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Navigating an airplane by "dead reckoning?"? |
Travel Info I was watching a movie about Charles Lindbergh and his New York to Paris flight starring Jimmy Stewart. In the movie he was asked how he was going to navigate accross the Atlantic from Newfoundland to Ireland. He said he could navigate across the ocean by using "dead reckoning?" What is that and how is it done? Travel Tips It means without checking your position with a sextant or other navigation device. To take a simple example, if you're driving due west for an hour at 100kph and there are no signs, and you assume that you're 100 km further west, that's dead reckoning. Using the same method to fly the Atlantic is far more problematic. For a start, you need to take account of the curve of the Earth over long distances. Then you need a good idea of windspeed and direction. Your track, that is, your actual path over the ocean, is the result of adding the direction your nose is pointed (your heading) and your airspeed, to the wind speed and direction. Lindbergh was very lucky he got it right. Wind forecasts in those days were hopelessly unreliable. Others I think it is the same as flying blind. But I would rather not find out. I think it is just a term for navigating without instruments. I think this was used alot during the early days of flight. Pilots used manual navigation techniques similar to that of ship captains. It involved having a navigator on-board and complicated mathematical equations and calculations involving everything from the curvature of the earth to the position of the sun. But it was somewhat effective for the time and for smaller planes. Dead reckoning is when you think negatively when youre a pilot and youre thinking you could die if you do it wrong. This man was obviously thinking negatively aboutt the flight Zee-prime is almost right. The same term is used for flying and boating. These days we have sophisticated stuff like radar and gps which give us a constant check on position course and speed. Dead reckoning still uses instruments such as compass but involves making an initial navigation plan to correct for tides or winds and then holding the planned course without any updating on the way. As said, to predict the winds is notoriously difficult and even getting the tides spot on is awkward as the exact direction can vary in some places depending on weather patterns. I know of one prime example where someone thought they were following the captains instructions by sailing a constant compass course overnight towards Falmouth, UK. Trouble was that they found it awkward to constantly stand up and check compass and they found that if they kept the wind indicator at 40 degrees they seemed to keep on course. So they forgot about the compass all together and kept the wind at 40 degrees. Next morning, they had to explain to the captain why their landfall was miles away from Falmouth as (of course) the wind had veered in the night. Moral of story - dead reckoning is working out in advance and setting a compass course from start to finish. With no checks on the way, stick to the set compass course and hope you get close enough to your intended destination for visual navigation to take over. |
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