#14 Prop Smacking, Part 1

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The Tailwheeler’s Journal #14
Prop-smacking, part 1
I fly with a lot of people who have little or no tailwheel time. What do many of these pilots have in common? Most are very concerned lest they smack that propeller on the runway.
Their fear originates with the realization that there is no nosewheel to prevent the prop from contacting the ground. So when I encourage them to raise the tail with full forward elevator on takeoff, many of them just don’t believe me. They don’t believe that they can be free with forward elevator and run no risk of prop smacking.
I have smacked a prop. I did it in front of thousands of air show fans at the Reno Air Races. When if comes to prop-smacking, I am the voice of experience. Believe me, it was a situation that none of you will ever experience (in fact, I asked Janae to put the video of that event on our website. You can see it there under “Reno Prop Smack”). You are probably concerned that you can prop-smack the runway by lifting up the tail too far on takeoff. Let me tell you something: It ain’t gonna happen. Let’s go back to fundamentals to see why: The horizontal stabilizer is actually an upside down wing. Normally, its job is to push the tail down more as the airspeed increases. In this way, depending on the trim, the horizontal stabilizer and elevator control airspeed through a dynamic process called the Phugoid Oscillation (that was for you, Jake). On takeoff, we ask the elevator and horizontal stabilizer to reverse their normal roll and raise the tail. That’s pretty easy. After all, in a tailwheel airplane, the horizontal stabilizer is angled to do just that when the tail is on the ground. So we place the control wheel or stick fully forward as the plane accelerates. As the tail comes up, the horizontal stabilizer becomes level with the direction of flight. If it rotates any further it incurs air loads that push it down. The more we accelerate, the harder the horizontal is pushed down and the more pressure it takes for us to try to make it come up past level. In fact, with full power and full forward stick it’s almost impossible to raise the tail enough to contact the ground with the prop. The slightest relaxation of forward pressure will keep the tail from going up any further. And that is why you don’t have to worry about smacking the prop on takeoff. The reason I try to get my students to keep that tail up is so that the plane won’t go “skippity-hop” off the ground as the weight gradually changes from the wheels to the wings. And that’s what started this whole discussion.
On landing and subsequent deceleration, you can smack the hell out of it if you are not careful and we will deal with that situation in the next journal.
Happy Swooping!