Boeing F-47 NGAD - Speculation and Theories

[F119Doctor]

The max demonstrated Mn of the YF-23 was published. The supercruise speed with the YF120 was not, although Wikipedia cites M1.72.

I do remember that the YF-23 was experiencing some canopy cracking. That may have been the limiting factor in their demonstrated max Mach. We don’t know, but there could also have been an inlet flow stability problem above M1.8, the inlets were redesigned for the F-23 EMD proposal.

 

[Hydroman]

The max demonstrated Mn of the YF-23 was published. The supercruise speed with the YF120 was not, although Wikipedia cites M1.72.

I do remember that the YF-23 was experiencing some canopy cracking. That may have been the limiting factor in their demonstrated max Mach. We don’t know, but there could also have been an inlet flow stability problem above M1.8, the inlets were redesigned for the F-23 EMD proposal.

The M1.8 number is a little deceiving, I'm pretty sure the through the grapevine max supercruise with the Y120 was around 1.8. The YF-23 would do Mach 2.0 but we (Northrop) wanted focus on other things apparently. We did do a lot of weapons bay vibroacoustics flight testing with the bay operating at various mach number and maneuvering conditions since the bay was pretty large in regards to volume. And we did have the canopy cracking issue but that got resolved. The refined production F-23 with the right engine and the new inlet design wold more than likely exceed M1.8 in supercruise.

 

[Elysium]

My understanding is neither the F-22 or YF-23 (or any 5th gen) does well on top speed. This is due to the skin being made of composite materials, which while possessing other advantages, isn't particularly resistant to heating. I guess that's another reason why they have fixed inlets.

 

[EmoBirb]

This is due to the skin being made of composite materials, which while possessing other advantages, isn't particularly resistant to heating.

"Composites" is a very broad term, there are many exceptional heat resistant composite materials, many of which seeing applications in the aerospace industry.

On average though stealth aircraft tend to be rather chunky and prioritize different attributes over outright maximum speed.

 

[NMaude]

prioritize different attributes over outright maximum speed.

Not to mention that M2+ speed causes a dramatic increase in an aircraft's IR-signature due to aerodynamic heating of its' airframe.