1.9ZOOK
Veteran Member
When it comes to an airplane engine,I think I'd rather have high RPM horsepower over
torque any day.
torque any day.
Not really....My Lycoming has a redline of 2700rpm! Mind you it's 320cu in with a 5 inch bore. Don't think I've ever seen a torque rating for it anywhere, but it makes 160hp.When it comes to an airplane engine,I think I'd rather have high RPM horsepower over
torque any day.
Yes, what you say is quite true. However, fortunately there ARE a few genuine companies who are actually capable both technically and financially to crack the FAA nut. SMA is the government of France, so they certainly can finance their certification projects, but more to the point, they are the ONLY one thus far to figure out that genav engines are far simpler when direct drive and only make sense when compression ignition. The 305/230 SHOULD have been installed in every airframe that needs that power and can manage the weight, but EADS/Socata/SMA/Renault was and is not very good at understanging the business climate in North America. When they say their 460 is nearing certification, I mean European, with FAA to follow. They have some exceptionally smart features (full mechanical backup, direct drive, air cooling, conventional layout) and there is no question they will get to where they have announced, not sure exactly when.I really love the 'near certification' or 'very near certification' language used to describe new engine projects in general aviation. Apparently, from looking at the wreckage of chapter 13, chapter 11, and completely dead companies that were very near certification, this terminology is a clear display of the 90-10-90 rule. That is, the design, engineering, manufacturing of prototypes, acceptance, starting of a test program, getting the FAA to promise to work on it, getting the work done, going through any number of test, re-engineer, re-manufacture, test again scenarios, and getting to that 'very near certification' point will take at least 90% of your funds, provided you have a budget measured in cubic $$. Getting past that last 10% hurdle will take the other 90% of your funds (meaning: at least 80% more than you'll ever raise).
Seriously, the herculean effort of trying to get a new engine certified these days explains very well why we aren't seeing any new engines making it to the certificated airplane engine market.
And the fun part is this: even if you manage to get an engine certificated, you still need to get a certificate for each and every airplane model you want to install it into. So if you want to install it into an airplane, and want to change anything about that engine compartment, you'll need to certify it yet again.
I think the GA market is going to evolve into foreign manufactured airframes and experimentals, with the latter taking the largest portion. And companies like Deltahawk, well, there aren't really companies, there's only Deltahawk. The only reason they've survived this far is with sales to the military who don't really need FAA certification to fly a drone. They have expended all the resources of several well-heeled investors, and the only reason they've survived is by selling the company to someone else (the Ruud family if my memory serves). Yes, they have made some very small fortunes, by starting with very large fortunes.
But that is the way it is with airplanes.
I want to build one, someday. But I'll probably be forced to content myself with rebuilding a Corvair engine (which compare very favorably with the similar offerings from lycosaur engines), and if I want to really jazz it up figure out how to do a blown direct injected 2 stroke with liquid cooling. A wankel will be fun to work on in the spare time, if I can figure out how to do a reduction drive that doesn't weigh more than a substantial boat anchor like the Ross unit does.
Or maybe I'll just rescue TDIs, turn them into trucklets, and go feral pig hunting to feed the family.
Cheers!
PH
Horsepower is simply an expression of the amount of torque multiplied by RPM to produce power. The shape of the torque curve determines the shape of the power curve, but the limit on RPM is propeller efficiency. The larger the prop diameter, the more efficient it is. The limit on prop RPM becomes the speed of sound. As the tips go into the transonic region, the noise made and efficiency of the system becomes a BIG problem, thus the 6' props out there will all stop at 2700 or less RPM. Gasoline engines (and little automobile diesels) need to turn up a fair bit more RPM to make enough power to get the power/weight ratio needed to drag an airplane off of the ground. Problem is: those gear drives are exceedingly difficult to make reliable and economically viable. Thus, direct drive, and those PRM ranges (2500ish for 200ish HP engines) are duck soup for diesels to run sufficiently high boost to get the torque curve fat enough to make the required power at that speed - without having to be a monstrous displacement.When it comes to an airplane engine,I think I'd rather have high RPM horsepower over torque any day.
There are four CERTIFIED diesel engines on the market: the 1.7 and 2.0 Centurion from now defunct Thielert (reduction drive problems killed the company - they sold THOUSANDS of engines first), the 2.0 Austro (installed in Da40 and Da42 Diamond single and twin and the SMA 5.0 direct drive that is STCd in a bunch of airplanes (including C182). The sad part is that when Thielert went under, one of their projects was an Audi 4.2 with PRSD to replace big HP 6 bangers in larger light twins (300-400HP class) and was flying in a B50 (Beech Duke). The up side is that TCM has bought the rights to develop SMA technology to a useful stage - and will start at the 200HP range and go on to the 400 end (this is a modular engine that was designed from the start to be direct drive OR reduction drive, 4, 6 and I imagine (as in HOPE) 8 cyl as well.
I am hoping that before I am too old to hold a medical, I can bolt a pair of 400HP diesel into a Ted Smith airframe (either 680/685 Commander or better yet, one of those AND an Aerostar). If anyone goes 500HP or more (easy with gear reduced, 10 litre SMA design) it would be SO SWEET on a D18S with 232 gal tanks (better yet the 266 gal version with all fuel in the wings).