XTI Trifan VTOL

XTI Trifan VTOL.


They're actually trying to crowd fund the development of a prototype.

How much money will they flush down the toilet before somebody says "Man, the drag from those ducts are totally murdering the range"....

The concept isn't completely insane, at least (think Garrow Verticopter)

However, it will be hard to optimize the ducts for static thrust and the advertised cruise speed of 340kts - variable geometry?

VTOLicious said:

The concept isn't completely insane, at least (think Garrow Verticopter)

However, it will be hard to optimize the ducts for static thrust and the advertised cruise speed of 340kts - variable geometry?

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With the amount of power needed for VTOL, I would think 340knots is not that unreasonable. The Epic has 1,200-1,500hp and can do 330knots with roughly the same payload capacity. Yes it is sleeker, but the Trifan will have several times more hp than the Epic...I think...

Crowd funding airplanes does not work. It worked only for a particular part of Synergy, didn't work for many many others, even did not work for Rutan RC. They will need I would estimate over $300mil for this project.

Nice find my dear Sundog.

VTOLicious said:

The concept isn't completely insane, at least (think Garrow Verticopter)

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I find your description of the Garrow Verticopter as being "insane" a little strong.

The company has been renamed Elytair and now Elytron Aircraft, and though they still haven't produced any full-scale article, they built a series of remotely-controlled scale-demonstrators that seem to have flown quite well (Proto1, Proto2, etc.). The latest prototype (Proto8) the Elytron design is quite different, being based on Prandtl's box wing configuration, but it seems like a sound design.

You'd think that a proof-of-concept / UCAV design would be a good start, easier to certify and can generate capital.

With the amount of power needed for VTOL, I would think 340knots is not that unreasonable. The Epic has 1,200-1,500hp and can do 330knots with roughly the same payload capacity. Yes it is sleeker, but the Trifan will have several times more hp than the Epic...I think...

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Horsepower does not equal speed...
For instance, a aircraft with a fixed low pitch propeller will never go fast. Therefore the variable pitch propeller was invented. The same is true for the duct of a ducted fan. It can either be optimised for static thrust or high speed, or it needs a variable air intake and outlet (what adds weight and complexity, and it requires variable pitch propellers anyways!)

The Bell X-22 might be a better comparison. It had a total of 3780kw and a max. speed of 221kts :'(

BR Michael

VTOLicious said:

With the amount of power needed for VTOL, I would think 340knots is not that unreasonable. The Epic has 1,200-1,500hp and can do 330knots with roughly the same payload capacity. Yes it is sleeker, but the Trifan will have several times more hp than the Epic...I think...

Click to expand...

Horsepower does not equal speed...
For instance, a aircraft with a fixed low pitch propeller will never go fast. Therefore the variable pitch propeller was invented. The same is true for the duct of a ducted fan. It can either be optimised for static thrust or high speed, or it needs a variable air intake and outlet (what adds weight and complexity, and it requires variable pitch propellers anyways!)

The Bell X-22 might be a better comparison. It had a total of 3780kw and a max. speed of 221kts :'(

BR Michael

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I work with race planes and works exclusively on prop jobs (I have even worked on wooden fixed pitch). I am fully aware hp does not always equate to speed...darn V^2 in the drag calculation...BUT power loading is a good yard stick for SWAGs and frequently used...ducted fans are supposed to be more efficient at higher speeds than the regular props. These blades I expect would be fixed as their RPM will be crazy high (tens of thousands) and probably will be optimized for cruise given their mission is to travel from A to B not hover for long periods.

PS the fixed pitch climb props on bush planes like a Cessna 180 puts out something like 1,100lbs of static thrust! We all know the 180 is not that fast...but yet a fast plane with an adjustable pitch prop has just around 400lbs of thrust at 250KTAS-300KTAS. Dynamic not the same as static...which leads me to the final point on this topic, every RCer should be familiar with how EDF fans have some really crappy static thrust yet can really get the smash on once the aircraft gets moving. I wonder if that issue will scale up to the VertiFan's Re#'s...

errr...this kind of contradicts everything i know about ducted fans.
Of course much depends on what design point you choose to optimize for, but typically ducted fans have good static thrust (suction on the duct lips) and poor high speed characteristics (the duct itself is a hindrance if it's designed with a flared inlet good for static, and adds wetted area).
This is why fast prop-driven aircraft have open rotors. The interest in having a ducted fan can be:


- Low noise if you can line the duct with suitable materials
- tolerates higher tip speeds, also smaller diameter usually, so direct-drive might be an option
- it's harder for people to walk into ducted fans
- Higher static thrust because the duct outlet prevents the exhaust from speeding up and contracting like in an open prop. For a properly designed duct/fan combination, this shows up as (ideally) a square root 2 reduction in power required for a ducted fan versus a propeller of equal diameter.
-Maybe you are diameter limited in your installation, and/or you need to fair the fans shut for high speed flight (Ryan Vertifan)


i suspect the poor static thrust of RC fans derives in part from poor inlet design, or deliberately not optimizing for static, which requires a bellmouth style inlet.

https://www.youtube.com/watch?v=A5tyDMMo-Ic

Skyblazer said:

https://www.youtube.com/watch?v=A5tyDMMo-Ic

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That's a nice video. Clearly someone put a lot of effort into it. So, the question is... WHY IS THE FRAKKING DUCT ON UPSIDE DOWN?!?!?!

Orionblamblam said:

That's a nice video. Clearly someone put a lot of effort into it. So, the question is... WHY IS THE FRAKKING DUCT ON UPSIDE DOWN?!?!?!

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Good catch. Notice in the next frame before it lifts off that is corrected. It must have been in landing mode!

XTI TriFan presentation and reveal by Jeff Pino (vice chairman)
...it seems they gonna use three 7ft (2,13m) fans, each providing 3000lb of thrust (@10:05). The downwash from an Osprey will be a mild breeze in comparison. Take-off from the front yard will be pretty wild

Edit: Btw, the X-22 had 7ft ducted fans from Hamilton Standard - pic attached

The prototype was apparently completed. What happened next? I wonder...