F-35 Joint Strike Fighter News, Videos and pics Thread

[escobar]

re: F-35 Joint Strike Fighter Thread

Well like all airplanes the F-35 has gained weight, as all the interested parties need this, or need that. This severely taxs the F-35 aerodynamically as well as the powerplants ability to provide the desired performance. In order to achieve the economy of scale, the F-35 has been thrust upon all three branches of service that have a need for a fighter bomber, the Navy, Marines, and the Air Force to "save" money. As weight goes up pieces that were likely well designed are machined, acid etched etc, to remove material and "save" weight. As we are finding, the aerodynamic loads are much greater than imagined. For example the A model of the Air Force is stressed to 9gs +, but has been equiped with the heavier landing gear required for carrier operations, as a result of these compromises, the inboard forward wing rib exhibits surprising stress fractures and will have to be redesigned to carry the additional load. The airframe exhibits buffeting in an unexpected area of the flight regime at fairly high mach, .85-.90, and median angle of attack around 20+ degrees, early suspicions are now showing the vertical stabiliser is being subjected to far more stress than expected and "may" need to be built up, although some changes to the flight control system are showing a "lot of improvement" as per the test pilots. So while the initial design is basically very simple and sound, and likely would have resulted in a beautifull little airplane that flew very well, hence my assertion that its not a bad airplane, all these additional expectations have resulted in an airplane with lots of issues, most minor, some probably not. My comments on our system of government are relevant in that lots of people and different nations, even are trying to have their needs for a fighter bomber met by one little airplane that has of necessity become three nice little airplanes that are being asked to do some difficult things. Some of these problems will be resolved, and some of the high expectations will likely have to be revised downward in order to get to full production. The QLR and POGO reports fully detail these concerns, as well as some possible fixes. IMO respectfully

so if I understand well they had no choice.

The US was settled by the Pilgrims who came from England to escape religious persecution, in order to be able to practice their Christian faith. Many of our nations founders were believers, and a carefull reading of our constitution and the bill of rights reflects the values and tenents found in the Bible. Respectfully

i know that but calling US a christian nation is a misuse of the term.
i would rather say that there are more christians in US than any other country

 

[Air Force Brat]

re: F-35 Joint Strike Fighter Thread

so if I understand well they had no choice.


i know that but calling US a christian nation is a misuse of the term.
i would rather say that there are more christians in US than any other country

You may say it any way you want sir, thank you for a respectfull response, I stated that "we have historically been" which is past tense, attempting to explain why it often appears that what we do is irrational and requires the "good faith" to do what is legal and expected even though we may disagree. Now back to the lovely, if slightly portly, little F-35. Sounds like they think the buffeting is from greater than expected loads on the verticle stab, which would make some sense, pulling some g's at higher mach numbers, may be causing some premature detachment of the airflow in the inlet fuselage juncture?, it will be very interesting to see what turns up in the windtunnnel. The buffet appears to be in the .85 to .90 mach range and around 20 degrees AOA, which in days past would have likely been about right. With all the aerodynamic tricks of the new century having a max AOA target of 50 degrees, you really don't expect this issue in that range, but maybe we should be pleasantly surprised when we don't have those issues? Any thoughts on that mr. scratch??

 

[Scratch]

re: F-35 Joint Strike Fighter Thread

Well, really, with those small bits of information flying around it's pretty much unsound to go into specifics. All I have seen suggests the vert stabs have difficulties coping with the g-load in tight turns. To me that doesn't really sound like vortices hitting them. But I can't refute that, either. Somewhere there seems to be an "unsmooth" corner or airflow interference causing that buffet.

Btw, I assume you mean 20° / 50° AoA? since %AoA is a strange unit to me. A modern aircraft already starting to buffet at half the maximum AoA isn't really that great.

 

[Air Force Brat]

re: F-35 Joint Strike Fighter Thread

Well, really, with those small bits of information flying around it's pretty much unsound to go into specifics. All I have seen suggests the vert stabs have difficulties coping with the g-load in tight turns. To me that doesn't really sound like vortices hitting them. But I can't refute that, either. Somewhere there seems to be an "unsmooth" corner or airflow interference causing that buffet.

Btw, I assume you mean 20° / 50° AoA? since %AoA is a strange unit to me. A modern aircraft already starting to buffet at half the maximum AoA isn't really that great.

You're absolutely correct, I must have been thinking percentage of designed max AOA, the buffeting is occuring at mach .85-.90 at around 20 degrees AOA, I must have been thinking half of design max AOA. When flying at a high angle of attack in the old 172 which is a high wing aircraft, the horizontal stab and elevator would begins shaking and quivering and you could actually see and hear the skin on the tail "oil canning". As disconcerting as this was, it provided ample warning over and above the stall horn going off that you were about to depart the aircraft. As the stall occured, the aircraft would pitch forward and possibly left or right depanding on which wing retained the most lift and as the angle of attack was reduced, the stall was broken and lift was reestablished. I'm thinking they are in fact talking about loads induced by this adverse airflow on the verticle stabiliser which is canted outboard to reduce radar signature, as the airflow is prematurely disrupted?

 

[navyreco]

re: F-35 Joint Strike Fighter Thread

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[navyreco]

re: F-35 Joint Strike Fighter Thread

Joint Strike Fighter may miss acceleration goal

The F-35 Lightning II’s transonic acceleration may not meet the requirements originally set forth for the program, a top Lockheed Martin official said.

“Based on the original spec, all three of the airplanes are challenged by that spec,” said Tom Burbage, Lockheed’s program manager for the F-35. “The cross-sectional area of the airplane with the internal weapons bays is quite a bit bigger than the airplanes we’re replacing.”

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[Air Force Brat]

re: F-35 Joint Strike Fighter Thread

Joint Strike Fighter may miss acceleration goal

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I told you she was growing on me, to much good stuff has caused me to gain a few extra myself, so now I'm starting to feel a little more sympathetic, I really think the extra wing area of the C might be a good thing. I did note the C has a design load limit of 7.5 gs +, down from the A models 9 g limit?

 

[Scratch]

re: F-35 Joint Strike Fighter Thread

The A model is indeed the only one the will be cleared for 9G, but for all I know that was planed a long time ago and is nothing related to current problems.
On the acceleration thing. I've read that, too, but it also said that those requirements were written based on clean F-16 /-18s. In that config, those planes really will sprint forward with their sleek body, compared to the large cross section F-35. But in clean config the first mentioned planes aren't really operationally usefull. However, even with a moderat combat load, a Viper or SBug will be considerably penelized in aerodynamic drag and RCS. A F-35, however, will retain it's "clean" config even at full combat load. So in that one case it's rather a formal problem then a performance one.

 

[navyreco]

re: F-35 Joint Strike Fighter Thread

Some good news

Panetta To Lift F-35B Probation at Pax River

Defense Secretary Leon Panetta will lift the probationary status tomorrow that the F-35B has labored under since his predecessor imposed one year ago. This lifts a dark veil from the program, which many have critics have targeted for elimination.

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[TerraN_EmpirE]

re: F-35 Joint Strike Fighter Thread

A F-35, however, will retain it's "clean" config even at full combat load. So in that one case it's rather a formal problem then a performance one.

No F35 retains a clean configuration with only internal weapons the majority of it's load is external. four missiles or 2 bombs and 2 missiles 4 weapons total not counting the cannon. Combat air patrol for a f16C at least from everything I have seen uses 2 sidewinders and 4 Aim120's. At It's full Combat load F35 uses it's four internal hard points and seven ( counting center line on a A model) external

---------- Post added at 04:48 PM ---------- Previous post was at 03:25 PM ----------

More!

Panetta says military committed to F-35B

But SecDef also issued this warning on the STOVL variant of the Joint Strike Fighter: It’s ‘not out of the woods yet’
By Robert Burns - The Associated Press
Posted : Friday Jan 20, 2012 15:04:47 EST

NAVAL AIR STATION PATUXENT RIVER, Md. — The U.S. military is committed to developing the Marine Corps version of the next-generation strike fighter jet, Defense Secretary Leon Panetta said Friday, but he warned that the program is “not out of the woods yet.”

Standing in front of one of the fighter aircraft at Naval Air Station Patuxent River, where the program is run, Panetta said the Pentagon needs “to make sure we’re on the cutting edge” of military technology.

“This fifth-generation fighter behind me is absolutely vital to maintaining our air superiority,” Panetta told about 100 people inside an aircraft hangar at the air station. Many in his audience work on the test program.

Before his address, Panetta visited an F-35 flight test simulator. He “flew” it briefly and also got briefings on progress made to resolve technical problems with the Marine Corps and Navy versions of the F-35.

The F-35 Lightning II is the Pentagon’s most expensive weapons program, and it has been troubled by schedule delays and cost overruns. Ten years in, the total F-35 program cost has jumped from $233 billion to an estimated $385 billion. Recent estimates say the entire program could exceed $1 trillion over 50 years.

Last year, former defense chief Robert Gates announced he was putting the Marine Corps’ variant on probation and said he would try to cancel it if problems were not resolved within two years.

In practical terms, that threat lost its power when Gates left office at the end of June. But Panetta made it official Friday.

The Marine version, he said, “has made, I believe and all of us believe, sufficient progress so that as of today, I am lifting the [fighter’s] probation.”

The military is developing three versions of the F-35 for the Navy, Air Force and Marines.

The new jet will replace the Air Force’s F-16 Falcon and the A-10 Warthog aircraft. A short-takeoff and vertical landing version will replace the Marine Corps F/A-18C/D and AV-8B Harrier aircraft. And the Navy is buying a model designed for taking off and landing on aircraft carriers.

Marine commandant Gen. Jim Amos welcomed Panetta’s announcement and said he will monitor the program closely. In a statement Friday, he said introduction of the fighter into the Marine’s training squadrons and combat units will be done responsibly based on the merits of the test program and its progress during the evaluations.

Amos added that the F-35 is the only fighter model capable of operating off of the large-deck amphibious warships, or in austere and remote expeditionary operations.