Vought 4 Ducted Fan Design

Hi All -

Mixed in with the Eaglet and Mini-Eaglet drawings was this single seat 4 fan design. Have no idea what this was meant for - nonetheless it is interesting!

Enjoy the Day! Mark

Thanks Mark, it looks like a Tandem Fan (TF) demonstrator. It would be interesting to know which turbines are powering it.

Amazing find my dear Mark.

Looks like the drawing shows 4 Rolls 250s, 2 per side with a fan on each engine.

I agree with Sundog, the size of the aircraft is similar to a Piper Navajo and the tandem shaft-driven fans are too small to generate sufficient thrust to be a practical single-seat tactical aircraft. 1980 would be about the same time frame as the Vought tandem fan fighter design, TF-120. Maybe this was a concept for a technology demonstrator for this type of design.

I still have an unhealthy tandem fan obsession, so this is great.

IMHO opinion this is a super genius design for quiet CAS. Why doesn't someone build it today w/ current tech it could be an amazing all spectrum stealth and high or low speed and altitude.

Thank you for postin Sir

The cockpit does have the look of a CAS aircraft, but the relatively small engines would *seem* to indicate a relatively low mass if it's meant for VTOL. Additionally, those are some excessively large wings if it is meant to be a developed, operational aircraft, but they might be just fine for a plane that is expected to land horizontally sometimes because something went amiss.

Well, it's set up as a ducted fan. So the assumption is a demonstrator for a configuration.

And you have to have a place to hang ordinance for CAS, and the high-aspect ratio helps squeeze out some range so that makes some sense. Maybe even a ESTOL config as opposed to V/STOL?

Given that the thrust vectors to the vertical, it would seem that at a minimum it would land vertically.

Sundog said:

Given that the thrust vectors to the vertical, it would seem that at a minimum it would land vertically.

Click to expand...

Hello gentlemen and ladies.
This was the post that first got me interested in this forum, so here goes.
Given the rectangular exhaust, these are most likely 250-C30, C40, or C47 engines.
Engine horsepower would be between 650 and 715 for take off per engine and 501- 613 continuous. That’s between 2,600 hp and 2860 hp for take off.
The engines are in tandem with carry through shafts attached to the engines Free wheeling units. If one engine fails the remaining engine on that side will power both fans.
According to the designer of the MD 500/600 Notar fan it produced 140lbs of thrust from 200hp. This was from a fan not even optimized for thrust and a mere 22 inches in diameter.
I met and talked with him personally so this is not conjecture.
That would be 2000lbs of thrust with an engine weight of +1000lbs.
I would put the fans on this aircraft, just eyeballing it at +30 inches and significantly more thrust per hp.
Around +3000lbs Total thrust, probably more.
Definetly VSTOL and possibly VTOL territory For a technology demonstrator.
The long ducted intakes definitely rob possible horsepower. Probably 15 to 30 hp per engine. These engines prefer bell mouths and that would obviously reduce thrust as well.
I have worked extensively on C30 ,Bell 206L3&L4, C47M MD600 Notar and C47B
Bell 407.
If anyone is interested I have parts from a Notar fan I could take pictures of and post.
I have a fan blade and stator. I believe it had 13 blades and 11stators both made of fiber reinforced injected poly propylene.
The fan is a high pressure, high solidity fan. The fan chord is longer than the span, and the fan has a large center body compared to the overall fan diameter.
Airbuses Fenestrons we’re just the opposite. Low solidity Very short chord compared to blade span, and relatively smaller center body.
This leads to the following.
For a similar sized helicopter, say MD600 size, an open tail rotor at max deflection will absorb approximately 125hp, a Fenestron approximately 160hp, and a Notar approximately 200hp. These are not exact, but just to show why you don’t see ducted propulsors more on helicopters.
I ramble.
I am also a fan of tandem ducted fans.
Just a quick update.
I have no idea if the Notar fan could structurally support 500lbs of thrust or absorb 715hp.
After looking at the drawings again, the fans are probably 40 inches in diameter and the second set of fan intakes are rotated 90 degrees in the drawing and actually pull the fan intake air from over the wing.
Considering the Doak VTOL had two 48 inch ID ducts and 500hp per duct from a single 1000hp engine, this aircraft actually could have decent performance.
just some info.