Mailing List flyrotary@lancaironline.net Message #45358
From: Tracy Crook <tracy@rotaryaviation.com>
Sender: <rwstracy@gmail.com>
Subject: Re: [FlyRotary] Re: Questions on buying a rotary plane
Date: Thu, 5 Mar 2009 10:55:05 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Ah Gee guys, it must the age of the memory but I remember that flight as fun.  Or maybe it was because it was before I installed insulation on my firewall and the heat kept my toes warm.  Didn't have an inside temp at the time but OAT was indeed 12 deg at 500 ft AGL.   I think Ed flew higher and the temps up there were probably sub zero.  Charlie more or less followed my erratic flight profile (low [~500 feet] and slow with occasional pop ups to to see if the awful head winds were better up there (they weren't). 

Charlie did burn less gas on that flight but in spite of the low speeds, that was not a good economy comparison run for the rotary.  I was down at 4300 - 4700 rpm for most of that long flight.  I find that I can't get into very aggressive leaning until the engine is above 5000 rpm.  I have speculated that the reason for this is the stratified charge effect due to the centrifugal force of the rotating intake charge forcing the heavier and richer part of the charge out toward the sparkplug side of the combustion chamber.  Where my particular plane and engine does well is at high altitude (15,500 is my preferred slot) with the engine turning 5600 rpm.  TAS is about 172 mph under these conditions and the throttle is not WOT.    Fuel burn is around 6.25 gph.  It's hard to get good comparison data with Lycomings under these conditions because Lycoming drivers tend to run WOT at these levels.  I have done WOT tests at 14,500 and at 500 ft.  At 14,500 TAS was 202  burning 10.2 GPH.   At  500 ft it was 224 IAS turning 7250 RPM burning 17 - 18 GPH (during 2004 Sun 100 race)  I still had some reserve power since mixture was still way lean of max power point but didn't go there since I was already 14 mph over airframe redline.  A brief test running at best power mixture gave 21 GPH fuel burn but did not wait to see what airspeed would result.

Tracy


On Thu, Mar 5, 2009 at 8:53 AM, Ed Anderson <eanderson@carolina.rr.com> wrote:
Yes, indeed, Charlie, remember that flight fondly - NOT!

 That flight also qualifies as the most miserable flight I have ever
encounter.  In addition to the low ceilings, Charlie mentioned and the cold
(my inside thermometer read 12F) and it was all my heater (which runs off
the coolant temp which were near 120F) could do to keep my toes from
freezing and falling off.  What made it worst was we had a headwind that at
times drop our ground speed to 115 MPH.  If you went higher the headwind
became stronger (prolonging the misery), if you went lower the turbulence
bounced you all over the place.  Then the turbulence on landing at Pecan
Plantation just about caused me to drag a wing tip.

Let's just say I have not flow with Charlie again {:>)

Ed

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Charlie England
Sent: Wednesday, March 04, 2009 10:56 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Questions on buying a rotary plane

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
>
>


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