With some exceptions the preflight inspection of a seaplane is similar to that for a landplane. The major difference is checking the floats or hull, and the airplane flight manual (AFM), pilot's operating handbook (POH), or manufacturer's recommendations will contain procedures for doing this in addition to the usual preflight actions, such as fuel sumping, control checks, etc.
a. Some operators haul seaplanes out of the water for dry land storage on a trailer or raft, making preflight more convenient for the pilot. However, the pilot should NOT conduct an abbreviated inspection just because a seaplane must be preflighted while in the water.
b. The pilot should first note how the seaplane rides in the water. If the stern of the floats or hull is very low in the water; i.e., float stern submerged or, in a flying boat, tail in the water, the seaplane could be loaded incorrectly or there could be a leak in a float compartment or in the hull. This is why floats and hulls must be inspected and bilge pumped before each flight.
(1) The pilot should first inspect floats and hulls for obvious or apparent defects or damage, such as dents, cracks, deep scratches, loose rivets, corrosion, separation of seams, punctures, and general condition of the skin.
(2) Because of the rigidity of float installations, the pilot should check fittings, wire or tubular bracing, and adjacent structures for cracks, defective welds, proper attachment, alignment, and safety wires and nuts.
(3) Pilots should check all hinge points for wear and corrosion, particularly if the seaplane operates on salt water.
(4) The pilot should inspect the water rudders, if installed, and their cables and springs for free and proper movement.
(5) The pilot should pump out each bilge or compartment of a float or the hull to remove water. A small amount of water; e.g., a cupful, is not unusual and can occur from condensation or normal seepage. (If the bilge pumps out no water, it is more likely that the pump itself is defective.) All water should be removed before flight by pumping or with a sponge because the water may critically affect the seaplane's weight and its center of gravity. Finding an excessive amount of water should cue the pilot to look for the source of the leak. If drain plugs and inspection plates are installed, the pilot should use a systematic (read "checklist") method to remove the plugs and plates and examine the compartments thoroughly. Of course, it is equally important to reinstall the plugs and plates systematically before a water takeoff.
(i) Some floats are equipped with a bilge funnel which does not require the removal of a cover to pump the bilge. However, if the funnel becomes disconnected, the pump will not produce any water, and there may still be water in the float. The answer is to be suspicious if no water emerges when bilging after an extended time on the water or in storage.
(ii) Floats stored in freezing climates must be inspected particularly closely because water in the floats expands upon freezing. Frozen water in compartment seams can cause severe leakage problems. Many operators who store the floats off the airplane for a season put them away upside down with compartment covers off to allow drainage.
(6) The pilot should assure that nothing is stored in compartments of floats not approved for storage. For those floats approved for storage of items, the pilot must ensure that the contents and their placement allow the seaplane to remain within its weight and balance limitations. Another consideration is that floats are certificated to continue to float after two compartments per float have been flooded. The potential for capsizing or sinking is increased if compartments are at their limit for storage and other compartments become filled with water after accident damage.
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