The Rutan VariEze
I first saw this unique and ground breaking airplane announced in a Popular Mechanics magazine when I was a kid.
It’s most striking feature is its canard, the stubby wing at the front. Whereas most airplanes use a tailplane (horizontal fins at the rear of the plane) a canard airplane has a “noseplane”.
A careful arrangement of a canard can make a plane resistant to stall. Stall occurs when the angle of attack is too great and the wing loses the ability to create lift. This can easily happen if an amateur pilot lifts the nose too high at takeoff or landing.
In the VariEze, the canard is set up to stall before the main wing. This means that if a pilot attempts to high an angle of attack, the canard will lose lift and the nose will not rise far enough to stall the main wing.
This is an example of Principle 22 – Blessing In Disguise, because the “failure” of the canard to produce lift beyond a certain angle of attack prevents the whole plane from falling from the sky.
Fighting for Control
This tendency of the Vari-Eze to maintain stability even when pilot input goes beyond a certain limit has an equivalent in the automotive world.
Almost all cars are tuned to understeer, which means that the front wheels will begin to lose traction before the rear during aggressive cornering. As a result, the car’s rate of turn will not exceed safe limits. This protects the inexperienced or distracted driver from oversteer, where the back wheels lose traction before the front, increasing the risk the car will spin out.
To provide the driver with a sensation of being in full control, sporty car manufacturers will aim to have both front and rear wheels lose traction at the same highest possible limit. Unfortunately this removes a margin of safety since the amount of grip front and rear will vary according to acceleration and braking. This means that a neutral handling car can suddenly switch to oversteer if, for example, the driver lifts off the throttle.
Paul Walker died when the Porsche Carrera GT he was passenger in left the road. The GT is a notorious example of cars which both permit, and require, full control from the driver. These cars challenge the driver to balance throttle, brake and steering to stay at the edge of stability and wring the most performance out of the car.