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xrearl

F-4 Mach 3 Fighter/ Spy plane (link)

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JediMaster    449

I remember reading that in one of my books about the F-4. As it never got very far it's not widely known, but it's an interesting "what if" up there with the F-108, TSR2, and YF-12.

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Stratos    752

I just printed it and will add to my Phantom reference book, such development planes are always cool.

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Toryu    149

You can't build a Mach 3 capable airframe by just bolting on water-tankss, tweaking the inlet-system and modifying the flight-controls of a Mach 2 airframe.

 

The most critical problem north of Mach 2 is shock-heating. You can go Mach 2.5 for a very short time in an aluminium-airframe (as actually demonstrated by F-4s during Project Skyburner), but that's about it. Aluminium will weaken a lot above 120°C, which is about the leading-edge temperature at Mach 2*.

 

If you want to go faster (even just on a dash), you'll need different materials: stainless steel (heavy) or titanium (a dog to work with - especially machining - thus gold-dust expensive).

The US had their strategic bird at this time (SR-71), and giving funds to Israel for tweaking a Mach 2 bird into a low-volume Mach 3 retrofit-program wasn't a politically and fiscally sane idea.

 

___

* Depends on a couple of factors, but generally Mach 2 is an upper-bound for aluminium-airframes for this very reason

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Fubar512    1,317

You can't build a Mach 3 capable airframe by just bolting on water-tankss, tweaking the inlet-system and modifying the flight-controls of a Mach 2 airframe.

 

The most critical problem north of Mach 2 is shock-heating. You can go Mach 2.5 for a very short time in an aluminium-airframe (as actually demonstrated by F-4s during Project Skyburner), but that's about it. Aluminium will weaken a lot above 120°C, which is about the leading-edge temperature at Mach 2*.

 

 

 

The F-104's Vmax was also limited due to thermal issues, it could attain a Mach number high enough to melt its windscreen (which if I recall correctly, occurred between Mach 2.25 and 2.5). I am sure a similar issue existed with the F-4.

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Toryu    149

There was a flight by an operational F-104C, using tweaked inlet-cones (similar to those on the NF-104) and the larger tail of the twin-seaters/ G-model.

They went out to about Mach 2.5 with acceleration still ongoing, when the pilot (Tom Delashaw) RTBed.

http://www.i-f-s.nl/f-104-records/

There used to be a pilot's account of Delashaw, but I can't find it now.

 

The F-104G has three limits concerning speed:

M 2.0 (mainly a stability limit)

750 KIAS (q-limit)

121°C Compressor Inlet Temperature

 

The windscreen-thing was probably an issue on all fightes back then. Luckily, the fuel wouldn't last too long anyway.

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