With the development of Global Positioning System (GPS) to determine one’s location by the use of satellites, an amazing and extremely accurate method of navigation has evolved. GPS navigational units are being installed in aircraft to such an extent that GPS mode of navigation is rapidly replacing the present method of airways navigation. Initially developed purely for military purposes, the GPS system consists of a constellation of 24 navigation satellites that orbit the earth. The precise time and position information transmitted by these satellites is used by a GPS receiver to compute a position fix. Only four of the 24 satellites need be locked onto by the receiver to compute the necessary information. The system provides continuous 3D (position plus elevation) coverage everywhere on earth. When adapted for civilian use the system has an accuracy of 25 meters or less. The military use has even greater accuracy but due to military security considerations, civilian use is degraded somewhat as to accuracy.
How does this system work? Each GPS satellite transmits its precise location and the start time of the transmission. A GPS receiver acquires the signal, and then measures the interval between transmission and receipt of the signal to determine the distance range between the receiver and the satellite. Once the receiver has computed range for at least three satellites, its location on the surface of the earth can be determined. A fourth satellite is needed to gain altitude information.
Small GPS handheld units not much larger than a package of cigarettes, powered by small storage batteries of A or AA size, can offer even a small non-electrical equipped airplane easy and accurate navigation capabilities. Even in sophisticated airplanes an electrical failure of navigational equipment could mean tragedy, especially in poor visibility weather. One of Nicholson Air Services chartered Piper Aztec twin engine airplanes fatally crashed in the Spruce Knob mountain area of West Virginia while descending in the clouds after a complete electrical failure resulted in the loss of all navigational aids. The pilot obviously thought he was located in the Cumberland area at the time. Had he possessed the advantage of a currently available handheld GPS the pilot could have determined his location and descended safely below the clouds into an area of lower terrain.
Early aviators, without any of our more modern navigation aids, made use of celestial navigation using the positioning of the stars and sun to guide their aircraft. This was the method used by Amelia Earhart in her attempted around-the-world flight, in the 1930’s. On the long over water journey clouds prevented her navigator, Harold Noonan, from using this means of affirming their position and thus resulted in tragically missing their destination.
Dead reckoning is the basic navigational means by the use of a compass for direction, a watch for timing ground speed, and the use of visual landmarks to determine an aircraft’s course and progress. Wind always affects the aircraft’s progress, and is a factor that must be considered for accurate navigation. Captain Arthur Amick’s Driggs Skylark open cockpit bi-plane had a drift meter in the rear cockpit which was installed in the floor in such a manner that the pilot could visualize, by a system of mirrors, the amount of wind drift in degrees over the ground. He could then apply the degrees of correction to his compass heading so as to maintain a proper correct course to the destination.
Pilotage or dead reckoning is the original and most primitive method of air navigation. Even as late as the 1930’s the Civil Aviation Administration did not require a compass as necessary equipment on aircraft. Many early airplanes were produced with only a tachometer, oil pressure and oil temperature gauges, and with but one flight instrument, an altimeter, to display height above the ground. Aircraft compasses and airspeed instruments were expensive and were often omitted. The author has observed a pilot spread a map on the ground, orient it to its proper direction, then visualize his aircraft, minus a compass, moving across the map and try to determine the proper direction to travel. Often modern pilots, without benefit of electronic navigational aids in their aircraft, will question their ability to fly by dead reckoning and will simply follow roads, railroads, or rivers to their destination. Recently a pilot flying a former Army Cessna L-19 Bird Dog airplane without any electronic navigational aids landed at the Greater Cumberland Airport while enroute to Texas, having departed Boston that morning. After refueling and departing the airport the aircraft was observed headed in a northwest direction rather than a southwest direction. Apparently the pilot wanted to follow Interstate 68 west then follow another interstate southwest to be assured of prominent and easily identified landmarks.
Bill Holbrook related that when he was serving as a co-pilot for Goodyear Flight Department one of his pilots, Tommy Carter, a former air-mail pilot during the twenties and thirties, showed Bill how to fly from Washington to Pittsburgh in poor weather with out climbing above 3,000 feet MSL. This most basic method was by following the Potomac River to Cumberland, turning south along the river to Keyser, WV, then west along the river through a narrow gap to Luke, MD. From there the routing was to leave the river just prior to the Westvaco Paper Mill and turn right to follow a narrow valley northwest to a saddle in the highest ridge. At that point the method was to proceed along the lowest ground of the high plateau to a big lake, fly over the lake to the dam at the headwaters, down the creek to Confluence, PA and then follow the B&O Railroad into the destination airport at Pittsburgh.
The author related that, during his U.S. Army Air Force flight training in WW II, almost every Texas town had a water tower with its name painted on the side. It was an acknowledged method and permissible by his superiors that, if lost, to fly low along side the water tower and read the name of town which was displayed on the tower, and thereby to determine one’s position.
Hollering to people on the ground is a long forgotten, but sometimes used, method of communicating and verifying position. In an open cockpit craft and throttling the engine to idle position, one can often yell loudly to people on the ground, if the noise level is sufficiently low. Charles Lindbergh often used this method, and did so when passing over Ireland on his New York to Paris flight in 1927.
Roger Cannon relates that he knew a pilot at Mexico Farms who had a tendency towards wild flying and had buzzed Roger’s home neighborhood on several occasions. One day Roger was outside of his home conversing with a neighbor when he recognized this particular pilot’s aircraft as it flew low over his home, circling a couple of times. This prompted the neighbor, aware that Roger was a pilot, to inquire who was the individual flying that particular offending airplane? Not wanting to identify the Mexico Farms pilot as the guilty aviator performing the buzz job, Roger stated he had no idea who was in the aircraft. Within a minute or so the overhead pilot throttled back the engine and in a clear voice shouted loudly for all to hear, “Hi Roger!” This obviously left Roger stunned, embarrassed, and at a complete loss for words with his neighbor.
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Wings Over Cumberland 