Originally Posted by markpierce
Better to land in glass seas or on four-foot-high waves? What is the maximum wave height considered safe for the typical float plane?
They can both destroy your plane and kill you. And no floatplane pilot would attempt a landing in four foot waves unless it was an emergency and there was no other choice. And he or she would do it knowing the plane would most likely come apart on touchdown.
(Big and consistently spaced swells, I should add, are another matter and there is a technique for landing and taking off in them that has a very good chance of working.)
The maximum wave height a floatplane can handle is dependent upon the size of the plane. A de Havilland Otter can handle rougher water than a Piper Super Cub. Floatplanes, unlike wheel planes and skiplanes, don't have shock absorbers. The float system is rigid to the airframe. Touchdown speed varies with the type of plane of course, but they can run from 40 to 60 mph. Imagine running across the water in a ski-boat at that speed and that's what you're dealing with.
So it's not just the size of the waves but the distance between them and their steepness that are critical factors in deciding whether to attempt a landing on rough water.
The bottom line is that a floatplane is far more susceptible to damage on rough water than one might expect just looking at one. The floats that look so large and heavy duty to the eye are actually quite fragile.
I landed a Beaver once in the Strait of Juan de Fuca to deliver a part to a boat and while the water looked pretty decent to me, when I got on it I found there was a low swell pattern that had not been apparent from the air. It's the only time I've ever thought an airplane was actually going to come apart under me. Once down and stopped I realized what the water was doing and so could plan my takeoff run and technique to minimize the pounding to a fair degree.
To a boater in a typical recreational cruiser like most of us here have, the water I landed in would probably have been considered fairly calm. There were no whitecaps, just fairly small wind ripples, probably less than a foot. This I could see. The gentle rolling swell pattern I couldn't.
Flying boats, by the way, can handle rougher water than a floatplane.