The value of a capable autopilot
The same can't be said of some of the equipment. Take the autopilot, for example. It's the same vintage as the airplane, but unlike the rest of the airplane, the autopilot is feeling its age. We've been struggling for weeks to solve a problem with it. When we try to engage the autopilot, the airplane takes off on roller-coaster-style up-and-down pitch gyrations. The local avionics shop has devoted hours to troubleshooting the system, cleaning components, bench-testing the autopilot computer, and replacing the attitude indicator, which provides the autopilot with pitch and roll information.
We're not much closer to solving the problem than we were a couple thousand dollars ago, but we press on regardless. The alternative is a transplant--a new system costing about $20,000, plus several weeks downtime. As I write, the avionics shop is planning to do some test flying to tweak and twiddle the old autopilot and, hopefully, move past head-scratching to a final fix-it strategy.
One outcome of our troubles is that I've been reminded of an autopilot's usefulness for cross-country and instrument flying. One recent six-hour round trip with every minute spent hand-flying was enough to make me appreciate the benefits of having a mechanical copilot, even one that is getting creaky with age. It's the old story--you don't realize how much you appreciate something until it's gone.
Not so long ago, autopilots were rarely seen in fixed-gear, four-place singles, but with the size, weight, and cost reductions made possible by digital technology, they have made their way down the chain to the smallest of airplanes, including experimentals. If you haven't yet flown an autopilot-equipped airplane, you soon will.
An autopilot performs two basic functions. Its first and most basic job is relieving the pilot of some of the workload of flying the airplane. Without an autopilot, the pilot must constantly concentrate on holding heading, pitch attitude in climb and descent, and altitude in level cruise flight. That's difficult to do in some airplanes.
Reducing pilot workload means more than just lessening the boredom and fatigue of hand-flying in level cruise for hours on end. It also means releasing the pilot to attend to other important business.
Using the autopilot allows the human pilot to spend more time on such critical tasks as looking for traffic, monitoring the flight instruments, and navigating and communicating. Autopilots are especially important when flying in the clouds. Without one, the pilot must devote nearly 100 percent concentration to just flying the airplane at a time when navigating, communicating, and maintaining positional awareness are of vital importance.
The second task of an autopilot is to fly the airplane more precisely than can the pilot. This becomes necessary in certain conditions such as in sustained light to moderate turbulence, in the clouds, and--most especially--on an instrument approach in reduced visibility when the pilot does not have visual contact with the horizon or ground.
Modern autopilots do an amazing job of controlling the airplane with remarkable accuracy. The more sophisticated ones will fly a precise precision approach in zero-visibility conditions down to 200 feet above the runway.
Autopilots come in many flavors, beginning with a basic one-axis (roll) wing leveler. When engaged, a wing-leveler autopilot controls ailerons to keep the airplane on the selected heading. The pilot still must establish, monitor, and adjust altitude using power and trim, but that is a simple, part-time task compared to hand flying. Now you are free to look for traffic, handle and study charts, and pay some attention to your passengers.
The next step up the sophistication ladder is adding pitch control to make it a two-axis autopilot. The autopilot controls the pitch of the airplane by manipulating the elevator/stabilator position. A valuable enhancement to pitch control is electric trim. This enables the autopilot to make small pitch adjustments by manipulating the elevator or stabilator trim tab. If the airplane has a two-axis autopilot but no pitch trim, the pilot must manually trim in response to an annunciator on the autopilot.
Altitude hold is nice on long trips in VFR conditions because it frees the pilot of constant hands-on flying. It's a virtual necessity in instrument meteorological conditions, where a pilot is required and expected to maintain the exact altitude specified by air traffic control. Everyone's safety depends on it. In that case, an autopilot performs both its functions--relieving pilot workload and flying precisely.
The most sophisticated general aviation autopilots incorporate a third axis, yaw. This makes for a more comfortable ride since it dampens turbulence-induced yawing. In high-performance twins, an autopilot with yaw control can be a tremendous aid in managing an engine-out situation.
For all of its functionality, an autopilot must be kept in perspective. Like a GPS navigator tied to a multifunction display, or a collision-avoidance device, an autopilot can become more of a crutch than an aid. A lazy pilot can become a slave to a capable autopilot, relying on it to fly the airplane from initial climb to crossing the numbers. Flying skills and confidence can atrophy, and that could be a problem if the autopilot decides to malfunction at an inopportune time.
The first task of a pilot new to an autopilot system is to become familiar with its features, functions, and limitations. You wouldn't turn over command of your airplane to a stranger; why give the flight controls to an autopilot that you haven't gotten to know well? National Transportation Safety Board accident reports contain many tales of pilots who had very bad days because they didn't know the problems the autopilot could cause if they misused it, much less all the ways to turn it off once things got out of hand.
Flying an airplane equipped with an autopilot means moving up the ladder of sophistication. An autopilot makes cross-country flying easier and less fatiguing. It also contributes to safer flying, provided the pilot knows who is really in charge.
Mark Twombly is a writer and editor who has been flying since 1968. He is a commercial pilot with instrument and multiengine ratings and co-owner of a Piper Aztec.
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