Bubblehead
Well Known Member
As much as I like my RV-8, it seems slow compared to others. I'm not formation qualified so have not flown formation to compare with others, and have not taken any trips, even short ones, with other RV flyers. Looking at the Vans website at performance numbers, or looking at some performance numbers in the forums, makes me believe my RV is, well, slow!
Today I went up and collected data to see what my actual airspeed was. I used my Garmin 496 to record ground speed at the four cardinal directions at altitudes from 5500 to 10,500 feet. I do not have an OAT indicator, so just used pressure altitude, not density altitude.
The weather was not the best for this test. There was about .8 cloud cover and a warm day, so there may have been thermals and downdrafts. There was a very strong wind - gusting to 30 kts at the surface. If the wind was steady it would come out in the averaging of speeds but with the gusts and changing weather there is probably some error.
I used WOT amd 2500 rpm, and converted mp and rpm to %pwr using an equation derived from the "rule of 48." The plane is a 2001 licensed RV-8 with a 180 hp IO-360, standard wing tips and wheel pants. Compressions were fine at the November condition instpection. It flies well and the ball stays centered with very little help from the rudder, so I think the plane was in coordinated flight during the data runs. The prop is a Hartzell constant speed prop recommended by Vans for the -8. Exhaust is a standard Vetterman 4 into 2 system for a horizontal draft engine. Fuel was 3/4 full and I was solo, so gross weight was about 1500 lbs.
75% power and 7000 feet gave TAS of 180 mph. This seems about 20 mph low for a 180 hp RV-8.
Any ideas? Here's a picture of the plane.
Today I went up and collected data to see what my actual airspeed was. I used my Garmin 496 to record ground speed at the four cardinal directions at altitudes from 5500 to 10,500 feet. I do not have an OAT indicator, so just used pressure altitude, not density altitude.
The weather was not the best for this test. There was about .8 cloud cover and a warm day, so there may have been thermals and downdrafts. There was a very strong wind - gusting to 30 kts at the surface. If the wind was steady it would come out in the averaging of speeds but with the gusts and changing weather there is probably some error.
I used WOT amd 2500 rpm, and converted mp and rpm to %pwr using an equation derived from the "rule of 48." The plane is a 2001 licensed RV-8 with a 180 hp IO-360, standard wing tips and wheel pants. Compressions were fine at the November condition instpection. It flies well and the ball stays centered with very little help from the rudder, so I think the plane was in coordinated flight during the data runs. The prop is a Hartzell constant speed prop recommended by Vans for the -8. Exhaust is a standard Vetterman 4 into 2 system for a horizontal draft engine. Fuel was 3/4 full and I was solo, so gross weight was about 1500 lbs.
75% power and 7000 feet gave TAS of 180 mph. This seems about 20 mph low for a 180 hp RV-8.
Any ideas? Here's a picture of the plane.
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