Page:CAB Accident Report, Northeast Airlines Flight 801.pdf/11

- 11 - to the aircraft, as well as Captain Marsh's testimony that the aircraft's nose may have been raised slightly just before impact, strongly suggests that the approach was being made visually by Briggs and that he inadvertently caused, or allowed, the air speed to drop markedly below the specified 140 mph approach speed, and to near the stall speed with its attendant extremely high sinking rate. This could well account for the similar testimony of both pilots in that neither remembers any instrument readings, including altimeter, during the last 300 feet of descent. The surface of the water was glassy, limiting its use as a medium of depth perception.

An important psychological factor enters into making an approach under the subject condition. It concerns the erroneous impression of altitude and is described in "The Sensory Illusions of Pilots," by P. P. Cocquyt, chief pilot of Sabena, the Belgian airline, published by the Flight Safety Foundation, Inc. He writes, "...The illusion of flying horizontally with respect to a landmark when flying more nose up than imagined is dangerous because the pilot believes himself to be higher than he really is. The angle at which a pilot observes a point of light on the horizon depends on his altitude and his distance from the point. Evaluation of that angle is not a matter of mathematics but is one of feeling (purely subjective).