Van's Air Force
Western Canada Wing
|
Van's Air Force
Western Canada Wing |
Very interesting day today. Had a chance to fly in a newly completed RV-6A equipped with the 72FM propeller, and thought some of you would be interested in some numbers.
The aircraft is RV-6A serial number 23678, built by Homer Rogers of Revelstoke, BC. The empty weight is 1053 pounds, equipped with a fuel injected O-360 Lycoming A4M. The engine has 245 hrs since factory remanufacture, with differential readings of 77-78 over 80 on all four cylinders. The engine is equipped with electronic ignition. This is a very clean aircraft with a lot of attention paid to detail, and is well rigged. With Roger doing the flying and me pushing the pencil this is what we came up with.
Surface temperature was 45°F, with no wind and an elevation of 1720 ft. Static run showed 2220 RPM and 27.7 inches of manifold press. Aircraft was fueled to give us a 1600 lb gross weight. Some of the following figures may be off a small fraction but are reasonably close.
Take-off roll, starting with full power from brake release, was 12 seconds (to airborne).
First climb to 8000 ft was done at full throttle and 120 mph indicated. Initial rate of climb was 1600 fpm.
The rate of climb at 8,000 feet was still 1200 fpm.
Leveling of at 8200 ft and flying into 8000 ft, the RPM quickly built to the red line of 2700. With everything stabilized, power had to be reduced to 21 inches MP to keep from running over 2700. The indicated airspeed at this point was 190 mph.
The second climb
was done at 25 inches MP and 120 mph to 6000, with 2280 RPM showing going
through 4000 ft at 1200 fpm. Leveling at 6000 and maintaining 2500 RPM--which
required 20.5 inches MP--we had a true airspeed of 182 mph. This was verified
with a hand held GPS, by flying all four headings. At a power setting of
2400 RPM and around 19 inches MP, the fuel burn was 7.2 US gallons per
hour (taken from the fuel flow meter). All cruise power settings were done
with the mixture leaned to peak minus 50 degrees.
Altitude |
Manifold Pressure |
RPM |
| 3,000 | 26.3 | 2,350 |
| 4,000 | 25.4 | 2,350 |
| 5,000 | 24.4 | 2,350 |
| 6,000 | 23.7 | 2,340 |
| 7,000 | 22.7 | 2,330 |
| 8,000 | 22.0 | 2,320 |
My RV-6 is constant-speed equipped and is 55 lbs heavier. With the exception of the slower initial acceleration on take-off, and slightly longer run and slightly lower initial rate of climb, I would be hard pressed to keep up with Roger's aircraft. Jim and I are just starting our fuselage for the -6A and, after today's experience, will probaably go with the fixed pitch prop on our 180 hp engine rather than a constant-speed as planned. If one has special requirements--such as short field work, high airstrips, or floats--I would stay with a constant-speed propeller.
All in all, my first impression is that Sensenich have really done their homework on this one, and have given us a chance to have almost-constant-speed performance at a saving of almost US$ 4,000.
Another interesting
thing happened during our testing. We got a bit too engrossed in the numbers
and let a tank run dry. Gets pretty quiet in a hurry. But what I learned
from this was that after we switched tanks and put the boost pump on there
was a fair delay in getting a restart. It looks to me with this particular
fuel system that a blown tank below 1000 ft could prove quite interesting.
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