William,
I'll throw my 2 cents worth in here. Regardinging fuel burn, I'm not overly concerned with bsfc, although its not that bad if you're running EFI. What we're really interested in is cost per mile. I have burned nothing but mogas in my 3-rotor Lancair. The last time I purchased fuel, it was $1.65/gallon. My N/A 3-rotor burns between 10 and 11 gph at around 20" MAP. So, it will cost me somewhere around $16.50 - $18.15/hr to fly. Other Lancair ES's are running IO-540's, or some derivative of the "540". From what I hear, they burn between 12 - 15 gph. With the cost of 100LL running around $4/gallon, that would cost between $48 - $60/hr in fuel. So, figuring cost per mile, I don't see how a Lycoming could come close to matching a rotary. The fuel savings alone will more than cover the cost of an overhaul.
And hope the Lycoming doesn't burn a valve, or any number of other common ailments which can take a serious bite out of your checkbook. Most of the things that break on a piston engine aren't even present on the rotary. If it ain't there, it can't break.
So, would I use a rotary if I were to do it over, yes, absolutely!
Mark S.
On Mon, Mar 2, 2009 at 11:31 PM, William Wilson <fluffysheap@gmail.com> wrote:
I have not found an accomodating A&P but I attribute that to the fact that I have not looked yet. Given that I live in Seattle I am pretty sure I can find one. Seattle is crawling (fluttering?) with homebuilt planes. If anyone has suggestions, I am listening, but I had not started searching yet.
Plan is not to take apart a perfectly good flying plane to change the engine, but ideally to get one with a rotary in it already, or replace only at overhaul time. In each case I save as much on the cheaper engine as I would lose on resale value... and if the plane has the rotary in it to start with, I get to pay the lower price up front too, which makes price difference just plain better.
For efficiency what I said was that homebuilt planes are more efficient than factory built, not that rotary are more efficient than Lycoming, though in that case it should be quite close. Bad fuel economy of rotary engine is overstated, economy is comparatively bad at low power & RPM but at high power it is not bad at all. As long as you are not turbocharged, you can run much leaner than a piston engine, making up for less efficient combustion chamber shape. Rotary BSFC in the lab has gone as low as .375 (for renesis), and .44-.46 measured in real world racing applications even with traditional type engine. So I think I would not see a significant difference in fuel economy between rotary and piston. Weight & drag of the plane it is in will matter more.
In any case all advice is welcome, even dissenting opinions ;)
William,
I highly recommend you check around to make sure you can find an A&P who will do a condition inspection with the rotary engine installed BEFORE you commit. Many A&Ps I've talked to dont want anything to do with Experimentals let alone an engine that looks nothing like what they are used to. There's simply too much potential liability (real or perceived) to go out on a limb like that. The A&P who used to do the condition inspection on the RV-6A I used to own (Lycoming powered) was willing to do it because the RV structure is similar to typical spam cans. He wont have anything to do with wet layup homebuilts (EZs, Cozys, etc...). He doesnt even like doing annuals on Diamond aircraft with the Rotax 912/914 and they are certified.
If you buy a flying homebuilt that is Lyc or Continental powered, before you convert it to rotary power seriously think about what you are doing to the resale value - if you could ever sell it that is. My guess is that you'll give up at least $10,000 in resale value, maybe much more. No big deal if you plan on keeping it for life.
I dont know where you got the idea that rotaries are more fuel efficient. Lycosaurs/Continentals typically have BSFCs in the low .40s. The commonly accepted number for a rotary is about .50. Some here seem to do better, others worse. With a grand total of 2 hours on my rotary I cant say what my experience will be but hope its close to the Lyc I used to fly.
Finally dont underestimate the effort required to make the change. I started building my RV-4 in late 1995. The airframe was essentially done in 2000. My first flight was last month. Granted I took longer than many and much of the trouble came from my desire to eliminate the cowl cheeks on an already cramped engine compartment. But thats eight years of tinkering to get the engine installed and running to the point where I had enough confidence in it to fly it.
Not trying to discourage you, but go into this with eyes wide open.
Mike Wills
RV-4 N144MW
- Show quoted text -
----- Original Message -----
Sent: Sunday, March 01, 2009 7:46 PM
Subject: [Norton AntiSpam] [FlyRotary] Re: Questions on buying a rotary plane
This is great news. Thanks Charlie and Bob :)
On Sun, Mar 1, 2009 at 7:34 PM, Charlie England <ceengland@bellsouth.net> wrote:
William Wilson wrote:
I am in the market for a plane and would prefer a rotary-powered, as I have lots of experience working with rotary engines. As a bonus, homebuilt planes all seem to get about twice as much fuel economy as factory built planes. So that is nice too. I know there are a few rotary powered planes available for sale, but not too many.
I have neither the time nor desire to build my own plane, so my question is more about maintenance and inspections. I'm not an official A&P and I don't know if I will be able to find an A&P to work on a home built plane with a car engine in it! I am happy to do engine maintenance, but am not entirely clear on the legality of it, since I would not be the original builder.
Similarly when it is eventually time for an engine rebuild, would I be able to remove the engine, take it down to Atkins (who are not far from me) and have them rebuild it, or rebuild it myself, and then reinstall it, and find an A&P to just sign off on the work?
Plan B is to buy whatever plane even if it has a Lycosaurus, but when time for overhaul comes, get rid of the Lycoming and replace it with a rotary. Thought in this case is to get the rotary tuned, a little broken in and running on a stand in the hangar in advance, so that when the time comes to do the swap it can be done with a minimum of downtime. (I know it cannot really be tuned for altitude in this way but it is better than nothing!). But again, the fact that I would not be the original builder makes me worry about legalities. I have heard that this has been done so question is more about the how.
I do not really understand all the law involved and hopefully somebody here can help. Thanks!
Experimental homebuilts can be maintained or modified by anyone. No FAA blessings required. Annual condition inspections must be performed by either the holder of the 'repairman's certificate' (only available to the builder of record) or by the holder of an A&P ticket (no IA required).
Once the airworthiness certificate is awarded, *anyone* can do any maintenance, repairs, modifications etc desired. The post-modification requirements vary somewhat from plane to plane depending on when the a/w was issued, but in general terms, you notify the FAA in writing that major mods were made, ask for a defined test area, make a log entry detailing the return to 'phase one' testing, fly test flights for (typically) 5 hours, then make another log entry saying that the plane has been tested with the mods & is being returned to 'phase two' (normal operational) status.
'Major modification' isn't clearly defined, but if you have to ask, it's major. :-)
The availability of an A&P to sign off condition inspections is all over the map (literally). It's never been a problem for me, but in some parts of the country people can't find an A&P who will sign off *any* homebuilt, no matter what engine. If you have that problem, get to know the guys who sign off the crop dusters in your area.
Hope that helps....
Charlie
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