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Hey guys, I just conducted an extensive test today to verify that my climb performance is low. I would appreciate any help or suggestions.

I have a Tecnam Astore LSA with 912iS and 3 bladed Sens prop. My plane is currently besting POH TAS cruise performance numbers by 10-15%, but underperforming in climb performance.

I'm seeing 4790rpm at max throttle on the ground (did a 10 second full throttle static ground test).

I am seeing 4670rpm during takeoff roll. That remains 4,670rpm in the departure climb and I noted still 4,670rpm climbing through 9,000'. For some reason, climbing through 12,000' that rpm increased by 50 to 4,720. 

At minimum idle after engine warm, I'm getting 1,480rpm. I'm considering having this increased by 200rpm so I don't drop like a rock so much when I pull power to idle over the threshold.

Based on reviewing all of the below numbers I'm getting, I've come to the conclusion that I probably need to lighten the prop pitch by one full degree finer. Would anyone agree or disagree? 

 

 

  • Re: Think I need my prop repitched. Any suggestions?

    by » 11 months ago


    I suggest you read some of the propeller pitch advise, given in a number of other threads on this Forum. There is a divergence of opinion.

    I favour the Rotax recommended STATIC rpm setting of 5200rpm Wide Open Throttle (WOT). STATIC means the aircraft is not moving, usually tied to something.

    Others like to have up to 5600rpm WOT at their preferred altitude.

    My preference will give you excellent Take Off (TO) performance and comfortable low stress  (on engine) Cruise and low fuel consumption/hr but is likely to deliver less than optimum air speed. Care should be taken to keep within the Rotax recommended 5800rpm/ 5 minute duration  however aircraft attitude can be used to slow/speed the engine.

    The other system is likely to deliver better/best air speed, at the cost of TO performance and will likely stress your engine, unless you employ a long ground role & shallow climb out. There is little or no option to use Max engine speed on TO. Terrain clearance may be a concern especially in high density altitude conditions and in aborted landings (slow to respond).

    I would recommend against using engine idle speed to reduce descent speed.


    Thank you said by: Jonathan

  • Re: Think I need my prop repitched. Any suggestions?

    by » 11 months ago


    Idle rpm has nothing to do with your speed. That is controlled by your stick. If you want a better climb prop then 5800 WOT at your average altitude works well. If you want a well balanced climb and cruise prop then 5600 - 5650 WOT at your average altitude is better. Since you don't  have an in flight adjustable prop then you have to pick a pitch that works in all conditions so just setting the pitch solely based and climb rpm is your best option because once climb is over then you need to consider what's  going to happen at cruise rpm, altitude factors and other engine performance. You cruise far more than just climb. Static rpm is used to get you in the ballpark, but you need to fly it to make final adjustments. 


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


    Thank you said by: Jonathan

  • Re: Think I need my prop repitched. Any suggestions?

    by » 11 months ago


    912isPower

    Tecnam probably had the prop set for a 5500 RPM climb to get their climb performance numbers.  That’s getting all the engine power, but will make your cruise slower so you may need a compromise.  Your current setting is getting you 4760 Rpm on climb, which for an 912is sport engine is delivering about 65kW or 87 HP at standard conditions.  The prop is set too coarse in my opinion, likely because Lockwood was trying to get you the published cruise speed. 

    I find there is a sweet spot on the 912iS Sport at about 5050-5100 RPM on takeoff.  The iS Sport makes its torque earlier than the standard 912 so you are not sacrificing that much HP at this setting.  At 5100 RPM you will be making about 70kW or 94 HP, and that 7 extra HP will make a big difference in climb performance. Of course max climb would be setting the prop for 5500 RPM climb, and some here like that setting.  I and some other folks have found that setting the prop to light (above 5200 climb) gives you a hotter (over 1600 deg f) exhaust gas temp during ECO cruise. This issue seems exclusive to the iS engine.  I believe this happens due to a lighter engine load which wastes more heat through the exhaust, and the injector mapping in ECO mode. This may not be true of all aircraft, but it is on mine and a couple others I know of with the iS engine.  My Bristell is set to get 5060 on takeoff/climb, and I get 750 at fpm (at 75 kts) initial climb on a warm day and similar weight to what you are testing at. Cruise speed is still decent at 112 kts true in ECO mode.  I can push it and get 115 kts true, but I don’t.  


  • Re: Think I need my prop repitched. Any suggestions?

    by » 11 months ago


    Jeff Blakeslee wrote:

    912isPower

    Tecnam probably had the prop set for a 5500 RPM climb to get their climb performance numbers.  That’s getting all the engine power, but will make your cruise slower so you may need a compromise.  Your current setting is getting you 4760 Rpm on climb, which for an 912is sport engine is delivering about 65kW or 87 HP at standard conditions.  The prop is set too coarse in my opinion, likely because Lockwood was trying to get you the published cruise speed. 

    I find there is a sweet spot on the 912iS Sport at about 5050-5100 RPM on takeoff.  The iS Sport makes its torque earlier than the standard 912 so you are not sacrificing that much HP at this setting.  At 5100 RPM you will be making about 70kW or 94 HP, and that 7 extra HP will make a big difference in climb performance. Of course max climb would be setting the prop for 5500 RPM climb, and some here like that setting.  I and some other folks have found that setting the prop to light (above 5200 climb) gives you a hotter (over 1600 deg f) exhaust gas temp during ECO cruise. This issue seems exclusive to the iS engine.  I believe this happens due to a lighter engine load which wastes more heat through the exhaust, and the injector mapping in ECO mode. This may not be true of all aircraft, but it is on mine and a couple others I know of with the iS engine.  My Bristell is set to get 5060 on takeoff/climb, and I get 750 at fpm (at 75 kts) initial climb on a warm day and similar weight to what you are testing at. Cruise speed is still decent at 112 kts true in ECO mode.  I can push it and get 115 kts true, but I don’t.  

    Thanks, Jeff. According to this photo I’m not even getting that RPM in climb. It’s as low as 4650 and as high as 4730. I’m now wondering if this low rpm speed also contributes to my high oil temps in climb. My EGTs are great though and always 1350-1450. So from what you’re saying I should expect hotter EGTs in addition to less cruise speed when pitching the prop finer to get higher rpm in climb to increase climb performance?

    Does anyone know how much of an rpm increase I would see with one degree of finer prop pitch? 

     

     

    36741_2_IMG_6094.jpeg (You do not have access to download this file.)

  • Re: Think I need my prop repitched. Any suggestions?

    by » 11 months ago


    No experience of 912iS;

    "It’s as low as 4650 and as high as 4730. I’m now wondering if this low rpm speed also contributes to my high oil temps in climb."

    If your aircraft cant even make 5200rpm in Climb, you are asking way to much from it and will almost certainly shorten its service life - high oil temperatures being but one symptom of an overloaded/stressed engine.


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