Posted for Scot Stambaugh <sstambaugh@qualcomm.com>:

I have the Aero Composites prop on my F1 Rocket but I haven't flown yet, so you can imagine my concern after seeing the recent posts about their inferior performance.  I posed the question to the Aero Composites guys and here is their response:

Scot:

Thanks for your email.  One needs to be sure that the whole story is being told in emails on the web before drawing definite conclusions!

The Lancair ES (with IO-550 Engine with 310-HP) test at Lancair referenced in your email was run with an existing 3-bladed AeroComposites test propeller with blade pitch change cups/pins installed for the higher horsepower TSIO-550 engine (with 350-HP).  This was the first flight for the AeroComposites propeller on the lower-powered Lancair ES and it was apparent from the testing that the low pitch stop angle was too aggresive (too high an angle) limiting takeoff rpm.  On first flights for a given aircraft/engine combination, the low pitch stop angle is often not initially set optimally.   The low pitch stop angle was adjusted once as much as it could be without changing out the blades for this ES testing. Takeoff rpm was increased but 2700rpm was still not achieved, which also limited rpm during Climb, thus slowing the Climb rate.

The problem was recognized early on and our Cup/Pin Bond Fixture was changed months ago, effectively reducing the low pitch stop by 3 degrees which has allowed subsequent tests on other aircraft with lower power to achieve proper takeoff rpm.  The blades in your propeller have this reduced angle setting.  With this lower low pitch stop angle, Climb performance is further improved for the AeroComposites propeller (it was already very good).

The comparitive performance of the 3-blade AeroComposites propeller and the 3-blade Hartzell propeller was described to John Violette and myself by Tim Ong at Lancair as being very close. Relative to MT propeller performance,  I have never been told by anyone that our propellers did not perform as well as MT propellers, quite the contrary.  Our propellers have consistently given outstanding Climb/Cruise performance and have helped owners win races (e.g. 2003 Air Venture race with Lancair IV-P).

As to the many significant benefits offered by the advanced technology composite AeroComposites propellers (compared with aluminum or wood-core composite propellers), these benefits are set forth in some detail on the AeroComposites website, including the fact that our entire blade, and more specifically the leading edge, stand up much better to hostile propeller operating environment than aluminum blades, whereas the comment on the Lancair website said that MT blades are even MORE prone to damage than the aluminum blades.  Just yesterday we had a phone call from a satisfied customer who commented on our blade leading edges; "every time I fly, I run my hand down the blade leading edges.  I can't believe that they feel as new and smooth as the day I first received my propeller".
Best regards,

Harry Griswold
AeroComposites