- 12 -
This illusion may have serious consequences. In fact, if the pilot without realizing it changes the angle of his airplane with respect to its initial position by as little as one degree, this error translates into differences in altitude of:
| 17.5 | meters for a landmark | 1 kilometer away |
| 35.0 | meters for a landmark | 2 kilometers away |
| 87.5 | meters for a landmark | 5 kilometers away |
| 175.0 | meters for a landmark | 10 kilometers away[1] |
The illusion cited above must certainly be a cause of many aircraft accidents occurring just before the airplane reaches the airfield, especially when no adequate landmark can be found in the approaches (for example: an airdrome located on the edge of the ocean)...."
In the above passage the author refers to a night approach toward a lighted airport, and particularly when this approach is over water. However, this particular accident happened under quite similar conditions, despite its being daylight. The runway lights were on and the last 3.2 miles of approach were over water. Insamuch as the surface visibility at the airport was being reported as only 1½ miles and was much less at the crash site, the flight had no adequate ground reference, merely lights on the approach end of the runway. Riker's Island was to the right and ahead of the aircraft at its point of contact with the water and only approximately one-fourth of mile away. Captain Marsh, on the right side, stated that he saw the near end of this island, but at best he could have seen it but vaguely and fleetingly; otherwise, he could have used it as a visual reference.
The lights on the approach end of the runway, as reportedly seen by the captain, can well be considered as a single visual reference point because of their apparent close spacing from an aircraft an appreciable distance away.
- ↑ In English units, these figures correspond to approximately 92 feet at one mile, 184 feet at two miles, etc.
