zaitcev
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Pete Zaitcev
Oh, about that. There's something I would like you to know about porpoising (if you don't already): it has nothing to do with rubber donuts in the gear of our Mooneys. What really happens is that the nose gear touches the ground first, and at that moment it tips the airplane nose up. When it does that, the angle of attack suddenly increases, the lift increases, and the airplane zooms immediately. The amount of the zoom is related to the nose-down angle at the time of contact, because that is how much AoA jumps. This is why porpoise increases amplitude with every jump: the airplane progressively approaches stall and becomes ever more ready to dip the nose, so it meets the ground in a steeper nose-down attitude each time. Eventually, it reaches a point where yoke full back will do absolutely nothing, just like it does nothing when airplane stalls high off the ground.
The problem with Mooney, specifically, is that our ground attitude is enough nose-up that at speeds about 85-87 mph the nose gear is guaranteed to touch the ground first. Note that if the springiness of the landing gear were the culprit, the amplitude of jumps would not grow when porpoising.
I found the discussion of porpoising in the FAA Airplane Flying handbook of great value. Our tax well spent. It even mentions how to apply the "yoke full back" technique, although the text cautions that exquisite control is necessary to succeed (which apparently neither of us had at the time).
