David-aviator
Well Known Member
Vans specs out the RV-8 max speed with 180hp at 75% power at 204mph.
N37DD came in at 203.86 this morning. (177 KTAS) Thats with no upper intersection fairings or with strut close out at wheel pants.
Catto was turning up at 2720 rpm. Power was set just rich of LOP but not at it. If I had spent time and set 100 ROP, the numbers might have been slightly better.
Also, I believe the GRT Sport EFIS TAS read out is accurate. It provides inflight wind vector/speed plus a headwind or wind component. When the aircraft is flown directly into the wind or directly away from it and the component is added or subtracted to ground speed the result agrees within a knot of the GRT TAS read out. This is using the GRT internal GPS or the the Garmin 295 ground speed which is always in agreement with GRT.
Another confirmation of GRT TAS number is with the an old Sanderson SC-3B computer. When 18C OAT is lined up over 8500' pressure altitude, 151 KIAS converts to 178 KTAS on the scale. Which of course brings N37DD in at 204.83 mph. That's using GRT IAS, if I used Vans steam gage IAS, TAS is about 4 knots faster, but common sense says EFIS is more accurate than steam. Each has its own pitot tube but share static pressure.
I admit to a compulsive disorder when it comes to performance numbers.
I flew N707DD, the -7A with the Subaru engines (2 of them) for some 400 hours thinking I had built a crooked airplane, its top speed was some 15 knots below Vans numbers for 180 hp. All that changed when I finally tossed in the towel on Subby and installed a BPE Lycoming engine - the airplane met Vans numbers easily - it was not crooked after all.
Total RV-8 time to date - 23.1 hours with 65 landings and still much to learn. On final now I say "take it lower, take it lower, take it lower...." in an effort to flare lower than has been the habit. It is beginning to sink in - had a couple decent landing today although they are wheel landings not 3 pointers.
N37DD came in at 203.86 this morning. (177 KTAS) Thats with no upper intersection fairings or with strut close out at wheel pants.
Catto was turning up at 2720 rpm. Power was set just rich of LOP but not at it. If I had spent time and set 100 ROP, the numbers might have been slightly better.
Also, I believe the GRT Sport EFIS TAS read out is accurate. It provides inflight wind vector/speed plus a headwind or wind component. When the aircraft is flown directly into the wind or directly away from it and the component is added or subtracted to ground speed the result agrees within a knot of the GRT TAS read out. This is using the GRT internal GPS or the the Garmin 295 ground speed which is always in agreement with GRT.
Another confirmation of GRT TAS number is with the an old Sanderson SC-3B computer. When 18C OAT is lined up over 8500' pressure altitude, 151 KIAS converts to 178 KTAS on the scale. Which of course brings N37DD in at 204.83 mph. That's using GRT IAS, if I used Vans steam gage IAS, TAS is about 4 knots faster, but common sense says EFIS is more accurate than steam. Each has its own pitot tube but share static pressure.
I admit to a compulsive disorder when it comes to performance numbers.
I flew N707DD, the -7A with the Subaru engines (2 of them) for some 400 hours thinking I had built a crooked airplane, its top speed was some 15 knots below Vans numbers for 180 hp. All that changed when I finally tossed in the towel on Subby and installed a BPE Lycoming engine - the airplane met Vans numbers easily - it was not crooked after all.
Total RV-8 time to date - 23.1 hours with 65 landings and still much to learn. On final now I say "take it lower, take it lower, take it lower...." in an effort to flare lower than has been the habit. It is beginning to sink in - had a couple decent landing today although they are wheel landings not 3 pointers.