I know there are some amphibious planes which can land on both water and land but how different is the their landing in comparison to that of a normal small aircraft?

Also, if seaplanes needs to go into some marsh, will that work for them?

  • $\begingroup$ If the ground is soft and wet: Yes, no problem. Avoid any solid objects, though! $\endgroup$ – Peter Kämpf Jan 14 '15 at 7:25
  • $\begingroup$ I suppose you mean without significant damages. Otherwise, the result is the same as landing without extending gear $\endgroup$ – Manu H Jan 14 '15 at 15:40
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    $\begingroup$ @ManuH: You will be surprised how sturdy the bottom of a float or seaplane hull has to be. After all, when planing all the mass of the craft is supported by a very small area. Water is 800 times more dense than air, and as a rule of thumb the structure of a seaplane fuselage is 50% heavier than that of a comparable landplane. $\endgroup$ – Peter Kämpf Jan 14 '15 at 21:39

A pure seaplane cannot land on a normal (land) airfield: The hull or floats would be badly damaged.

An amphibious aircraft can land on both water or a normal airfield (pavement, grass, gravel, etc.), because it has both wheels and floats, but with amphibious aircraft you're either operating as a seaplane (on water) or a landplane (on solid ground), and you would follow procedures appropriate to the type of operation you're conducting.

As I understand it amphibious aircraft would not be suited to landing in a "marsh" or "swamp": The water and mud would render the wheels ineffective (and possibly dangerous: If the wheels dig in to the mud the aircraft could flip over), and the dirt/land portions of the area would damage or destroy the floats/hull.
It may be possible to put the aircraft down in such an area, but it would be very unsafe, bordering on reckless, to do so in a non-emergency situation.

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    $\begingroup$ It also depends on where it's on floats or whether it's a flying boat. The Grumman line of flying boats, like the Albatross, have retractable wheels. Also, terminology wise, it's amphibious floats $\endgroup$ – rbp Jan 14 '15 at 13:36
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    $\begingroup$ @rbp: Both flying boats and float planes can be amphibious and neither have to be. The large flying boats of early days were not, because at the time there were no runways they could use anyway. On the other hand float conversions of utility aircraft often are, because they want to land on lakes in the bush, but on airports in the cities. $\endgroup$ – Jan Hudec Jun 22 '15 at 13:31
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    $\begingroup$ Yes that was exactly my point. $\endgroup$ – rbp Jun 22 '15 at 13:33

Back in the early 1970s I belonged to a Civil Air Patrol (CAP) squadron that had a J-3 cub with an 85 horse engine on it. During the summer we would operate it on floats, during the winter on wheels. At the end of summer, we would land it on the grass alongside the runway at the Springfield, OR airport (no longer there, it's a big Walmart now) and replace the floats with wheels. In late spring, we'd replace the wheels with floats and take off from the grass.

The joke was that for takeoff you were supposed to line up all the cadets and have them pee in unison along the path the floats would take to aid in the takeoff. Actually, that wasn't necessary since western Oregon gets a lot of rain. Even with wet grass though, for the takeoff we'd get the initial movement by pushing, and we were always careful to ensure that the grass had nothing on the takeoff path that would damage the floats.

With the floats on, you could fly when the airspeed said 40 mph (yes, it was indicated in mph) which is about 35 knots. You could generally count on at least 5 knots of wind right down the runway when it was raining, so at 30 knots across the grass you were good to go.

You can go to YouTube and search "floatplane landings on grass" to see some examples of landing on grass. "Floatplane takeoffs on grass" will show some takeoffs, but a quick look showed using a dolly, which I think we did once or twice before my time with the group but then figured it was easier to just use the grass.

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    $\begingroup$ CAP = Combat air patrol? $\endgroup$ – asawyer Jan 14 '15 at 15:58
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    $\begingroup$ @asawyer Civil Air Patrol $\endgroup$ – The Guy with The Hat Jan 14 '15 at 16:45
  • $\begingroup$ @TheGuywithTheHat That would make more sense. Thanks! $\endgroup$ – asawyer Jan 14 '15 at 18:48

Seaplanes can land on land (pun intended) if the ground has a soft cover. This could be snow, tall grass and landing in a wet peat bog is also possible. However, any solid object close to the surface (logs, stones) will damage the hull.

Historic cases are the landings of Amundsen with a Dornier Wal on arctic ice or the landing of Gronau's Wal when it was transferred to the Museum in Munich (actually, this was the same aircraft). It was landed in winter on a snow-covered meadow close to the Isar river in central Munich.

This was in no small part possible due to the flat hull shape of Dornier flying boats. They were optimized with water tunnel studies for the heavy and inefficient engines of their time. Modern hulls have a keeled shape, where the bottom is v-shaped to reduce the load factor when planing in rough sea. Landing such a seaplane on land needs more snow and should not be attempted on grass.


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