I did two climb performance flights six days ago, on Saturday, 14 Sept. I meant to post about them earlier, but we had family visiting, which ate up most of my spare time.

I had done some climb performance testing shortly after the first flight, in 2008. But that was with the original Hartzell prop, and I had never done any similar tests with the current MT prop. The weather was clear on Saturday, and the temperature was fairly close to standard (15 deg C at sea level), so I decided to have a go at this.

Ballast strapped in rear seatI used some cheap exercise weights as ballast, in a very tough military duffle bag, strapped down in the rear seat. Additional ballast went in the forward baggage area, to get the take-off weight up to about 1835 lb. The design gross weight is 1800 lb, so I wanted get data at that weight. The weight decreases as the fuel is burned during the test flight, so the starting weight must be above 1800 lb. I have approval to fly at up to 1900 lb.


I had hoped to get climb data starting as low as 1000 ft above ground level, but the surface winds gusting to 15 or more knots created too much low altitude turbulence to allow good quality testing. I finally found smooth air from 3000 ft and up, so I chose a test block of 3500 ft to 5500 ft. I timed two climbs at speeds from 60 kt to 130 kt, in 10 kt increments. The winds were predicted to be from 340 degrees, so the two climbs at each speed were at 070 and 250 degrees, to put the wind on the wing tip. I averaged the rates of climb from each of the two runs at each speed.

Rate of Climb vs IAS at 4500 ftThe raw data from the morning flight at an average test altitude of 4500 ft shows the classical variation of rate of climb with airspeed. The maximum rate of climb would be at approximately 96 kt, but the curve has a fairly flat top, so the rate of climb is within 95% of the maximum from 82 kt to 111 kt.


Rate of Climb vs IAS at 11,000 ftAfter lunch I gassed up, and did another series of climbs from 10,000 ft to 12,000 ft. The speed for maximum rate of climb decreased as the altitude increased, as expected. At 11,000 ft, the speed for maximum rate of climb has decreased to 87 kt.


I also had my ancient PowerBook G4 running to record data, so I’ll look at that to hopefully get a bit cleaner curve of rate of climb vs speed. I’ll also correct the results to 1800 lb and standard temperature.

I hope to get another set of data at higher altitude in the next week. I’ll turn on the oxygen and do some climbs around 17000 ft.