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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: Stephen Seidel <thinairltd at earthlink.net>

Date: Sat, 13 Apr 2002 03:31:50 UTC


Message:

  Dave

 Thank you for the very concise observations. I always wondered.........

Stephen Seidel
P-S2A

Dave Swartz wrote:

> 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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