Good stuff here but I have had difficulty finding anything on washing a seaplane. So I drafted my own. Comments appreciated.
Floatplane Washing instructions
Intro
Floatplane operations on both fresh and salt water necessarily invites corrosion to metal components. Cleaning, drying, lubricating and protecting are critical actions to reduce the effects of corrosion. This guide will discuss procedures and recommendations for slowing the effects of corrosion on floatplanes. It is focused on aluminum and steel based planes but can be applied to any airplane operating on or near water.
Takeoff dynamics
The takeoff phase in a floatplane is when the fuselage, wings and engine cowling will be exposed the most to water spray. As the plane transitions from displacement through plow, step and liftoff phase, water tends to get into everything. Wave spray will often hit the propeller and cause the spray to be thrown further onto the aircraft. The point is the airplane will be soaked, then during flight will dry off, leaving salt and mineral residue on the exposed surfaces of the aircraft. Water may also access inside the tail a surprising distance and is often injected from the tail up into the fuselage. Propwash heavily sprays the underside of the left wing. When washing down the airplane after flight, all areas that have been exposed to salt water, in particular, must be rinsed and allowed to dry.
Washing procedures
The key point in washing a floatplane is to get lots of fresh water onto all surfaces that have been sprayed in the takeoff and landing phases. Step one is to do at least one splash-and-go in fresh water before final landing in order to rinse the airplane as much as possible. For amphibian floats, it is important to lower the landing gear while in fresh water and allow the gear to be rinsed. This step is specific to salt water operations but is very important.
Step 2 is to use a hose to flush the inside of the tail and rear fuselage sections where saltwater penetrates during takeoff. This is a key step that is often misunderstood. The saltwater has gotten in there, putting fresh water in to rinse is critical. The hose should spray up inside the tail section to the point that fresh water runs out the weep holes in the bottom of the fuselage. At this point, check that all the weep holes are draining. They do get plugged occasionally and will hold corrosive water. Also, at least at annual, check that all the bays in the bottom of the fuselage do drain fully when the plane is in “parked position”. We recently had a case where one of the fuselage bays did not have a weep hole and held considerable water when parked. These are located under the floor covers and do not get easily noticed.
Step 3 is to pump the floats and ensure that no salt water is left in them. The aluminum of the floats is corrosion resistant to fresh water but not for saltwater. Yes, that means you can use the hose to add water to the floats and then pump it back out. The additional point to remember is that while the aluminum in the floats is corrosion resistant to fresh water, the steel hardware of the float fittings and fasteners are less tolerant. More about protecting metals other than aluminum in the protection section.
Lubrication
Moving parts, like pulleys and cables, require lubricants that protect while allowing movement.
This includes using “sticky” lubricants like LPS-3 or Para-Ketone on parts that move and on parts that come in contact with the corrosive elements, i.e water.
Use LPS-3 or other similar lubricants that, when dry, tend to reject water and salt, while still allowing smooth movement of the parts. This is used on the rudder hinges, cable pulleys, and other moving parts. Wheel planes often use graphite or other non-greasy lubricants for control hinges but there the worry is attracting dust. On a floatplane we are more concerned with rejecting water.
Protection
Protecting the finish of the plane is critical to staving off damaging corrosion. Wash Waxall and Rejects are recommended (by local paint shops that deal daily with the effects) for washing and waxing the exterior of floatplanes. Extra attention should be given to tail surfaces and the underside of the left wing (think propwash).
An often overlooked item is the float hardware that is visible inside the float compartments. The nuts and bolts live in a very humid environment, especially in summer then the floats heat up with water in the bottom. To protect these, I have found that reaching in with a handful of grease like Lucas Red and smearing it on the nuts inside the floats really helps. Be sure to apply grease to the nuts and bolt shafts of the float covers
