F-89 & Swept Wings

The starting point of the N-24/XP-89 was a semi-tailless flying-wing similar in layout to the XP-79Z (which was a penetration fighter study with a single J34 under the fuselage with either a prone-pilot or a normally seated configuration) with the exception of it having three engines and two crew-members (normally seated one behind the other).

According to the book "Flying Wings and Radical Things: Northrop's Secret Aerospace Projects & Concepts 1939-1994", by Tony Chong, it states the following on page 43

Work began on the design and almost immediately configuration problems surfaced, especially concerning the swept-wing layout. After a harsh September 1946 mockup inspection review by AMC, the company instituted several design changes, including the substitution of a very thin, straight wing made of aluminum rather than the originally proposed magnesium.

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I'm not sure what exact problems existed with the swept-wings (though I can think of a few possibilities), I'm curious why they didn't just modify the swept-wings, rather than go with a straight-wing. Would the harshness of the review play a role?

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Nobody have anything?

I don't have Mr Chong's book Zipper - so I'm not familiar with what this N-24 looked like but I did a bit of searching on that Secret Projects site (where obviously no one can keep a secret) and I think I found it. Is this it? Looks extremely fat and ugly. These AMC reviewers - maybe it wasn't just the wings that upset them....?

Graeme said:

I don't have Mr Chong's book Zipper - so I'm not familiar with what this N-24 looked like but I did a bit of searching on that Secret Projects site (where obviously no one can keep a secret)

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so true...

Looks extremely fat and ugly. These AMC reviewers - maybe it wasn't just the wings that upset them....?

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I figured the problem had to do with technical matters. Off the bat, I could think of...

• Stability: Many tail-less aircraft (excepting deltas) had all their mass bunched up in the middle to allow sufficient pitch control, and it sometimes made aircraft either very twitchy or inadequately controllable (I've never heard of the latter popping up)
• Aeroelasticity: Since swept-wings flex-more in flight, you end up with potential problems with control-surface reversal (in this case affecting pitch/roll control simultaneously)