Regarding efficiency.  You probably know our Legacy prop is cut back 3 inches in diameter from the original full size Hartzell blade for nose clearance.  The guys here at Spruce have switched their SX300 (Swearingen) to the Hartzell Legacy prop but uncut--so they get the extra 3 inches in diameter.   Some are running the IO540, some IO580.   The Hartzell is getting those guys an extra 5-7 knots and possibly more versus the non-Legacy prop.

I am told by the fellow doing some of the testing for Hartzell that if the Legacy had the extra 3 inches diameter we would also benefit.  I don't know the figure.   I don't know if it would be more than flap hinge redesigns (read: fairings for us low IQs) but the question that comes to mind: What factors have to be considered for a 3 inch larger diameter Legacy prop?  

Some things that come to mind:

1) Hartzell approval

2) prop clearance with flat strut and tire (not enough now for a larger prop)

3) dynamics--how do the flight characteristics change and would tests be required

4) Is there a benefit

Feel free to start a new thread if someone has thoughts.

Paul

Legacy

On 2013-01-26, at 2:24 PM, vtailjeff@aol.com wrote:

Charley,

I would like that!

Jeff

Sent from my iPad

On Jan 26, 2013, at 1:07 AM, Charles Brown <browncc1@verizon.net> wrote:

I have Hartzell's efficiency analysis for their 3-blade and 2-blade props for the Legacy / IO550, if anyone's interested.  (I suspect that they would apply equally to any airframe and engine combination).

On Jan 25, 2013, at 1:32 PM, Bill Bradburry wrote:

Fred,

I have never been great at reading graphs, but the diagonal line is airspeed, not HP corrected for prop efficiency.  That is the vertical line. Or am I wrong??

How do you do this if you have an alternative engine and have no idea of what your HP is?  It seems that you are guessing about the prop efficiency and I would have to do the same for HP.  Perhaps if someone gets a FP drag number for the Lancair Legacy FG, I could work backwards and find the HP?

Bill