Why use a firm landing on wet runway

[A Squared]

Typhoon pilot,

It is possible to waterski an airplane on the water. I know people who have done exactly that. It can be used to land on an otherwise too short sandbar in a river. You can put the airplane’s wheels on the water and start slowing the airplane down, so that you are at or below what otherwise would be the stalling speed as you roll up onto land. A few years ago, Mountain Pilot Magazine (now defunct) ran an article complete with photographs of this technique. Incidentally, I can assure you that you do not need to have your brakes locked to do this. Don’t ask how I know this.

Getting back the subject of the thread, this is a result of hydrodynamic planing, not surface tension. Hydrodynamic planing is what keeps a water skier up, or a power boat or jet ski "on the step" and on top of the water. Hydrodynamic planing results when the force required to displace the water exceeds the weight of the waterskier or boat, or airplane. It has nothing to do with surface tension.

Surface tension is a weak and fragile phenomenon. It is what allows a water strider insect to walk on top of the water or enables you to fill a glass slightly above the rim without spilling, or if you are very, very careful it enables you to leave a common pin suspended on top of water. Pour water into a glass until it is slightly above the rim. Touch the water with your finger and it will spill out, because the surface tension has been disrupted.

I’m sure that you have seen a water skier, and have seen his wake and the roostertail that he throws up. It’s pretty obvious that the waterskier has thoroughly disrupted the surface tension of the water, so it’s not much of a factor.

Now, it is possible, I suppose that in a thin film, surface tension (not hydrodynamic planing) has some effect on braking. I don’t know, I’m skeptical though. The fact that someone carries a title such as "Chief Test Pilot of the British Civil Aviation Authority" does not prove anything. It’s a bit like those idiots who try to prevail in an argument by claiming they have more flight time than someone else .... ummmso what? Does he have a rational explanation of the phenomenon which is solidly based on scientific fact? If so, let’s see the explanation, if not, well repeating someone’s job title is a pretty unpersuasive argument. Any explanation of surface tension which involves waterskiers is factually incorrect and serves only to illustrate a flawed understanding of surface tension and hydrodynamic planing.

 

[TurboS7]

Unless you have waterskiied with a Super Cub you aren't a real Alaskan pilot. My instructor at school grew up in Palmer, he showed us pictues of him doing that in a Cub. I guess when you are a teenager up there that is what you do for kicks.

 

[typhoonpilot]

Now that we have established that water skiing an airplane is possible and done fairly often in Alaska lets go back to the original debate. My point about water skiing an airplane was a corallary to what would happen if you touch down on a wet runway too smoothly. So let's ask the question, " what would happen to your Piper Cub if you touch down on the lake too hard ? "

I may not be able to explain the physics of that, but I think we can all picture it pretty well. Can anyone say, "cartwheel" ?


Typhoonpilot