Anyone ever heard of this thing? Wiki has nothing, and a google search shows no hits.
Center line thrust from two Allison 250-C20S engines spinning two counter rotating props.
Two engines on the nose... talk about 10lbs of crap in a 5lb. box
It popped up on an instagram post and all I could do was screen shot it. I will post those.

On a Caravan? I recall some sort of frankenstein plan like that.

Cessna 340

Pic

I think you may be remembering the Soloy (sp?) conversions for the caravan. I believe it was two small turbines driving a single prop/gearbox.

This was strictly a concept test bed.

The photo is of the final flight where the tip tanks were removed to test the effects on speed. With only the wing aux tanks (30 gal each?) it was practically in a fuel emergency at takeoff.

I don't have any numbers, but I believe that performance was not quite as good as expected.

Props and prop control system were highly non-standard and a bit awkward. It was said that this project paid the McCauley engineering budget for a year. The drive path for the front and rear propeller were independent and isolated from each other except for the necessary intershaft bearing or in the case of major structural failure. Gearbox was from a small specialty shop with minimal testing beforehand (it was spun, but not under power or prop load.

Holy cow, I can't believe there was room to cram two engines and the nose gear in there. Are those Allison engines tiny?

I'm wondering why they wouldn't try it with a single larger turbine like a PT-6?

Pratt and Whitney Twin Pack.
2 engines, 1 gearbox, one prop.

https://www.skybrary.aero/index.php/C08T

The turboshaft version without the full propeller reduction gearbox are pretty small, used on Bell 206's and such.

Thinking behind the concept was to get the most of the redundancy advantages of a twin without the disadvantages (VMC, nacelle drag) of a conventional twin.

Without the dual pack Cessna was so close to having a competitor for the Malibu or later Meridian well before Piper. Marketing never saw the potential?

Bill, any ideas why they didn't use a 400 series fuselage for their concept? It seems like if you are going to dump a tone of money on two (or even one) turbine engine, you would at least put a real cabin behind it.

I've always thought a 421C (or 425) fuselage with a single PT-6 or (my favorite) a TPE-331 on it would have made a heck of an airplane with tons of parts commonality with the existing fleets.

This is the same airframe with a Walter 601D engine installed in New Smyrna after the wings and fuselage were purchased from a scrap yard.

the problem is they took out the only viable baggage area that the 340 even had. 414 would have been much better.

I think we used what was available and the purpose was to test the propulsion concept as opposed to prototyping an actual planned configuration.

The problem with a large turboprop single like you mentioned was meeting the stall speed requirement, as well as market acceptance back then. On a TPE-331 single in particular, the exhaust gets a little awkward. Obviously, things have changed now.

Thanks Bill!