With a turbo that (per their plans) delivers close to full rated horsepower at FL250 you don't think that greater than 135kias is possible? A Cirrus can do close to 150kias there according to the specs.

I don't mean to say that I think this will be a 300ktas plane, but thinking about what might be reasonable it seems that 200 is pretty conservative.

Though I don't know much about the experimental world, it seems that automotive engines are not a popular choice. Is that right, and if so, what are the drawbacks?

With good design, yes. 135 KIAS at FL250 is about 200 KTAS.

It takes a lot more power to indicate 135 KIAS at FL250 than it does at 0 MSL.


The automotive engine is designed for highly variable power output, smooth operation at various power, and not for continuous high power operation. A car typically cruises at less than 20% max power.

Mike C.

Would an automotive diesel power plant handle continuous high power loads better than a gas engine? Thinking about industrial applications like generators where load is continuous...

And regarding requiring more power at FL250 than at 0msl to achieve the same indicated airspeed, is the difference propeller efficiency or something else?

Propeller efficiency can have a bit to do with it but it's mostly because of true airspeed.

power = thrust x true airspeed

thrust is fairly constant for a given indicated airspeed at different altitudes

It has to do with part throttle optimizations and designing for intermittent duty. The history of automotive conversions for aircraft use is not good.


They are usually very heavy engines that turn slowly. Very low power to weight ratios. Easy to make that last a long time.


Let's say the thrust you need for 135 KIAS is that same at 0 MSL and FL250. The distance the prop generates that thrust in an hour is 135 nm at 0 MSL and 200 nm at FL250. Same force through more distance is more power.

Further, the faster true airspeed means higher prop blade angle. As the angle increases, the thrust vector forward is the cosine of the blade angle, so it reduces as well.

Net effect, it takes considerably more power to fly same indicated airspeed up high, in this case about 50% more power to go from 0 MSL to FL250.

Mike C.

Am I the only one that think canards look ridiculous unless its a starship or the wright flyer?

Another area of skepticism for me on this project is the price/parts list: http://www.raptor-aircraft.com/ordering.html

This list includes 62 parts. Obviously many of them are assemblies or collections of parts, but it still seems radically simple relative to any other high performance aircraft.

What are they missing?

The pricing for individual parts/assemblies they do list seems reasonable to me. Whether there is $46k of markup in those parts that they can shave off is questionable.

Also, I found a longer version of their "story" on an old Indiegogo project https://www.indiegogo.com/projects/rapt ... aircraft#/ Gives you an idea of what parts of his plan have changed and what has stayed the same since their early design stage (that version used a turbine). Kit price excluding the engine, avionics, paint and interior at that point was $80k. $190k for a finished piston version.

Yes, the marketing is coming along nicely.

I'm not sure what universe they plan to build it in, the numbers they give certainly aren't from ours.

Mike C.

I have to be honest. This really burns me up. Clearly there's NOBODY involved in this project with any real experience in aircraft development. It's a friggin Cozy and AT BEST will perform like a Cozy. I don't have the time nor patience to point out the dozens of bogus claims and horrible design flaws of this future disaster. They will vaporize every investor dollar and leave yet another scar in the history of aircraft development programs.

Guys like these do FAR more harm than good to our industry. If you don't know anything about aircraft development or refuse to hire people that do, then please take your entrepreneurial enthusiasm elsewhere. We've got enough unrealistic failures that have scared away would-be investors for programs that truly have a chance.

One example of the insanity:

11 GPH making 300 HP is 0.246 lbs/hp/hr specific fuel consumption.

World record for a 4 stroke diesel is 0.271 lbs/hp/hr.

http://www.gizmag.com/wartsila-31-world ... ine/38120/

That's a marine engine that makes 13,000 HP, 25 ft long, and weighs 85 tons.

(It also has a 32,000 hour TBO!)

Mike C.

Hmmm?

I read...

"A high speed cruise using about 230hp will get you about 190 kias or 285 ktas burning about 11gph resulting in about 29mpg. If you throttle back to 150hp you will see about 155 kias or 232 ktas on about 7 gph resulting in about 38mpg. "

http://raptor-aircraft.com/engine.html

Fellas,

I didn't start this thread as an effort to introduce controversy or disharmony. I started it because I thought it was pretty cool that someone was actually designing and building a new aircraft. One that seemingly answered many of the shortcomings we have all encountered over the years.


Do I think that they'll accomplish all of their goals? The pragmatist in me thinks prolly not. But the optimist is hoping that they get close.


Time will tell.

Yes! ( LongEZ builder and flyer)