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after completing a high speed cruise test run with all of the gear fairings finally completed (215 mph at 8,000 feet and 75%), i noticed something unusual on a remote peak...
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after completing a high speed cruise test run with all of the gear fairings finally completed (215 mph at 8,000 feet and 75%), i noticed something unusual on a remote peak...
during fairing fitting i have made several separate high speed cruise runs, all conducted with multiple legs recording both TAS and GPS groundspeed, stabilized at a density altitude of 8,000 feet using the autopilot...
TAS and GPS averages have all been within one or two mph on each run. %power is as shown on the EIFS but generally is from full throttle giving about 23 inches and 2600 rpm.
gear intersection fairings look to have added 2-3 mph at the very most. the first run prior to fitting them showed and average of 212, lowers brought that to just under 214, the uppers bring it just up to 215... it really gobbles fuel at these speeds though; 13.4 gph when pushing the cruise speed limits! dialed back a bit i see 200 mph at 9.5
the engine is a standard lycoming IO-390 sea level rated at 210 hp at 2700.
Several years back this area got a record snowfall of something like 150 feet..you'll need a bigger shovel.Is the cabin for sale and are the roads plowed in the winter?![]()
Neat photos.after completing a high speed cruise test run with all of the gear fairings finally completed (215 mph at 8,000 feet and 75%), i noticed something unusual on a remote peak...
I completely agree with Kevin that WOT at 8000 DA is more than 75% on an RV and that there is observable MP boost at typical RV high speeds. I usually see >1" over ambient.Neat photos.
If the IO-390 percent power vs rpm, MP and altitude is similar to that of the IO-360-A series engines, 2600 and 23" at 8000 is about 81% power (assuming standard temperature), if the IO-360-A series power chart is to be believed. If you want 75%, that would be more like 2450 rpm and 23" at 8000 ft.
Note: some folks will tell you that 2700 rpm and full throttle should give 75% power at 8000 ft. That might be true if the air box was less efficient, and the TAS was lower so there was not so much ram pressure rise. But, RVs, with their well designed air boxes and high TAS realize higher MP than many other aircraft.
I completely agree with Kevin that WOT at 8000 DA is more than 75% on an RV and that there is observable MP boost at typical RV high speeds. I usually see >1" over ambient.
However, 81% of 210 is 170.1 and at best-power SFC, that should be about 14.175 gph (using 6#/gal). To get 170.1 from 13.4 gph would require a best-power SFC of .4727.
Kevin, what's the right approach to this?
Right and just south of Darington. I see I was wrong, it was built in 1970 by the forest service but now maintained by the climbing club. Pretty cool to fly over!Looks like the lookout on Three Fingers, East of Arlington, WA.
Some people don't like company and will go to great lengths to avoid it.
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Bob Axsom
Some people don't like company and will go to great lengths to avoid it.
![]()
Bob Axsom
Nice post! I like seeing true speed numbers posted with the corresponding fuel flow. My 16 year old HR2 with 285 HP and GAMIs, large tires, caked mud (from my strip) and 2 more cylinders cooking easily tops 200 knots in level flight burning 14 Gph.
There's no substitute for HP...
Smokey
I would like to drop-in for a visit.
Kent
The structure I photographed there is a monastery of Meteora just north of Kalambaka but there are private homes there built on huge vertical walled "rocks" in the same manner and style. We visited there on a Trafalgar tour called "The Best of Greece". It was a great trip by the way.
Bob Axsom
Let's start with power. I calculate you are getting (23 x 2600) roughly 74% at those numbers = 155.5 BHP. If I'm right about that, then your best power SFC is .516. Conversely, if your SFC is the normal .500, then your BHP is 160.9 = 76.6%. I won't go into detail here, but based on my airplane, the 155.5 is more likely to be correct. This balances to your fuel burn at .516 SFC.
Now that we have that, we have the minimum drag, too (skipping the details, I used my spreadsheet, linked below). Your minimum drag should be a little less than mine (7 vs 7A) plus or minus individual airplane issues. I used 146.4 pounds at 110.5 mph for your airplane. Close, but probably not perfect. It matches my 150# corrected for the difference in nose wheel using Van's delta. I've ignored weight here, but my specs and yours appear to be a solo weight so the differences are small.
Taking an academic chance, if we use those numbers for a guesstimate, your Thrust HP at 215 at 8000 is 135.42 and that makes your WW 200RV prop 87.1% efficient. Considering that the prop was designed to be about 90% efficient at 8000 and 150 HP, but for an RV8 going 220, this is very close to design specs. Even if your BHP is the higher figure, your efficiency is 84.2%. If I use your 75%, it is 86% efficient.