How would pilots ever get around so easily without the help of navigation aides? Navigational aides have been around for almost as long as aircraft have been flying in the skies above us. The first navigation system was composted of just a high intensity-flashing beacon. These beacons were placed on the flight routes that were popularly flown in the mid 1920’s. With more time more of these technologies that help us navigate the world will be even simpler than today. This paper will explain how some navigational aides work and how some of them came into existence.
Flight Management Systems
Flight management systems are one of the best navaids in commercial aviation. The flight management system (FMS) is made up of four systems in an aircraft, the FMC (flight management computer), the autopilot and flight director, the auto throttle, and the IRS’s. According to Boeing the FMS could be defined as, being capable of four dimensional area navigation (latitude, longitude, altitude, and time), while optimizing performance to achieve the most economical flight possible. The flight management system can give you gross weight of the aircraft, and the best speeds (i.e. holding, approach, climb, cruise, descent, etc…) by taking inputs from the fuel summation unit when it is given the zero fuel weight and the MACTOW (mean aerodynamic cord at takeoff weight). The position of the aircraft can also be determined by referencing the IRS, along with GPS and the radio position updating.
Global Positioning Systems
GPS is a navigational aid that is satellite based. It is made up of a network of 24 satellites in orbit around the world. The first satellite was launched in 1978 and the last was put into orbit in 1994. Every 10 years another satellite is put into orbit because each satellite is made to last that amount of time. The system began as a military application but in the 1980’s the government decided to make it available to everyone, anywhere, anytime. The system finds your position by measuring the time it takes to receive the signal back to the satellite. It then does that with other satellites to triangulate your position in relation to the earth. To calculate a position in 2D the system has to be locked on to at least three satellites, but for a 3D representation you need to be locked on to at least 4 satellites. Once the position is found the GPS can calculate much more info like speed, bearing, track, distance, etc… The GPS system is very accurate; Garmin (a leader in GPS technology) states that their newest receiver is accurate up to an average of 15 meters. With the implementation of WAAS (wide area augmentation system) the receiver accuracy can get closer to three meters. There are many different signal errors that can occur with GPS, ionospheric and tropospheric errors are when the signal slows down as it is passed through the ionosphere or the troposphere. Signal multipath error happens when the signal is reflected off of objects. There are many other errors that could happen with relation to GPS that have not been mentioned in this paper.
VHF Omni-Directional Range
VOR’s are one of the most widely used navigational aides in aviation. Fifty years ago the VOR was introduced and it is still the primary navigation system in the country. VOR’s are very easy to understand. A VOR site sends out two signals simultaneously. One signal is the same in every direction and the other changes as it goes around the station. As the aircraft intercepts the signal, the receiver on the aircraft reads the two signals and determines where you are at in relation to the station, which is called a radial. Once you find out what radial you are flying on, you can very easily find out what direction you need to fly to get to a point by looking on either your VFR or IFR enroute charts to see where the VOR station lays in relation to that point.
Non-Directional Beacons NDBs may be located on the surface of airports, or may be within a few miles from an airport. Sometimes they are co-located with the Outer Marker in ILS approaches. The NDB provides two principal functions; (1) homing for VFR operations, and (2) ADF instrument approach capability for IFR operations. NDB frequencies are received on the ADF receiver in the aircraft. The frequencies that NDB’s operate are within the range of 190 to 535 KHz. The ADF in the aircraft has two separate antennas to which it picks up the NDB frequency, the loop antenna and the sense antenna. The loop antenna can sense the direction of the signal from the station, but cannot discriminate whether the station is in front or behind the aircraft. The sense antenna can discriminate direction, and solves the ambiguity of the loop antenna.
Navigation aides are vital to the aviation industry. You can only fly so far by dead reckoning before you get lost and need assistance to find your way. With the help of navaids people are now able to fly internationally to wherever in the world they want. Without the help of navigation aides the aviation industry would have never gotten to the point it is today and would never have gotten off the ground.

References

http://www.navfltsm.addr.com/vor-nav.htm

http://www.garmin.com/aboutGPS/

http://www.b737.org.uk/fmc.htm