• Early pilots looked out of their open cockpits for roads, rail lines, and airports to find their way in daytime flight. Pilots watched the horizon to make sure they were flying with the aircraft's nose and wings in the proper position relative to the ground, called attitude. As airmail pilots began flying at night and in all kinds of weather in the early 1920s, new equipment helped pilots navigate and maintain aircraft attitude when they could not see the ground. Navigation aids were developed for use inside the aircraft and also to guide the pilots from the ground.

• In 1929 - Lawrence Sperry and his Gyroscope Company introduced important new technology—the Artificial Horizon—that operated on gyroscopic principles.

• 1930s - new mechanical aids emerged, some based on Sperry's gyroscope and others based on the rush of air through intakes under the wing or the aircraft belly to measure speed and altitude.

• 1933 - about 200 miles (322 kilometres) apart along the 18,000-mile (28,968-kilometer) system of lighted towers and rotating beacons.

• By 1935 - about 20 more towers had been erected. Based on pilot radio reports, a controller would follow each plane with written notes on a position map. The controller would clear an aircraft for takeoff or landing, but the pilot still could decide on the best path for himself.

• Until World War II - radio navigation relied on low frequencies similar to those of an AM radio.

• Before World War II - , the Civil Aeronautics Administration relied on pilots to radio their position relative to known navigation landmarks to keep the aircraft safely separated. During the war, radio detection and ranging (RADAR) was tested. Radar's primary intent was, and still is, to keep airplanes separated, not to guide them to a specific point.

• In 1956 - a TWA Lockheed Super Constellation with 64 passengers and six crew and a United Airlines DC-7 with 53 passengers and five crew collided over the Grand Canyon, killing all 128 people

• Today's aircraft are tracked as computer-generated icons wandering across radar display screens, with their positions, altitude, and airspeed updated every few seconds. Pilots and controllers communicate using both voice and data transmitting radios, with controllers relying on radar tracking to keep aircraft on course.

• New technologies, though, have led to a debate as to whether the federal government, using fixed electronic stations, or the pilots should control navigation like in the earliest days. The global positioning system (GPS) is one technology that allows pilots to accurately determine their position anywhere on the Earth within seconds, raising the question whether they need any help from the ground.

• GPS is becoming the primary means of navigation worldwide. The system is based on satellites in a continuous grid surrounding the Earth, each equipped with an atomic clock set to Greenwich, England, called ZULU time. The GPS units in the aircraft, or even in a pilot's hand, find the nearest two satellite signals in a process called acquisition. The time it takes for the signals to travel creates a precise triangle between the two satellites and the aircraft, telling the pilot his latitude and longitude to within one meter or a little more than one yard. In coming years, this system will be made even more precise using a GPS ground unit at runway ends.

Navigation is the art and science of getting from point "A" to point "B" in the least possible time without losing your way. In the early days of aviation, navigation was mostly an art. The simplest instruments of flight had not been invented, so pilots flew "by the seat of their pants". Today, navigation is a science with sophisticated equipment being standard on most aircraft.

• The type of navigation used by pilots depends on many factors. The navigation method used depends on where the pilot is going, how long the flight will take, when the flight is to take off, the type of aircraft being flown, the on-board navigation equipment, the ratings and currency of the pilot and especially the expected weather.

• Starting point (point of departure)• Ending point (final destination)• Direction of travel• Distance to travel• Aircraft speed• Aircraft fuel capacity• Aircraft weight & balance information

With this information flight planning can commence and the proper method of navigation can be put to use.

PilotageFor a non-instrument rated, private pilot planning to fly VFR

(Visual Flight Rules) in a small, single engine airplane around the local area on a clear day, the navigation is simple. The navigation process for such a local trip would be pilotage. (Bear in mind, however that the flight planning and preflight for such a trip should be as thorough as if the pilot is preparing to fly cross-country.)

The pilotage method of navigation developed naturally through time as aircraft evolved with the ability to travel increasingly longer distances. Flying at low altitudes, pilots used rivers, railroad tracks and other visual references to guide them from place to place. This method called pilotage is still in use today. Pilotage is mainly used by pilots of small, low speed aircraft who compare symbols on aeronautical charts with surface features on the ground in order to navigate. This method has some obvious disadvantages. Poor visibility caused by inclement weather can prevent a pilot from seeing the needed landmarks and cause the pilot to become disoriented and navigate off course. A lack of landmarks when flying over the more remote areas can also cause a pilot to get lost.

• "Dead" Reckoning (or "Ded" for Deductive Reckoning) is another basic navigational method used by low speed, small airplane pilots. It is based on mathematical calculations to plot a course using the elements of a course line, airspeed, course, heading and elapsed time. During this process pilots make use of a flight computer. Manual or electronic flight computers are used to calculate time-speed-distance measurements, fuel consumption, density altitude and many other en route data necessary for navigation. 

The estimated time en route (ETE) can be calculated using the flight distance, the airspeed and direction to be flown. If the route is flown at the airspeed planned, when the planned flight time is up, the destination should be visible from the cockpit. Navigating using known measured and recorded times, distances, directions and speeds makes it possible for positions or "fixes" to be calculated or solved graphically. A "fix" is a position in the sky reached by an aircraft following a specific route. Pilots flying the exact same route regularly can compute the flight time needed to fly from one fix to the next. If the pilot reaches that fix at the calculated time, then the pilot knows the aircraft is on course. The positions or "fixes" are based on the latest known or calculated positions. Direction is measured by a compass or gyro-compass. Time is measured on-board by the best means possible. And speed is either calculated or measured using on-board equipment.

Navigating now by dead reckoning would be used only as a last resort, or to check whether another means of navigation is functioning properly. There are navigation problems associated with dead reckoning. For example, errors build upon errors. So if wind velocity and direction are unknown or incorrectly known, then the aircraft will slowly be blown off course. This means that the next fix is only as good as the last fix.

• Radio Navigation is used by almost all pilots. Pilots can find out from an aeronautical chart what radio station they should tune to in a particular area. They can then tune their radio navigation equipment to a signal from this station. A needle on the navigation equipment tells the pilot where they are flying to or from station, on course or not . 

• Pilots have various navigation aids that help them takeoff,fly, and land safely. One of the most important aids is a series of air route traffic control , operated throughout the world. Most of the traffic control uses a radar screen to make sure all the planes in its vicinity are flying in their assigned airways. Airliners carry a special type of radar receiver and transmitter called a transponder. It receives a radar signal from control center and immediately bounces it back. When the signal got to the ground, it makes the plane show up on the radar screen.Pilots have special methods for navigating across oceans. Three commonly used methods are:

• 1. Inertial Guidance. This system has computer and other special devices that tell pilots where are the plane located.2.LORAN Long Range Navigation. The plane has equipment for receiving special radio signals sent out continuous from transmitter stations. The signals will indicate the plane location3.GPS Global Positioning System. is the only system today able to show your exact position on the earth any time, anywhere, and any weather. The system receiver on the aircraft will receives the signals from sattelites around the globe.

• ADF Automatic Direction Finder. An aircraft radio navigation which senses and indicates the direction to a Low/Medium Frequency non-directional radio beacon (NDB) ground transmitter.

• DME Distance Measuring Equipment. Ground and aircraft equipment which provide distance information and primary serve operational needs of en-route or terminal area navigation.

• EAT Estimated Approach Time• EFIS Electronic Flight Instrument System , in which multi-function CRT

displays replace traditional instruments for providing flight, navigation and aircraft system information, forming a so-called " glass cockpit ".

• ETA Estimated Time of Arrival• GPS Global Positioning System . A navigation system based on the

transmission of signals from satellites provided and maintained by the United States of America and available to civil aviation users.

• HDG Heading. The direction in which an aircraft's nose points in flight in the horizontal plane, expressed in compass degrees (eg. 000 or 360 is North, 090 is East)

• HSI Horizontal Situation Indicator. A cockpit navigation display, usually part of a flight-director system, which combines navigation and heading.

• IFR Instrument Flight Rule . prescribed for the operation of aircraft in instrument meteorological condition.

• ILS Instrument Landing System . consists of the localizer, the glideslope and marker radio beacons (outer, middle, inner). It provides horizontal and vertical guidance for the approach.

• INS Inertial Navigation System. It uses gyroscopes and other electronic tracking systems to detect acceleration and deceleration, and computes an aircraft's position in latitude and longitude. Its accuracy, however, declines on long flights. Also called IRS, or Inertial Reference System.

• KNOT (kt) Standard Unit of speed in aviation and marine transportation, equivalent to one nautical mile per hour. One knot is equal to 1.1515 mph., and one nautical mile equals to 6,080 feet or 1.1515 miles. One knot is equal to one nautical mile per one hour.

• LORAN C Long Range Navigation is a Long-Range low frequency Radio Navigation. Its range is about 1,200 nm by day to 2,300 nm. by night.

• MAGNETIC COURSE Horizontal direction, measured in degrees clockwise from the magnetic north.

• MACH NUMBER Ratio of true airspeed to the speed of sound. Mach 1 is the speed of sound at sea level. Its values is approximately 760 mph.

NDB Non-Directional Beacon. A medium frequency navigational aid which transmits non-directional signals , superimposed with a Morse code identifier and received by an aircraft's ADF.

RMI Radio Magnetic Indicator. A navigation aid which combines DI ,VOR and /or ADF display and will indicate bearings to stations, together with aircraft heading.

RNAV Area Navigation. A system of radio navigation which permits direct point-to-point off-airways navigation by means of an on-board computer creating phantom VOR/DME transmitters termed waypoints.

TACAN TACtical Air Navigation. Combines VOR and DME and used by military aircraft only.System which uses UHF frequencies , providing information about the bearing and distance from the ground station we have tuned into.

TCAS Traffic Alert and Collision Avoidance System. Radar based airborne collision avoidance system operating independently of ground-based equipment. TCAS-I generates traffic advisories only. TCAS-II provides advisories and collision avoidance instructions in the vertical plane.

TRANSPONDER Airborne receiver / transmitter which receives the interrogation signal from the ground and automatically replies according to mode and code selected. Mode A and B wre used for identification, using a four digit number allocated by air traffic control. Mode C gives automatic altitude readout from an encoding altimeter.

• VFR Visual Flight Rules. Rules applicable to flights in visual meteorological conditions.

• VHF Very High Frequency. Radio frequency in the 30-300 Mhz band, used for most civil air to ground communication.

• VOR Very High Frequency Omnidirectional Range. A radio navigation aid operating in the 108-118 Mhz band. A VOR groun station transmits a two- phase directional signal through 360 degrees. The aircraft's VOR receiver enables a pilot to identify his radial or bearing From/To the ground station . VOR is the most commonly used radio navigation aid in private flying.

• VORTAC A special VOR which combines VOR and DME for civil and military used . System provides information about the bearing and distance from the ground station we have tuned into.

Tactical air navigation system

A compass is one of the pilot's dearest friends, if not always one of his or her "truest" friends. There are times when a pilot must wonder whether a compass is working for him or against him.

The wily compass can find so many ways to lie to a pilot. It's readings will be wrong, if:

the aircraft is turning—it can even swing in the opposite direction of the turn!

the aircraft is climbing or descending. the aircraft is accelerating or decelerating. the aircraft is flying through rough air. there are metallic objects near the compass. the radios are turned on vs. turned off.