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Correction changes Chichester's course

Jan 1, 2003

There was a small error in a recent nav problem ("Biplane sextant sights," Issue No. 62). On his 1931 flight, Chichester actually took his departure from a harbor in the north of New Zealand, not from Auckland as shown.

Chichester accomplished this remarkable feat of navigation by precalculating his observed altitude (ho) and setting his sextant to those readings for set times. By steering a course that would carry him west of Norfolk Island, he was able to turn right 90° when his LOP became his course line.

Interestingly, investigators trying to solve the disappearance of Amelia Earhart have found artifacts on a reef that would have been on an LOP that her navigator would have gotten from a morning sun sight. This reef is several hours flying from Howland Island, which was Earhart's destination. It is now theorized that the aircraft had been carried south of its intended course, rather than north as they had thought. This resulted in tragic consequences when Earhart turned right on their LOP to try to find Howland.

When sailing a southeasterly course say from Florida to the Virgin Islands, it is useful to take the afternoon sun sight when the body bears 90° to the course. The LOP then coincides with the course line, very comforting for the navigator to plot on his chart.

Kenneth E. Clark lives in Sarasota, Fla