Just What Exactly is a Seaplane?

Just What Exactly Is A Seaplane?

Right off the bat, let’s go back to the basics and discuss exactly what a “seaplane” is, as well as other common terms applicable to this subject area. Formally speaking, a “seaplane” is any “airplane” that is designed or equipped to be able to operate (both take-off from and “land”) on water. Specifically then, an “airplane” is first a fixed-wing, heavier-than-air, powered aircraft and as such that excludes, blimps, balloons, dirigibles, zeppelins, helicopters, and gliders – all of which are aircraft but not airplanes.

There are two basic types of seaplanes the floatplane and the flying boat. A floatplane is an otherwise standard “land” airplane that has been modified by the installation of external floats mounted on struts underneath the airplane which replace its original wheeled landing gear. A flying boat by contrast is an airplane designed from the start as a seaplane by incorporating an integral, boat-like hull on the bottom of its fuselage or main body such that it is able to “land” directly on the water. Note that even though most (but not all) flying boats are also equipped with smaller, lateral “balance” floats out near their wingtips, that does not make them “floatplanes.”

Floatplanes and flying boats are further divided into two sub-categories – amphibian or not. An amphibian, even outside of aviation, is something that operates equally well on land or in the water. Floatplanes and flying boats are considered to be amphibians too if they are also equipped with retractable wheeled landing gear. With the wheels “down” they can operate from solid ground just like any other standard airplane and with the wheels “up” they can take-off from or land on the water.

Trailer TakeoffFloatplanes with “straight” floats do not have retractable wheels built-in and so generally speaking they can take-off from and land only on the water. (Occasionally a “daredevil” will fly a “straight” floatplane off of a trailer that is towed down a runway by a car or truck, but that is not considered to be a standard operating procedure.) Similarly, a “pure” flying boat is a one that was built without any kind of built-in retractable wheeled landing gear and so it is capable of operating only to or from the water. In both cases, in order to perform major maintenance or for purposes of dry storage for two examples, they must be hoisted out of the water or picked up using an external wheeled cradle or other detachable wheels.

Picture: C172 Amhib Courtesy of Wipaire, Inc.

Therefore, there are both straight versus amphibious floatplanes and pure versus amphibious flying boats – but all of them are equally “seaplanes” because they all meet the definition given above. The primary advantage of an amphibian, either on floats or in the form of a flying boat, is that it is always equipped and ready to go or operate absolutely anywhere. The disadvantage, at least just in comparison to a comparable floatplane with “straight” floats or a “pure” flying boat, is the extra weight of the built-in retractable wheeled landing gear. By comparison, “straight” floatplanes and “pure” flying boats are usually much lighter and less complex and as a result typically have lower empty weights and comparably higher useful load capabilities.

After you have landed in the water, shut-down the engine, opened the door, started listening to the sound of the water lapping against the hull, and enjoying the fresh air and the feel of the sunshine on your face, nothing else really matters.

In a similar vein, there are respective advantages and disadvantages of floatplanes and flying boats. Floatplanes are currently much more numerous and common, especially in terms of single-engine, General Aviation aircraft. Accordingly, it is easier to find float-specific training than it is to find training geared toward flying boat operations in particular. Until the recent advent of new, small, Light Sport (LSA) category amphibians, there were relatively few flying boats in the GA fleet.

Maybe because of that, the FAA does not distinguish between the two types in terms of training requirements because both are ‘seaplanes.” On the other hand, insurance companies almost always do make that distinction for the pilots and aircraft that they cover. There are likely to be much more type-specific requirements for a check out in a relatively rare flying boat like a Republic RC-3 Seabee or Lake Amphibian (LA-4, Buccaneer, etc.) than there will be for initial or transition training in different float-equipped Cessna’s.

One major limiting consideration for all seaplanes is wave height and the basic “rule of thumb” is that any particular seaplane can handle waves half the height of their floats. By that measure, a floatplane with floats 2 feet high can handle waves up to 12 inches high. A flying boat with a main hull 6 feet high can handle waves up to 3 feet high – and that is a big difference. That wave height factor is specifically more important than any semantic distinction between “seas” or any other bodies of water. Even though they are still “seaplanes” most floatplanes are practically limited to the relatively calm or smooth waters of lakes and rivers and open-ocean operations are typically more the realm of flying boats.

HU16 AlbatrossIn terms of performance, generally speaking and with all other things being equal, flying boats are typically faster and able to carry heavier loads than floatplanes. The fundamental reason for that should be obvious; the installation of large, heavy, external floats on an airplane originally designed to meet certain performance goals without them automatically penalizes it with their significant weight and drag. In terms of operational parameters too, flying boats are often more capable, but they are also typically more complicated and expensive to build in the first place or to repair later. Rarely however are all other things equal and more often than not, such comparisons are matters of “apples versus oranges.” As with any airplane being operated for other than just personal pleasure, the actual mission is what ultimately matters in the end.

Outside of specific mission requirements, just as with the classic Cessna versus Piper / high-wing versus low-wing debate, a lot of it comes down to exposure and experience. Most pilots prefer what they are used to. After you have landed in the water, shut-down the engine, opened the door, started listening to the sound of the water lapping against the hull, and enjoying the fresh air and the feel of the sunshine on your face, nothing else really matters.

Dave Marion is the Technical Content Editor at Seaplanemagazine.com. As A&P and IA with 29 years of experience in aircraft maintenance, he is also a Commercial Pilot with Airplane, Single & Multi-Engine, and Instrument ratings. He has a BA from Colgate University in 1984 and also graduated cum laude from Embry-Riddle Aeronautical University (DAB) with a BS in Aviation Technology in 1990. He can be reached along with all of the editors via E-Mail: editor@seaplanemagazine.com

NEXT: An RO-5E is an RO-5E is an RO-5E

Sign up now for the free SeaplaneMagazine.com Newsletter!

Share This!