Raptor Composite Aircraft

18 GPH on takeoff power would cook my TSIO 520. I’m looking for no less than 32, preferably 34 out of the hole; 22-25 in the climb. However, I know nothing about Diesel engines.

 

Was just reading a thread that mentioned the BWB "Atlantica" design from the early 2k period. I had hopes for that design as well. Then started reading the specs. 5 place, pressurized, deicing gear, 240MPH cruise, and remember the less well documented design and build leading up to the high speed taxi hop and crash. Lots of performance claims, kit prices established, not sure if they were taking deposits but I think I remember they were at the time but they were looking for investors, don't know if they found any. Followed along thinking if they pull this off it will really be something special.

And something started seeming familiar for some reason...

 

I think the attitude that it is ok is actually similar to any consumer that is buying any other auto engine combination if not anyone doing it on their own. Gumption is what is the driver. It might need more running but he has no industry anchor that has published how much they have tested. It’s all hush hush. The best out there are not sharing how much development went in past press blerbs. What is the fails to success ratio?

More thoughtful designs start on better footing from the start but probably don’t incur the testing everyone here thinks they do. I think there is more luck that people here want to admit. The designers are usually capable of going out and testing live without worry. That is the belief system. If this combo was not being watched by the world, it would have already have tried to fly. Most don’t do NASA test programs; it’s kick the tires and light the fires. The group here are more thoughtful if not more sticklers than the average. The average person building a Vans does not want to think about it, they want a lego airplane that does all they want. Vans has done such a good job with this that everyone thinks it’s the standard instead of the anomaly.

With so many watching and checking behind, there is no quiet failure like if done in private. Up against the wall not for engineering but for audience. The difference from one to his is he is not from the start cocky enough to do all the flight testing himself. Old school was designer did it and if it worked, the reputation built. Now here is a reputation with nothing to back it up.

 

He may well be cooking his 3.0 TDI as well. At that fuel flow he should be seeing upwards of 350-400HP with a properly matched turbo/intercooler setup. Though he didn't provide any engine data, previous runs have reflected high EGTs. If he really wants to use that engine, spending more time resolving his high EGTs and low thrust should be a priority - followed by a reasonable amount of run time at full power before progressing to any part of the aircraft leaving terra firma.

 

Yes, unless the prop setup is garbage he is making 200 +/- hp and blowing the rest of the fuel into the turbos!

 

Wasn’t the Mark Z’s comment meant to say that 18gph is running too lean, and not too rich, or did I misunderstand?

 

Diesels don't run 'lean'. They either have enough air to complete the burn or they don't. If there is excess air then it is a complete burn. If not there is smoke. 18 gph is equivalent to 350+ hp if there is enough air to burn it.

 

Too much fuel is what kills a diesel. Get too close to stochiometric, it will fail. Black smoke is a warning sign. On some of his run ups, you can see black smoke in the prop blast. There is no such thing as too lean for a diesel. The Raptor is using an awful lot of fuel for it's apparent 200hp. That extra fuel will be heating something up way past its design point.The turbos are completely wrong, which is strangling the engine. It would work a lot better with one of them removed. Peter rebuffed Ross's turbo advice offer.
MT props aren't known for sucking. Though it's not unheard of for people to put pusher props on backwards...

 

If your 520 was capable of running diesel bsfc numbers then it would be making upwards 550 hp.

 

Sorry, in post#1786 i was referring to post#1781, and I accidentally attributed Mark Z’s comment to Farmboy. That has been corrected now.

 

Ok, that clears it up. Thx.

 

Just to confuse things a bit more, there's "Mark Z" and there's me - Marc Z. Note the first name spelling difference - some folks just spell their names incorrectly . We're NOT the same person, I don't think.

 

AAAAARRRRRGGGHHHH!!!
Thanks MarC, I’ve corrected my post again... both of them.

 

Ya but you're using a lot of excess fuel to cool the engine. His engine has liquid cooling.

 

Not enough liquid (or low static pressure radiator area) to keep from melting his pistons if he continues to run excessive EGTs.

 

That’s right, I overlooked that. So what would be a good fuel burn quantity (gph) to get his advertised HP?
I’ll answer to anything especially a call to dinner.

 

Peter has been calculating his hp from fuel burn, using a slightly optimistic BSFC for a well tuned engine. His engine is a long, long way from well tuned. Fuel burn might be ~5% higher for an engine actually producing his claimed hp. Thrust figures suggest that he is making somewhere around 60% of the power that he has calculated and claimed.
He has avoided measuring the actual bhp, despite having the equipment to measure prop thrust fairly accurately and plenty of inter-nerds on hand to crunch the numbers for him. That leaves us conspiracy theorists with nothing more than a smoking engine and rules of thumb to point at.

 

Which is why the first flight is always interesting. Will have to run full power for at least 2-3 minutes and deficiencies in cooling are one of the first things to show up.

 

It's been a long since I have run a TSIO 520 but the IO 520 Operator Guide had some charts for fuel flow and BHP. I'll see what those have to say.

 

Did anybody else catch his reply to somebody asking about Pic's Aileron Shimmy Syndrome (which I think deserves an acronym PASS)? He said he did what he could months ago and what he has now is what he's going with. The cliche 'You couldn't make this stuff up' is so apt.