I would love to see a graph showing (even estimated plots) of an NA and TN airplane theoretical TAS from SL to, say, 18k. Does one exist?

If true, this is a pretty shocking miscalculation that indicates this was never real. At this stage in the game shouldn't we expect detailed, accurate numbers with some reasonable margin for error?

In light of all this, the video title "Turbo Math for Dummies" is pretty funny...

You guys don’t get it.
This thing will have grooved skin coated with slickerthanteflon ice protection, thus shrinking the perceived frontal area to that of a photon.

FIFY

I had no luck trying to find some charts plotting the expected loss of propeller efficiency based on density altitude. Do you know of any? All I could find was general statements that propellers are less efficient at high altitude.

What effect does a constant speed prop changing its angle of attack have on maintaining efficiency in high density altitudes?

Well based upon the Cereal box. If the thing can make 200kts at sea level, it could dom250kts. I would take that.

it cant and it wont. This dream cant be dead because it was never alive.

http://www.nar-associates.com/technical ... screen.pdf

Start of page 3 has a nice graph showing a hypothetical power to KTAS.

Tim

Yeah, I had a hard time finding such a chart, too. I dug into my old college textbooks, Aerodynamics for Naval Aviators, etc, but couldn't find a simple chart or formula. I did find formulas that showed that prop thrust decreases as TAS increases, so that sort of accounts for altitude in an indirect way. He obviously hasn't even taken that into account.

So, I asked about it on the forum used by the pilots of the airline I fly for. It's amazing what you can find out when you tap into a talent pool of 14,000 professional pilots! I've flown with pilots who were aeronautical engineers for Boeing, test pilots, airshow pilots, etc, etc. So, as luck would have it, a guy responded who had worked for a major prop manufacturer. He said you won't typically find a chart like that because it's to specific to a given prop / engine combination. But he did run some numbers for a project that he had dealt with to show how prop thrust decreases with altitude. This was for a variable-pitch, constant-speed prop; assumes constant power from SL to 25,000ft, standard atmosphere, 150kts KCAS. % Thrust is the percentage of thrust compared to SL thrust.

% Thrust Altitude (Ft) KTAS
100.00% 0 150 59
92.4% 5,000 162
85.7% 10,000 174
78.3% 15,000 189
70.3% 20,000 205
62.3% 25,000 224

(Apologies for the formatting!)

So, even assuming constant power from SL to FL250, the thrust at FL250 was 62.3% of what it was at SL. The Raptor guy is not factoring that in, which is a major oversight. Even after I pointed out to him, and he admitted I was right, the over-inflated performance claims remain on his website. Even given the most charitable interpretation, that he just didn't know, the fact that he hasn't revised his performance numbers is deceptive, IMHO.

Perhaps he could re-run the numbers on how he is going to get 300HP+ continuous from a a 3L auto diesel conversion for more than an hour. And how it’s going to do that on 7 GPH.

Perhaps he could re-run the numbers on how he is going to get 300HP+ continuous from a a 3L auto diesel conversion for more than an hour. And how it’s going to do that on 7 GPH.

Not gonna work. Diesels don't use carburetors!

Particularly when the peak horsepower of that engine, in its automotive configuration, is 240 HP. I know, I drive one. Sure, there's chip tuning that could be done, and higher HP can be had that way, but...

I'm thinking of Ferris Beuller- Jim? Jim? Jim Bede?

Its all in the physics- how many BTUs do you need to get from diesel fuel to produce enough HP to get the speed you want? 7 gallons per hour ain't enough BTUs, period!

The bane of auto engine conversions has always been
heat rejection
reduction gearing
longevity at high outputs they weren't designed to produce continuously.
What is the HP the engine was designed to produce CONTINUOUSLY ?
To say it can pull 280 HP on the dyno is one thing, to do it for hours on end is another world entirely.

Thank you.