F-35 makes it's active duty debut at Eglin AFB

[simon]

Coudano, I am back to answer your questions, which were:

Can you tell me /EXACTLY/ how many tails had to have longeron refurb/replace before being returned to flyability. How many never made it back from those inspections? How many were already down that wouldn't have made it if they were still in service at the time of that grounding? Any idea what exactly is that caused the longerons to fail over time?

The one and only structural failure of an F-15 was in 2007 and was caused by a manufacturing defect in the right upper longeron, where the material was thinner than specified in the blueprint. Instead of being the specified 0.090-0.110in (2.3-2.8mm) thick, the flat top, or web, of the aluminum longeron that failed was as thin as 0.039in – less than a millimeter - in the area when the fatigue crack formed. These cracks expanded under life cycle stress. Weakened by the crack, the posts fractured as the aircraft pulled almost 7.8G in an air-combat turning maneuver. The fractured post led to the other longerons failing as well. The cockpit separated from the fuselage, the pilot ejected but suffered a broken arm when the canopy snapped off.

As a result of these findings, the entire US F-15 fleet was grounded pending inspections along with most of the foreign owned fleet. This meant 665 US and over 400 foreign aircraft, a total of around 1,100.
The thinning was caused when the longeron was machined by McDonnell Douglas during production of the aircraft, which was delivered in 1982. Similar manufacturing defects - undercuts, ridges or surface roughness that could potentially cause stress concentrations – were detected in upper longerons in 40% of the fleet.
The inspections were thorough. The USAF ultrasonically inspected 84 specific locations on each upper longeron on every F-15A-D. That is 168 data points per aircraft, and if any one was under blueprint, then the aircraft remained grounded. This was a very conservative approach.

By January 10, 2008, 60% of the entire F-15 fleet was approved for return to service. The defects were caused by manufacturing between 1975 through 1985, which covers the A through D models. No E models were affected.

In addition to the F-15's found with longerons below blueprint specification, nine aircraft were been found to have cracks in their longerons.

Kits were designed to replace the longerons. 15 were originally ordered. The cost of the replacement longeron was $10,000, but the cost of the repair was $250,000. Compared to the new cost of an F-15E ($55m), it was a relatively small, but at this point the service life of the aircraft and the future plans for the USAF fighter fleet came into the discussion.

The fleet was already old at the time of the crash. The Air Force first began flying the F-15 in 1972. By the time a jet fighter has been in service for 30 years, it will be fatigued and possibly nearing the end of its design life. The actual life of individual aircraft is based upon inspections using crack growth methodology.

The accident aircraft had already exceeded the original design life of the first F-15's.  A-B models were designed with a life of 4,000 hours. The useful life was doubled to 8,000 hours with the F-15C, and then doubled again to 16,000 hours with the F-16E Strike Eagle, which are expected to remain in service past 2025. The accident aircraft had accumulated 5,700 flight hours, below its design life as a C model but also 11,000 "equivalent spectrum hours" taking in account the additional fatigue stress imposed by high-G maneuvering. The longeron itself was projected to last 31,000 hours, well past the life of the aircraft, but there is no doubt that by 2008 a substantial portion of the F-15 fleet was nearing the end of their design lives and therefore the value in repairing that part of the fleet grounded with below specification longerons was questionable.

In the end, 182 F-15's that were found to have below blueprint longerons were grounded. It is unknown how many of the repair kits ordered were applied to the grounded aircraft and how many, if any, made it back into service. None of the affected aircraft were F-15E Strike Eagles, which are still in service.

The question is really whether the F-15E Strike Eagle is still a worthy fighter and should be considered as an aircraft that the Air Force should continue to manufacture (Along with the F-16 and F-18) in lieu of the F-35. The F-15 is a small fraction of the cost of an F-35.

It is also worth noting that this aircraft has decades of combat and worldwide deployment history in which the creases have been ironed out.  Its vices are known. There is real value in that. The Air Force just last week returned the F-22 fleet to service after a four month stand down due to 12 incidents of crew hypoxia over the last 3 years. They still haven't found the cause of the problem, but they are going to fly them anyway and use a risk mitigation strategy. So even the latest and greatest aircraft in the Air Force fleet have problems and even then, it is early days for these aircraft.

[simon]

You should check your facts before you blast someone else for being uniformed. The F-22 was export forbidden due to the technology on board. The F-35 program, however, is RELYING on foreign buyers to keep the program afloat.

At last count the UK, Italy, the Netherlands, Austrailia, Canada, Denmark, Norway, Turkey, Israel and Singapore have contributed funds to the program and are considering buying or already have aircraft on order.

Correct. I misread the ban as being on the F-35. Even more to my point though, because it shows that in addition to the F-22 being a failure internally, it was not allowed for export even though countries like Australia specifically asked for it instead of the expensive and forever overdue F-35.

Australia has ordered 14 F-35's. Think about this for a second: 14 airplanes spread over a country as large as the mainland US. Can you imagine the infrastructure support cost at multiple locations? They are not even scheduled to have the squadron operating for another 7 years.

http://www.theaustralian.com.au/national-affairs/defence/us-air-force-needs-troubled-f-35-fighter-jet-which-is-also-bound-for-australia/story-e6frg8yo-1226141544067

As Australia's existing fleet of F-18's ages, it is now reevaluating alternatives to the F-35 in case the US is unable to deliver or suffers another blowout in costs. The original estimate from Lockheed was $25 million per aircraft. It is now expected to exceed $200 million, plus lifetime support costs, generally at least as much as the cost of the aircraft.

Estimates used to bait governments and quash votor dissent should just have a zero added to them.

[simon]

At last count the UK, Italy, the Netherlands, Austrailia, Canada, Denmark, Norway, Turkey, Israel and Singapore have contributed funds to the program and are considering buying or already have aircraft on order.

Let me update you on "At last count":

UK: Orders reduced from 138 to 40.

Italy: Looking at cutting order numbers by up to 60 – mostly the STOL variant.

The Netherlands: The have quit the program completely.

Australia: With a recent change in government, now reconsidering all orders due to cost and delays.

Canada: On the fence. Rumors are the escalations in purchase cost could be a tipping point for the government at the next election. However, they are still hanging in there.

Denmark: They have quit the program completely.

Norway: All orders on hold because Lockheed would not commit to a country specific missile regarded as mandatory.

Turkey: All orders on hold because the US would not reveal the technology, e.g. source code to the software.

Israel: The only country still full speed ahead. Of course.

Singapore: Still considering entering the program as of July. The only Asian country.

So you are right, one of the justifications of the F-35 was foreign sales, most of which were either pipe dreams or are rapidly evaporating. Any way you cut it, the program is a disaster. Leaders in foreign countries don't even want to talk about it.

[BradM]

Wouldn't you go into areas with advanced Russian made SAMs with cruise missiles and a stealth fighter bomber like the F-35 in the first waves and then when much of the SAMS are taken out follow with 4th Gen fighter bombers as well that can carry more payload? So we would need F-22s, F-35s, cruise missiles, and the cheaper 4.5+ Gen fighters and fighter/bombers.

[simon]

Strategy for taking out Russian SAMs is best answered by an expert.

I will however, add that AGM-129 advanced cruise missiles, with a range of 1,500 miles, can be carried by the B-2 stealth bomber, which can launch from Whiteman in the US, fly fully armed to any location in the world with aerial refueling (As they have done many times in actual combat missions), deploy the missiles and return without ever getting close to Russia's longest range SAM, the S-400, which has a range of 250 miles. The S-400 is not maneuverable enough to take out a low flying cruise missile.

If it is a short/medium range SAM, maybe the strategy would be different. But this is just an example where you might not even need the F-35's. Plus the B-2's are already flying and paid for. Or at least on credit.

As to whether you would actually try and do that to take out a SAM, I am just guessing really. Again, an expert is best to chime in.

It is worth remembering that stealth technology isn't 100% against some of those very good Russian SAMs. I *believe* an F-117 was taken out by one.

[PHall]

It is worth remembering that stealth technology isn't 100% against some of those very good Russian SAMs. I *believe* an F-117 was taken out by one.

The F-117 was hit by a SA6 Gainful (aka Three Fingers of Death) mostly because the F-117 pilot flew right into it's engagement zone.
Stealth is nice but it can't overcome stupid.

[lordmonar]

Not to mention that the F-117 was 1970's stealth...

That is why the argument for just building more F-16/F-15/A-10's is not necessarily the right one.

You have to remember that our potential advasaries are building new weapons all the time....if we want to remain the most powerful air force in the world we have to research new technilogies....like the F-22 and F-35.

[simon]

I agree with the research part but the cost has ballooned into an untenable situation.

It was a big ask from the outset. Develop one design to satisfy the needs of the Air Force, Navy and Marines. One strong enough to perform carrier landings, compact enough to fit below deck, powerful and light enough to perform vertical takeoffs, fast enough to go supersonic, stealthy enough to avoid radar detection, carry enough armaments to provide primary close air attack / support and be the best air to air fighter in the world.

(I could talk how the job was farmed out to one contractor whose prime objective is to maximize profits, but that would be off topic.)

It is really such a mess that I have no answers on what to do with the program. Like I said earlier, it is a political hot potato worldwide. Hence I offered the simple solution: Re-energize our perfectly good fleet that can kick anybody's butt worldwide. The US doesn't have the money for this plane. It has bigger fires to fight.

[lordmonar]

That we can still kick but world wide is no longer a given.

The Europeans, Russians and Chinese all have new jets on the production line that equal or surpass the F-15/F-16/F-18.

The A-10 does not have much life left in it as MANPAD SAMS are getting so much better.

The F-117 and the F-14 are both already mothballed.  The Harrier is only alive because we still need a VSTOL platform.

So just building new F-16 and F-15...while would put a perfectly good airplane in the air that would last another 30 years......will only mean we will get our butts kicked by someone who bought the next gen fighter.

[BradM]

That we can still kick but world wide is no longer a given.

The Europeans, Russians and Chinese all have new jets on the production line that equal or surpass the F-15/F-16/F-18.

...

So just building new F-16 and F-15...while would put a perfectly good airplane in the air that would last another 30 years......will only mean we will get our butts kicked by someone who bought the next gen fighter.

I agree. If we are facing a 4th gen fighter then we can put up a 4.5+ Gen fighter to shoot it down. If we are facing 5th gen fighters we need the F-22 and the F-35 to go up against them. Unless we have an armed stealth UAV with air to air missiles that can take out the 5th gen fighter like the PAK FA and the J-20 in the near future? The Russians plan on putting the PAK FA into production in 2015. The Chinese will probably try to put their J-20 into production around 2017-2020.

[simon]

The Europeans, Russians and Chinese all have new jets on the production line that equal or surpass the F-15/F-16/F-18.

Enlighten us all. Save me the effort of Googling it.

I am especially interested in the European fighters in production that are superior to the F15/16/18.

[lordmonar]

The Europeans, Russians and Chinese all have new jets on the production line that equal or surpass the F-15/F-16/F-18.

Enlighten us all. Save me the effort of Googling it.

I am especially interested in the European fighters in production that are superior to the F15/16/18.

The Eurofighter  Typhoon.

http://en.wikipedia.org/wiki/Eurofighter_Typhoon

And the rest of the list

http://en.wikipedia.org/wiki/Fifth_generation_jet_fighter

[Mustang]

The Super Hornet is a last generation jet. Cancel the F-35 and use the money to develop a next generation jet.
And this time get it's role defined before you freeze the design, not after...

The F-22 and F-35 are last generation jets too.  Last generation of manned jets, that is.