Seaplane Rating

Studying for my SeaPlane Rating which I am doing on San Diego harbour in April is proving mighty interesting. In addition to airspeed and groundspeed, one has water currents to contend with and you have a "waterspeed" as well. 

Waterspeed

Therefore if you are moving with the current at 5 knots you would have an airspeed and groundspeed of 5 kts and a waterspeed of 0 kts, as the plane is moving in the direction the body of water is flowing in. It is usually more preferable to take off downcurrent than upwind as a take-off against a 5 kts current would need an airspeed of 25 kts to counter the effect of drag on the floats with the current.

Taking off in a SeaPlane has 3 stages of taxiing at idle or displacement speed, ploughing, and on the step planing as in the illustration above.

Sailing the SeaPlane backwards

Integral to learning to handle the SeaPlane is learning to sail it, as much as learning to take-off and land, as the plane is mobile the second you cast off from the dock. The plane automatically weathervanes, so sailing usually means backwards as the wind and/or current carries the plane while you use your airrudders and waterrudders to steer backwards similar to reversing a car... left rudder and left aileron down causes the plane to move

backwards to the right for example.

Direction limited

Often one needs to take off in confined spaces, such as rivers or canals where the direction of take-off is limited, so crosswind take-offs are common. Similarly lakes or bays are often surrounded by trees and mountains where again the most suitable take-off direction is limited. Glassy water surfaces also present their own problems and other users of water space - swimmers, boats, kayaks, windsurfers, kite-surfers and waterskiers create obstacles (as well as potential floating obstacles.. logs, debris etc) as well as water disturbance to consider whereas land planes usually have controlled airspace and clear level runways to take off from.

All fascinating stuff. The SeaPlane course is on San Diego harbour and involves my obtaiing FAA acceptance of my foreign licence and an American licence being obtained with my SeaPlane rating at the end of the course and after an exam and a "checkride" /flight test by an FAA examiner.


Take-offs can also follow a curved path as seen in the illustration where one has to take account of centrifugal forces and wind direction for optimum take-off handling.