![]() |
Speed Question
Hey All, I'm new to an RV6 and I have a FP prop with a O360 power plant. I don't know the specs on the prop, but I will get that when I go to the airport next. I also have the old wheel pants and landing gear fairings.
At 2300 rpm I'm getting about 142kts indicated. I hear stories of 160+ kts in a 6, and talked to a guy yesterday that is getting 155 with an O320. What do I start with to find where I'm bleeding speed from? Thanks in advance for your thoughts! Eric eric at StopFlyingScared dot com |
Here are the Van's performance numbers for the -6/-6A. Note that they were measured with the Hartzell 2-blade CS prop. All speeds are in MPH TAS.
https://www.vansaircraft.com/rv-6/#aircraft-details-2 |
To measure cruise speed you need to specify altitude. Do you mean 142 kts true or indicated?
2300 rpm cruise for a FP is very low. I cruise at about 2550 rpm. You're bleeding speed by pulling throttle back too far. Quote:
|
What are your TAS numbers? All the published numbers are true, not indicated, so that is the first place to start your comparison. Go up to 8,000ft density altitude. Run it wide open, note the RPM, TAS, FF and post those up.
EDIT: I see everyone beat me to it while I was yapping on the phone. I am a little slower than I would like, think my prop is a bit underpitched. I see 168kTAS at 8,000DA 2750 RPM. (O-360 FP Catto). I would expect about 172-3. |
Quote:
with an FP prop, you need to be turning much closer to 2600 or 2700 for higher speeds. 2300 is way too low. If that RPM is achieverd with WOT at 8000', you are WAY over pitched. Just my opinion, but a properly pitched prop should turn 2700 somwhere between 8K' and 12K' (based upon your goals) when WOT and 100* ROP. Larry |
Thanks!
Thanks all!
I will go do a test, maybe even later today. 8000 ft density, wide open and report back on the speeds I see. I guess my old days of 23 sq with CS are hurting me :( Eric |
Quote:
|
Quote:
Open her and see what she can do! |
Quote:
Indicated air speed is nearly useless for doing speed comparisons. Using my fixed pitch O-360 powered RV-6A as an example - At 11,500 ft and a fuel flow of 7.8 - 8.0 GPH I can get true air speeds of about 195 MPH but my indicated airspeed is often 160 MPH or less. |
Some data
Did a short flight tonight
8,000 ft Density Alt Turning about 2650 RPM TAS right at 160 KTS - 184MPH I don't have a fuel flow yet, so I have no idea where that was. The spike was some issue with the data. ![]() Thanks for the help, I just need to push the throttle forward a bit more I guess. |
| All times are GMT -6. The time now is 07:11 AM. |