Dead Reckoning On May 21, 1927 Charles Lindbergh landed in Paris, France after a successful non-stop flight from the United States in the single-engined Spirit of St. Louis. As the aircraft was equipped with very basic instruments, Lindbergh used dead reckoning to navigate. Dead reckoning in the air is similar to dead reckoning on the sea, but slightly more complicated. The density of the air the aircraft moves through affects its performance as well as winds, weight, and power settings. The basic formula for DR is Distance = Speed x Time. An aircraft flying at 250 knots airspeed for 2 hours has flown 500 nautical miles through the air. The wind triangle is used to calculate the effects of wind on heading and airspeed to obtain a magnetic heading to steer and the speed over the ground (groundspeed). Printed tables, formulae, or an E6B flight computer are used to calculate the effects of air density on aircraft rate of climb, rate of fuel burn, and airspeed. A course line is drawn on the aeronautical chart along with estimated positions at fixed intervals (say every ½ hour). Visual observations of ground features are used to obtain fixes. By comparing the fix and the estimated position corrections are made to the aircraft's heading and groundspeed. Dead reckoning is on the curriculum for VFR (visual flight rules - or basic level) pilots worldwide. It is taught regardless of whether the aircraft has navigation aids such as GPS, ADF and VOR and is an ICAO Requirement. Many flying training schools will prevent a student from using electronic aids until they have mastered dead reckoning. Inertial navigation systems (INSes), which are nearly universal on more advanced aircraft, use dead reckoning internally. The INS provides reliable navigation capability under virtually any conditions, without the need for external navigation references, although it is still prone to slight errors. Transcontinental Airway System In 1923, the United States Congress funded a sequential lighted airway along the transcontinental airmail route. The lighted airway was proposed by National Advisory Committee for Aeronautics (NACA), and deployed by the Department of Commerce. It was managed by the Bureau of Standards Aeronautical Branch. The first segment built was between Chicago and Cheyenne, Wyoming. It was situated in the middle of the airmail route to enable aircraft to depart from either coast in the daytime, and reach the lighted airway by nightfall. Lighted emergency airfields were also funded along the route every 15–20 miles. Construction pace was fast, and pilots wishing to become airmail pilots were first exposed to the harsh wintertime work with the crews building the first segments of the lighting system. By the end of the year, the public anticipated anchored lighted airways across the Atlantic, Pacific, and to China. The first nighttime airmail flights started on July 1, 1924. By eliminating the transfer of mail to rail cars at night, the coast to coast delivery time for airmail was reduced by two business days. Eventually, there were 284 beacons in service. With a June 1925 deadline, the 2,665 mile lighted airway was completed from New York to San Francisco. In 1927, the lighted airway was complete between New York City and Salt Lake City, Los Angeles to Las Vegas, Los Angeles to San Francisco, New York to Atlanta, and Chicago to Dallas, 4121 miles in total. In 1933, the Transcontinental Airway System totaled 1500 beacons, and 18000 miles. The lighted Airway Beacons were a substantial navigation aid in an era prior to the development of radio navigation. Their effectiveness was limited by visibility and weather conditions.Beacon 61B on a modern display tower, originally installed on route CAM-8 near Castle Rock, WA 24 inches (610 mm) diameter rotating beacons were mounted on 53-foot (16 m) high towers, and spaced ten miles apart. The spacing was closer in the mountains, and farther apart in the plains. The beacons were five million candlep