighter role. It was critisized for being a jack of all trades master of none. It was slower, and couldn't carry the bombs as far. It was a "mix" a multirole aircraft that replaced multiple types (including the A-6 with the Marine Corps). How did it work out? I would say it was a success. If the mission was not attack/fighter though, it the mission was "high altitude recon" merged with "low level attack" it could not be done.  TFX was penetrating striker, merged with interceptor, Which then changed with "need for dogfighter" too. I had also heard an anecdotal that said McNamara was allergic to spending any kind of money on it, including cases where a little more cash would have made it more feasible, but he constantly jumped on the cheap solution only and it simply could not be overcome, along with lessons learned in vietnam (it simply couldn't be a missile plunking fleet defender now)

The A-10 replaced the A-7/F-100 (which was being supplanted by A-7), A-37, and A-1 skyraider. So the A-10 replaced multiple types, its original 1966 CAS mission was changed to prep for killing tanks in europe and it was built around a huge anti armor gun. It was deliberately made simple, with many basic things (for example a Inertial navigation system) left of, thus it was primitive than what it replaced in some cases (especially the A-7)  I'll let former A-37, A-7 and F-16 pilot say it better:

Quote
The Sluf armament system used a very primitive computer and the inertial platform data and basic ballistics data for bombs to provide extremely accurate bombs. Oh yeah, a real HUD from Marconi. The Hog would only have had to used a simple range radar to enable a computer to provide the bomb impact dot on the HUD, but not requiring a cosmic radar like the Sluf had ( we had terrain following and terrain avoidance and two ground map modes and a beacon mode and bomb delivery mode that provided the computer with slant range).

It is no wonder why we Sluf folks laughed and laughed when we saw what USAF was selling to Congress just to get the plane funded and stop the Army Cheyenne. Of course, the plane was being developed to fight in 'nam, and that war was ending. The big cannon was about the only thing that we did not already have, plus the stupid weather requirements that only a helicopter could meet....

- We A-37 and A-7D folks understood the new plane would basically be a jet-powered A-1, and would supplement the A-7D. We knew the A-37 would never see combat again after 'nam except for a COIN scenario. The emphasis was upon CAS and CSAR and such, with a bit of BAI thrown in.

Thinking and actual force build up at the time was the A-7D replacing the F-100 and supplementing the F-4 for interdiction. And the SLUF was very good at CAS. The only two planes with in-country FAC ratings of 15 meter CEP were the SLUF and Dragonfly. We have the 7th AF Corona Harvest documents to back up my assertion.

- Somewhere along the way the Cheyenne popped up and USAF was afraid of losing the CAS mission. Then there was the Fulda Gap. And if I was writing a book, I would call it "How a valley in Europe designed a (not so) modern warplane".

The gun came along after the initial RFI and maybe even RFP. And let's face it, the rounds were lots cheaper than Mavericks. Even so, the A-10 was a decent shooter once we got the IIR missile, as tgt acquisition was a bear with the EO version even with scene mag. The Pave Penny sensor also let the grunts designate the tanks, so acquisition was easier ( but nearly as good as slaving the seeker with fairly cheap avionics)

- We attack folks wanted both the A-X and the A-7D. The LWF program was just gaining traction, but we all thot it would mainly complement the Eagle and have a limited A2G capability to supplement the F-4, A-7 and A-X. F-100 wings would be replaced by A-X or A-7D. Maybe an F-4 wing would go, and all the Thud outfits were moving to Guard and Reserve.

Congress wanted as cheap an airplane as they could get, and USAF sold the A-X as not needing computers or high-tech stuff to do the job. My editorial back in 1974 made this clear and I was harshly reprimanded for saying so. Interestingly, my CO and wing DO saw the letter before I mailed it and had no qualms.

As a result, we had a significant period of reduced A2G capability in the late 70's and early 80's until the Viper came onboard in numbers, and we should all thank God the plane was such a great design.

- And then there was the significant drawdown after 'nam. We were equipping Guard units with the A-7D as early as 1973, and we stopped the A-7D fleet at three active duty wings. The stateside units and those in USAFE remained pretty much in place, so it was all those bases in 'nam and Thailand that bit the bullet. For example, the F-100 wing out of Tuy Hoa, I think, was moved to England AFB and then converted to the A-7D. Myrtle Beach was same. And Davis-Montham. Cannon absorbed 'vaarks...

...So we see what we needed for the Vietnam scenario and realize that the Hun, Thud and Double Ugly ain't gonna hack it for CAS and BAI. Talking about 1969 or 1970. The A-1 and the A-37 did super work in that environment from mid 60's to early 70's.

To get the A-10 we had to "dis" the A-7 and admit the Hun and 'vaark and Thud were not well-suited for CAS. We also had to move from piston motors to jets, so the A-1 was off the table. The A-37 was off the table because it was a superb COIN plane but could not meet the new requirements that included tank-busting and large payload.

The A-7D was so gold-plated that the Viper did not come close until the late 80's. It ( the Viper) had great A2A capability and a decent ground map radar and such. Sweet.

But USAF CAS mafia had sold Congress the AX, and contrary to some here it was not a single mission jet. It would replace the F-100, the F-111, the F-105, the A-1, the A-37 and the A-7D. So we Sluf folks asked, "what about interdiction"? Also asked about precision weapon system and a hundred knots extra speed. Oh yeah, what about a computed weapon delivery system and both an INS and a Doppler nav system and a ground map radar and an autopilot and a projected map display and.... No matter. They said the A-10 would be cheap, simple, and we could have many of them


Is the A-10 compromised? Is its world famous gun a part of what compromised it from being more versatile, or faster? etc? would it have been better served with a radar like the A-7?   ???

Are all CVN aircraft inherently compromised by heavy structure needed to land on ship with cats and traps? A Super Hornet weighs as much as an F-15 for example.

You can look at Rafale, which replaces no less than 6 aircraft types with the French Air Force. including two carrier types, thus requiring Carrier capability in the original design from the outset. Is the Rafale thus compromised?

But its part of a larger trend of multi-role aircraft taking over not just one type, but many.

So from engineering stand point, is the F-35 compromised to the point it can't do its mission? I would say no. but lets look deeper, how did STOVL requirements shape the F-35? how did it shape other JSF competitors? STOVL knocked out the McD design we know that. X-35, F-35 has the following considerations:

Forward hinging Canopy, Dual Intakes like the F-22-- rather than say the F-16, Wingspan dictated by the requirement to fit 6 on the back of an L-class ship. Weight constraints, though I would argue that is not a bad thing-- the SWAT effort made lighter F-35As by 3,000 lbs and had helpful savings on the F-35C as well. However it did drive up the cost, and delayed the program by 18 months:

http://www.airspacemag.com/military-aviation/weight-watchers-13117183/?no-ist


The original manufacturing plan saved money, but not weight.

I think the aircraft being a LO shape had more impact than STOVL in terms of aerodynamics. That just my opinion.

The goal with ASTOVL and the USMC, was making a hovering F-18. when they were merged into CALF with the USAF the USMC basically deferred to the USAF so long as it hovered, and the USMC and USAF goals were very aligned. Both the USMC and USAF were fine for example with a 1,000 lb bomb load. the USAF was looking for a multi role F-16 replacement, the USMC multi role F-18 replacement with the ability to do STOVL. both favored single engine, both favored lighter as opposed to more advanced hi-end design etc. BF-1 just did its 1,000th VL, so I would say the propulsion system is damned good, and presuming the propulsion system is good I think its actually trickier in this case to meet the USN goals, the F-35C is the most "different" of all the variants I believe.

The next post can be about the politics, but to keep it simple, I would say that there was absolutely no way the USMC/RN could have ever been able to independently procure an advanced STOVL airplane by themselves, and even under the large JSF umbrella it was the version that most people suggested ending, most often including the RN being forced by politicos to briefly go to the C, before going back to the B. So I don't think it could have ever happened if it wasn't merged with other aircraft, but having said that the STOVL version of JSF benefits massively from the other variants in terms of advanced capability. There is simply no way the USMC or RN were ever going to get a jet (especially STOVL) that advanced all by themselves. Whats funny is there seems to be a much bigger market for the STOVL variant (turkey just announced its buying F-35Bs) than there ever was the F-35C.


So I would say that
1. There is a historical precedent set for replacing multiple types with a single type with success all over the globe
2. I would say that the missions of the JSF across the services and partner nations are aligned and that  the main differences with the JSF variants are how they take off and land
« Last Edit: May 08, 2016, 12:50:36 AM by taiidantomcat »
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Offline kitnut617

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Re: The Joint Strike Fighter Program
« Reply #13 on: May 08, 2016, 01:02:26 AM »
Not wanting to be a JMN, but I thought that when the engine is driving the fan, it is never in after-burner mode ---- happy to be corrected of course --


Quote
Extra thrust for hovering

But, for hovering, the F-35B can rely on 40,000 pounds of thrust without having to use reheat. The F135's full-authority digital engine control (FADEC) software runs the engine at a higher temperature for hover flight than it does during conventional flight, producing more "dry" thrust than the engine normally develops without activating its afterburner.

"We de-rate for CTOL (conventional take-off and landing)" operations, explained Dan Tennant, Pratt & Whitney's F135 system demonstration and development program manager.

When the F-35B is hovering, all 40,000 pounds of thrust is directed downwards, not backwards. It also can be directed anywhere in between, and even slightly forwards, said Tennant.


- See more at: http://www.space.com/4778-supersonic-hover-35-flies.html#sthash.lxxO3a44.dpuf

 :)


It's as I thought, it's none afterburning while in hover mode, it's a 20,000 lb thrust engine, with 20,000 lb coming from the lift fan. Harold's comment of 40,000 hp going to the drive shaft threw me off (Roll Royce equates 1 lb of thrust as about 1 hp)

My McDonnell Douglas Harrier Alternative idea has a similar set-up, only when in forward flight it has 45,000lb of 'dry' thrust, just like thousands of engines already being used everyday today. That's based on a 20,000lb dry thrust hot core and 25,000 thrust of cold air. It would be classed as a low-bypass turbofan I supposed, about 1:2.3
« Last Edit: May 08, 2016, 01:12:57 AM by kitnut617 »

Offline GTX_Admin

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Re: The Joint Strike Fighter Program
« Reply #14 on: May 08, 2016, 05:12:20 AM »
Re the question of "compromise" let me just say that any design (even when people make outlandish claims such as "not a pound for Air-to-ground") is a result of compromises.  Anyone who says otherwise is lying!
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