USMCFLYR,
I can only speak to what I've seen. As for the majority of times I was in the Middle East the fleet was only doing one small package a day, max two. I'm assuming trap times drive sortie length, which in turn limits time over Iraq. The time I spent in the container with USN / USMC assets was a fraction of USAF equipment (no this is not an us versus them flame - I'm reporting what I saw during multiple rotations in theater).
Biff

 

And I'm not trying to drive it to a 'flame fest' either but I'm not saying who is doing more work - I thought we were talking about FLE and airframe fatigue here. The carrier can't possibly produce what a land based squadron can - that is not their strength. My land based squadron alone would outfly the entire carrier air wing probably on a daily basis during OIF1 (I was Al Jaber based and comparing our sorties (not hours) and ordnance dropped to some of my peers out of the gulf and the med) - but they are not only flying missions in the box either and they rely on tanker support for those long 4-6 hour missions or so; but I digress.

Point was about "If you want to roll back all the way back to pre-Desert Storm 1 then just pull up the flying hours of ALL the fighter aircraft (I'm keeping this narrow folks) involved and look at which fleet has the most hours for it's age."
The Hornet fleet is averaging between 5,000-7,000 right now depending on model. Four things kill a Hornet: 1) Pure hours (10,000 is the newest number), Landings (17,000 is what I was told last night), Cat/Trap (you should see how quickly the Navy scarfed up the older Marine planes with no cat/traps) and 4) basic fatigue (pulled so many G's over time)
Now I don't know what the average F-15/F-16 airframe life is out there; but if in the above highlighted quote you were including USN/USMC fighter aircraft then we haven't even broached the subject of how many hours the F-14 had on them!

 

It is tough to make some of these comparisons but I will give it a shot from the F15 side. From 92-96 I was stationed at a base with a/c bought during the 85-86 FY. Two of the three squadrons sent jets to Desert Shield / Storm and all the rotations afterwards. Those tails started to hit 4 & 5 thousand hours in the 95-96. What they have now is unknown. By comparison Eagles bought in FY 78-79 that we are just now getting on our ramp have 6-7 thousand hours on them. The jets we are retiring are 75-76 FY jets and they have 5-6 thousand on them. Some bases / a/c did lots of SWA flying while others did just training or minimal rotations.
I think our airframe life is sitting at 7.5k, which is up from 5k at time of production. If I know the USAF they will up the limit again when needed to keep jets flying. Thank God the MacAir engineers designed a plane then added 10% just to make sure.
I guess for the Hornet fleet you would have to look at the amount / percentage of flying actually used for taskings over Iraq. I know that the USN flies at a higher rate than the USAF partly due to requirements for or around the boat. My above comments showed how things compared for the Eagle with jets that went to the desert vice those that didn't.
Wasn't the Tomcat made up to 1990? I'm not sure it would be a good example as it's production life was long with not that many made (or at least it would be a difficult comparison at best).
Biff

 

Except on 40% of the longerons........

 

Actually that 10% rule applies to 100% of the longerons. It appears only one failed due to faulty manufacturing. Not bad for a jet designed for 5k / 7.3G's originally with slide rules.

 

Quote:

Originally Posted by bifff15

Actually that 10% rule applies to 100% of the longerons. It appears only one failed due to faulty manufacturing. Not bad for a jet designed for 5k / 7.3G's originally with slide rules.

I'm not following.

Fact: 40% of the F-15A-D aircraft have longerons that are thinner than the design called for.
Only one failed because it was the thinnest of the sub-standard longerons and it cracked and failed first. Once the accident happened in Nov, the inspections started and at least 6 more cracked longerons were found. Those would have failed "due to faulty manufacturing" too if they'd been allowed to continue flying.

Those that hadn't cracked yet are now on an enhanced inspection schedule to avoid flying cracked and "failing due to faulty manufacturing". The fact that there's only been one catastrophic failure has nothing to do with some inherent design strength of the Eagle, but rather, an aggressive stand down, inspection and ID of the cause for the original failure.

Don't get me wrong, Biff, I’m not bashing the Eagle. I’ve got 2000 hours in it and there’s not another fighter on the planet I’d rather take into combat again. I'm just not sure I agree with the logic of this last post. MD porked away this longeron thing and this accident is on them. The fact that they designed the jet with a slide rule for 5k hours and 7.33G doesn't give them a pass on under spec longerons. If they were all IAW the design specs and all developing cracks, I'd be on the same page as you.

 

Fact: The jet that crashed was one of the top ten or fifteen most over g'd F-15's in the USAF.
Fact, the aircraft was originally designed for 7.33 g's and a much shorter lifespan.
Fact, MD asked the USAF to supply one F15 for destructive testing to determine if there were any weaknesses that needed to be worked since the jet was going well beyond it's "USAF directed design spec's".
Fact, the USAF said no.
While you would like to hang this noose around MD I would say not so fast.
Fact: 40% of the longerons were not to manufacturing specs.
Fact: 100% of the jet was not designed from the onset to be a 9g 7.5k jet
Fact: 100% of the F15A-D's are not flown as the USAF envisioned when it laid out the requirements.

Remember the F100-100 made good power originally, until you moved the throttle. Why is there dual flameout procedures in the Dash-1? Because they had them. No, the motor wasn't "designed" to have flame outs but it did. It also operated fine with how the requirements were laid out. And PW finally fixed them with the advent of the DEEC. And the ANG finally got the rest of the Eagle community to buy into the DEEC program.

A vertical tail came off the jet at Eglin doing the F22 AIM9X shots. Was it designed to do that? Nope, it failed due to water intrusion yet the restrictions still remain on the aircraft even thought they have all been repaired. Whose fault was that? MD? USAF poor mx habits?

I agree, there is no better jet to go to combat in. I've only got 2700 hours in this thing but still trust it like no plane I've ever flown. However, if a part fails well past it's design life, on a jet that is over it's initial design life, after a lifetime of over g's I would think a bit longer before I started pointing fingers. Culpability rests with all players, not just MD.

 

Biff,
We may just have to agree to disagree, but I’ll come at it one more time just in case. If you still want to wave the BS flag, I’ll give you the last word.

Quote:

Originally Posted by bifff15

Fact: The jet that crashed was one of the top ten or fifteen most over g'd F-15's in the USAF.

All these facts you list simply bolster my argument. The choice to fly the Eagle beyond its original lifespan and utilize OWS to expand the G envelope was done using what was assumed to be accurate design information and engineering data. Had the longerons on this aircraft been IAW the original design, this “abuse” and exceedance of the lifespan/G limit wouldn’t have resulted in the failure. The reason the rest of the properly built Eagles aren’t breaking up in flight is because they were over-engineered and able to exceed the original expectations. This Eagle and the other problem children are “under-engineered” and obviously unable to meet the demands of flying beyond the originally projected lifespan. Again, if all the Eagles were cracking, the above “facts” would come into play.

Exactly – The choice to fly the Eagle as a “9g, 7.5K jet” AND fly it differently from the way the “USAF envisioned” was made with the incorrect assumption that the longerons were the proper thickness. If all the longerons were designed and documented like the one on the failure jet, we’d probably have a boneyard full of Eagles. MD and the USAF wouldn’t have been able to make the numbers support a 9g/7.5K program.

The rest of the stuff you mentioned falls into the apples and oranges category, IMO. I can’t speak very well to the engine issue. I first flew the jet in ’89 and honestly don’t remember duel engine flameout being an issue. If you’re talking problems from the initial fielding in the ‘70s, then I really don’t see the point. The engines weren’t de-tuned then, they had turkey feathers that were flying off and any new aircraft is going to encounter some issues. Were these flameouts a result of improper design? No. Improper use? Yes. Big difference. The fact that an analog engine control can’t hack the daily abuse of a BFM engagement and a digital control can really has no bearing on our longeron discussion.

Water intrusion can have many causes but I know for a fact, that vertical stab didn’t roll off the assembly line in St. Louis with that problem. The choice to not fly the Eagle up to 800 CAL any longer may simply be an acknowledgement of all the exceedances you’ve mentioned. Not that guys were bumping up against that limit on a daily basis, anyway. Choosing to impose additional limitations on a 30 y/o airframe based on solid engineering data and consideration of the use/abuse it’s gotten up to this point is one thing. That’s significantly different than a catostophic failure resulting from parts that never met original design specs – never mind attempting to tap into the 25% of a 125% design and finding out it was never there to start with.

Cheers.
AD

 

AD,
My point is if the jet weren't over engineered by some margin when it was first designed (as a 7.33g jet) then the envelope would never have been enlarged to 9g's.
Obviously MD thought something might give eventually or they wouldn't have asked the USAF for one to destroy.
My point with the engine analogy is that regardless of how well something might be designed the engineers can't think of everything.
Yes, that longeron was not up to manufacturing specs for a 9g jet. However, it did last longer 5k and 7.33g's. The USAF has a program to determine the lifespan of a jet. All recorded G's, over G's, total hours, etc are entered. That jet was with in a small hours margin of the end of it's lifespan regardless of where it stood on the 7.5k front.
Biff

PS The USAF can track G's on the Eagle up to 7.5, then again at 9.0 (the counter readings from 5R). They have no ideal what goes on between 7.5 and 9.0 as the OWS tells the pilot only.

 

Folks this is scary. I detect gentlemanly conduct and respect for each other in this discussion. Is maturity at work here ? I am really enjoying your "points of view" without the usual insults (On other threads)to each other, family, college, second cousin twice removed, dog and the persistent use of $$%^^& and ))(*& adjectives.

Thank you from an old school type.