RV-9/9A POH (PDF format)

[Wahi-Air]

Reading these POH, I am wondering why my plane is quite a bit slower than the other RV9…..

My set-up:
RV9a
YO 320-D2G, 160hp
Sensenich fixed pitch 70CM7S9-0-79 (as recommended by Vans)
Magneto ignition

This is what I get:
- DA 6000ft full power, leaned and 77% (shown on Dynon): 2530RPM, 24.5MAP, 151KTAS with 34 liters/hour (8.9us gal)….
My gear is covered with boots, the intersections from to the wings are not perfect, but existant. I am sure I can get another 2-3kts out of improvements of the gear cover, but it looks like I am missing around 10-15kts…. Never reached 160KTAS.
And sure, maybe my system is off. But even without wind, my groundspeed is not reaching these numbers… And as far as I am not completly off, TAS should not be less than GS in almost no wind conditions….

Would be great if you have a word of wisdom where to look for…

Cheers
Sunit

[Dugaru]

I've got a Hartzell CS but otherwise the same setup. At that altitude, mp, and rpm, back-of-the-envelope, I'd say you're "missing" about 10 knots.

As a first step, I would definitely run a test of your system to confirm you're getting correct measurements. Sounds like you are, but it's important to know and easy enough to figure out. https://www.kitplanes.com/flight-tes...from-gps-data/

Originally Posted by Wahi-Air

Reading these POH, I am wondering why my plane is quite a bit slower than the other RV9…..

My set-up:
RV9a
YO 320-D2G, 160hp
Sensenich fixed pitch 70CM7S9-0-79 (as recommended by Vans)
Magneto ignition

This is what I get:
- DA 6000ft full power, leaned and 77% (shown on Dynon): 2530RPM, 24.5MAP, 151KTAS with 34 liters/hour (8.9us gal)….
My gear is covered with boots, the intersections from to the wings are not perfect, but existant. I am sure I can get another 2-3kts out of improvements of the gear cover, but it looks like I am missing around 10-15kts…. Never reached 160KTAS.
And sure, maybe my system is off. But even without wind, my groundspeed is not reaching these numbers… And as far as I am not completly off, TAS should not be less than GS in almost no wind conditions….

Would be great if you have a word of wisdom where to look for…

Cheers
Sunit