Single Pilot Cockpit Techniques, Part III

Use your autopilot.

I give you the conclusion first, and if that’s all you need, fine, but autopilots are much misunderstood and therefore misused, and are worth some further thought.

The Basics. Autopilots are classified by axis, one, two, and three, corresponding to the three axis about which the aircraft rotates: roll, pitch and yaw. A simple, one axis autopilot, often called a wing leveler, controls the roll axis. A two axis autopilot controls roll and pitch, and in its simplest form is therefore both a wing leveler and pitch hold, with altitude hold, altitude preselect, heading hold and nav tracking being useful complements to the basic roll and pitch commands. A three axis autopilot (often erroneously used to describe a “full” autopilot with altitude hold and preselect and all nav and approach functions), is normally only found on turbine powered multiengine aircraft, and provides for engine out control by the autopilot: the third axis, yaw, provides the rudder power to maintain directional control with an engine out and varying degrees of power from the remaining engine or engines. Even with the third axis of control, it normally is only coupled when in the approach and go around modes: climb, cruise, and descent are normally uncoupled from the yaw axis and still require manual rudder input or rudder trim on the part of the pilot. (The reasons for this are very complex and have to do with autopilot certification standards, balancing autopilot functionality with negative consequences of autopilot failures, a very technical topic beyond the basics of autopilots.)

Some aircraft have yaw dampers (or dampeners), which is not an autopilot per se but does use the rudder to counter unwanted yawing, usually caused by unwanted rolling motions. Sweep winged aircraft are particularly susceptible to this uncomfortable rolling, yawing motion—the dreaded Dutch Roll—which on earlier swept wing aircraft could reach uncontrollability if left unchecked: one of the required maneuvers on the Boeing 727 type rating check ride was to regain control after the yaw dampener had been turned off and a big yaw intentionally induced. As I remember, the yaw damper was a no-go item. But a yaw damper is not part of the autopilot system and is not powerful enough to negate the adverse yaw resulting from an engine out.

Any autopilot is better than no autopilot, but the minimum for single pilot VFR flight is a single axis, or wing leveler, type autopilot (and with a heading hold or heading bug could be quite useful), while the minimum for IFR flight would be a two axis with at least heading hold and altitude hold. Each allows you to let go of the aircraft in order to do all the other things a single pilot has to do: read charts, set power, lean mixtures, write down frequencies, keep a flight log, pick up the pencil that dropped on the floor, change fuel tanks, look ahead and so on and so on. The reason I believe you need both heading hold and altitude hold for IFR is because altitude control is so much more critical on an instrument clearance than it is on a VFR flight. If the altitude nudges upward or downward a hundred feet or so VFR while looking away, you haven’t violated an assigned altitude clearance, the aircraft is still firmly under control, and a little pressure or pull on the control column will easily get it back on altitude again. But the same thing IFR is a serious enough deviation from your assigned altitude to either cause problems with ATC if left uncorrected, or take so much attention that whatever it was that you needed to do besides fly the aircraft doesn’t get done.

Pilots often feel that using the autopilot is a sign of weakness—a crutch—and if the best pilot in the airplane is the autopilot, there is some truth to that. An autopilot is no substitute for basic flying skills which, in the case of an instrument rated pilot means more than just being able to hold altitude and heading, but also being able to shoot accurate approaches to minimums. And there is no substitute for hand flying to keep those skills tuned. But assuming your basic flying skills are acceptable, and you could hand fly the airplane throughout its full profile from climb out through the approach if necessary, there is absolutely nothing wrong with using the autopilot so that you can concentrate on the rest of the job—managing the flight—without the distraction of having to constantly keep scanning and correcting. That’s what it’s there for.

A couple of examples from the world of turbine aircraft may help illustrate this. The Cessna Citation SP is certified for single pilot operation, but only if the autopilot is functional. Makes sense. And let me tell you a little secret: It is an incredibly easy airplane to fly, much simpler than a typical reciprocating general aviation twin. The straight wing is as forgiving as a Cessna Skylane, with near centerline thrust an engine out is very easy to handle, and the power couldn’t be easier to manage: one power control, push forward for more, pull back for less. The fuel is either on, off, or crossfeed. The rest of the aircraft systems can be covered in a day of ground school. And the FAA still requires a fully functioning autopilot to be flown single pilot.

MNPS (Minimum Navigational Performance Specification), the document that describes equipment and procedures necessary to fly from FL 290 to FL 410 over the North Atlantic, one of the most heavily trafficked, non-radar controlled airspaces in the world, specifies that an autopilot be used at all times when in that airspace. Aircraft separation along these tracks is predicated on accurate tracking of course and very accurate maintenance of altitude, and it simply won’t allow for a pilot’s momentary lack of concentration. Anytime you’re in congested airspace, you would be wise to do the same.

At ATA Airlines, we trained to hand fly approaches to below standard minimums, and were required to demonstrate, on our check rides, the ability to hand fly an engine out approach to minimums and then do a go around. But in line flying it was ATA’s policy to do all approaches to minimums on the autopilot, and to do all Cat II (below standard minimums) and Cat III approaches (no minimums) using not just one but all autopilots, which in the case of the Boeing 757 meant all three autopilots (two for the Lockheed 1011). The reason for that was mostly redundancy—if one failed at normal minimums the approach could be continued to an autoland on the remaining autopilot or autopilots—but also accuracy: each autopilot monitored the other both for deviations from standard and for increased accuracy. If airline pilots have to use three autopilots in certain circumstances, I wouldn’t feel too bad using one. Again, that’s what it’s there for.

So train by hand flying and practice by hand flying when conditions allow, but the rest of the time, use your autopilot. It’s one of the best ways to make your job easier, your results better and, all things considered, be a better pilot.