Navaids in Aviation

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