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Date: Wed, 04 Mar 2009 21:56:01 -0600
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Questions on buying a rotary plane
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Tracy, Ed & I (RV-4 with Lyc 160hp) flew together from my home near 
Jackson MS to Bill Eslick's rotary event near Ft Worth several years 
ago. I flew off Tracy's wing & followed his flight profile for almost 
the entire trip. We both topped off at Bill's airport; I topped off from 
the airpark's avgas fuel farm & Tracy topped off from Bill's mogas 
transport trailer. My Lyc burned about 10% less gas (a little over 2 gal 
difference), but this was based on the measurement of Bill's system. I 
don't remember if he had a calibrated meter or they 'guesstimated' the 
amount they pumped. (I'm not afraid to lean aggressively, and I do burn 
premium mogas regularly.)

BTW, that had to be just about the most miserable flight I've ever 
experienced. Something like 1500' ceilings to start (Tracy was at 
cow-tipping levels trying to stay in ground effect), temp in the cockpit 
was in the 20's F with the heater going full blast, 20-30kt headwinds 
all the way, and I've never flown that slow for that long in an RV, 
before or since (thanks, Tracy :-) ).

Charlie

Mike Wills wrote:
> Dave,
> I remember looking at this when you posted about it previously. Not 
> sure a race is quite what I had in mind, but better than nothing. I 
> think documented performance numbers at typical cruise configurations 
> would be more useful. Cant argue with your bang for the buck numbers - 
> one of the primary reasons I went rotary as well. I still dont think 
> it's fair to claim an economy victory based on the price/use of Mogas 
> because you CHOOSE to burn it and your Lyc powered RV buddies CHOOSE 
> not to.
> I dont know about you guys but the typical questions/comments are:
> 1) It will weigh more than a Lyc powered RV (in my case true).
> 2) It will be slower and climb slower than a Lyc powered RV (the jury 
> is out in my case).
> 3) Those rotaries burn more gas than an aircraft engine.
> 4) You're crazy to fly behind a car engine.
> My responses to 1 and 2 are maybe, to 3 is it varies depending on how 
> its operated. My response to 4 depends on my mood and how the comment 
> is made.
> Anyway, it would sure be nice if a number of guys flying did as good a 
> job of documenting and advertising their performance as they do 
> documenting their build process. There are enough flying now to have 
> some statistical relevance. I'd like to be able to point to a website 
> when someone quizzes me on performance.
> Mike
>
>     ----- Original Message -----
>     *From:* David Leonard <mailto:wdleonard@gmail.com>
>     *To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
>     *Sent:* Tuesday, March 03, 2009 9:12 PM
>     *Subject:* [FlyRotary] Re: Questions on buying a rotary plane
>
>     Hey Mike,
>
>     I have done such a real world direct comparison.
>
>     We did a race where where were filled tanks before and after to
>     compare fuel burn as well as speed. Scroll down here to see the
>     results:
>     http://www.rvproject.com/race.html
>
>     Bear in mind:
>     1) the fastest 2 planes were tandem, and had an advantage.
>     2) the slowest 2 planes were trying to win the efficiency contest
>     rather than the speed contest.
>
>     Of the 5 remaining planes, mine was right in the middle in terms
>     of speed and fuel burn. All other planes were 180 or 200 hp lycs
>     with c/s props. I had the only f.p. prop and my installation cost
>     at least $15k less than any of the others. Because I was the only
>     one able to use MOGAS, my fuel cost were the cheapest (of the
>     non-economy flight profile group).
>
>     Bottom line: the rotary proved to be very comparable in terms of
>     power and fuel burn. (as others have noted).
>     ---------
>     I now have 370 hours and almost never remove the cowl anymore. I
>     fly it hard and put it away wet. I have not had an engine or
>     engine systems issue in nearly 200 hrs.
>
>     Compare that the the first 100 hrs where I was putting in almost
>     10 hrs of maintenance for each our of flying and she has really
>     come a long way.
>
>     Way worth it!
>
>     -- 
>     David Leonard
>
>     Turbo Rotary RV-6 N4VY
>     http://N4VY.RotaryRoster.net
>     http://RotaryRoster.net
>
>
>     On Tue, Mar 3, 2009 at 7:55 PM, Mike Wills <rv-4mike@cox.net
>     <mailto:rv-4mike@cox.net>> wrote:
>
>         Glad I woke you guys up! :-)
>         While it may appear from my post that I was trying to
>         discourage this guy and am not happy with my rotary powered
>         airplane that is not the case. I'm very happy with it. Will be
>         even happier once I get all of the little glitches fixed so I
>         can just fly it.
>         I simply wanted to make sure William understands what he's
>         getting into. What appears to be a fairly straight forward mod
>         is a lot more complicated than it appears and there are
>         potential pitfalls that are not necessarily obvious.
>         My bad on the misread regarding fuel efficiency - he was
>         talking about homebuilt aircraft versus factory built planes,
>         not rotaries versus certified engines. I think he's still way
>         off base here which was why I replied to his post.
>         Al, I dont know anyone who actually KNOWS what BSFC they
>         acheive with their Lyc/Cont. I know that low .40s is a
>         published number that is stuck in my head. I know what kind of
>         fuel consumption I got with my Lyc powered RV-6A at cruise and
>         I know there are certainly enough flying Lyc powered RVs to
>         pretty firmly establish a cruise performance baseline. Since
>         there are more flying rotary powered RVs than other types,
>         seems like we should be able to get at least an idea of how
>         they compare. Lets challenge the rotary RV fliers here to post
>         real cruise performance (altitude, TAS, fuel consumption) and
>         answer the question. Or give me a year and 100 hours and I'll
>         let you know how my RV-4 stacks up against the -6A for a data
>         point.
>         As for your performance against conventional powered
>         Velocities, thats great news. I think thats one of the
>         significant short comings of our little group here. Common
>         perception is that rotaries are gas hogs and we dont do
>         anything to accurately document and advertise our performance.
>         Mark, I agree that burning Mogas definitely makes a big
>         difference economy-wise. But that's a red herring. You could
>         legally burn Mogas in a Lyc/Cont also - just that most guys
>         who are too conservative to choose an auto conversion are also
>         too conservative to burn Mogas. Burning Mogas isnt the
>         exclusive territory of the rotary. I personally know a guy
>         with a 200HP Lyc in an RV-8 who has burned Mogas exclusively
>         for years. Really what it comes down to is convenience and
>         comfort. Lets be fair, compare apples to apples, and while
>         we're at it throw in the additional cost and hassle of having
>         to pour in 2 stroke oil for your rotary (assuming you do that
>         as most seem to do).
>         I do totally agree with you on the price of parts. And that
>         was one of my huge motivations for going this route. But
>         really the biggest motivation was to do something a little
>         different. When my RV-4 finally makes it's appearance at a
>         fly-in (hopefully this year) it's not going to be lost in the
>         sea of belly button RVs that show up.
>         Mike Wills
>         RV-4 N144MW
>
>             ----- Original Message -----
>             *From:* Al Gietzen <mailto:ALVentures@cox.net>
>             *To:* Rotary motors in aircraft
>             <mailto:flyrotary@lancaironline.net>
>             *Sent:* Monday, March 02, 2009 9:51 PM
>             *Subject:* [FlyRotary] Re: Questions on buying a rotary plane
>
>                 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.
>
>                 Mike;
>
>                 I’m not disagreeing with the points in your message;
>                 but I am wondering if you know anybody actually flying
>                 a Lyc/Cont and achieving BSFC in the low 40’s. I see
>                 numbers like .43 or .45 bandied about, but I guess no
>                 one leans enough when flying to get that for fear of
>                 burning out a valve – or worse. I’ve yet to hear from
>                 anyone flying a Velocity like mine with a Lyc who can
>                 surpass the speed/fuel burn that I get with the 20B. I
>                 don’t know why – it surprised me; but there it is.
>
>                 I think in the real world operation the BSFCs are
>                 comparable. I may have a bit lower drag because of
>                 smaller cowl; or other factors.
>
>                 Al
>
>