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 12.14.06

Last week I was flying a Cessna 172SP. Before engine start I noticed the slip/skid ball in the Cessna's turn coordinator (I like how the instrument's miniature airplane has a high wing in 1996-and-after Cessnas) was sitting, before engine start, deflected about half a ball to the left. The airplane was sitting level on the ramp, with a balanced fuel load -- so the deflection was the result of instrument installation error (it wasn't mounted quite straight), or the panel itself was not mounted squarely in the fuselage. I made a mental note of the skewed slip/skid position.

After takeoff and settling into climb, I was putting in enough right rudder to compensate for yaw, but when I scanned to the turn coordinator I saw the ball to the left. So I gave it a little less right rudder until the ball centered on the instrument. The performance effect was almost immediately apparent -- rate of climb reduced, and airspeed decreased a couple of knots. Centering the ball resulted in worse performance. Why? Because "centered" on the instrument wasn't "centered" for real.

Check the ball

Returning the ball to the half-ball-left position returned speed and climb rate to optimum. This was the "true" ball-centered position. Flying with the ball in this position resulted in less drag because the airplane was more closely aligned with the relative wind. Improved performance was the result.

I saw the same thing in cruise. After leveling off, holding enough rudder to keep the slip/skid ball centered added about three knots to the indicated airspeed.

If I was flying an airplane with rudder trim the results would be the same; I would have to trim so the ball remains in its "true" centered position. An autopilot should do this automatically; it does not sense the slip/skid ball, but instead the actual aerodynamic motions that drive it.

Aero-tip of the day: Check the position of the slip/skid ball before engine start. If the airplane is sitting level, what you see will be the true centered-ball position in flight as well.

FMI: Aero-Tips