Tuesday, July 3, 2012
The Lively Bird
Highly refined, impeccably built and what a delight to turn loose on the sky
The Courier (named after Schlitter's enduring affection for another STOL bird, the legendary Helio Courier) curves happily through the sky but also showed me some impressive "Impossible Turn" performance.
Climbing at max power, we simulated takeoff engine failures by chopping throttle at full power on the 100 hp Rotax 912 ULS, establishing best glide speed (65 mph), then turning at a 35- to 45-degree bank through 180 and 270 degrees of heading to simulate a turn back to the airport.
The biggest altitude loss during a 180-degree turn was 180 feet. For a 270-degree turn, we lost just 270 feet. That kind of floaty efficiency is reassuring: Even if you double minimum altitude for a 270-degree airport turnback, that's still just over 500 feet...and we were well above 4,000 feet MSL.
What other praises to sing for this lovely taildragger? Takeoff: Give 'er the gun, the tail comes up pretty much on its own, and she's off in a surprising few seconds. Ergonomics: Plenty of room for big feet on both sets of pedals. The stick-top electric elevator trim is rigged for light, quick taps—just right. Visibility even from the rear seat is very good, with lots of window area. And the overhead skylight brings good forward view in steeper banks.
Headroom in the rear and front seats is about the same: I'm 5'11" and had a good four inches clearance below the airframe. A 6'6" pilot might feel a bit challenged here, but it's probably doable.
More on handling: Light, quick-response personality that prefers fingertip rather than ham-fist/lead-foot control inputs. Block the rudders to keep from overcontrolling, suggests Ms. Morenz. Once trimmed, she says 10-hour trips are easily done without undue fatigue: This docile bird doesn't need an autopilot.
Stalls? Typically LSA benign: There are no nasty wingovers or other silliness, and they're preceded by gentle burbled warnings around 40 mph indicated. Courier feels inherently forgiving.
And then there's flying with the windows open, one side or both. So, as we motor back to the airport, I'm happy to be alive and breathe in the great blue sky, enjoy Jana Morenz's pink-hatted pony-tail dance in front of me, and feel snug as a bug in the most excellent Rans S-7 Courier, an airplane any pilot who loves sheer flying will enjoy on the very first date.
Taming Adverse Yaw
|What is adverse yaw, and why is it something designers try to minimize in their aircraft?
Making a turn, let's say to the left, requires banking the wings by moving the left aileron upward and the right aileron downward. The left aileron deflects air upward, pushing the wing down. The right aileron does the opposite by pushing air down and raising the wing.
Here's the aerodynamic challenge: When that right aileron drops downward, it also increases lift, which induces more drag than the other left aileron. That increased drag tends to tug the right wing backward or counter to the direction of the left turn. That's why airplanes have a rudder: to coordinate turns by keeping that nose from moving right in a left turn. The same phenomenon, of course, occurs in a right turn. Crafty designers decades ago found a neat way to partially minimize adverse yaw by rigging ailerons differentially— arranging linkages mechanically so ailerons move more in one direction than the other—with the greater deflection always being upward. In other words, in our left turn, the left aileron goes up more than the right aileron goes down. Likewise, in a right turn, the right aileron goes up more, and the left one goes down less. And it works, because when the greater lift-producing (and drag-inducing) aileron is prevented from creating as much drag, it won't pull the wing backward as strongly.
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