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Hello All,

 

So I have upgraded into a new aircraft with a 912ULS, and an in flight adjustable prop, and have been doing a bunch more reading, and have some questions.

My last aircraft also had an inflight adjustable prop and at full throttle it would sit at about 5200 at WOT and cruise at about 105.

This one works similar in that it simply has a button on the dash that allows to go course or fine, but with all the reading I am doing with WOT and MAP, I am now totally bamboozled.

I went back and had a look at a video I took when ferrying the new machine home (Screen Shot attached) that shows 7500ft, MAP 22, RPM 5300, and a fuel burn of over 23LPH.

So I am looking for someone who can help me really understand what is going on, and how to get the best out of this prop. I am lookling for 2 things.  1) a good way to cruise around casually, and the other is to get there as quick as possible, but without necessarlity chewing gas for nothing.

If you can help me understand what is going on, and how to best use this system, I would be grateful.

Cheers
J

8567_1_dash.jpg (You do not have access to download this file.)
  • Re: Another in flight adjustable question

    by » 4 months ago


    OK... I think I might have answerd my own question, but if someone can confirm my way of thinking below, I would be grateful.

     

    I have atached the ROTAX performance chart for Variable Prop.

    So... my way of thinking.... If I am up in the cruise, I can roll on the power and coursen up the prop, as long as the manifold pressures are not above the listed requirements.

    For example.... If I am in the cruise, and I wind my prop in, and the RPM drops to say 4800, and I am at full throttle, and a MAP below 26, then I should not be having any issues.

    However, if MAP hits 26, I need to fine the prop up or reduce the power settings, to bring it back in line.

     

    Fair statement - Is that it in a nutshell?

    Please let me know if there is something a miss with my way of thinking.

    Cheers

    J

     

    29294_2_rotax MAP.jpg (You do not have access to download this file.)

  • Re: Another in flight adjustable question

    by » 4 months ago


    Yes, I believe that is correct.

    I normally cruise at 5200 rpm and 23 in 100 kt IAS 17 l/hr

    In a hurry 5300 26 inches 110 kt  23 l/hr

    Max continuous 5500 rpm and 29 inches 120 kt 27 l/hr

     

     

     


  • Re: Another in flight adjustable question

    by » 4 months ago


    John,

    the attached Rotax chart may be a usefull guideline, too.

    Regards

    Peter

    29297_2_2F635909-4C5A-4A60-842C-33A8F685C916.jpeg (You do not have access to download this file.)

  • Re: Another in flight adjustable question

    by » 4 months ago


    Thanks lads,

    So the question is... seing my picture above (5380 rpm and 22in MAP) if I could course the prop up a few more notches, which would bring that RPM down to near 5000, would I get a little more IAS out of her?  MAP would probably go up a bit, but given the altitude, the ROTAX graph says that should be OK?

    Thoughts?


  • Re: Another in flight adjustable question

    by » 4 months ago


    depends on so many factors....Prop efficiency, Airframe drag curve, density and temp on the day...

     

    Go fly and try it out...it is likely different for your plane


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