The plane-landing-at-the-wrong-airport thread brings me back to a harrowing experience I had as a kid and a question I’ve had ever since - about seaplanes. We had flown into a little lake to fish and when we were leaving, the pilot (of a little Cessna float plane) was pretty much backed up as far as he could go on the lake. The water was pretty flat, and I wondered if that was a factor, but when he hit the gas and pulled back on the steering post? wheel? device? the nose of the plane went up, but we didn’t leave the surface. As I remember it (some 60 years ago, I’d guess) he sort of rocked the front of the plane up and down as we neared the farther shore, and then we suddenly went up and cleared the trees by what looked like about 4 mm. Ever since, I’ve wondered if there’s some extra difficulty breaking the adhesion when flying out of a calm lake. Maybe my memory is distorted after all the years of telling the story, but maybe there is something a pilot here could tell me about the experience. Dopers?
xo,
C.
Yes, a calm lake will not provide air bubbles under the floats. This will increase the amount of drag on the floats and thus the amount of speed needed to get over the “hump”, the highest point of water resistance on the floats before they “step up” to the planing attitude / takeoff.
Here’s a good link that goes over seaplane takeoffs in detail:
It’s true that a lake that tilts downhill will let the plane pick up speed faster, too.
But you can’t take off upstream in a river. That’s just like a treadmill.
Ah, yes, the material in that link reminded me of another feature of the liftoff that I had forgotten: the pilot also sort of suddenly tilted the plane in what seemed to be an effort at tearing off one of the pontoons from the surface first. The liftoff was a sort of two-phased business - one, jerking one side of the plane off the water, the other pulling up and off the lake completely. I think he must have been pretty good, because there’s not much room for error in a situation like that, and he did get us out of there.
What about a treadmill in a river?
at least you had enough gas … that’s the stuff that Will Rogers and Wiley Post ran of back in the late 1930’s and wound up landing upside down on the next lake.
Float plane pilots will sometimes make a circuit of a calm lake to create some wake prior to attempting take-off.
Actually, it was a tidal lagoon near Walakpi, and I’m pretty sure it was engine problems, not fuel, as they crashed just after takeoff.
We like to kayak a portion of the Allegheny River around Foxburg, PA. There is a guy with a float plane we’ve met on the river. The first time he landed while we were paddling, scaring the crap out of us, was a real experience.
I always thought that was to check out the “runway” for obstacles like logs, stones, boats or swimmers.
They were nose-heavy due to having the wrong floats on the plane, too.
They had made it that far without issue. The floats were determined to be serviceable for the aircraft, and they had left both Anchorage and Fairbanks without a problem. There were reports of the engine laboring after takeoff from the lagoon where had they stopped for directions, not to take on cargo or fuel. At that point, they would have been lighter than at any other time since leaving FBX.
I heard about a pilot’s conference once where a similar subject came up. They were debating whether to takeoff (or land) upstream or downstream, and depending on the wind. Finally one old bush pilot in the back said “takeoff and land downstream.” Everyone asked him why. He said that if there were any branches or debris in the water, the current would bend them downstream; if the airplane hit them you’d skip over the top rather than have them snag on something.
I did a college internship at a company that built floats. I was flying with the owner once and he did a takeoff like that (it’s also mentioned in Dorjän’s link) so it seems to be a well-known technique.
I always wondered why seaplanes don’t have hydrofoils on the pontoons to lift them up out of the water during takeoff. Obviously the foils would have to retract for landing. Like most things I assume it’s just a matter of cost. But it would seem like a hydrofoil on a seaplane taking off would make for improved takeoffs, lifting it up and out of the water.
Another issue, I imagine, would be that if the water on the lake is totally still, it probably means there’s no wind either. Given that aircraft fly due to airflow over their wings, it is usually advantageous to try to fly upwind on takeoff, as any headwind will allow the plane to take off over a shorter distance (this is usually true of landings as well). On a land-based runway, this means taking off from the end of the runway that lets you fly upwind. On a lake, it would mean largely the same thing, depending on the shape of the lake.
A seaplane on a river would probably have difficulty going upstream for takeoff just because the water would be pushing against the plane, making it more difficult for the aircraft to attain enough airspeed to become airborne. Traveling downstream, depending on wind conditions, would seem the easiest way to generate a headwind for the plane.