Posted: 1/14/2008 5:33:53 AM EDT
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From today's Boeing News: Manufacturing Defect At Root Of F-15 Grounding Aviation Week & Space Technology 01/14/2008 Author: Amy Butler One hundred eighty-two of the U.S. Air Force’s F-15A-Ds remain grounded because of unreliable primary structures that service officials recently discovered were poorly manufactured in the 1970s. The upper right-side longeron supporting the cockpit of a Missouri Air National Guard F-15C failed Nov. 2, causing the fighter to break in half behind the cockpit during a typical combat maneuver in training. The pilot ejected from the cockpit when it was inverted, and he survived with injuries. Manufacturing errors that went unnoticed until now set the stage for this crash, and have manifested into major fractures in at least nine other F-15C models and produced defects in F-15A/B/D aircraft. The F-15 was originally manufactured by McDonnell Douglas, which was acquired by Boeing in 1997. McDonnell Douglas built the problematic longerons, and Air Force lawyers are now exploring whether Boeing will be held responsible. The process will be long, however, as records documenting the condition of the F-15s at the time of transfer to the Air Force appear to be lost but, according to the service, could have been destroyed years ago by the contractor. This is apparently a by-product of shifting some records to microfiche and of document transfers during the merger. Air Force officials say it’s typical for those records to be managed by the contractor, not the service. The dramatic structural failure prompted Air Combat Command chief, Gen. John Corley, to ground the F-15 fleet almost immediately. The later models, F-15E Strike Eagles optimized for ground attack, were returned to flight. They contain a different longeron—which is the primary structure holding together an aircraft fuselage—than those used for the A-D models. In the course of the accident investigation, Air Force officials discovered the failed longeron was never manufactured to design specifications. The portion that broke is an area where it angles to connect the forward and aft sections of the aircraft near the rear of the cockpit canopy. Nine other F-15Cs have been found to contain similar fractures in their longeron structures. The Air Force has inspected 90% of its F-15A-D fleet, and checks are ongoing on the remaining aircraft. Of those inspected, 182 show manufacturing defects. They include the longeron structure’s being too thin, containing ridges that will not carry stresses properly, or roughness on the surface, which makes the longeron more prone to cracking. The Air Force has not decided whether to repair these aircraft or retire them ahead of schedule. Maj. Gen. Thomas Owen, commander of the Warner Robins Air Logistics Center, Ga., which oversees F-15 maintenance, says new longerons cost about $10,000 per unit. However, each one will require about $250,000 to install, a large bill for the already cash-strapped Air Force. This also calls into question an earlier plan to upgrade 177 of the most pristine “Golden Eagles” and keep them in service up to two decades beyond current projections. “All options are on the table” to handle the gap. Yet, the Air Force is clearly leaning in the direction of buying more stealthy Lockheed Martin F-22s; 183 are expected, though the service says it required 381 Raptors prior to this recent F-15 problem. Uniformed Air Force officials are pushing hard to convince senior Pentagon civilians to extend the F-22 buy until the F-35 Joint Strike Fighter—an A-10 and F-16 replacement—is in full production. Boeing is building F-15s for allies and could sell them to USAF. In 2006, Boeing offered to sell 150 F-15E variants with new active, electronically scanned array radars to the Air Force for $60 million apiece. They would be optimized for ground attack, although they could support the air sovereignty mission in the U.S. Corley says his ability to ensure air sovereignty in the U.S. has been limited; F-15s are a primary component of the North American Aerospace Defense Command’s interceptor fleet. F-22s and F-16s are supporting Norad’s mission, but the F-15 grounding has interrupted the pipeline for pilot training in all three fleets. Last fall, the Navy moved the USS Enterprise from the Persian Gulf to the northern Arabian Sea to pick up the slack left by grounded F-15s in air support to forces in Afghanistan. |
I think it makes sence. If the 'non-defective' parts are flying without the cracks, and the only ones that are having problems are the ones with the 'defects', then I think they're right. -K |
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Love this gem "Uniformed Air Force officials are pushing hard to convince senior Pentagon civilians to extend the F-22 buy until the F-35 Joint Strike Fighter—an A-10 and F-16 replacement—is in full production.". I'd love to see the F-35 try CAS like an A-10. Hell by the time the F-35 reaches full production, it will cost just as much if not more than a F-22. |
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eodtech2000: remember no one said democracy was cheap. ----------------------------------------------------------------------- Every new generation of fighter planes has its controversy. Remember these are the people who said that we need to cut back our defense establishment to give more money to the poor. Probably 40 years ago, that no one noticed that we had a problem, and whether it was a problem back then we will never know. All of the engineers are gone(either laid off or retired). We should bite the bullet and give them their number of planes the USAF wants |
Bullshit. We don't know exactly what happened. The odds are low that these non-conformances did not recieve scrutiny by liaison engineers at minimum, and at least in the beginning, the strength staff. It's also unlikely the quality system broke down that far and bought nonconforming parts that were never squawked. Possible, but extraordinarily unlikely, particularly at that date. |
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Saw some animation reconstruction of what the inflight breakup was supposed to look like..Is this accurate? I didn't know it was that bad. www.youtube.com/watch?v=2R7BWrqmgac |
Aero is right, they did last almost 40 years of service. When we wanted to make a new docking modual recently, you know what NASA did? They went to the museum and cut apart the old one, to see inside, to see what made it tick. Most of the engineers aren't just retired... they are dead.  That's right, much of the old "know how" is dead, all we have left are massive stacks of drawings (in microfilm) which aren't sorted. And some of it has been destroyed. We will be stuck with having to reinvent some stuff if we don't fix the knowledge gap. look what happened to the A10!!! The wing spars all had to be replaced! Actually, the wing spars were replaced years ago and are still being replaced. Bring Back the Tomcat! 
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That looks about right. I figured it was in a high G manuver, but it looks like it whiplashed a few times and broke up in level flight.  I had read the cocpit broke off from the airplane. How did we discover the defect wing spars in the A10? inspection? The F15 is still bad ass. I Vote for a modernized (using the same design) steath A10 Made out of kevlar and carbod fiber goodness. A-10 Stealth! 
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So do AIM-120 Amraams which are the longest range AAM we have now, as is only a medium range AAM on top of that. |
In this particular case there are dozens of engineers that worked those problems still working, even if they should have retired. That doesn't mean they remember particular details about one of thousands of part numbers they've dispositioned. The A-10 has a "thin wing" and a "thick wing" version. A new wing is being designed just upstairs, but it's mostly an effort to not do anything dumb and fix only the old problems. Most of the old problems look like they were in the thin wings. |
lol, the Tomcat was the worst I've heard with regards to maintainance issues... |
"The weapon system consists of an AIM-54 guided missile, interface system, and a launch aircraft with an AN/AWG-9 weapon control system." Looks like it just came down to the Tomcat being the only bird with the needed radar. |
Yeah, but that's 1980 dollars vs. 2006 dollars. |
IIRC, they are developing an AIM-120D that, when combined with F-22's supercruise could provide a range somewhat close to the old Phoenix. It should also be noted that the AIM-54 was designed to target bombers, it was not as well suited against smaller and more nimble fighter planes. |
Not bullshit, if this statement is true: "In the course of the accident investigation, Air Force officials discovered the failed longeron was never manufactured to design specifications." Granted, it may have indeed been caught by engineering and/or quality and the subsequent paperwork lost granting the part in question to continue to be used, but given the numbers of aircraft that have these bad parts, it sounds like it was not caught. |
That animation was made by the AF and is accurate. Link to the higher quality version of the video on the AF website Link the the Accident Investigation Board Report |