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gible tendency for the airplane to rotate or "yaw" about the point at which the retarding force acts. Directional stability on the water is neutral. If the flying boat is landed in tail-low attitude the point at which the water retarding forces act is definitely to the rear of the center of gravity. This tends to provide positive directional stability. If, on he other hand the flying boat is landed in a nose—down attitude, the decelerating force acts forward of the center of gravity tending toward directional instability unless controlling forces are promptly applied. Serious consequences may result if the airplane happens to be turning or if it has any leeway or side motion relative to the water.
We are forced to the conclusion, therefore, first, that the subject aircraft was landed in an unduly nose—low attitude, and second, that at the time of first contact while in that attitude, it was moving sideways relative to the water. It appears from the record that there were no extraneous turning forces which might have been caused by non—uniform application of power or by faulty rudder tab setting.
Having arrived at this conclusion as to the manner in which the airplane struck the water, we must determine whether this resulted from faulty operation of the airplane by the pilot.
Captain Lorber testified that he was handling the throttles during the approach and landing at San Juan. This duty is sometimes performed by the flight mechanic who handles the engine's controls under the captain's direction while some captains handle the throttles themselves. This is a matter of personal preference varying with different captains. The fact that Captain Lorber handled the throttles himself appears to have no significance in this accident.
Captain Lorber, First Officer Breaux, and Flight Mechanic Donnelley testified that the approach up to and including contact with the water was not abnormal as far as they could observe.
Captain Lorber testified that he retarded all four throttles immediately upon the aircraft's first contacting the water and that he did not subsequently apply any power except that which he applied to the two right—hand engines in an effort to arrest the swerve. The Chief Pilot of the Eastern Division of Pan American, Captain Fatt, testified that the correct manner of handling the throttles during the landing of the subject type of aircraft consists in making the final approach with about 16 or 18 inches of manifold pressure with the engines running at about 2230 r.p.m. and continuing this condition for a period varying between 10 and 20 seconds after the aircraft first contacts the water. The purpose, according to Captain Fatt in allowing the power so to continue was to have enough control of the airplane to prevent the nose from being forced further into the water. He states that the aircraft has this tendency and that a sudden cessation of power augments it. Another reason that has been advanced an favor of maintaining the amount of power existing at the time of first contact is to make sure that the aircraft has made permanent contact with the water, rather than having touched the top of a swell, before the power is reduced.
According to other experts, the proper landing procedure consists of making the approach with from 12 to 14 inches of manifold pressure and about 2200. r.p.m. and then in completely throttling the engine at the time of contact. The landing maneuver is not subject to regularly established procedures in regard to throttle manipulation as that is affected by many variables such as slight changes in attitude of the aircraft and condition of the water surface, as well as the loading and weight disposition of the aircraft, and, of course, the primary consideration, that of wind.
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