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F-15QA may give USAF upgrade path for F-15C

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posted on Feb, 26 2018 @ 01:12 PM
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a reply to: Blackfinger

I remember reading some cutaway book as a kid that went into some pretty deep detail on the construction of an F-15, stating that there was a ton of CNC'd billet involved and some pretty huge billet forgings were needed to be eventually cut down into the final fuselage structures, and that exponential increase in manufacturing costs was a big part of why there was such a cost jump from the 3rd gen fighters to the 4th gen ones.

Makes sense, as the high speed programs of the early 60s like the SR-71 and the XB-70 pioneered a bunch of innovation in terms of exotic high-strength structures and such, and while the 3rd gens were already on assembly lines by the time the technologies matured, when the WVR maneuverability requirements of the 4th gens dictated building aircraft larger than F-4s and F-105s that could pull the sorts of G loads more fitting for an Extra 300, I'm sure it was nice that the big contractors had all this new know-how when it came to building incredibly light, incredibly strong (and incredibly expensive) structural components.

It's also why you could make a pretty compelling argument that 3rd to 4th was the last truly great leap in jet fighter design, and that 5th and 6th generation fighters, in that context, are little more than 4th gen birds with fancy body kits and glass cockpit upgrades.
edit on 26-2-2018 by Barnalby because: (no reason given)




posted on Feb, 26 2018 @ 03:56 PM
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Going from pressed sheetmetal light aluminium frames in the 40,s to machined frames in the 60,s plus I think its down to power and weight.It was probably a lot quicker to CNC machine a solid bulkhead than assemble a multipart sheetmetal bulkhead of the same strength.With CNC the accuracy is a lot better especially with jigging and sub part assembly.



posted on Feb, 26 2018 @ 05:21 PM
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a reply to: Blackfinger
Hard to say whether its quicker or not but its certainly stronger with less stress raisers or failure points than a frame made up of riveted sections. Therefore a lot easier to predict how it will perform. Sometimes fasteners dont do as advertised. I have a nice little pic or two I took the other day of a lower wing fence that illustrates perfectly that sometimes the structure fails before the fasteners, when as you know its meant to be the other way around.



posted on Feb, 27 2018 @ 03:21 AM
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Ahhh the black ring of chafe



posted on Feb, 27 2018 @ 03:57 AM
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a reply to: Blackfinger
No this wasn't the classic smoky rivets. It was due to impact with another eerrmm... wing tip. Specifically 744 meets A380 on the south runbay to be precise.



posted on Feb, 27 2018 @ 04:29 AM
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Bugger.Hope they swapped insurance



posted on Feb, 27 2018 @ 05:33 AM
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originally posted by: Blackfinger



It's mostly stainless steel construction, isn't it?

Titanium wing spars and probably fuselage centre section..Rest is most likely cast /forged or CNC milled aluminium bulkheads with extrusion stringers.Skin panels are Honeycoam/aluminium sandwich like most gen 4 aircraft.
F15 factory shots

Okay, thanks. Are they cheap to build now that we've done it for forty years or so, or still pretty pricey?


originally posted by: Zaphod58
a reply to: face23785

Personally, I'd rather they had been replaced, even with new F-15 airframes before now, but hey that's just me. It's a good airframe, and if they're going to activate the quad racks, which it looks like they are, it's a great missile truck to keep around.

Okay, I missed this post earlier. I thought you might agree. I was thinking the same. We can build these new fairly affordably too, can't we? By which I mean to say $40 million vs $250 million or whatever for something else?
edit on 27-2-2018 by TheBadCabbie because: (no reason given)



posted on Mar, 4 2018 @ 08:42 PM
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It was actually the forward fuselage and mid fuselage splice areply to: Zaphod58




posted on Mar, 4 2018 @ 09:30 PM
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a reply to: airyspace2015

The longerons for that section failed on the MA, and were found to be cut below requirements on many other aircraft.



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