F-35 suffers setback

The F-35 program suffered a pretty significant setback, with the Pentagon lowering the standards for the aircraft. The standards for transonic acceleration, and sustained G loading have been reduced, pretty significantly in the A and B aircraft, but in all three models. Flight testing during 2012 had been going well for awhile, with several significant goals being met, including weapons release goals.

The G load for the A has been reduced from 5.3Gs to 4.6Gs. The B goes from 5Gs to 4.5Gs, and the C from 5.1 to 5.0Gs. The acceleration for the A added 8 seconds for acceleration from Mach 0.8 to Mach 1.2. The B added 16 seconds, and the C added a whopping 43 seconds.

This is on top of the horizontal tails suffering delamination and scorching during high speed/high altitude flight. The B and C are also suffering transonic roll-off and buffeting issues, the C more than the B due to the wing area.

Probably the biggest news was that the fatigue testing airframe had to stop testing in December due to cracking found in the bulkhead flange on the underside of the fuselage during the 7,000 hour check.

The US Department of Defense is lowering the performance bar for the Lockheed Martin F-35 Joint Strike Fighter according to a new report by the Pentagon's director of operational test and evaluation (DOT&E).

The specifications for all three variants pertaining to transonic acceleration and sustained turn rates have been reduced. Worst hit in terms of acceleration is the US Navy's F-35C carrier-based model.

"The program announced an intention to change performance specifications for the F-35C, reducing turn performance from 5.1 to 5.0 sustained g's and increasing the time for acceleration from 0.8 Mach to 1.2 Mach by at least 43 seconds," reads the report prepared by J Michael Gilmore, the Pentagon's DOT&E. "These changes were due to the results of air vehicle performance and flying qualities evaluations."

The US Air Force F-35A's time has slipped by eight seconds while the US Marine Corps short take-off vertical landing (STOVL) F-35B's time has slipped by 16 seconds. However, turn rates for both the A and B models have been impacted more severely than the USN variant. Sustained turning performance for the F-35B is being reduced from 5G to 4.5G while the F-35A sinks from 5.3G to 4.6G according to the report.

www.flightglobal.com...

They're just lawn ornaments, to us Canadians. We're so smart, we bought them without engines.......

reply to post by shefskitchen


So does the US. That's how the contract works, you buy the airframe from Lockheed Martin, and then you have to go negotiate a separate contract from the engine manufacturer. That way both of them make their billions per quarter.

So what do you suggest we do, scrap the plane?
What then?

The DOT&E office has also talked about the software. The Block 1 software is not complete, so Block 2 and 3 aircraft have been delivered with significant variances in expected performance. Block 2A, which is for training was late, and only half ready at the time of the report. Block 2B is late, Block 3i has lagged in testing (it's supposed to bridge the Block 2B and 3F software).

The PAO used in the avionics system poses a significant risk to both pilot and aircraft, as it's highly flammable and if it leaks it could immediately incapacitate the pilot and lead to loss of both. A weapons test caused a fire and a leak rate of 2.2 gallons per minute.

The latest report on the F-35 program by Michael Gilmore, the Pentagon’s director of operational test and evaluation (DOT&E), spotlights growing problems with late software deliveries for the stealthy fighter.

Software releases in 2012, the report says, ran late as compared to the schedule adopted after the 2010 technical baseline review, which was carried out in part to correct optimistic projections made before that date. (The program’s leaders had underestimated the amount of regression testing — tests to make sure that changes had not induced problems in previously tested functions — and overestimated test rates and productivity.)

Block 1 software is not complete. Lot 2 and Lot 3 aircraft have been delivered “with major variances against the expected capabilities,” the report says.

Source

I think we are reaching the limits of jet aircraft if want to make any further giant leaps we will need to find a completely new propulsion system.

reply to post by Alxandro


It's too late to scrap it. If they want to get the program back on track, make Lockheed responsible for fixing the major problems, on their own dime. They have repeatedly told the Pentagon that they were farther along than they were, so let them get the software and other aspects up to where they said they were on their dime instead of ours.

reply to post by Zaphod58


That will never happen. These aircraft were designed for one simple function and only one simple function.

TO MAKE MONEY!

That is it in a nutshell. If they do not deliver to spec, the specs will be reduced to match the performance.

The public will wear it! Typical of a free society where multinational companies are free to make money with inferior goods.

P

Well, they paid for development of a plane we cannot build with current knowledge and materials. I suppose we still have to pay the contractors even though they didn't develop an adequate product. In the real world you can deceive someone and not be held liable if you have enough power.

I suppose this doesn't really matter to us brits, we were supposed to be buying about 120 of them, now we're only buying 50, which we'll mothball (because we have no carriers) until we get coerced in to another joint-buy system.

how do you solve the buffeting issues without changes to the aerodynamics?

and I thought some planes were already being delivered in the US?

Originally posted by Dispo
I suppose this doesn't really matter to us brits, we were supposed to be buying about 120 of them, now we're only buying 50, which we'll mothball (because we have no carriers) until we get coerced in to another joint-buy system.

The first Queen Elizabeth class carrier will be in operation in good time for the bulk deliveries to start. Technically the Royal Navy already have 1 F-35B delivered (in July 2012) but it is continuing its testing in the US (not sure if it's at Pax River or Eglin though, SME might know?).

The reason for the initial order of 48 units was the decision to keep HMS Prince of Wales (due to enter service second in 2018) as a STOVL configuration which reduces its size considerably and limits the complement of aircraft it could handle however, depending on the mix of aircraft each carrier could comfortably accommodate up to 40 aircraft.

I would expect another 48 to be ordered in the Strategic Defence Review of 2015.

I think twould be good idea if Canada purchased some russian fighters instead......
These dogs are gonna be dropping like flies when the shtf.

reply to post by maintainright


They are being delivered. There are four or five combat coded aircraft at Yuma MCAS (not that they could fly in combat if they wanted to). You can actually fix a buffet problem with a fairly minor change to the airfoils if you do it right. The F-15 originally had straight horizontal stabilizers, but when they flew it they had a flutter issue. They cut the sawtooth out of the leading edge, and it went away, and we have the look we have now. It might be as simple as that.

Originally posted by PW229
. Technically the Royal Navy already have 1 F-35B delivered (in July 2012) but it is continuing its testing in the US (not sure if it's at Pax River or Eglin though, SME might know?).

They're at Eglin. The second one was delivered in October, and flight crews have started flight training on them. Norway has their first one as well.

reply to post by pheonix358


Actually the Air Force has stopped payment until certain test points were reached once already. It would be easy enough to do the same thing again until they at least deliver the software. The rest will be fixed over time and are things I would expect with any flight test program, but the software needs to be done now.

Apparently the original design of the F-35 was longer, and more narrow, but the tail started to get heavy, so they had to "squish" it and make it shorter and fatter. The cross section of the fuselage creates a sharp rise in drag in the transonic region of flight. There's probably not much they'll be able to do about that problem. This was a known issue, and a year ago Lockheed brought it up during an interview.

Yikes, the hits keep on coming. At this rate, the airframe might be obsolete or made mediocre by the time they get the kinks worked out. Could the F35 be the most expensive blunder in the history of powered flight? Zaphod, hypothetically speaking, if the F35 program turns out to be a total write-off, what's the USAF and Navy's next move?

Originally posted by Zaphod58
reply to post by maintainright

 

They are being delivered. There are four or five combat coded aircraft at Yuma MCAS (not that they could fly in combat if they wanted to). You can actually fix a buffet problem with a fairly minor change to the airfoils if you do it right. The F-15 originally had straight horizontal stabilizers, but when they flew it they had a flutter issue. They cut the sawtooth out of the leading edge, and it went away, and we have the look we have now. It might be as simple as that.

Yeah, was going to mention the "dogtooth" but looking at the aerodynamics profile (what little info there is publicly available) I'm not sure it will solve much. I'm wondering if a move to central spar by extending the body back and hence forming a stabilator would solve it. The F-35 has a very strange hinge/ actuator system for the horizontals:



Not sure I've seen it used before. As you can see from the production picture (source .pdf link available below) it seems to have a dogtooth built in at the blending point with the body. That's a LOT of work being done in a very small area.

If it was me being asked (and of course it isn't) I'd say, "Get rid of that goofy hinge and go central spar stabilator." Would probably be lighter as well.

Sources for additional reading:

Aircraft Level Dynamic Model Validation for the STOVL F-35 Perfectly safe .pdf from an established source.

EDIT: That photo is NOT a vertical surface, it is a horizontal in a vertical brace

Originally posted by Orwells Ghost
Zaphod, hypothetically speaking, if the F35 program turns out to be a total write-off, what's the USAF and Navy's next move?

I was talking this over with someone else recently and his idea is that they're going to eventually cancel the F-35 and bring up a black project that they've developed to replace it. We know there are four or five black projects that are at the flying stage, so it's theoretically possible that they would.