"Beast One" - the next generation Microjet

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Scheny

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Hi fellow homebuilders!

This is the thread where I am answering all questions about the "Beast One" Microjet that I am building.

BeastOne_001_01.JPG

The "Beast One" is meant as a successor to the infamous BD-5 and as a better alternative to the JSX-2. In years of research I have analyzed all shortcomings and whether there is a possibility to overcome them by modern technology.

Specs:
Beast OneMetricImperial
Wingspan5.8m19ft
Length5.2m17ft
Wing area4.9m²53ft²
Empty weight180kg*400lb*
MTOW380kg*840lb*
Beast OneNauticalMetricImperial
Stall speed57kt105km/h64mph
Cruise speed230kt426km/h261mph
Max speed Vd**300kt555km/h340mph
Alt ceiling18000ft~5500m18000ft
*calculated values, **Vno 250kt (VFR limit)

This is the first time I am designing an aircraft, but I got supported by a famous german aerodynamicist who invented airfoils with benefits at lower Reynolds numbers, an Austrian aerodynamicist and test pilot, who continuously reviews my design changes and calculations and a formula race car engineer, who has helped me with carbon layup schedules required for the fuselage.

The mission goal is to have an aircraft which allows affordable jet flying at the cost of a four-seater, do some crazy aerobatics whenever you want to but enable you to go 50% further than any competition if you want to go for the exclusive 500$ hamburger. Is 50% a vapourware number? No! It's ambitious, but I calculated all parts down to what screws are used and it has way better aerodynamics (+30% wing L/D at low speeds), 15% lower weight at the same payload, etc...

In addition, it incorporates a few state of the art gimmicks, such as BRS, safety cell, energy absorbing nose, bullet proof center tank, docile stall characteristics, solid state electronics (less switches), etc., etc...

So, feel free to ask any questions, while I am posting the progress here!
 

Jay Kempf

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How much fuel capacity out of your 440lb useful load?

where is your inlet? Very far aft? I think you said your turbine is basically at the tail pipe.

Pretty chunky aft fuselage: is that aerodynamic, structural, fuel, baggage?
 

Scheny

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Fuel is ~40 gallons. The hump is still subject to optimization. It is split in 4 compartments: the top is the multi-function bay (baggage or smoke system), in the middle there is the fuel around center of gravity and below you have (aerobatic) header tank, hydraulics and main gear. Behind the bulkhead (firewall), there is the parachute and its rocket system.

The calculations are done to allow a MTOW of 450kg if aux tanks in the wings are used.

Inlets will likely be just aft of the trailing edge with side-scoops and yes, the turbine is located in the rear. In order to save weight, it uses a cleverly combined frame for the vertical rear spar, the elevator main spar and turbine mount.
 

don january

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I have to wonder if there is enough wing area to handle the load your asking of the craft ?
 

TurbAero

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I have to wonder if there is enough wing area to handle the load your asking of the craft ?
Hi Don,

The Lightning Bug being operated at up to around 1000lbs has 40 sq.ft. of wing area with a top straight and level speed of around 200 knots and it behaves very nicely all the way down and into the stall. 53 sq.ft. for this aircraft should be fine in my opinion.

Scheny, I love your concept. You are a man after my own heart!
 

John.Roo

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Hello!
I wonder under what registration you want to operate this airplane.
If you are from EU (Vienna/Austria), than you will have hard time with CAA authorities.... Unless you want to testfly and operate your airplane out of UE try first start discussion with your local CAA.

Your specs are really high end...
Beast OneMetricImperial
Wingspan5.8m19ft
Length5.2m17ft
Wing area4.9m²53ft²
Empty weight180kg*400lb*
MTOW380kg*840lb*
Beast OneNauticalMetricImperial
Stall speed57kt105km/h64mph
Cruise speed230kt426km/h261mph
Max speed Vd**300kt555km/h340mph
Alt ceiling18000ft~5500m18000ft
*calculated values, **Vno 250kt (VFR limit)

Jet fuel density is 0,8 kg / lit.
40 gal = 150 lit = 120 kg
180 kg EW + 120 kg of fuel leaves only 80 kg for pilot (at planned MTOM 380 kg). Experimental may don´t have required pilot weight. In UL world we have to achieve safe CG range for pilot weight 70-110 kg (for one-seaters).
So unless is this plane built only for you pls. don´t make mistake at the beginning and calculate with larger reserve for pilot size and weight. I personally know more pilots between 90-110 kg than 70-80 kg :)
For alt. ceiling 18 000 ft you will anyway need to add oxygen system (also some weight).

This types are far from my "gliding and TMG world" but would be nice to see this small plane on some airshow :)

By the way....
My friend was testpilot of Blanik with JET engine.
Fuel consumption in average 1 lit / min. (if I remember well)
Jet engine from PBS had ax. thrust 1 000 N.
 

Scheny

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It uses the same PBS engine, which has 1200N by now and there is even a 1600N version which is in some sort of beta testing right now.
I have to wonder if there is enough wing area to handle the load your asking of the craft ?
The wing area is rather way too big than to small. If you create a constraints diagram (everyone will/should start with that), it will tell you that this aircraft is impossible to build, with the nearest point of achieveable located at a wingloading of 120kg/m². The Beast One only has 80kg/m² which is comparable to a 180hp 4 seater aircraft. This makes it better at speeds <=120kt, but creates a MAJOR problem for the Va speed. I had to go through great lengths to raise Va to 140kt. For comparison, the pattern speed is 120kt (using flaps 1) and the slowest cruise you can achieve clean is 150kt !!!! (due to idle thrust of ~150N).
Look at the Subsonex or yes the BD5 for sizing. If you are going for a smaller layout thing are getting sporty!
I have read a few articles on how the BD-5 behaves and built the whole aircraft in a way to avoid all shortcomings. I don't want to discuss everything here, as it contains months of research that I want to keep as intellectual property.
Apart from the secret fixes, the BD-5 had the problem of:
  • high thrust line makes trimming impossible, as it depends on thrust AND speed
  • high thrust line makes the plane pitch up and stall immediately after engine out
  • bad stability (pitch scillations)
  • bad directional stability, as the prop contributed to stability
  • harsh stalling behavior (this is where my magic airfoils create 30-40% improvement --> already windchannel proven)
 

Scheny

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Vienna, Austria
I calculated the weight and CG range also with extreme values, so a 120kg pilot is absolutely no problem. As stated before, the aircraft has 450kg MTOW reserved for future changes. But in case you want to do heavy aerobatics, the 120kg pilot will have to sacrifice some of the kerosene.

At the moment I am not incorporating it, but there is the possibility of having a long range version wing aux tanks in the wing with minor modifications and I included this use case in the CG calculations.
 

Wayne

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This is a fantastic contribution Scheny - thank you very much for sharing! On the note of being "small and light weight" - having just returned after 4 days "on the road" bringing the Light Sport back from Florida to Chicago - how do these lighter aircraft fare as far as pilot comfort goes in chop? I can see a great use case for these types of aircraft to "get to the cabin" for the weekend quickly and cost effectively.
 

berridos

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57 kt stall to 230kts cruise would be a killer. You will sell more planes than Musk sells teslas.
You power it with a ducted fan?
Nice project.
 

DangerZone

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Sep 5, 2011
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Zagreb HR
Hi fellow homebuilders!

This is the thread where I am answering all questions about the "Beast One" Microjet that I am building.

View attachment 105184

The "Beast One" is meant as a successor to the infamous BD-5 and as a better alternative to the JSX-2. In years of research I have analyzed all shortcomings and whether there is a possibility to overcome them by modern technology.

...

So, feel free to ask any questions, while I am posting the progress here!
Out of curiosity, why did you not decide to plan building a high wing version so that you would not have issues with the thrust line and allow better visibility bellow the aircraft?

You airplane is beautiful. Yet you had to add a fin under the tail to cope for the jet engine being installed too low and risking a tail strike. This moves your engine way too much to the back, too.

Horst Malliga made a beautiful pusher aircraft in Austria with a central wing to deal with the thrust line issues, maybe you could find a way to contact him and ask him about his issues?
 

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Scheny

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Feb 26, 2019
Messages
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Location
Vienna, Austria
What is this 250 kt VFR limit? If you fly IFR can you go faster?
I had one meeting with government officials from Austria beginning of this year when I still had a sponsor. They argued that IFR experimental is not allowed and I also don't want that, as it is very hard to install NAV antennas in the very confined dimensions. In addition, this would require for the inlet to be icing approved, where even Diamond aircraft had major problems achieving that. So for VFR, you are bound more or less to the 250kt speed limit for below 10k feet. Of course you can always ask ATC for unrestricted speed.
Out of curiosity, why did you not decide to plan building a high wing version so that you would not have issues with the thrust line and allow better visibility bellow the aircraft?
...
Horst Malliga made a beautiful pusher aircraft in Austria with a central wing to deal with the thrust line issues, maybe you could find a way to contact him and ask him about his issues?
The higher the wing, the more aft the spar needs to be due to the seat. I have a problem with the CG being to far at the front already. I even had to change from the original (failsafe) dual spar design, to move the wing an additional 6 inch to the front. The next problem would be, that your head would be located exactly between the two wings, so visibility would suffer huge. I did multiple layouts and created renderings how visibility would look like. Low wing was the best by far.
...
Funny, government agent spoke about Malliga and asked me about the concepts I would use to not fall into his pitholes. If I remember correctly, it was prone to flutter. There even is a video on Youtube.
57 kt stall to 230kts cruise would be a killer. You will sell more planes than Musk sells teslas.
You power it with a ducted fan?
Nice project.
Thanks! Only numbers for now, but they are very far on the conservative side. The trick is the wing profile which has an enormous Ca at low speeds, but also has partial laminar flow (comparable to NACA 64xxx) and almost symmetrical profile to behave better at high speeds (also beneficial for inverted flight).
 

DangerZone

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Zagreb HR
The higher the wing, the more aft the spar needs to be due to the seat. I have a problem with the CG being to far at the front already. I even had to change from the original (failsafe) dual spar design, to move the wing an additional 6 inch to the front. The next problem would be, that your head would be located exactly between the two wings, so visibility would suffer huge. I did multiple layouts and created renderings how visibility would look like. Low wing was the best by far.
...
Funny, government agent spoke about Malliga and asked me about the concepts I would use to not fall into his pitholes. If I remember correctly, it was prone to flutter. There even is a video on Youtube.
You probably meant this video:


However, this is not only flutter. This is a very common problem of close coupled horizontal stabilizer and wings, the tail ends up in the wing root wake. You might have the same issue with your design.

IIRC, there was a BD-5 version with a V tail, with horrible handling. Hence the later versions all had a conventional tail which was pushed further back, as much as possible, and adjusted for wing wake.


Have you got a top view with the LG position? You might resolve you forward CG issue by building some kind of Swearingen LG, to counterweight your pilot's mass.
 
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