We have just fitted a 1940 hour Rotax 912ULS to our Lightning Bug aircraft.

The aircraft has been test flown with a fixed pitch 62" X 93" Prince P-Tip prop.

The performance figures we have achieved so far are as follows:

Static rpm (1013hpa/30degc day) is 4800rpm.

Initial climb at 120ktas gives 5000rpm and 1100fpm.

Straight and level figures at a density altitude of 4500' are as follows:

5500rpm - 175ktas
5800rpm - 181ktas
6000rpm (tested once for a short duration) - 184ktas.

The engine was at nowhere near WOT at 6000rpm.

So, we clearly need more top end pitch and less bottom end pitch, i.e. an IFA prop.

I have contacted the usual suspects (Airmaster, Woodcomp, Ivoprop, Variprop etc.) but with a limiting prop diameter of 62" (maybe 64" at a pinch) the IFA prop manufacturers struggle a bit for a blade that will suit the slow turning, small diameter high speed application.

We may need to consider a custom blade to suit one of the hubs.

Before we go to that extent, does anyone have any suggestions for this application? I my well have overlooked options.
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