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ACRO E-mail Archive Thread: [Acro] RE: MT prop performance questions

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ACRO E-mail Archive Thread: [Acro] RE: MT prop performance questions



                


Thread: [Acro] RE: MT prop performance questions

Message: [Acro] RE: MT prop performance questions

Follow-Up To: ACRO Email list (for List Members only)

From: Dave Swartz <djswartz at bellsouth.net>

Date: Thu, 11 Apr 2002 04:20:16 UTC


Message:

  On Monday, April 08, 2002 12:31 PM, jeffery at texas.net [SMTP:jeffery at texas.net] 
wrote:
> This has been kicked around on the Exploder before, but I've slept since 
then.
>
> I'm considering swapping out the 2-blade Hartzell on my S2-B with a 3-blade
> MT.  I've heard that it will increase low speed pull (e.g., better
> accelerations off the top, etc.), but that it may take a few knots off of
> cruise speed.  Fact or fiction?  Is there a substantial difference in the way
>
> it will snap or hammer due to lower gyroscopic forces?  Are there any AD's
> against the MT?  Any other observations?
>
> Jeffery Poehlmann
>
>
>
>
>
I switched from the Hartzel 2 blade to the new 203cm MT in December on my S2B. 
 The longer MT (STC'd just last August) provides significantly better 
performance than the older short bladed version (I have about 20 hours in an 
S2B with the short blades).  The new prop gives me a max speed of 175 MPH at 
1500 feet on an 80 degree day where the 2 blade resulted in 180 MPH in the same 
conditions.  Interestingly, my cruise speed with the new MT is 5 MPH FASTER 
than with the 2 blade ( 2200 RPM, 25 inches = 165 vs 160 with the 2 blade).  I 
can only assume that the 3 blade is more efficient at the lower RPM settings I 
use for cruise.  Acceleration from stall speed to about 140 seems much faster 
than the 2 blade but I have no numbers to back that up.  I have noticed that I 
have more speed for snaps at the top of loops.  Acceleration from about 140 to 
max speed appears to be slower than with the 2 blade.  Again, I have no numbers 
to back this up but I find that my final speed at the end of the box after a 
capping maneuver at the far end is about 10 MPH slower.  The prop is much 
smoother in operation and the noise level in the cockpit is reduced.  I'm still 
adjusting my flying technique to get the most out of the prop but I already 
feel that the performance gains in low speed acceleration outweigh the 
reduction in top end acceleration and top end speed.

I find that my snaps and slow rolls are faster with the MT (especially at slow 
speeds) but I'm also having to adjust my technique for stopping the snap.  The 
torque differences are significant enough that you will need a few hours 
practice to adjust your technique on figures like hammers and humpties.



Dave Swartz
Fort Lauderdale, Florida



                


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