Planing Position Planing Position

   Basically, the planing or step position is best attained by holding the elevator control full aft and advancing the throttle to full power. As the seaplane accelerates it will then gradually assume a nose high pitch attitude, raising the bow of the float or hull and causing the weight of the seaplane to be transferred toward the aft portion of the float or hull. At the time the seaplane attains its highest pitch attitude, back pressure should be gradually relaxed, causing the weight to be transferred from the aft portion of the float or hull onto the step area. This can be compared to a speedboat's occupants moving forward in the boat to aid in attaining a planing attitude. In the seaplane we do essentially the same thing by use of aerodynamics (elevators). As a result of aerodynamic and hydrodynamic lifting, the seaplane is raised higher in the water, allowing the floats or hull to ride on top of rather than in the water.

   The entire process of planing a sea plane is similar to that of water skiing. The skier cannot make the transition from a submerged condition to that of being supported on the surface of the water unless a sufficiently high speed is attained and maintained.

   As further acceleration takes place the flight controls become more responsive just as in the landplane and elevator deflection must be reduced in order to hold the required planing/pitch attitude. This of course is accomplished by further relaxing back pressure, increasing forward pressure, or using forward elevator trim depending on the aircraft flight characteristics.

   Throughout the acceleration, the transfer of weight and the hydrodynamic lifting of the float or hull may be seen from the cockpit. When the seaplane is taxiing slowly, the water line is quite high on the floats or hull as compared to "on the step" (Fig. 15-3). At slow taxi speeds a small wake is created close to the bow of the float or hull and moves outward at a very shallow angle. As acceleration commences, the wake starts to move from the bow aft toward the step area and the wake now turns into an outward spray pattern. As speed and lifting action increase, the spray pattern continues to move aft toward the step position and increases in intensity, i.e., slow speed spray may be approximately one foot outboard compared to about a 20 foot outboard spray at higher speed on the step position. Some seaplane pilots use the spray pattern as an additional visual reference in aiding them in determining when the seaplane has accelerated sufficiently to start easing it over onto the step.

   After the planing position has been attained, proper control pressures must be used to control the proper pitch attitude/trim angle. Usually this will be maintained with slight back pressure. As for the amount of pressure to be held, the beginner will find a very "thin line" between easing off back pressure too much or too little. It can perhaps best be described as finding the "slippery spot" on the float or hull. Too much back pressure, acceleration rate decreases. Not enough back pressure or too much forward pressure also decreases acceleration rate. So that fine line or "slippery spot" is that position between not enough or too much back pressure.

   If one does not want to take off and just wants to continue to taxi on the step, a reduction in power is initiated at approximately the time the seaplane is eased over onto the step. Power requirements to maintain the proper speed with wind, load and current action will vary. More power will be required taxiing into the wind or an upcurrent or with a heavy load. However, 65 to 70 percent of maximum power can be used as a starting point.

   From either the plowing or on the step position, if power is reduced to idle, the seaplane will decelerate quite rapidly and eventually assume the displacement or idle position. Care must be taken to use proper flight control pressures during the acceleration phase because weight is now being transferred toward the bow and drag is increasing; hence, some aircraft have a nose over tendency. This is of course controllable by proper use of the elevator controls.