Pan Am navigators on the Boeing 314 Clipper used innovative ways to determine the plane's position and bearings.
Last week, we looked at just how luxurious it was to fly on Pan Am's Boeing 314 Clipper, for those who could afford it.
But the differences between flying across the ocean these days and in the years leading up to World War II go beyond the quality of the meals and sleeping accommodations.
Doug Miller works with the Pan Am Historical Foundation and is a producer of "Across the Pacific," an upcoming documentary on Pan Am and the adventure of flying across the ocean before it was routine. He took the time to explain to us just how complicated navigating the Clipper was in the days before GPS and satellite communications.
Step one was finding the plane's bearing, the direction it was headed in. That was done with a system specially developed for Pan Am transoceanic flights that provided bearings as far as 1,200 miles from land, on top of the plane's radio direction finding capabilities.
To figure out where the plane actually was at any given time, on board navigators looked to the stars. With a tool called the bubble octant, they could use celestial navigation to find their position.
Pan Am's navigators also had a clever system for dead reckoning (calculating position based on a previously determined position and estimated speed, time, and direction), Miller explains:
They would drop a glass flask filled with aluminum powder from the plane (and they usually weren't flying all that high - 8,000 ft or less) and the resulting shiny spot (or flare at night) could be followed with a device something like a surveyors transit.
This would give the navigator some idea of the drift they were experiencing. Sometimes the pilot would fly a triangular course while the navigator did this, which would allow for more accurate estimation of the winds they were experiencing.
On the 314, which didn't fly especially fast or high, running out of fuel was a serious concern. So knowing where the plane was — and how far it had to go before landing, was critical. Says Miller:
When you're flying in a plane going say 125 or 140 miles an hour, and they winds you encounter are either aiding or inhibiting your ground speed, you'd want to know how long you could stay in the air before you ran out of gas.
It was not uncommon for flights to turn around after many hours in the air if it was uncertain that they would have the fuel to get to their destination. They used a chart called a "how-goes-it" chart, with pre-computed time vs. distance curves, including curves that provided for losing an engine in flight (that wasn't all that uncommon either in those days.)
When the United States entered World War II, the Clipper was pressed into service to transport materials and personnel. Pan Am helped out, too: At its school in Miami, it taught American and British aerial navigators how to guide their planes over the oceans. Some of those navigators went on to fly with Jimmy Doolittle on the famous aerial raid of Japan in April 1942, according to Miller.
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