EAA Sport Aviation

The FAA’s certification rules do not require pleasing control harmony. There are maximum stick forces specified that an airplane cannot exceed, and there are phrases in the rules like “normal pilot strength” or “no unusual pilot skills,” but ideal harmony among the control forces is not a rule. However, the rules do require that stick force be positive, meaning it always takes more force on the controls to increase the pitch, roll, or yaw rate.

Most certified airplanes—except for the smaller and lighter ones—end up with some type of artificial force added in pitch in order to meet the rules for positive stick force across the CG and operating airspeed range. The most common artificial force system is a spring that pulls the control wheel forward, adding force when the pilot tries to pitch the nose up. The down spring would almost certainly not be required when flying with a forward CG but is necessary to keep stick force positive with the CG all the way aft.

Another technique for adding pitch force is the bob weight. A weight mounted on a lever arm is attached to the down circuit of the elevator controls. The weight applies a steady nose-down force, but its real function is to add stick force per g. When the airplane pitches up or down, g-force amplifies the force of the weight through the lever, increasing the nose-down or -up force the pilot feels through the controls.

Over the decades airplane designers have learned many techniques to tailor control force and harmony. The pressure of the certification rules has been a factor, but more important is the competition of the market. A nice flying airplane is simply more desirable and has a better chance to succeed.

I find it interesting that the one light airplane I have flown that comes closest to the perfect 2-4-6 control force harmony is the Cessna 162 Skycatcher. The light-sport aircraft rules are the least stringent when it comes to flying qualities, but Cessna engineers set their own standards and met them. With a clean sheet design, and the experience of building thousands of two-seat trainers, the Cessna people knew how to design the control system and the control surfaces and where to locate the control hinges to achieve near perfection. Good flying qualities are essential for safety, but also for learning. I think the 162 may be the most effective trainer Cessna has ever built.

THE MOUNT MITCHELL RIDE

To get to the southeast coast and on to Florida and the Bahamas from our still new home base in Muskegon, Michigan, I have to fly over the southern

part of the Appalachian Mountains. Actually, it is the Black Mountain chain of the Appalachians, the highest mountains east of the Mississippi River, that are the issue.

Mount Mitchell is the star of western North Carolina’s mountains topping out at 6,684 feet. Mount Mitchell is just northeast of Asheville and is so special that it is the center of an enormous state park, the first state park in all of North Carolina. The peaks of the Black Mountain ridgeline are pretty uniform, so it’s sometimes hard to pick Mount Mitchell out from other summits, several of which are only a few hundred feet lower than Mitchell.

Lots of people—probably most—love mountains. But I hate mountains. Maybe if I didn’t fly, I would come to love those big rocky lumps, but I do fly, and mountains only mean one thing to me—turbulence and bad weather. And Mount Mitchell delivers both.

To avoid flying over the mountains and on my way southeast I file over the Spartanburg (SPA) VOR, which takes me a little east of the direct course to Savannah or on to the east coast of Florida. The route usually keeps me out of the clouds that stick to the Black Mountains most days, but the turbulence is another matter. If the wind aloft is from the west, there are going to be bumps, usually pretty big bumps, as I pass the mountains.

Not long ago Stancie and I were cruising along in nice smooth clear air headed southeast with the wind blowing off the right wingtip and not doing much of anything to our groundspeed. We had a good view of the mountains as the cloud bases were above the peaks, which is not often true. It seemed like we were past the turbulence danger zone when I said something stupid like, “Guess there are no bumps today.” Seconds later the airplane started climbing, the autopilot pushed the nose over to maintain altitude, and I yanked the throttles back to keep airspeed under control. Then we hit the wake of the mountain. The airplane shook violently for about 15 to 20 seconds with stuff, and us, bouncing around the cabin. Suddenly, the turbulence ended and we sailed on in clear skies and a smooth ride.

Mount Mitchell is named for a professor from the University of North Carolina who first determined its elevation. Professor Mitchell died on the mountain when he fell off a cliff into a waterfall, was knocked unconscious, and drowned. I plan to keep an eye on that mountain and be ready for what it can dish out. Maybe someday I’ll even get to fly past it in smooth air.