Old designs with modern engines

[Old Wombat]

Turbo-prop Beaufighter! 

[Mossie]

The Sikorsky S-55 and S-58 were both converted to turbine power by Westland (and the S-58T by Sikorsky. But the US Military never used any turboshaft variants. Real world upgrades with whiff potential. I vaguely remember Martin may have done a US S-58T?

[Diamondback]

The thrust difference isn't that extreme, assuming the Speys aren't afterburning. The Avon 208s in the Sea Vixen put out 11,000lb each, while a dry Spey was good for 11,030 to 11,995lb depending on the version. THe main advantage would be massively lower fuel consumption: 0.932 lb/(lbf⋅h) for the Avon and 0.63 lb/(lbf.h) for the Spey.

It's not thrust, it's a technological mis-match. The Sea Vixen was behind the times when it entered service and lasted a relatively long time for that era, adding new engines might have prolonged it way beyond its sell by date.

Yep: from what I can see there was no plan to update the radar, and that would have been stone-aged by the time a Spey Vixen got into service.

Same thing that ultimately obsoleted the F-106, being designed around and limited to the garbage Hughes Falcon missile. IMO they could have gotten more mileage out of it if they'd converted the weapons bay into a fuel tank and gone to an F-15-style set up with two rails and a hardpoint on each wing station. Other things had room for improvement but that was the Achilles heel.

[Scotaidh]

Turbo-prop Beaufighter! 

A "TurBeau"!

[Scotaidh]

I've always wanted to do a turboprop Whirlwind.  The problem, for me, was/is finding a donor kit with engines that visually appeal to me ... I think I finally decided on the Pucara, since the engines are (to me) weird-looking and I've no interest in building Pucara.

[Mossie]

F-104 & F-4 upgraded with P&W F101 to see them through the 80's and 90's.

[jcf]

In regards to the T-28, NAA built three YAT-28E conversions.

You cannot view this attachment.

[Weaver]

The Sikorsky S-55 and S-58 were both converted to turbine power by Westland (and the S-58T by Sikorsky. But the US Military never used any turboshaft variants. Real world upgrades with whiff potential. I vaguely remember Martin may have done a US S-58T?

There were several schemes for turboshaft Bell 47/Siouxs - I wonder why none of them went into production? It's not like the Alouette II didn't sell...

[Weaver]

I've always wanted to do a turboprop Whirlwind.  The problem, for me, was/is finding a donor kit with engines that visually appeal to me ... I think I finally decided on the Pucara, since the engines are (to me) weird-looking and I've no interest in building Pucara.

Since you'd need to compensate for the much lower weight of the turboprops, you could put a plug in the fuselage behind the cocpit and have the cannons in a Hunter-style ventral pack instead of in the nose, where the muzzle flash blinds the pilot in the dark.

[Weaver]

The thrust difference isn't that extreme, assuming the Speys aren't afterburning. The Avon 208s in the Sea Vixen put out 11,000lb each, while a dry Spey was good for 11,030 to 11,995lb depending on the version. THe main advantage would be massively lower fuel consumption: 0.932 lb/(lbf⋅h) for the Avon and 0.63 lb/(lbf.h) for the Spey.

It's not thrust, it's a technological mis-match. The Sea Vixen was behind the times when it entered service and lasted a relatively long time for that era, adding new engines might have prolonged it way beyond its sell by date.

Yep: from what I can see there was no plan to update the radar, and that would have been stone-aged by the time a Spey Vixen got into service.

Same thing that ultimately obsoleted the F-106, being designed around and limited to the garbage Hughes Falcon missile. IMO they could have gotten more mileage out of it if they'd converted the weapons bay into a fuel tank and gone to an F-15-style set up with two rails and a hardpoint on each wing station. Other things had room for improvement but that was the Achilles heel.

I did a bit of plastic fondling with this idea and it seems to be that there's enough fuselage below the wing to have F-15-style corner stations for Sparrows on a 106. You might have to work some fin pockets in amidships, but it seems doable. You could then have simple, single Sidewinder rails outboard, as on the Mirage III, and another pair forward of the undercarriage bays in the style of F-4 inboards.

If the corner stations didn't work out, you could replace the weapons bay with a fuel pack with F-4-style troughs for Sparrows in the bottom of it. At least 3, and maybe 4 should be possible with staggered fins, Tornado F3-style.

[jcf]

The old (dates back to 2005) engine swap/upgrade topic has five pages worth of good info and discussion.
Aircraft Engines. Swapping and upgrading

[Weaver]

F-104 & F-4 upgraded with P&W F101 to see them through the 80's and 90's.

There were at least two proposals (Boeing and IAI) to fit "ultimate F-4s" with PW1120 engines.

[Mossie]

In regards to the T-28, NAA built three YAT-28E conversions.

You cannot view this attachment.

Reminds me of another turbopop trainer, but on a vegetarian diet. Turbo Chipmunk with a Rover turbine. I think it would look the part with the RCAF bubble canopy.
https://abpic.co.uk/pictures/model/De%20Havilland%20Canada%20DHC-1%20Turbo%20Chipmunk%2021

Apparently, the MoD were interested as it was getting difficult to source spares for the Gypsy engines. Lycoming or Continental engines were preferred.
https://www.pprune.org/aviation-history-nostalgia/54469-rover-v8-engined-chipmunk.html

There are other turbo-chippies, although these were designed for racing and heavily modified.

[Mossie]

F-104 & F-4 upgraded with P&W F101 to see them through the 80's and 90's.

There were at least two proposals (Boeing and IAI) to fit "ultimate F-4s" with PW1120 engines.

Ah, pipped my memory, there were quite a few Phantom upgrades proposed in the 80's and 90's IIRC, with various fits.

[Mossie]

Here's something interesting that came up while reminding myself of that Rover powered Chippie, a turbo Auster. 
https://commons.m.wikimedia.org/wiki/File:Auster_J.1_Rover_G-AGVI_BLA_23.07.66_edited-2.jpg

You cannot view this attachment.

I'm assuming similar issues with Gypsy spares fueled this one too.