Seaplane Terminology

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337 / Form 337 - 

Amphibian - A seaplane with retractable wheel-type landing gear that can be extended to allow landings to be made on land.

Anchor - A heavy weight and/or hook like device that can be connected to a seaplane by a line that is intended to dig into the bottom below the water or on a shoreline and keep a seaplane from drifting.

Auxiliary Fin - An additional vertical stabilizer installed on some floatplanes to offset the increased surface area of the floats in front of the center of gravity

Beaching - Pulling a seaplane up onto a suitable shore so that its weight is supported by ground (above or below the water) rather than by water.

Beaufort Wind Scale - A standardized scale ranging from 0-12 correlating the velocity of the wind with predictable surface features of the water.

Bilge - The lowest point inside a float, hull or watertight compartment.

Bilge Pump - A pump used to extract water that has leaked into the bilge of a float or flying boat.

Bulkhead - A structural partition that divides a float or a flying boat hull into separate compartments and provides additional strength.

Buoyancy - The tendency of a body to float or to rise when submerged in a fluid.

Buoys - Floating objects moored to the bottom of a body of water to mark a channel waterway or obstruction.

Can Buoys - Cylindrical buoys marking the left side of a channel for an inbound vessel. They have add numbers which increase from seaward.

Capsize - To overturn.

CARS - CARS is the acronym for the seaplane pre-takeoff checklist Carburetor Heat, Area, Water Rudders Up, Stick Back

Cast Off - To release or untie a vessel from its mooring point.

Center of Buoyancy - The average point of buoyancy in floating objects. Weight added above this point will cause the floating object to sit deeper in the water in a level attitude.

Chine - The longitudinal seam joining the sides to the bottom of the float (or hull of a flying boat). The chines serve a structural purpose, transmitting loads from the bottoms to the sides of the floats. They also serve a hydrodynamic purpose guiding water away from the float, reducing spray, and contributing to hydrodynamic lift. 

Chop - A roughened condition of the sea surface sauced by local winds. It is characterized by its irregularity, short distance between crests, whitecaps.

Combination Ski - A type of aircraft ski that can be used on snow or ice, but that also allows the use of the airplane's wheels for landing on runways.

Crest - The top of a wave.

Cross Wire - A wire that is attached between the bow of seaplane floats to allow a pilot to walk across it from one side of an airplane to the other, from one float to the opposite float.

Current - The horizontal movement of a body of water. 

Day Beacons - An unlighted navigational beacon used a day mark.  

Daymark or Day Marker - A day mark or a day marker is a structure such as tower constructed on land, that serves as an aid to navigation on the water. Similar in concept to a lighthouse, though a daymark does not have a light and so it is usually only visible during daylight hours. Some disused lighthouses remain useful by serving as day marks. 

Deck - The top of a float, which can serve as a step or walk way. Bilge pump openings, hand hole covers, storage compartment hatches, and mooring cleats are typically located along the deck

Displacement Position - The attitude of the seaplane when its entire weight is supported by the buoyancy of the floats or hull, as it is at rest or during idle taxi.

Dock - To secure a seaplane to a permanent structure fixed to the shore. As a noun, the platform or structure which a seaplane is secured.

Downswell -  Motion is the same direction the swell is moving.

Fetch - An area where wind is generating waves on the water surface. Also, the distance the waves have been driven by the wind blowing in a constant direction without obstruction. 

Floatplane - A seaplane equipped with separate floats to support the fuselage well above the water's surface.

Floats - The components of a floatplane's landing gear that provide buoyancy to keep the airplane afloat. 

Floats on Skids - A type of helicopter float design where the floats sit on top of the fully functional landing gear skids. During water operations, the floats support the weight of the helicopter, and on hard surfaces the skids support the weight of the helicopter. 

Float Pump - Usually a hand pumped suction device used to pump a seaplanes floats of water that may accumulated in a float compartment. 

Flying Boat - A type of seaplane in which the crew, and cargo are carried inside a fuselage that is designed to support the seaplane on the water. Also, called a hull seaplane.

Glassy Water - A calm water surface with no distinguishable surface features, with a glassy or mirror like appearance. Glassy water requires great care as it can deceive a pilot's depth perception on landings and decrease takeoff performance.

Height to Length Ratio - The ratio between the height of a swell to the length between two successive crests (swell length).

Hydrodynamic Forces - Forces relating to the motion of fluids acting on solid bodies in motion relative to them.

Hydrodynamic Lift - For seaplanes, the upward force generated by the motion of the hull or floats through the water. When the seaplane is at rest on the surface, there is no hydrodynamic lift, but as the seaplane moves faster, the hydrodynamic lift begins to support more and more of the seaplanes weight.

Idling Position - The attitude of the seaplane when its entire weight is supported by the buoyancy of the floats or hull, as it is when it is at rest or during idle taxi. Also, called the displacement position.

Keel - A strong longitudinal member at the bottom of a float or hull that helps guide the seaplane through the water, and, in the case of floats, supports the weight of the seaplane on land.

Leeward - Downwind, or the downwind side of an object.

Moor - To secure or tie a seaplane to a dock, buoy, or other stationary object on the surface of the water.

Nun Buoys - Conical buys marking the right side of a channel for an inbound vessel. They often have even numbers that increase as the vessel progresses from seaward.

Plain Ski - A type of aircraft ski that can only be used on snow or ice, as compared to combination skis, which also allow the use of the skiplane's wheels for landing on runways.

Planing Position - The attitude of a seaplane when the entire weight of the aircraft is supported by the hydrodynamic and aerodynamic lift, as it is is during high peed taxi or just prior to takeoff. This position produces the least amount of water drag. Also, called the step position or "on the step."

Plowing Position - A nose high, powered taxi characterized by high water drag and an aft ward shift of the center of buoyancy. The weight of the seaplane is supported primarily by buoyancy, and partially by hydrodynamic lift.

Pop Out Floats - Helicopter floats that are stored deflated on the skids or in compartments along the lower portion of the helicopter, and are deployed in the the event of an emergency landing on water. Compressed nitrogen or helium inflated the floats very quickly. 

Porpoising - A rhythmic pitching motion caused by an incorrect planning attitude during takeoff. Porpoising can also be induced by crossing a boat wake or encountering waves.

Port - The left side or the direction to the left of a vessel.

Primary Swell - The swell system having the greatest height from the trough to crest.

Ramping -  Using a ramp that extends under the water surface as a means of getting the seaplane out of the water and onto the shore. The seaplane is typically driven under power onto the ramp, and slides partway up the ramp due to inertia and engine thrust.

Sailing - Using the wind as the main motive force while on the water.

Sea - Waves generated by the existing winds in the area. These wind waves are typically a chaotic mix of heights, periods, and wave lengths. Sometimes the term refers to the condition of the surface resulting from both wind waves and swells.

Sea State Condition Number - A standard scale ranging from 0-9 that indicates the height of waves.

Seaplane - An airplane designed to operate from water. Seaplanes are further divided into flying boats and floatplanes.

Seaplane Landing Area - Any water area designated for the landing of seaplanes.

Seaward - The direction away from the shore.

Secondary Swells - Those swell systems of less height than the primary swell.

Sister Keelsons - Structural members in the front portion of floats lying parallel to the keel and midway between the keel and chines, that add to directional stability when on the water.

Six Pack -

Skeg - A robust extension of the keel behind the step which helps prevent the seaplane from tipping back onto the rear portion on the the float. The skeg also provides additional directional stability when taxing a seaplane. 

Skids on Floats - A type of helicopter float design where the rigid portion of the landing gear rests on the floats. The floats support the whole weight of the helicopter in water and/or on hard surfaces.

Skipping - Successive sharp bounces along the water surface caused by excessive speed or an improper planing attitude when the seaplane is on the step.

Sponsons - Small wing mounted floats that extend from the wings of most flying boats. Sponsons can also be, short winglike projections that extend from the sides of a hull of a flying boat near the waterline. Their purpose is to stabilize the hull from rolling motion when the flying boat is on the water, they may also provide some additional buoyancy, hydrodynamic lift and even aerodynamic lift depending on the state of the flying boat.

Spray Rails - Flanges attached to the inboard forward portions of chines of floats or flying boat hulls to reduce the amount of water spray thrown into the propellor.

Spreader Bars - Text

Starboard - The right side or direction to the right of a vessel.

Step - An abrupt break in the longitudinal lines of the float or hull, which reduces water drag and allows the pilot to vary the pitch attitude when running along the water's surface.

Step Position - The attitude of the seaplane when the entire weight of the aircraft is supported by hydrodynamic and aerodynamic lift, as it is during high speed taxi or just prior to takeoff. This position produces the least amount of water drag. Also called the planing position.

Supplemental Type Certificate - 

Swell - Waves that continue after the generating wind has ceased or changes direction. Swells also are generated by ships and boats in the form of wakes, and sometimes by underwater disturbances such as volcanoes or earthquakes. The waves have a uniform and orderly appearance characterized by smooth, rounded, regularly spaced wave crests.

Swell Direction - The direction from which a swell is moving. Once set in motion, swells tend to maintain their original direction for as long as they continue in deep water, regardless of wind direction. Swells may be moving into or across the local wind.

Swell Face - The side of the swell toward the observer. The back is the side away from the observer. These terms apply regardless of the direction of the swell movement.

Swell Length - The horizontal distance between successive crests.

Swell Period - The time interval between the passage of two successive crests at the same spot in the water, measured in seconds.

Swell Velocity - The velocity with which the swell advances with relation to a fixed reference point, measured in knots. There is little movement of water in the horizontal direction. Each water particle transmits energy to its neighbor, resulting primarily in a vertical motion, similar to the motion observed when shaking out a carpet.

Tides - The alternate rising and falling of the surface of the ocean and other bodies of water connected with the ocean. They are caused by the gravitational attraction of the the sun and moon occurring unequally on different parts of the earth. Tides typically rise and fall twice a day a vary in amplitude with the moon's phase cycle. The largest tides occur at full moon and new moon.

Tip Floats - Small floats near the wingtips of flying boats or floatplanes with a single main float. The tip floats help stabilize the airplane on the water and prevent the wingtips from contacting the water.

Transom -  As it applies to seaplanes, the rear bulkhead of a float.

Trough - The low area between two wave crests.

Upswell - Motion opposite the direction the swell is moving, If the swell in moving from the north to south , a seaplane going from south to north is moving upswell.

Vessel - Anything cable of being used for transportation on water, including seaplanes.

Water Rudders - Retractable control surfaces on the back of each float or a flying boats hull that can be extended downward into the water to provide more directional control when taxing in the surface. They are attached by cables and springs to the air rudder and operated by the rudder pedals in the cockpit.

Weathervaning - The tendency of an aircraft to turn until it points into the wind.

Windward - Upwind, or the upwind side of an object.

Wing Floats - Stabilizer floats found near the wingtips of flying boats and single main floatplanes to prevent the wingtips from contacting the water. Also called "tip floats."