Before flying west for our trip to the Utah back country, we wanted to know how the high altitude would affect the Bearhawk.
We emulated a high altitude takeoff by only giving partial throttle and found the Bearhawk takes off best with 10 degrees of flaps and tail up. We tried tail up and tail down takeoffs, no flaps and 10 degrees of flaps. Tyson was pretty sure more flaps would be too much drag. Ten degrees of flaps was a clear winner. Tail up was definitely better than tail down, but subtle differences in pilot technique mattered a lot. Tyson’s shortest takeoff was 200 feet shorter than mine.
Tyson wanted to emulate taking off from a strip 5,000′ above sea level on a hot day. The lower pressure from high elevation and temperature affects the engine, the propeller, and the wings. We could simulate reduced engine performance. The wings and propeller, we couldn’t do anything about. Using an online calculator, http://www.pilotfriend.com/pilot_resources/density.htm, I find that at 5,000′ above sea level, temperature 80F, dew point 50F, and reference sea level pressure at 29.95 inches Hg, the station pressure at the airport would be 24.92 inches Hg. Most engines loose an inch or so of pressure due to inefficient air intake. We reduced the throttle by a few more inches to simulate the reduced lift on the wings. So that’s how we decided on 22 inches of Hg for the throttle.
We set up cones every 100 feet on the usable grass at Jaffrey. The wind was calm to 5 kts headwind.
I flew first. We estimated the plane weighed 2284 lbs and the center of gravity was 12.6 inches aft. Density altitude 1600′. The Bearhawk flew nicely in my opinion. It was even quiet.
- tail up, no flaps: 900ft
- tail up, no flaps repeat so I could do it better: 900ft
- tail down, no flaps: 900ft
- tail up, 10° flaps: 900ft
- tail down, 10° flaps: 900ft
On each of my takeoffs, the wheels left the ground several times between 700 and 800 feet, but settled back down again. I couldn’t get the Bearhawk off for good until 900 feet.
We measured landings too. Mine were 700ft, 530ft, 750ft, 675ft, 375ft but touched short of the threshold. Tyson had many critiques for all of them.
Tyson went next. We made a guess at fuel burned and estimated the plane at 2266lb, CG 12.51″. The weather station reported a density altitude of 1700′.
- tail up, no flaps: 850ft
- tail up, 10° flaps: 800ft
- tail up, 10° flaps: 700ft
- tail up, no flaps: 720ft
Tyson quickly decided the airplane needed more nose up trim. He also found the Bearhawk would fly at 40kts if he held the stick back firmly. It didn’t settle back to the ground. The flaps helped a little with performance, and a lot with visibility. With more flaps, it was easier to pick the tail up higher and see over the nose.
Tyson’s landings were much shorter than mine: 415′, 350′, 350′, 350′. It’s typical for planes to have a shorter landing roll than takeoff, which leads to people landing places and getting stuck. We can’t compare absolute distances to a real five thousand foot elevation runway.