(US) Air Force Fighter Fleet in 'Crisis'

"We are operating a fleet of aircraft to battle the now defunct Soviet Union, except our current enemies are uneducated, third world thugs armed with AKs and RPGs.

Wait until China get their military upgrades completed in the next decade."

We don't stand a chance against China now or 10 years in the future if we try to stay conventional, we will inly go broke trying to prepare for a conflict we can't win.

Look at the news article today about China "only" having 100,000 workers killed in on the job accidents THIS YEAR! And they say this is good because it represents a reduction (10%) fom last year.

If China trys a land grab anywhere in the world, they will be sucessful unless Nukes are used early and often against them. Plus, they understand the theory of strategic attack as opposed to our reliance on tactical attack only.

If you ask a teenager if he wants a low end pickup or a Ferrari as his work truck, they will pick the Ferrari every time. We need to stop letting these jetjocks pick their dream hotrods (unless they want to foot the bill.).

I was looking for an article that gave the flight hours of the mishap F-15 that forced this grounding, and here is finally is. Sounds to me like this one definately did not make it's numbers.

Manufacturing defects caused cracks that downed USAF F-15

Fatigue cracks started by manufacturing defects in a fuselage longeron caused the in-flight break-up of a Boeing F-15C Eagle on 2 November 2007, the US Air Force accident investigation has concluded.

Longeron cracks have been found in another nine F-15Cs, and manufacturing defects that could potentially cause fatigue cracking have been detected in a further 182 F-15A-Ds. All of these aircraft remain grounded.

Examination of the wreckage of the crashed F-15 revealed the right upper longeron, a critical load-carrying component in the forward fuselage, failed because of a fatigue crack that formed where the metal 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 aluminium longeron that failed was as thin as 0.039in – less than a millimetre - in the area when the fatigue crack formed.

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 – have been detected in upper longerons in 40% of fleet.

This was by far the worst thinning of a web discovered by the fleet-wide inspections that followed the crash, says Maj Gen Thomas Owen, commander of Warner Robins Air Logistics Center, the USAF’s F-15 depot.

The accident aircraft had accumulated 5,700 flight hours, says Owen, or 11,000 “equivalent spectrum hours” taking in account the additional fatigue stress imposed by high-G manoeuvring. But the longeron was projected to last 31,000h, well past the life of the aircraft, he says.

In the 2 November in-flight break-up, the cockpit separated at canted fuselage station 377, where the forward and aft sections of the two-piece upper longerons are spliced. The fatigue crack had formed just forward of the splice, in an undercut produced when a sloping transition was machined in the underside of the longeron.

Investigators say the crack started on the underside of the longeron, working its way upwards and outwards through the over-thin web until it reached the outer “posts”, which carry the bulk of the forward fuselage loads.

The "real solution" to the aging F15 needs to be implemented before the F15s are so worn out as to be useless. There needs to be an overlap period.

All sorts of plans get tossed out the window when an unexpected flaw threatens to ground the backbone of the USAF air supremacy fleet. All of a sudden, the luxury of knowing there will be enough F15s on hand for another 10-20 years gets thrown out the window. That brings up more questions. Speed up F16 upgrades? Increase capacity to make more F22s faster? Start a crash program to get UAVs to replace the missing F15s?

Even if it costs "only" $1million to fix each each F15, you just don't mail the parts out to each squadron, and have them install it on a weekend. The part will have to be designed, and then tested to make sure it fixes the original problem, and doesn't introduce new ones down the road. Each F15 will have to be flown, gently, back to the factory, or a major depot, and be torn down into little pieces and then reinstalled around the new longeron. Who knows if there will be other nasty surprises waiting when a more complete teardown is done?

If they had a part designed today, and a fixed price to do the repair, it would take a couple of years to cycle all of the aircraft through the system. That would then bring us right back to where we were before that F15 broke up in mid air: how many new F22s should we build? What is the role of UAVs? How much time do we have to debate these questions before it's too late, and we have to work with whatever we have on hand at that moment?

And those wonderful B52s, still flying after 50 years, are still in the air because a lot of money was spent to upgrade and fly them, and because there are 500 or 600 older B52s in the boneyard available to strip for parts that can no longer be made for any amount of money. This wasn't some grand design of the USAF, it was a matter of survival when follow-on bombers were never produced in enough numbers to take the load off the B52.

I assume you read my post #85. The accident aircraft had "accumulated 5,700 flight hours ... or 11,000 “equivalent spectrum hours”".

Also, the longeron that failed was 0.039 inch thick at the point where it failed, where the spec called for 0.10 inch plus or minus 0.01 inch. That's only 40% of the specified thickness.

The part did not meet it's manufacturing tolerance (thus was defective) and did not meet it's design lifetime (quoted as 31,000 hours.)

It was 40% of the thickness it should have been, and lasted 40% as long as it should have.

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