What's going on with the F-15?

Does anyone know what the structural failure is that causes the crashes?

The Missouri Air National Guard has lost 2 already this year and the Air Force just grounded all 700 aircraft with the exception of mission-critical combat aircraft.

It looks like they have grounded all of them.

``All F-15 aircraft have been grounded, not just non-mission critical flight ops,'' the Air Force said. ``The grounding will remain in effect until conclusions are made'' by the safety investigation, the service said. Aircraft assigned to Afghanistan and patrols over U.S. airspace will be on ground alert in case of a major emergency, the service said.

Bloomberg.com

Here is a link to KY3.com. That link has pictures and video of the crash scene and some information about the first MANG F-15 crash from earlier this year in Indiana.

The F-15 was originally designed for 4000 to 8000 flight hours before it hit the end of its structural lifetime. They found that that would be about 7600 "hard" hours, or up to 12,000 "soft" hours. They were planning on the F-15C being around until up to 2030, but that's based on 270 flight hours a year. The F-15E was designed to handle up to 16,000 flight hours before the end of its life.

[edit on 11/5/2007 by Zaphod58]

Simply put, they are overworking nearly all of the USA military equipment. Consider the age of the airframes, then all of the normal flight hours USA pilots get every year, and then all of the military engagements with the associated stress of weapons on the wings.

It's not just the human element that is being exhausted by the Iraq and Afghanistan conflicts, the equipment is suffering as well. Something needs to change ASAP to maintain the integrity of our military before it degrades into a complete mess.

reply to post by Zaphod58


A bit more info from flight global.
www.flightglobal.com...

In a statement released on 4 November, the US Air Force said the cause of the F-15C crash remains under investigation, but preliminary findings indicate that a possible structural failure of the aircraft may have occurred. It described the suspension of non-mission-critical flight operations as a "precautionary measure".
A report on the incident is expected to be completed in 60 days.
This is the second Missouri ANG Eagle crash this year. The May crash of an F-15D in Indiana was caused by a jammed control cable. Four USAF F-15s have been lost so far this fiscal year, compared with one in FY2006.

how close are the air frames to being time expired?( we have had many years now of combat operations) i know an airframe can be re life`d - but its a massive job needing massive money - the engines will be routinely swapped as well - i`ve seen the figure of 1,000 full cycles being used to describe the hot core life.

reply to post by Harlequin


Well according to the info here if you take the average of 270 hrs a year to an airframe and the 15 that just crashed on Nov 2 2007 was built in 1980 the plane would have around 7290hrs on the airframe.

Originally posted by Zaphod58
The F-15 was originally designed for 4000 to 8000 flight hours before it hit the end of its structural lifetime. They found that that would be about 7600 "hard" hours, or up to 12,000 "soft" hours. They were planning on the F-15C being around until up to 2030, but that's based on 270 flight hours a year.
[edit on 11/5/2007 by Zaphod58]

So with that info and if the plane was flying hard hours it was already over the limit though I'm sure it flew a combination of mission types. I'm interest Zaph in the 2030 timeline. Maybe a bit of research of when these planes rolled off the line and is in order. (Q-400 flash back)

reply to post by Canada_EH


Here is a bit more info on the airframes. Just giving Zaphod's info a source and a bit more context.

The F-15 initial operational requirement was for a service life of 4,000 hours. Testing completed in 1973 demonstrated that the F-15 could sustain 16,000 hours of flight. Subsequently operational use was more severely stressful than the original design specification. With an average usage of 270 aircraft flight hours per year, by the early 1990s the F-15C fleet was approaching its service-design-life limit of 4,000 flight hours. Following successful airframe structural testing, the F-15C was extended to an 8,000-hour service life limit. An 8,000-hour service limit provides current levels of F-15Cs through 2010. The F-22 program was initially justified on the basis of an 8,000 flight hour life projection for the F-15. This was consistent with the projected lifespan of the most severely stressed F-15Cs, which have averaged 85% of flight hours in stressful air-to-air missions, versus the 48% in the original design specification.

Full-scale fatigue testing between 1988 and 1994 ended with a demonstration of over 7,600 flight hours for the most severely used aircraft, and in excess of 12,000 hours on the remainder of the fleet. A 10,000-hour service limit would provide F-15Cs to 2020, while a 12,000-hour service life extends the F-15Cs to the year 2030. The APG-63 radar, F100-PW-100 engines, and structure upgrades are mandatory. The USAF cannot expect to fly the F-15C to 2014, or beyond, without replacing these subsystems. The total cost of the three retrofits would be under $3 billion. The upgrades would dramatically reduce the 18 percent breakrate prevalent in the mid-1990s, and extend the F-15C service life well beyond 2014.

www.fas.org...

So if the aircraft was intially tested and rated for 4000hrs then increased to double that at 8000hrs the aircraft off the line in the early 1980s will be reaching that mark and hence the reasons these accidents are increasing since I'm unaware of any current changes to the flight rules goverening the operation of the 15 and how the maitenance proccedure is changing from year to year.

[edit on 22/08/06 by Canada_EH]

hmmmm, now do the USAF rotate airframes closer to end-of-life to ANG units? if so , then i would hazard an educated guess and say these F-15`s are allready time expired - given very heavy action in 1991 (GW1 - total allied sorties were over 2500 per day) kosovo 1999 , and of course afghanistan (2001 > present) and Iraq (2003> present)

They rotate late flight birds to the ANG, and retire the early flight birds the ANG is flying. For example, when Hawaii got their F-15s, they were looking at 1974-75 A models, but over time they rotated them out and got replaced by 77-78 A models. Still A models, but with a few hundred less hours on them. As the F-22s come online, they'll replace the As with the earlier model Cs that still have a pretty good bit of life left to them.

reply to post by Zaphod58


It was a C model that crashed , and the entire discussion of this thread is about the ANG airframes being time expired - i would say for sure a 1970`s F15 would be long gone by now unless it was a `low mileage found in the corner` type - 1977 A models are 20 years old and have had a hard life.


edit:

ISn`t Hawaii ANG thats getting F22`s? it would explain the end of life of there A models (which i would also say are way over time) and the lack of suitable C models.

[edit on 7/11/07 by Harlequin]

Not necessarily. The C models were the ones used in Desert Storm and Iraqi Freedom, not the A models. So they would have a lot more "hard" time put on them than the A models would have. You have a lot of ground time on the A's as they sit Alert, and more routine flights on them.

reply to post by Zaphod58


So basically the planes that are moving into the ANG have ALOT more hardtime on the airframes. More hardtime equals more strain on the airframe and hence the problems being run into at the "7290 hrs" mark.

Also the Hawaii ANG works in tandem as far as I know with regular base personel or fulltime airfroce personel and the F-22 going there will be worked on and possibly flowen by both ANG and Reg forces.

reply to post by Zaphod58


that maybe be so , but the A models are at least 20 years old now and whilst they might not have as much air time , they have had 20 years of sitting around in the elements - and sea air is notorious for corosion.

so , given the hard time the F15`s had during 1991 and 2003 (its war and they don`t give fighters a day off - the airframe will be in the air) and strike missions of `high intensity` would be 8 hours + each day - so thats at the very least 60 hours a week and more likely 100 hours a week of combat ops - 400 per month , so for GW1 your looking at least 1000 hard hours put on the aircraft for the duration....

hmmmm i would hazard a guess and say the C frames are more shot that they want to admit and thus a good reason for more F-22`s (without telling opposition your gear is likely to fall apart)

reply to post by Canada_EH


Only the C-17s, and eventually the F-22s are a combined unit. The F-15s are entirely an ANG unit. The C-17 unit there was the first of its kind, and an experiment to see if it would work.

Harlequin, the A models have a lot of time sitting, but that can be a GOOD thing. The C's that were seeing combat ended up having PDMs on the deferred, where the A's didn't, which let them catch a lot of corrosion and cracking problems.

If they would put in a big order of F-22s the price of them would drop big time. They should build more F-15s in the mean time.

Why? By the time they were built and operational the F-22s would be taking their place. There are already several F-22 squadrons formed and operational.

reply to post by Zaphod58


If the A`s are in that mucg better condition then TBH i can see them bining the C`s straight to dosposal as time expired and just replace them with F22`s (erm isn`t that what goins on ) and the ANG units have the A`s for a few more years yet.

SOME of them are in better shape than the C's, because the C's are the workhorse of the USAF. There are some units that do need to change over to C's as soon as they can.

Am I crazy, or is that limit of 8000 hours for a F-15 fairly pethetic? Airliners fly over 80 000 hours before they get retired. Granted, the F-15 is not an airliner, but then again, it's designed for pulling 9g's.

?