Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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 Posted: Thu May 26, 2011 2:56 pm Post subject: Prop Pitch Re-Visited |
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Posted from another source.
Roger,
Kinda my thoughts too... thanks.
If this weather would ever give me a chance I would just go out and enjoy the plane - guess there are advantages to living in AZ but I wouldn't trade places in a couple of months - grin!!
Btw you might fwd all this to the Matronics site as I have no idea of how to do it as a package - probably at least a couple of others wondering about pitch settings. Your original explanation to me about not striving for 5800 rpm and setting up the prop for 5500 rpm WOT at cruise altitude to capitalize on the 5000 - 5300 best power range for cruise was right-on. Proved by the T/O performance, cruise speeds AND backed up by Warp Drive.
I think I asked this before but would you change the oil and filter now I have 13 hours on the engine. As Rotax is a "new animal" on the block, my thoughts go back to my previous A&P days dealings with new or overhauled Lycoming and Continental motors where we change the oil at 10 to 15 hours and took a really good look at the filter to see what was going on - or wait till the 25 hr inspection IAW Rotax? I think you said wait till 25 hours.
Vann, You might want to open a dialog with Roger. He has a wealth of information on care and feeding of Rotax Engines and happily shares it with us.
Tnx
Phil
On Wed, May 25, 2011 at 6:19 PM, roger lee <ssadiver1> wrote:
Hi Phil,
You are not over pitching a prop if you can achieve 5500 rpm at WOT. So long as you are within the proper prop length for your plane, which you are, then it doesn't matter about the pitch numbers. each plane is a tad different and you need to set a prop for your plane and that may differ ever so slightly from another persons even with the same plane. You only care at this point about what the idle is, 1700-1800, and what WOT is at your normal cruise altitude which should be right around 5500-5550 rpm. Everything else in the middle will take care for itself. looks to me that your numbers are just fine. just go fly and enjoy your plane.
The engine torque is taken care of by making sure the engine sees the proper rpm. If we had an in flight adjustable we could have the best of all worlds, but since we have a ground adjustable we need to balance climb, cruise, fuel, torque and rpm.
Roger Lee
--- On Wed, 5/25/11, Philip Smith <madriver42> wrote:
From: Philip Smith <madriver42>
Subject: Re: pitch
To: "vann covington" <vanncovi>
Cc: "roger lee" <ssadiver1>
Date: Wednesday, May 25, 2011, 4:06 PM
Vann,
Tnx I'll look into it.
I wasn't blindly adjusting the pitch - I had a conversation with the folks at Warp Drive about reducing the diameter of the prop supplied through Zenith of 70" dia that would have been set at 11.0 to 11.5 degrees to blades supplied from Warp Drive at 68" dia that are set at 13.5 degrees.
I just wasn't comfortable with the ground clearance at 70" dia. When I decided to use the shorter blades the value for pitch was given to me from Warp Drive as 13.5 degrees.
I find that at WOT throttle at 4500 - 5000 feet (field elevation 3660), OAT 60 F I get about 5500 rpm - right where Roger Lee says I want it. I then use 5000 - 5300 for cruise and get about 85 indicated at 5000 and about 95 at 5300.
Where did you get your info - are you confusing it with the MOI figures that are published by Rotax???? Btw the 68" dia prop with nickel leading edge is right at the MOI limits suggested by Rotax according to my measurements.
Haven't heard the problem of too much torque and as always am interested in any and all information. Notice I am forwarding this to Roger Lee as well for his input.
Tnx
Phil
On Wed, May 25, 2011 at 9:34 AM, vann covington <vanncovi> wrote:
Just saw your message on metronics. A word of caution. 13.5 pitch on the warp is too much in my opinion. It creates too much torque on uls. 11 to 11.5 is more like it. You may damage your engine trying to get that extra cruise. I believe there was a rotax notice about over pitching. Check it out.
Fly safe,
Vann Covington N701EV
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
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