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Q-talk 100 - Slip Slidin' Away

How do you know if you are in coordinated flight? In other words, how do you know for sure that the tail of the airplane is directly in trail with the front and not actually flying out to one side? The first answer that comes to mind is, "center the ball." That may be a certainty on factory aircraft that are jigged and rigged properly. But what about our less than perfect (who said that) homebuilt?

When it was time to install a turn/bank indicator in my plane, I didn't want to spend $400-$800 for an electric one (I don't have a vacuum pump), so I bought a cheapo bubble leveler like one that might used on a camping trailer. I leveled the airplane and mounted the device to the instrument panel. It looked great. Unfortunately, while static on the ground, the bubble would only indicate whether or not the wings were level. It would not represent whether or not the tail would actually be directly in trail in flight.

Once 1 was finally in the air, I noticed while in level flight that I had to step on a lot of left rudder to center the ball. When I did so, it felt uncomfortable in the cockpit, like I was in uncoordinated flight. I had a chase plane follow me and confirmed that I was, in fact, throwing the plane into a yaw vs. coordinated flight when I applied rudder. This was also confirmed by having to put in opposite aileron to maintain a heading. What to do?

After several hours of twisting and tossing through the air, I came upon a highly technical solution. I realized that since there was an air vent located on each side of the fuselage at the same relative location, I could use my air inlets to determine when the plane was in coordinated flight. When I could feel air equally through both inlets, I knew the tail was perfectly in trail. If I could feel air through only one at a time, I knew I was either in a skid or a slip.

Solution: Again calling upon my incredible technical skills, honed by hours of sanding, I slotted an attachment hole in one end of the bubble leveler. On the next flight, I took along a screwdriver. I loosened the leveler, applied enough rudder to allow air to enter the inlets on both sides of the cockpit equally, centered the leveler ball by moving the attachment base and retightened the screw.

I validated the results by centering the ball and seeing that I could now track a heading without corrective aileron displacement. It worked! Now, in the final turn, I feel a lot more comfortable knowing that I am in coordinated flight when the ball is centered.


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