FLOATS-ON-SKIDS —A type of helicopter float design where the floats sit on top of the fully func- tional skids. During water opera- tions, the floats support the weight of the aircraft, and on hard surfaces the skids support the weight of the aircraft. 

FLYING BOAT —A type of sea- plane in which the crew, passengers, 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 can deceive a pilot’s depth perception. 

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 and the effects of fluids acting on solid bodies in motion relative to them. 

HYDRODYNAMIC LIFT —For seaplanes, the upward force gener- ated 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, hydrodynamic lift begins to support more and more of the seaplane’s weight. 

IDLING POSITION —The atti- tude of the seaplane when its entire weight is supported by the buoyancy of the floats, as it is when at rest or during a slow 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 —T secure or tie the seaplane to a dock, buoy, or other stationary object on the surface. 

NUN BUOYS —Conical buoys marking the left 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’ runways. 

PLANING POSITION —The atti- tude 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 step position, or “on the step.” 

PLOWING POSITION —A nose high, powered taxi characterized by high water drag and an aftward 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 deployed in the event of an emer- gency landing on water. Compressed nitrogen or helium inflates the floats very quickly. 

PORPOISING —A rhythmic pitch- ing motion caused by an incorrect planing attitude during takeoff. 

PORT —The left side or the direction to the left of a vessel. 

PRIMARY SWELL —The swell system having the greatest height from 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 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, adding structural rigidity and adding to directional stability when on the water. 

SKEG —A robust extension of the keel behind the step which helps prevent the seaplane from tipping back onto the rear portion of the float. 

