Zoom - delta_november — LiveJournal
Jun. 4th, 2014
07:31 pm - Zoom
[LJ albums seem to be broken right now, so posting pretty pictures from Majorca will have to wait.]
probabilisticand I took the Mooney up on Sunday to see just how fast we could make it go. At 8000' indicated, +13C outside air temp, we managed 158.5 knots. That's at max RPM, full throttle, with ram air on. It's fast, but not the advertised 175 knots that's written on the side.
There are a couple pilot things that I maybe should have done:
- Shifting both seats all the way back to move the CG aft, reducing the load on the tailplane.
- Exact trimming, to reduce the tailplane camber. [A special Mooney thing, due to the backwards tail.]
- Slight opening of cowl flaps, as some pilots have reported speed boosts.
I suspect much of the speed loss is out of my hands:
- Stock 2-blade prop was replaced with 3-blade prop for reasons of "sex appeal". This is known to impact speed, both by increasing induced drag and moving the CG forward.
- Speed numbers are probably stated without optional equipment. My plane is studded with antennas for 2 VHF systems, microwave transponder, UHF DME, MF ADF and a lightning-strike detector. All of these antennas add drag.
Finally, I continue to feel that the propeller isn't giving me quite the RPM that it should. I don't trust the tachometer. The mechanic says he used a digital tach to verify it. I wonder if I can find a calibrated strobe light to absolutely determine the prop speed.