Mark Wrathall wrote:

Sorry to send while you are leaving Paul, but I just found this site.

http://jetbeetle.com

The guy is selling quite large Inconel turbines.

Mark

Wow! Cool! Another turbine we can use for experimental turbo compound engines.

It would be a waste to use this on a ultralight. A couple of these
on a very small single place all carbon fiber airplanes would make a great
toy. You won't travel far.

300 pounds of thrust at 350 MPH is 280 HP. If the gross weight is
1500 pounds the initial acceleration is .2 G or 6.4 fps per fps.

A short QB program yields the following take off chart. On the ground only.
No rotation. A rotation will slow the aircraft.

Check my calculations here as I have been known to make mistakes.

Paul Lamar

I forgot the landing gear was down so the drag would be much higher on
the ground. To be conservative I changed the Flat Plate drag to 1.

What happens when you rotate is the induced drag due to lift becomes a major
factor so you need to get the gear up as soon as possible.
This is a small wing area design. Say about 50 square feet.
1500/50 is a wing loading of 30 pounds per square foot.
At a C sub L of one means minimum take off speed and stall will be
around 110 MPH. You want to keep it on the ground well beyond that.

I would not try to fly something like this in less than a
3500 foot runway.

If you can get the flat plate drag down to .3 or so top speed should
be close to about 450 to 500 MPH or more. Assuming of course he achieves
the thrust he thinks he will.

Paul Lamar

Why does it need to be that heavy?  The little Cosman 1 we built for Jim
Cosman had, if I remember correctly 48 ft2 of wing and weighed about 650
lbs empty, swap some Cont A-75 weight for fuel and you're still okay.

Chris Cosman

Just a wild ass guess on my part.

You might get a few hundred pounds out of it depending on how
much fuel you wanted to carry. That should shorten the take off roll
and lower the stall speed a bit.

I notice the BD5 J with only one engine empty weight is about 360 pounds.

http://www.bd5.com/my5j.htm

You take the Micro turbine engine out of the fuse and replace it with a larger
fuel tank as the BD5 J only carries 32 gallons. Placed roughly behind the pilot where
the Micro Turbine  went. 32 gallons 192 pounds of fuel and a 200 pound
pilot gets the BD5 gross up to 752. Empty weight to payload on the BD. J is
therefore right around the industry average of one to one.

The BD. is probably about 2 feet wide and 3 feet high.
24 x 36 x 36 inches for a total fuel volume of 115 gallons in the fuse.
268.8 cubic inches per gallon. That is about 700 pounds of fuel.

If you add more fuel weight and speed you need to beef everything up.

I notice the Microturbo  SFC is 1.25 for a somewhat more sophisticated engine
while this engine claims about 1.44 SFC. (Pounds of fuel burned per pound
of thrust per hour.) Seems reasonably. 432 pounds per hour or about 72 gallons
per hour. 115 gallons of fuel 1.6  hours at 300 MPH and the range is
starting to look reasonable.

700 pounds of fuel plus 200 pound pilot = 900. If the payload to empty weight ratio
holds so gross would be about 1800 pounds. Rutan does a lot better with carbon
fiber so take off 290 pounds and you get 1500 pounds.

Paul Lamar

So a pretty good guess then!

Chris

Yes I would say so.

Paul Lamar
 
The Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2004 All world wide rights reserved.