Hi Mom,

I'm a private pilot, an old one who over the years has forgotten most of the things I'm supposed to know about why I do what I do. I use right rudder in left turning climbs because I'm supposed to, because it keeps the ball closer to centered, and because it keeps flight instructors from yelling at me so much on flight reviews. I know there's some other good reason for it too, but like a lot of the other old guys out there, I've forgotten why. I could look it up, but I thought it would be more fun to ask you to explain it. Please? Love the blog.

Thanks,

Walking the Walk, But Forgetting the Talk

Well, walk this way, my friend, and we'll see if we can't clear up the mysteries of aerodynamics to your satisfaction once more:

I'll trust that you've noticed the constant need for right rudder whenever you're at a high power setting OR at a high angle of attack. In a straight ahead climb, both of those conditions clearly apply, so the fact that you really have to step on it shouldn't surprise you. I'm equally sure that you've discovered through practical experience that level left and right turns each require at least some small amount of same direction rudder pressure. With me so far? Good. So, here you are in a straight ahead climb, foot sitting heavily on that right rudder pedal, just as it should be. Lotsa right rudder going on here. A left turn requires relatively little left pressure compared to what you're applying with your right foot for that full power climb. A whole lotta right plus a little bit of left equals...a little bit of right. See? Easy. You can think of it as easing off the right rudder pedal a bit for that left turn, or stepping a little to the left while continuing to hold lots of right pressure. Either way nets you the same results-a little right rudder in a climbing left turn, a well centered inclinometer, and a less apopleptic CFI come flight review time. Win-win-win. While we're at it, let's review where the need to be stomping to the right comes from in the first place, shall we?

Torque and asymetrical propeller loading are the primary culprits when we consider the aerodynamic left turning tendencies induced by a climb. Torque is short for, "For-every-action-there-is-an-equal-and-opposite-reaction," AKA Newton's third law of motion. What's going on here is that as the crankshaft and prop rotate in one direction, the rest of the airplane will be inclined to rotate in the opposite direction. See that prop turning to the right? The part of the airplane you happen to be seated in will be inclined to roll to the left as a matter of simple physics. Those clever aeronautical engineer types used to design wings that would produce a just bit more lift on the side forced downward in order to balance things out. The modern solution to the question is usually just to cant (tip) the engine a wee bit so that in cruise flight, the rolling motion is negligible or nonexistant.  In some cases, you even get aileron trim to fine tune for yourself. Nifty. Our friends with the pocket protectors can't build in solutions for every flight condition, though, so in a climb it's up to you to correct for Newton's law with right rudder. The corkscrew effect caused by spiraling slipstream adds to the effect, particularly at high propeller speeds and low airspeeds...which sounds a lot like our climb, now doesn't it? Air strikes the left side of the vertical stabilizer, forcing the tail to the right and causing the airplane to pivot around it's CG-sending the nose yawing and rolling left. Ah ha. Yet another reason to step to the right. An increase in forward speed mimimizes this so that, once again, cruise flight will seem much more balanced with less effort from our intrepid (not to mention better educated) pilot.

P factor, or asymetric loading, is the other major player in this game. In a climb, you've got yourself a high angle of attack. You've tipped that prop up at an angle to the relative wind such that the descending blade (on your right, of course, as you're sitting in the cockpit contemplating aerodynamics) has a higher resultant velocity than the ascending blade on the left. It's moving forward into the onrushing atmosphere rather than back and so it moves faster, getting a bigger "bite" of air, producing more lift. The additional lift generated on the right side of your prop pulls that side forward, swinging your trusty airplane lefterly yet again. Step right. Hold that right rudder. More right. Harder right...

There's a great and well illustrated discussion of how all these factors fall together to literally keep you on your toes to be found in the Pilot's Handbook of Aeronautical Knowledge. It's an FAA publication. Haven't read it yet or lately? Get it here!

In the meantime, add right rudder as you add power, maintain right rudder through your climb-yes, even in your turns, and keep that ball centered already, would ya?

Mom