F-15s Grounded

updated 41 minutes ago
Flaw may permanently ground 160 jets, Air Force general says
STORY HIGHLIGHTS
NEW: General: Manufacturing flaw may lead to suspension of quarter of
fleet
F-15C Eagle broke apart in mid-air in November; the pilot survived
Report: Defective metal beam in the airframe disintegrated during
flight
Some aircraft remain grounded as the Air Force continues to
investigate
Next Article in U.S. =BB
WASHINGTON (CNN) -- A manufacturing defect blamed for the mid-air
breakup of an F-15 Eagle fighter may cause the Air Force to ground a
quarter of its fleet of those warplanes permanently, a top general
said Thursday.
The mid-air breakup of an F-15 fighter jet is being blamed on a a
manufacturing defect.
Gen. John Corley, the head of the U.S. Air Combat Command, said about
160 of the jets may never return to service after an investigation
into the November 2 crash that left the plane's pilot seriously
injured.
The single-seat F-15C broke up in a 500-mph turn during a combat
training mission over Missouri, with its fuselage breaking in half
behind the cockpit, an Air Force probe of the crash determined.
Investigators concluded that a critical piece of the jet's airframe
broke during the flight because of a manufacturing defect. A defective
longeron -- a metal strut that runs lengthwise down the fuselage --
was cut improperly by the manufacturer, Boeing, and led to a series of
cracks over the plane's lifespan, Corley said. Watch a report on the
plane and its problems =BB
"Some of these airplanes will never return to flight," Corley said.
"The age, the fatigue on these airplanes has been manifest as we
looked under the hood extensively over these last two months."
The Air Force has been flying the twin-engine, supersonic F-15 since
the early 1970s. The C model involved in November's crash is credited
with 34 of the 37 "kills" credited to Air Force pilots in the 1991
Persian Gulf war, according to Thursday's report on the accident.
Don't Miss
Air Force again grounds most of F-15 fleet
The service has about 700 F-15s in its fleet, all of which were
grounded after the November crash. Most were returned to service after
being checked out, but about 40 percent of the Air Force's 442 F-15
models A through D remain grounded.
"I flew these airplanes 30 years ago," Corley told CNN "This is a
fleet of airplanes that's 25-plus years old on average. That constant
pulling and pushing and twisting has also caused fatigue."
If the grounded planes are retired, the Air Force would still have
about 240 of the older fighters and nearly 300 of the newer F-15E, a
two-seat version used for ground-attack missions in Afghanistan and
Iraq.
Investigators released the results of the Missouri crash at a news
conference Thursday in the St. Louis suburb of Bridgeton, home of the
Air National Guard wing involved in the accident. The pilot, 37-year-
old Maj. Stephen Stillwell, told reporters that his plane broke up in
a turn that produced about eight times the force of gravity.
"I had no idea what was happening," he said. "I knew something bad was
happening, but I didn't know what it was."
Stillwell suffered a broken arm and still has problems with his
shoulder. He credited his survival to the training he received. "You
always prepare for the worst-case scenario," he said.
"I think luck played a small part in it, but a large part of it was
due to the training I received and my faith in God," said Stillwell,
who is also a pilot for Northwest Airlines.
Col. Bob Leeker, the wing's commander, said the first four of his
F-15s took off Thursday after receiving clearance. Six other planes in
the 131st Fighter Wing have not been released, but three are expected
to be once additional examinations are completed, he said.
The F-15 was first built by McDonnell-Douglas, and it's now
manufactured by Boeing. The service is trying to determine whether
Boeing would be liable for the defect after 30 years.
The A through D models are used in the United States for air-defense
missions. After the initial grounding, the service had to move F-16s
to cover for F-15 missions, and Canadians had to help cover missions
over Alaska, according to Air Force officials.
The defect was discovered as the Air Force continues to fight for more
advanced F-22 Raptors, seen as the future of the service's fighter
fleet. Congress allowed the purchase of only 183 of the almost 400 the
Air Force wanted, but the service continues to ask for another 200.
Corley said suggestions that the service is trying to use the problems
with the F-15 as leverage to get more of the Lockheed-built F-22s
"makes me just outraged, because it's just flat wrong."
"I'm the one who looks into the eyes of the moms and dads, the sons
and daughters, the husbands and wives that I put in that airplane," he
said. "To think that I would put one of those individuals at risk, to
almost kill one aviator and to risk other aviators, that is beyond my
possible belief."
Reply to
crw59
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I never thought I would say this. But I was at an airshow here in Ft. Worth, TX a few months back. There were quite a few F-15C's parked for display. It amazed me how ' old ' they looked when you got up close. Kinda hard to explain ... but the birds looked kinda like an old house with too many coats of paint and worn out weather stripping might look. I guess 20-25 years of banking and yanking takes it toll.
I remember at an air show back in 1979 when an F-15 put on a solo show and knocked our socks off ! It was the ' El Supremo ' of fighter jets. Always has been.
Chris
Reply to
CCBlack
The incident over MO was a couple months ago, maybe a bit longer ago...the grounding followed shortly after. Haven't heard much else.
Reply to
Rufus
Here's the latest:
AIR FORCE Magazine Online Journal of the Air Force Association
Daily Report Friday January 11, 2008
"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.
Reply to
Curt
But highly convenient in timing. ;-) Ever hear about this?:
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you have to measure airframe fatigue in the older-build F-15s and the danger that poses to their pilots...against unexpected bugs in the new F-22, and the danger they could pose to their pilots. What I'd do is permanently ground (or at least placard them with G-limits as far as maneuvers go and relegate them to basic aircraft familiarization training with no severe aerobatics allowed) the old F-15s, but wait till we have a few years of operations with the F-22 under our belt before buying more as replacements for the grounded F-15s. By waiting a few years to see how the F-22 works, any needed modifications can be built right into the aircraft on the "Batch 2" production line, rather than having to be retroactively fitted to already built aircraft. We'd better hope that nobody comes up with a way around the F-22's stealth in the near future, because without it, it's not that much better than a late production standard F-15 with all the current updates,while being a hell of a lot more expensive.
Pat
Reply to
Pat Flannery
Well, they never had a problem with the wings breaking off the Tomcat. Better pull some of them off death row so the AF will have something to fly.
WmB
Reply to
WmB
Bottom line is that the aircraft was DD-250'd and accepted within the constraints of contract - any discussions of "blame" are irrelevant.
Process will be to determine the cause of the failure and access impact on the Fleet, if any.
Reply to
Rufus
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Heh...you'd think it would be that simple, wouldn't ya? Well, it ain't...
Reply to
Rufus
I don't think there were that many of them to begin with (by WWII standards...), and chopping something up is a LOT easier to do than putting it together.
Given how long it's taken the story of the F-15 breakup to reach the public, and the political urgency of containing black market Tomcat parts I'd think de-milling F-14s would have been given a pretty high priority after Fleet stand-down.
Someone once posted a link to Davis-Monthan's aircraft inventory, but I didn't keep it and I can't seem to find it using a quick Google...
BTW - this is interesting:
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Reply to
Rufus
I was at DM two weeks ago and there are still (D model I believe) Tomcats still in mothballs just sitting. You can see them thru the fence as you drive around the boneyard.
Mark
Reply to
Mark M
That what I've been wondering now...someone posted a link to DM's inventory once, and I didn't save it - should have, would make a nice reference. Can't find it now...as I recall you could browse the inventory by BuNO.
Reply to
Rufus
Yea, I was surprised to see them as I too thought they all had gone to the shredder as well.
Mark
Reply to
Mark M
And as far as "years more hard stress than it was expected to bear", one might want to have a peek at this McDonnell-Douglas 1994 airframe hours chart which shows the F-15A's good until 2013 even in the most conservative 8,000 hour estimate of airframe life:
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Pat
Reply to
Pat Flannery
It will be interesting to see just how long the Raptors stay in service before being replaced with something unmanned in the fighter role. The handwriting has been on that particular wall for some time now.
Pat
Reply to
Pat Flannery
How many F-15s do we have at AMARC that were stored after the end of the cold war? At one point we had around 100.
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were retired after around 15 years of service, so would have lower flight hours than many still in service nowadays.
Pat
Reply to
Pat Flannery
I'm kind of expecting that there was/is some root causality to be discovered in the incident that triggered the grounding, and that it just happened to be an "old" aircraft.
Reply to
Rufus
Not really replaced, but in conjunction with, yeah. And that's going on right now in growing numbers.
I expect F-22 will be in service a long time, and that it will take even longer to develop the next successor than it did to develop and deploy the Raptor.
Reply to
Rufus

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