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Hi Sproket,
Yes it is similiar. The Comet failed in the fuselage skin. Due to fatigue the skin would crack and you would get an explosive decompression and break-up. In the case of the F-15 it appears to be a failure of a structural support member. So the acrual causes are a bit different one related to skin and -pressure and the other related to a framework member. HTH.

The Comet suffered from cracks beginning at rivets at the corner of cabin windows, which were the result of the flexing of the skin during increases and decreases in altitude. This was proven by placing the a/c into a tank of water, and pressurizing and de-pressurizing repeatedly the cabin with high pressure air. The failure occurred far sooner than was expected, and because the failure occurred in a controlled environment, the pieces were available for careful examination, and a relatively simple redesign cured the problem. However, Comet (a very attractive aircraft) was never able to win back the confidence of the public, and quickly faded from the scene. However, RAF versions were very successful, serving for many year.

The problem with the F-15 is thought to be a stress failure of one or more longerons (main structural framework that runs from front to rear - lengthwise - which bears much of the high "G" induced stress the aircraft is subjected to) which appears to me to be the result of years of high "G" maneuvers during combat and training. Only time and careful testing will reveal the truth. The cure will also, most likely to a while in coming.

Ron

The "cure" will be the F/A-22. But we aint' buying 700 of em'.

Old airframes, 20+ years of high G loads, this isn't rocket science. Stuff is gonna break eventually.

Air Guard To Secure, Monitor Northeast


SOUTH BURLINGTON, Vt.-The Vermont Air National Guard will provide security and emergency response in the Northeast as a result of the Air Force's decision to ground all of its F-15 fighter jets. The F-15s will be inspected following an investigation into a Missouri Air National Guard plane crash Nov. 2 that found defects in the aircraft's fuselage. The Vermont Air Guard, which flies F-16s, will continue the mission after the inspections while the F-15s are moved from Otis Air National Guard Base on Cape Cod to a base in Western Massachusetts. The transition could take longer than a year. The Air Guard's mission is expected to have little impact on Burlington International Airport, said Brian Searles, airport director.

--AP

sprocky wrote:Just for my understanding (english is not my first language): Does your post mean it could be something similiar that happened to the civil a/c de Havilland Comet decades ago?

From the AF Daily report 3 Dec 07

Focusing on the C Model?: A senior officer at Warner Robins Air Logistics Center in Georgia has told Gene Rector of The Telegraph that the center's analysis of the F-15 that crashed Nov. 2 and at least two other C models shows a "manufacturing discontinuity" in the longeron, a metal rail that connects the fuselage. This was the finding that caused Air Combat Command to ground the fleet a second time. Technicians and engineers at the ALC have been working to provide an inspection procedure that units in the field can use to search for telltale cracking. Col Stephen Niemantsverdriet, 880th Aircraft Sustainment Group commander, said last week that the ALC team was about 80 percent of the way through the procedural instructions, using "proof of concept" inspections on F-15s at the depot. They expect field units to use a dye penetrant technique to find cracks, if any. He told the newspaper, "If the longeron is cracked, we will ground the aircraft."

GZR_Sactargets wrote:Air Guard To Secure, Monitor Northeast


SOUTH BURLINGTON, Vt.-The Vermont Air National Guard will provide security and emergency response in the Northeast as a result of the Air Force's decision to ground all of its F-15 fighter jets. The F-15s will be inspected following an investigation into a Missouri Air National Guard plane crash Nov. 2 that found defects in the aircraft's fuselage. The Vermont Air Guard, which flies F-16s, will continue the mission after the inspections while the F-15s are moved from Otis Air National Guard Base on Cape Cod to a base in Western Massachusetts. The transition could take longer than a year. The Air Guard's mission is expected to have little impact on Burlington International Airport, said Brian Searles, airport director.

--AP

Marv,

At least they picked a good Wing to cover security and emergency response in the Northeast while the F-15C's are grounded and the MA ANG are transitioning from Otis to Barnes.

To me it seems like deja vu all over again as back in the day we had 2 Deuces on 5 minute alert, 1 on 15 minute and 1 on 30 minute 24/7 and intercepts like the one depicted in the screenshot below happened occasionally.

Mike

It will be interesting to see what's going on the next time I fly into KBTV. Mike you think they will fly regular CAP missions or just sort of on an add hoc basis? Putin is probably loving all this.

MIKE JG wrote:It will be interesting to see what's going on the next time I fly into KBTV. Mike you think they will fly regular CAP missions or just sort of on an add hoc basis? Putin is probably loving all this.

Mike,

The articles in the local papers have not been very specific or detailed on what providing security and emergency response in the Northeast actually entails other than having some number of aircraft on alert 24/7. Since the KBTV tower now closes during the late night and early morning hours, there has been been some talk of the need to expand ATC coverage back to 24/7, but with the current ATC staffing levels that may be difficult to impossible to achieve.

Right after 9-11 the VT ANG participated in Operation Noble Eagle which did include CAP missions, but so far I haven't been able to find out if this responsibiliy for providing security and emergency response in the Northeast will require them. My best guess is that they will have at least a couple of F-16C's, aircrews and ground crews standing alert 24/7 in one of the flightline hangers.

Mike

http://www.sj-r.com/News/stories/21414.asp Tis is a more expanded report-they are going to NAS New Orleans

More Vipers Fly for Eagles: With USAF's F-15 fleet of A-D models grounded indefinitely, Air National Guard units that fly F-16 Vipers have been subbing around the country for Air Guard units that fly F-15s on Operation Noble Eagle air sovereignty missions. The Missouri ANG's 183rd Fighter Wing has sent some 50 airmen to New Orleans to cover missions normally flown by the Louisiana ANG's 159th FW, reports the Journal-Register. Before the Missouri team arrived, the Alabama ANG's 187th FW had flown the ONE missions

http://206.204.189.217/AFA/Features/org ... 7worse.htm

Eight and Counting: The Air Force has now found eight F-15s with cracks in their upper longerons, the problem identified as the likely cause of the Nov. 2 crash of a Missouri Air National Guard F-15C on Nov. 2. The Air National Guard, which flies some of the oldest F-15s, has five of the eight-four at Oregon's 173rd Fighter Wing and the fighter from Missouri's 131st FW. Three belong to active-duty units-two with the 18th Wing at Kadena AB, Japan and one at the 325th FW at Tyndall AFB, Fla. Unit maintainers are continuing to inspect each of the F-15 A-D models, even as the Warner Robins Air Logistics Center in Georgia is working out new procedures to narrow the focus of future inspections.

More to Worry About: The continued grounding (see above) of the F-15 A-D fleet is a nightmare come true. Air Force officials now believe that years of patches made to the aircraft, coupled with flying high-stress missions far longer than anticipated, has caused the current problem. And, even if the Eagles fly again by mid-January, it will take the Air Force more than six months to get its F-15 pilots re-qualified. Read more in "It Just Got Worse."

From AF Daily Report 11 Dec 07

Some Return to Flight: Air Combat Command at Langley AFB, Va., yesterday cleared a portion of the Air Force's F-15 A-D model fighters to flying status after more than two months of stand down resulting from the Nov. 2 mid-air breakup of an Air National Guard F-15C. It also recommended a limited return to flight for Air Force F-15s worldwide following engineering risk assessments and data received from multiple fleet-wide inspections. "The priority in resuming operations for a portion of the F-15 fleet is the defense of our nation-America deserves nothing less," Gen. John Corley, ACC commander, states in the command's Jan. 9 release. "Aircraft inspection results and counsel from both military and industry experts have made me confident in the safety of a portion of the fleet. As a result, I have cleared those F-15s to return to fly." The decisions apply only to about 60 percent of the Air Force's approximately 440 F-15 A-D models "that have cleared all inspections and have met longeron manufacturing specifications," ACC says. The longerons are structural support beams around the cockpit. The Air Force believes that catastrophic failure of a longeron caused the Missouri ANG F-15C to break apart during a routine training sortie over eastern Missouri. Corley plans to hold a press conference today in the Pentagon, accompanied by the head of the accident investigation and maintenance, logistics, and operations deputies, to discuss the F-15 situation and what will become of the Eagles still grounded. The Daily Report learned yesterday that senior Air Force leaders believe that 159 F-15s may never fly again. (Read "Should Eagles Dare?")

Should Eagles Dare article is at:
http://206.204.189.217/AFA/Features/mod ... eagles.htm

From AF Daily Report 10 Jan 08

GZR_Sactargets wrote:senior Air Force leaders believe that 159 F-15s may never fly again.

Guess we'll need some more F-22 now, secretly I think that's what the AF brass really wants.

I would agree they want NEWER airplanes in the inventory. But I am sure there is nothing staged in the F-15 crash and subsequent inspections and grounding. They are OLD airplanes.

And some new aircraft they should have. You shouldn't have to beg congress to allow the military to acquire new technology that will ultimately improve the success rate of those using it. Trying to get by the on cheap will only lead to more loss of life that could/should have been prevented.

The Pavehawk, Sea Dragon, Stratotanker, Sea King, etc... are at the end of their life cycles but little to no progress is being made in fielding replacements.

Computer animation of the St. Louis F-15C crash:

http://www.acc.af.mil/shared/media/docu ... 10-018.wmv

HUD display(sort of):

http://www.acc.af.mil/shared/media/docu ... 10-028.wmv

SMOC wrote:Computer animation of the St. Louis F-15C crash:

http://www.acc.af.mil/shared/media/docu ... 10-018.wmv

HUD display(sort of):

http://www.acc.af.mil/shared/media/docu ... 10-028.wmv

Great Stuff! Thanks for sharing!

Very interesting, especially since it finally failed as he was rolling level. Thankfully we can talk about only the airplane being hurt, not its driver. Although sounds like he got some serious lashing from the airstream.

It is kind of odd that it snapped at almost the completion of his turn. Report says it began shaking violently side to side around 450 knots and just under 7.9G which was prior to rolling wing level. In the audio you can hear "Mick 2 , knock if off", this occurs after the plan begin to shake but prior to snapping.

Who knows if the pilot will fly for the ANG again... sounds like his shoulder was pretty much shattered. But stranger things have happened: http://www.af.mil/news/airman/0497/eject.htm

Well that unit is integrating into the new combined ANG/Active Duty B-2 squadron over at Whiteman, so maybe he will.

"This is Huge": About 40 percent of the Air Force's F-15A-D aircraft-182 aircraft-are grounded indefinitely until they can be invasively tested for cracks in the coming months, Air Combat Command chief Gen. John D.W. Corley said yesterday at a Pentagon press conference in which he formally announced the results of an accident board into the Nov. 2, 2007 crash of a 28-year-old F-15C. Corley had cleared 259 Eagles to fly on Wednesday, but said that the absence of 40 percent of the fleet will be a serious operational problem for some time to come. "This a big deal," Corley said. "This is huge." Corley said having such a large percentage of the fleet down "does not allow air sovereignty alert" F-15 operations over the US and means F-16s and F-15Es that have been filling in for the grounded Eagles will continue to be "pulled" from planned deployments to Iraq and Afghanistan. There is no estimate of how long it will take to inspect the grounded aircraft, even though the specific fault being sought is now known. In the meantime, training operations will be truncated, classes of new F-15 pilots will be drawn out or delayed, and the Air Force will have to make some hard choices about whether it's worth the money to fix some of the aircraft, which already average over 25 years of age.

-John A. Tirpak

Cracks: The culprit in the Nov. 2 F-15 crash was a crack in a longeron behind and to the right of the pilot. The longeron was supposed to have a design life of 31,000 hours, which is longer than the anticipated life of the airplane. The part was improperly made, having a thickness in some areas that was too thin by several thousandths of an inch, and years of fatigue stress have caused it to crack. Cracks similar to that on the mishap aircraft have been found on nine other F-15s, but there is no rhyme or reason to them-they did not come from a particular lot, batch of materials, and affect aircraft made from 1978 to 1985. Accident Investigation Board director Col. William Wignall said the pattern is "random." That, however, poses a dark question-what other bad parts might be lurking in the fleet? The Air Force expected to begin retiring some F-15s in the mid-1990s. Air Combat Command chief Gen. John Corley, observing the fact that his Eagles are long past retirement age, said, "100 percent of my fleet is fatigued." (AIB executive board summary; see The Document File for multiple-volume AIB report)

Lucky to be Alive: The pilot of the F-15 that crashed is "lucky to be alive," Air Combat Command boss Gen. John Corley reported. The pilot, in the second round of air combat maneuvers during the mission, was in a turn, pulling between seven and eight Gs. He realized something was wrong and relaxed back pressure, but the airplane was already coming apart, and seconds later, the nose separated from the aircraft, ultimately coming to rest about a half mile from the rest of the airplane. The canopy was ripped off the separated nose and struck the pilot's left shoulder, causing serious injury. Able to use only his right hand, he ejected from the tumbling nosecone in an inverted attitude. Upon reaching the ground, he elected to remain still until civilian rescuers reached him. The pilot performed well under the circumstances and was in no way responsible for the accident, Corley said.

Who's to Blame?: Add "vanishing paperwork" to "vanishing vendors" as another byproduct of the Air Force's operating an unprecedented old fleet. An improperly made part was to blame for the Nov. 2 crash of an F-15. But who made it? The aircraft was built in 1980 by McDonnell Douglas, and the company was to maintain the Air Force acceptance form, DD250, which it put on microfiche. Then Boeing acquired McDonnell Douglas, and there was the Paperwork Reduction Act, leading to missing papers that are making it hard to trace the provenance of the longeron in question. Gen. John Corley, head of Air Combat Command, told reporters yesterday that it's "premature" to think about liability, especially when the culprit part had been subjected to years more hard stress than it was ever expected to bear. He also thanked Boeing for being forthcoming in helping with the investigation and noted that the company itself discovered the flaw that caused the accident.

23 Page Incident Report in PDF Format:
http://206.204.189.217/NR/rdonlyres/4B3 ... xecSum.pdf

From Air Force Daily Report- 11 Jan 08