RV-7(A) Cruise Performance Numbers

[dhall_polo]

I have not used the iphone app but I presume it is similar to the widely used NPTS method, ntps.
My understanding is that these methods are more accurate and do not calculate TAS from IAS/CAS corrected for altitude or temp. Instead they use trigonometry/maths (totally beyond me) to calculate TAS and the wind direction and strength.
I am sure someone with more maths intelligence than me could explain it better.

Fin
9A

Yes, the iphone app leverages fellow VAF'er Doug Gray's formulas for GPS->TAS from back in 1998. I believe the NTPS stuff is derived from the same. There are some spreadsheets and java applets available that do the same thing. The iphone version is just more transportable.

Here's a link to Kevin Horton's write-up with a lot more detail:
http://www.kilohotel.com/rv8/rvlinks/ssec.html

 

[hydroguy2]

I haven't done any actual speed runs or calibrated anything yet, but while I've been breaking in my engine I have been getting numbers I like. 2 way runs have been averaging 175kts, 23" 2450rpm 7200'msl

Today was my first time away from my local area. I ventured all the way to Helena(KHLN). On my way in,
Helena Tower asked "experimental 155BK say type and speed"
Me: "Vans RV-7 showing 218mph groundspeed, level at 6500, 8 miles east"
Tower: "5BK, I need you to slow up for spacing with HorizonAir Dash-8 from the north"
Me: PRICELESS

 

[bnther]

5.5gph ??

Did anyone see the article in the Jan issue of Kitplanes -- "Around the world in an RV-7" Article stated that this particular IO-360 burned 5.5gph in cruise. That's got to be a misprint... or am I smoking crack?

 

[Kevin Horton]

Did anyone see the article in the Jan issue of Kitplanes -- "Around the world in an RV-7" Article stated that this particular IO-360 burned 5.5gph in cruise. That's got to be a misprint... or am I smoking crack?

If you are looking for maximum range to handle long legs, you need to fly at the speed for minimum drag. This is a very slow speed, and the fuel burn would be very low, certainly less than 5.5 gph unless you were at high altitude. If you can afford to give up some range, you fly a bit faster, and you might very well burn 5.5 gph. If you don't care about range, you fly much faster, and burn much more fuel.