Aero-Tips!

A good pilot is always learning -- how many times have you heard this old standard throughout your flying career? There is no truer statement in all of flying (well, with the possible exception of "there are no old, bold pilots.")

Aero-News has called upon the expertise of Thomas P. Turner, master CFI and all-around-good-guy, to bring our readers -- and us -- daily tips to improve our skills as aviators. Some of them, you may have heard before... but for each of us, there will also be something we might never have considered before, or something that didn't "stick" the way it should have the first time we memorized it for the practical test.

Look for our daily Aero-Tips segments, coming each day to you through the Aero-News Network.

Aero-Tips 12.11.06

An airplane that is in rig is one which, in cruising flight, presents the straightest alignment between relative wind and the airplane's longitudinal axis. That is to say, a well-rigged airplane will "fly straight" without unusual control inputs.

What is rig?

Airplane rig is the sum total of the way it was put together-whether the wings and tail were mounted precisely to specifications, flaps and primary control surfaces were hung correctly, and the landing gear struts are properly attached and inflated (this last item is, of course, negated in most flight regimes in retractable-gear airplanes).

Why is rig important?

Airplane rig is important for a couple of reasons:

• Reduced need for compensating trim increases airplane performance
• Lack of need for active pilot input reduces pilot workload and fatigue

Let's say you're flying an airplane that's a little out rig-for instance, one wing was mounted a millimeter off square. In cruise flight you'll need to compensate for this out-of-rig condition with trim. Compensating trim corrected for an out-of-rig condition, but it does so by deflecting a trim mechanism, and therefore a control surface, into the slipstream. Now the airplane "trims up" properly (i.e., it flies closer to "hands off"), but extra aerodynamic drag created by the deflected control reduces airspeed.

If the pilot does not (or cannot) trim off the pressures resulting from an out-of-rig condition, he/she will have to manually overcome the condition with control inputs. This will still result in reduced performance from control deflection, but additionally robs part of the pilot's attention (increasing workload and reducing situational awareness) and adds to fatigue if this constant input is necessary throughout the duration of a flight.

Other rig factors

Other factors besides airplane construction can affect rig. Have ground-adjustable trim tabs (those flat pieces of metal on the trailing edge of many control surfaces) been bent out of position? If the airplane asymmetrically loaded (more fuel in one wing than the other, or a lot of the passenger or baggage load on one side of the cabin)? These factors will affect rig as well. When assigning passenger seats or loading cargo, consider the left-right loading as well as weight-and-balance loading along the longitudinal axis.

Aero-tip of the day: Know and account for the performance, workload and fatigue effects of an out-of-rig airplane.

FMI: Aero-Tips