Air Navigation

Looking up at the sky in the wee hours of the morning, one cannot fail to admire the contrails left by jet planes buzzing around. But very few of us give thought to how these planes - carrying hundreds of passengers whilst travelling at speeds usually exceeding 500 miles/hour - safely get from one point to another with such clockwork precision. In the early days of flying - a dearth of navigational aids required pilots to literally follow physical ground based landmarks for guidance: following rail tracks, rivers and even sometimes inter-state highways - or use a rudimentary magnetic compass; but with advancements in radio technology - bolstered by the First world war- radio based navigational aids started aiding pilots in finding their way around the sky. The radio compass - which started appearing on aircraft around the 1920s and 1930s - notified a pilot of his/her aircrafts bearing from the transmitter station to whose frequency the compass had been tuned to. Slowly, as expected the instrument became an aviators necessity. Even Amelia Earhart's ill-fated Lockheed Electra E10 had carried a slightly advanced version of the basic radio compass/radio direction finder. Over the next three decades - the almost exponential increase in air travel and the subsequent advent of the jet age: necessitated much more accuracy, and importantly less dependence on ground stations. Radio Navigation was built upon- with newer versions such as the Non-Directional Beacons and VORs (Very High Frequency Radio Ground Based Navigation System) which substantiated for the need for accuracy, but a plane using radio navigation still had to depend on ground stations. The reasonable alternative just could not be a pilot using a sextant - on a jet plane. Research and development brought about a new revolutionary technology- the inertial navigation system. The system uses gyroscopes (which measure rotation), accelerometers (which measure motion) and a small onboard computer to calculate via dead reckoning the position of the aircraft relative to its starting position. INS systems slowly got more advanced and accurate, as they became the primary source on large planes for long distance navigation. These days, a modern plane, like the Airbus A320 or the Boeing 787, makes use of about five or six different types of navigation systems at one time - all working in unison to provide the highest level of accuracy as well as redundancy. A plane also carries a GPS system, which though not as accurate as the INS, can be extremely useful for situational awareness may other systems fail. Pilots interact with the avionics suite on board a plane through the Flight Management Computer - keying in all navigational parameters such as the route that the airplane is planned to follow and the necessary waypoints it must cross. After takeoff - the auto-pilot, upon the discretion of the pilots, takes over and accurately controls the medial and lateral control surfaces of the plane to follow the course set in the Flight Management Computer - while the pilots get time to sit back and relax. So next time you see contrails in the sky, try to appreciate the feat of technological development which has rendered air travel such safe, and widespread.