The F-35 No Holds Barred topic

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overscan

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Nice pic of F-35 weapons bay from Aviation International News July 17th (Farnborough)
 

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Matej

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I am just thinking about if it is necessary to have all that stuff, cables and equipment inside... For the first time it looked to me as a junkyard. I hope it is only test equipment in pre-production machines.
 

sferrin

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Matej said:
I am just thinking about if it is necessary to have all that stuff, cables and equipment inside... For the first time it looked to me as a junkyard. I hope it is only test equipment in pre-production machines.
I think part of the reason you see that (the F-22 is the same) is because they are also convenient access points for maintenance and repair.
 

elmayerle

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That and there's a fair bit of actuated equipment, that needs linking into the aircraft's "nervous system", in each weapons bay (the weapons do swing out to clear the fuselage). I can assure you, from experience, that there's not a lot of wasted volume on board.
 

elmayerle

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*chuckle* On the other hand, I can just go down to the plant floor or out to the flightline (and I've done that on some problem resolution efforts - got kudos for a timely resolution, too) and get "up close and personal with one. THen again, I'm also a designer on that program. Some very nice and advanced bits of equipment going into this one.
 

elmayerle

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The fit on the F-35A? I'll agree that it's not that aesthetically-pleasing, but the shapes were determined more by low observables and aerodynamics than by aesthetics. The gun that's an optional fit to the F-35B and F-35C is a podded affair that's not totally aesthetically-pleasing either.
 

cold0

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Pratt & Whitney gave an official release for the new F135 JSF engine.

CTOL/LV
Maximum Thrust: 43,000 lbf (191.3 kN)
Intermediate Thrust: 28,000 lbf (128.1 kN)
Bypass Ratio: 0.57

STOVL
Maximum Thrust: 43,000 lbf (191.3 kN)
Short Take-off Thrust: 38,100 lbf (169.5 kN)
Hover Thrust: 39,400 lbf (175.3 kN)
Main Engine: 15,700 lbf
Lift Fan: 20,000 lbf
Roll Post: 3,700 lbf
Bypass Ratio

Conventional: 0.56
Powered Lift: 0.51


http://www.lockheedmartin.com/data/assets/12791.zip
 

JonCatalan

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Some years back there was a F-22 at the Miramar Airshow, in San Diego, when it was still a prototype. A JSF-35 landed in Miramar about two weeks ago. I'm hoping it'll be at the airshow this October. :D I will take pics!
 

elmayerle

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Hmm, now that's interesting. I thought both X-35s were in museums and the first F-35 won't fly for a little while longer.
 

TinWing

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cold0 said:
Intermediate Thrust: 28,000 lbf (128.1 kN)
What do they mean by "intermediate thrust?"

I would assume that the term implies partial use of the afterburner?
 

elmayerle

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TinWing said:
cold0 said:
Intermediate Thrust: 28,000 lbf (128.1 kN)
What do they mean by "intermediate thrust?"

I would assume that the term implies partial use of the afterburner?
Full power without the afterburner engaged.
 

flateric

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LOCKHEED MARTIN F-35 COMPLETES FIRST GROUND TAXI TEST
FORT WORTH, Texas , December 8, 2006 --

The F-35 Lightning II moved under its own power for the first time on Thursday afternoon, initiating the last series of tests before the fighter jet’s first flight.

The first F-35 Lightning II taxis along the runway at Lockheed Martin in Fort Worth, Texas, on Dec. 7. The test initiated the last round of evaluations before the jet's first flight, and marked the first time the aircraft moved under its own power.

F-35 Lightning II taxis along the runway (JPG, 4.78 MB High-Resolution Photo)
http://www.lockheedmartin.com/data/assets/13800.jpg

After a series of systems checks at Lockheed Martin [NYSE: LMT] in Fort Worth, F-35 Chief Pilot Jon Beesley advanced the throttle and the F-35 moved out of its hangar to begin taxi tests. The jet then traveled at up to 30 knots (~ 35 m.p.h.) on the runway, testing systems such as brakes and nosewheel steering in advance of first flight. Medium-speed taxi tests of 65 knots (~ 75 m.p.h.) and 80 knots (~ 92 m.p.h.) are planned next, weather permitting. The first Lightning II is powered by the Pratt & Whitney F135 turbofan, the most powerful engine ever installed in a fighter aircraft.

The stealthy F-35 is a supersonic, multi-role, 5TH Generation fighter designed to replace a wide range of existing aircraft, including AV-8B Harriers, A-10s, F-16s, F/A-18 Hornets and United Kingdom Harrier GR.7s and Sea Harriers.

Lockheed Martin is developing the F-35 Lightning II with its principal industrial partners, Northrop Grumman and BAE Systems. Two separate, interchangeable F-35 engines are under development: the Pratt & Whitney F135 and the GE Rolls-Royce Fighter Engine Team F136.



Headquartered in Bethesda, Md., Lockheed Martin employs about 140,000 people worldwide and is principally engaged in the research, design, development, manufacture, integration and sustainment of advanced technology systems, products and services. The corporation reported 2005 sales of $37.2 billion.

Contact:
John R. Kent, 817-763-3980; e-mail john.r.kent@lmco.com
John Smith, 817-763-4084; e-mail john.a1.smith@lmco.com
 

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Sundog

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There are reports it may fly on Monday if everything is OK. At least that's when it is scheduled.

The front gear door looks huge since they made it a single piece. I understand why, just saying.
 

elmayerle

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More like mid-week as we're doing further, and higher-speed, taxi tests today and tomorrow. After that, the availability of suitable weather is the driver. Assuming weather permits, I'd expect first flight on Wednesday or, more likely, Thursday.

Oh, Sundog, that door's changing to two-piece on later aircraft as the design matures.
 

Sundog

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Thanks for the update!
I'm glad the nose gear door is changing to a two piece, it will look better and I can't help thinking in it's current guise it's just looking for a crosswind to push the nose around. ;)
 

Sundog

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I just found this site, for anyone who is interested. It's too bad we can't access the first flight webstream!

https://www.teamjsf.com/jsf/data.nsf/75frame
 

elmayerle

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When they went through the data from the high-speed (110-knot) taxi test conducted on Tuesday, they found an anomaly that could be traced to a sensor component in the air data system. This is being replaced with a one-day slip in first flight to this coming Friday. I got involved on the edges of this because my group does the installation drawing for this component. It took a bit of scurying around, but so far we appear to be "good to go".
 

sferrin

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elmayerle said:
More like mid-week as we're doing further, and higher-speed, taxi tests today and tomorrow. After that, the availability of suitable weather is the driver. Assuming weather permits, I'd expect first flight on Wednesday or, more likely, Thursday.

Oh, Sundog, that door's changing to two-piece on later aircraft as the design matures.
The two-door change was implemented as part of the weight reduction efforts as it allows smaller (lighter) actuators and such. I'm guessing the reason they went with one huge door to start is it's one less seam to worry about from a stealth perspective.
 

Sundog

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The two-door change was implemented as part of the weight reduction efforts as it allows smaller (lighter) actuators and such. I'm guessing the reason they went with one huge door to start is it's one less seam to worry about from a stealth perspective.
Yeah, that's what I figured. I've been following it closely in Aviation Week and know they've been doing everything possible to get the weight down. What I find interesting is that the canopy is single piece with the frame inside. I don't know if that is just to strenthen it against bird strikes, or if they always wanted the frame but making it internal is the best way to handle it in terms of the low observables since you don't have the discontinuity in the canopy then. Probably a combination of both and easier to manufacture, but it isn't anything you really notice unless you see a close up picture of it.

Of course, I think the F-35 is one of the first new fighters where the most exciting thing about it is the cockpit. It will definitely be one of the simplest cockpits to model when good kits of it are finally out. ;)

Thanks for the updates on the first flight Evan, because I keep checking the Lockheed-Martin news at their website and turning on CNN to see if it's flown. I figured something happened or the weather wasn't good enough for the flight until you gave us the update. Aviation Week had a good rundown of the first flight plan in this weeks issue.
 

elmayerle

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They ran a second high-speed taxi this Thursday afternoon to verify that the replacement sensor works and all indications before I left work tonight were that they will fly this Friday. It's an "off Friday" on our 9/80 work schedule, but I'm tempted to go in and watch the flight over real-time streaming video from my desk; the high-speed taxi was impressive that way.

Sundog, I won't say we're doing everything to get weight down, there comes a point where further weight reduction runs manufacturing costs up way too high. On the other hand, we've done a thorough job of meeting our weight targets without compromising the structure. There are reasons behind why the canopy is the way it is, including the forward hinge (ghod, what a PITA (Pain In The Ass) that is for systems routing to clear the hinges).
 

Matej

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Pictures and a short high-res video here:

http://images.teamjsf.com/main.php?g2_view=core.ShowItem&g2_itemId=3182
 

Sundog

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There are reasons behind why the canopy is the way it is, including the forward hinge (god, what a PITA (Pain In The Ass) that is for systems routing to clear the hinges).
In Aviation Week, they claimed the canopy was that way because it offered the minimum weight solution. I'm not saying it's true, that's just what the Lockheed Rep told Aviation Week. ;)

I was wondering what having the hinges and actuation system for the canopy up front would do for everything in the nose. I mean, it isn't like you guys don't have enough to put up there. So knowing it was a PITA to work around makes sense. Although it must be easier in terms of ingress/egress for the pilot.
 

flateric

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LOCKHEED MARTIN F-35 LIGHTNING II STEALTH FIGHTER COMPLETES FIRST FLIGHT
Fort Worth, Texas, December 15, 2006 --

The Lockheed Martin [NYSE: LMT] F-35 Lightning II lifted into the skies today for the first time, completing a successful inaugural flight and initiating the most comprehensive flight test program in military aviation history.

The first F-35 Lightning II flew for the first time on Friday, Dec. 15. The plane is shown climbing out shortly after takeoff from Lockheed Martin in Fort Worth, Texas. The stealthy, multi-service F-35 is the most powerful single-engine fighter in history, and is designed to replace the F-16, F/A-18 Hornet, the Harrier and the A-10.

F-35 Lightning II lifted into the skies today (JPG, 1.79 MB High-Resolution Photo)

F-35 Lightning II First Flight Photo (JPG, 2.04 MB High-Resolution Photo)

The Lightning II performed beautifully,” said F-35 Chief Pilot Jon Beesley following the flight. “What a great start for the flight-test program, and a testimony to the people who have worked so hard to make this happen.” The most powerful engine ever placed in a fighter aircraft – the Pratt & Whitney F135 turbofan, with 40,000 pounds of thrust – effortlessly pushed the F-35 skyward.

The flight of the conventional takeoff and landing (CTOL) F-35 variant began at 12:44 p.m. CST at Lockheed Martin in Fort Worth, Texas, when the jet lifted off and began a climb-out to 15,000 feet. Beesley then performed a series of maneuvers to test aircraft handling and the operation of the engine and subsystems. He returned for a landing at 1:19 p.m CST. Two F 16s and an F/A-18 served as chase aircraft.

The stealthy F-35 is a supersonic, multi-role, 5TH Generation fighter designed to replace a wide range of existing aircraft, including AV-8B Harriers, A-10s, F-16s, F/A-18 Hornets and United Kingdom Harrier GR.7s and Sea Harriers.

“The first flight of the F-35 Lightning II is an historic moment because, for the first time ever, we are seeing the dawn of an aircraft with all the 5TH Generation attributes – including advanced stealth, fighter agility, sensor fusion and greatly improved supportability – combined in an affordable package,” said Ralph Heath, president of Lockheed Martin Aeronautics Co. “The F-35 will be the most advanced and most capable multi-role fighter on the international market for many, many years to come.”

Dan Crowley, Lockheed Martin executive vice president and general manager of the F-35 program, said the aircraft has continued to meet or exceed expectations during its assembly and pre-flight checkouts. It has now embarked on a 12,000-hour flight-test program designed to validate tens of thousands of hours of testing already completed in F-35 laboratories. “The F-35 will enter service as the most exhaustively tested, most thoroughly proven fighter system in history,” Crowley said. “And thanks to its all-digital design, an exceptionally talented international engineering team and the world’s best assemblers and mechanics, the F-35 has completely rewritten the book on fighter assembly precision and quality.”

The United States and eight international partners are involved in the F-35’s funding and development. The U.S. Air Force, Navy and Marine Corps, and the United Kingdom’s Royal Air Force and Royal Navy plan to acquire a total of 2,581 F-35s. Italy, the Netherlands, Turkey, Canada, Australia, Denmark and Norway also are partners in the program and are expected to add about 700 more aircraft to the total. F-35 sales to other international customers could push the final number of aircraft to 4,500 or beyond.

“We believe the F-35 is poised to become the world standard-bearer of fighter aircraft,” said Tom Burbage, Lockheed Martin executive vice president and general manager of F-35 program integration.

Three versions of the F-35 are under development: a conventional takeoff and landing (CTOL) variant for conventional runways, a short takeoff/vertical landing (STOVL) variant for operating off small ships and near front-line combat zones, and a carrier variant (CV) for catapult launches and arrested recoveries on board the U.S. Navy’s large aircraft carriers.

Lockheed Martin is developing the F-35 Lightning II with its principal industrial partners, Northrop Grumman and BAE Systems. Two separate, interchangeable F-35 engines are under development: the Pratt & Whitney F135 and the GE Rolls-Royce Fighter Engine Team F136.



Headquartered in Bethesda, Md., Lockheed Martin employs about 140,000 people worldwide and is principally engaged in the research, design, development, manufacture, integration and sustainment of advanced technology systems, products and services. The corporation reported 2005 sales of $37.2 billion.

Contact:


John R. Kent
817-763-3980
e-mail: john.r.kent@lmco.com

John Smith
817-763-4084
e-mail: john.a1.smith@lmco.com
 

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elmayerle

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Sundog said:
There are reasons behind why the canopy is the way it is, including the forward hinge (god, what a PITA (Pain In The Ass) that is for systems routing to clear the hinges).
In Aviation Week, they claimed the canopy was that way because it offered the minimum weight solution. I'm not saying it's true, that's just what the Lockheed Rep told Aviation Week. ;)

I was wondering what having the hinges and actuation system for the canopy up front would do for everything in the nose. I mean, it isn't like you guys don't have enough to put up there. So knowing it was a PITA to work around makes sense. Although it must be easier in terms of ingress/egress for the pilot.
Well, it's a minimum weight solution for a common arrangement for all three variants. With the differences between the CTOL and Carrier-based versions on one hand and the STOVL version on the other, this is one of the few methods that would work and be common and is probably the lightest.

Anyway, I can guarantee that all of us on the program were most gratified with the flight. The next SDD aircraft will be the first "B" model and things should start getting interesting then.
 

Sundog

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So if they had gone with a conventional canopy it's actuation system might have interfered with the lift fan and it's systems? I was thinking that, but wasn't sure.

I just wish there were some videos up of the first flight. I know there will be soon, but I wanted to see in flight video and pics. Aviation Week reported part of the flight was cycling the gear. Did you see it fly with the gear up? I know there will be plenty of pics in next weeks Aviation Week, but I'm impatient. ;)
 

elmayerle

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Sundog said:
So if they had gone with a conventional canopy it's actuation system might have interfered with the lift fan and it's systems? I was thinking that, but wasn't sure.

I just wish there were some videos up of the first flight. I know there will be soon, but I wanted to see in flight video and pics. Aviation Week reported part of the flight was cycling the gear. Did you see it fly with the gear up? I know there will be plenty of pics in next weeks Aviation Week, but I'm impatient. ;)
Well, there's a difference in canopies between the CTOL/CV versions and the STOVL version, the STOVL canopy doesn't extend as far back because it blends with the fairing for the lift fan. Additionally, a rear-hinged canopy would put the mechanism squarely across the boundary between two modules of the aircraft and that's just asking for extra problems (from what I've heard, the realization of this is one corporate memory from the A-12 program, there were, I'm told, some real problems that way).

The flight plan definitely included cycling the gear and I assume it was done, but most of that would've been done in a designated test area about 100 miles west of here (yes, at work I've got the powerpoint file of the final first flight briefing - I'm not sure, without looking at it, if I can share it, though).
 

overscan

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http://www.alert5.com/2006/12/f-35-first-flight-web-extra.html

Video of first flight
 

elmayerle

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Well, anything I come across that I can share with y'all, I will. I don't guarantee how much that'll be, but I'll share what I can. There were supposed to be some good PR shots done as well as some serious testing, I hope they turn out well. :D
 

Sundog

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I haven't any doubt L-M will have some video out as soon as they edit it and put it together at their web site, just as they did with the F-22.

It sure did accelerate rapidly (it has the most powerful engine of any fighter in the world!...OK, I say that slightly tongue in cheek, since every L-M press release seems to have that in it.) But it definitely looked good and smooth.

Here are some links to more pics;

http://www.lmaeronautics.com/f35firstflight/

http://www.accuconference.com/f35.html%5C

http://www.militaryphotos.net/forums/showthread.php?t=99989

The following article states the gear wasn't cycled due to a sensor bug.
http://www.dallasnews.com/sharedcontent/dws/bus/stories/121606dnbusjsf.12b8da6.html
 

elmayerle

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And we're glad to get there. If anyone doubted, the nozzle clearly shows the benefit of the LOAN program.
 

harrier

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Just got this from a chap at LM - 2nd F-35 flight, this time with wheels up.
 

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overscan

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Renamed thread to be more appropriate.
 

elmayerle

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Sentinel Chicken said:
What belongs to that air scoop above the right intake?
I believe that's the intake for the ECS heat exchanger but I'm not totally certain. If I'm wrong, I'll get back to you.
 

Deino

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First take-off with AB !!! .... Ohhhhh what a sound !!! :eek:

http://www.network54.com/Forum/211833/thread/1176308327/last-1176339260/F-35+afterburner+take+off+and+roll+test+video+%289th+flight%29

Cheers, Deino
 

Deino

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Are there any status updates on the flight testing and especially any information about the "B"-prototype ??? ... It't very much "quite" around for a while !

Deino
 

flateric

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http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=aerospacedaily&id=news/F35051707.xml

Power Failure Cuts F-35 Test Flight Short


May 17, 2007
David A. Fulghum/Aerospace Daily & Defense Report

FORT WORTH, Texas - A loss of primary electrical power in the first, preproduction F-35A Joint Strike Fighter (JSF) forced its pilot to cut short its 19th test flight.

On May 3 test pilot Jeff Knowles was flying aircraft AA-1 at 38,000 feet and Mach 0.78. He executed a planned, full-stick, 360-degree roll and experienced a power loss in the electrical system about halfway through the maneuver.

The system automatically reconfigured and restored power to the flight control system, says Jon Beesley, chief test pilot for the F-35 program. The electrical system detected the problem and reconfigured its architecture to provide alternative pathways. Knowles completed the maneuver and returned to the Joint Reserve Base at Fort Worth.

It was not a serious problem and the pilot "never lost control of the airplane," Beesley says. However, the aircraft did land after only 45 minutes of flight. Other Lockheed Martin officials identified a component in the 270-volt power supply as the culprit in the incident. Lockheed Martin Aeronautics has a team of engineers analyzing the anomaly in an effort to determine what happened. Most members of the engineering team are veterans of the F-22 program.

The JSF's new technologies include the 270 VDC-based electrical system, whose failure terminated the test flight, as well as "electric muscle" that features compact, multifunction electro-hydrostatic actuators for the flight control system.

So far, company officials say they don't expect any delays to the flight-test program as a result of this incident. The program was nearly at the end of the current test phase, so the test team decided to move into the next, nonflying part of the program - for engineering review and upgrades to the flight software - that's scheduled to last into the first or second week of June, company officials say.

Changes will include improvements to on-board prognostic health management and adjustments to flight parameters based on the initial test flights.

Plans call for the fighter to return to flight status in June to begin air-to-air refueling tests, followed by a move to Edwards Air Force Base late this summer. There testing will be focused on air start tests of the Pratt & Whitney F135 engine. Edwards offers test pilots a vast desert area to land if the engine fails to restart in the air."

http://www.flightglobal.com/articles/2007/05/15/213885/jsf-recovers-from-in-flight-power-loss.html
DATE:15/05/07
SOURCE:Flight International
JSF recovers from in-flight power loss
By Craig Hoyle

Partial failure cuts short 19th test sortie of lone F-35

Lockheed Martin has launched a planned software modification to its lone F-35 test asset, after suffering an unexpected power failure during the aircraft's 19th and most recent test flight on 3 May.

"We had some very unusual electrical transient through the airplane," says Joint Strike Fighter programme executive officer US Air Force Brig Gen Charles Davis. "All the electrics dropped offline and came back after a few milliseconds."

Lockheed confirms: "The test pilot observed a partial failure of the electrical power system. The issue required that the pilot return to base and the 45min flight was slightly shorter than planned. Although the aircraft's redundant systems worked, we wanted to recover the aircraft to investigate the fault as soon as possible."

The conventional take-off and landing aircraft - AA-1 - has been returned to its run station for an engineering review and to receive flight software update FTU-2, which Lockheed says will adjust its flight parameters following the 20h flown to date and introduce on-board prognostic health management systems. "The F-35 team does not expect any overall delays in the flight-testing programme as a result of the incident," it says.

Expected to fly around six sorties a month and to remain in use until early 2009, AA-1 has so far reached a maximum altitude of 38,000ft (11,600m) and achieved a 20° angle of attack, says Davis. "The systems that we thought were really going to give us problems have performed almost flawlessly," he told a Royal Aeronautical Society lecture in London last week. The recent fault has "given us a lot of good ideas of things we have to continue to tweak and improve for the next version of the airplane", he says.

Davis says the JSF programme's nine partner nations last month participated in the first joint executive steering board meeting, during which they approved the final software configuration for the aircraft. A critical design review for the short take-off and vertical landing F-35B will be held next month, with the first aircraft - BF-1 - expected to make its first flight in May 2008.

Davis voiced concern over a proposal by the US House Armed Services Committee to reinstate the F-35's alternate General Electric/Rolls-Royce F136 engine (Flight International, 8-14 May). "If one of the committees or Congress bring the second engine in the programme I want to make sure that they fund it adequately," he says. "I want to be able to keep the development programme intact."

Ongoing challenges facing the project include addressing weight growth in the STOVL and F-35C carrier variants and Pratt & Whitney F135 engine, and negotiating the first low-rate initial production contract, says Davis.



http://www.aviationweek.com/aw/blogs/lebourget/index.jsp?plckController=Blog&plckBlogPage=BlogViewPost&newspaperUserId=703fd128-d069-40de-813b-a73b428e169b&plckPostId=Blog%3a703fd128-d069-40de-813b-a73b428e169bPost%3a4fb4ec09-d53f-4ea2-bd4f-ef3ec5b982d6&plckScript=blogScript&plckElementId=blogDest
JSF: Buy Now and Save
Posted by Bill Sweetman at 6/21/2007 6:39 AM

Joint Strike Fighter partner countries are being encouraged to commit to buying aircraft early, with the promise of lower prices, according to program vice-president and general manager Tom Burbage.

The goal is to get international customers to commit to early orders and to smooth out the slope of the increasing production rate, Burbage says."All we're trying to do is stabilize the production plan. We want to take advantage of [the partner countries'] parliamentary process, where they don't micromanage on an annual basis.If they make a long-term commitment we can stabilize our supply processes and reap an economic benefit." What Lockheed Martin is exploring is a consortium buy of JSFs.

Burbage insists that the plan does not call for firm and final sales contracts, which still run two years ahead of delivery(three years for long-lead items). However, committing to numbers and dates of deliveries will give customers a firm price (not fixed, but constrained) even in low rate initial production (LRIP) batches.

To get the new program rolling and to avoid a step in the production ramp-up, Burbage says, the JSF program office is looking for commitments soon: "The end of this year would be great, but it could spill into next year."

Burbage is still predicting a "mid-July, early August" return to flight for the first F-35, AA-1, following an electrical power problem that momentarily blacked-out the largely electric fighter on May 3 and disabled the right horizontal stabilizer. The problem has been traced to arcing inside the electrical unit that provides power to the electro-hydraulic actuator, during a roll maneuver that demanded high power at 40,000 feet. The problem has been traced to a unit which did not conform to specifications.

http://www.flightglobal.com/articles/2007/06/05/214381/pw-jsf-engine-damaged-in-test.html

DATE:05/06/07
SOURCE:Flight International
P&W JSF engine damaged in test

Driveshaft breaks after deliberate 'hard stall' during ground run with mock-up of lift-fan inlet planned for STOVL F-35

Pratt & Whitney is rebuilding an F135 Joint Strike Fighter engine damaged last month during ground testing of the short take-off and vertical landing propulsion system.

The F135 was damaged when a deliberate "hard stall" of the shaft-driven lift fan caused its driveshaft to break and debris was ingested by the engine, according to Bill Gostic, P&W vice-president, F135 programmes.

The propulsion system was being tested with a mock-up of the lift-fan inlet planned for the STOVL version of the Lockheed Martin F-35, to check airflow around the open inlet door while in the hover.

During testing of the engine on an outdoor stand at P&W's site in West Palm Beach, Florida, the Rolls-Royce lift fan was stalled deliberately to determine stall margin. This was achieved by closing the variable-area vanebox nozzle below the fan.

"We stalled the lift fan 28 times by closing the vanebox area 250% beyond normal operating conditions," says Gostic. "On the 29th time we went to 300% for a particularly aggressive stall and fractured the shaft connecting the lift fan to the engine." The shaft separated from the engine and fan.

"It stalled really hard," says Rob Burns, propulsion director for the Joint Strike Fighter programme office. Pieces of the hollow metal shaft and test instrumentation were ingested by the F135, breaking aero­foils through the engine, he says.

Burns adds that the test was "pretty far out" and, in operational use, protection algorithms in the control system would prevent the lift fan stalling. "We would never expect to see a stall as hard - or at all," he says.

Gostic says that the need to rebuild the damaged engine will not affect the schedule for flight clearance of the STOVL propulsion system, planned for early next year to support a first flight of the F-35B in May 2008.
 
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