Computers You Should Know

Flight Computers

Universal Avionics UNS-1 FMS: One of the first computerized flight management systems

Universal Avionics UNS-1 FMS: One of the first computerized flight management systems

Navigating an aircraft has been on an ever-improving path since flights lasted more than a few minutes. Getting from Point A to Point B in an aircraft is much like navigating a ship, but with an extra dimension thrown in. Since the late 1970s, Flight Management System (FMS) computers have been used to aid in navigating aircraft. The FMS has grown in capability and scope over the years since.

The earliest flight navigation systems consisted of a compass, stop watch, map, and pilot. Dead reckoning was in use for many years until more sophisticated systems came along. The first major improvement came in the form of slide-rule-type computers for calculating range, wind speed, wind correction and fuel burn. Known colloquially as the E6B, the latest version is still used by general aviation pilots and some airline pilots to check their computers even though it was introduced just before WW2.

The venerable E6B

The venerable E6B

Soon radio and other systems were introduced to help with navigation. Automatic Direction Finder (ADF) systems used radio beacons and could be used by the pilot and an ADF receiver to determine heading and, if two signals were available, a rough location. Soon this was augmented with VHF Omnidirectional Range (VOR) systems which transmit a master signal and a secondary signal that is out of phase with the master by a second for the number of degrees. So, if you were flying past a VOR transmitter at 90 degrees, you would receive the master signal (non-directional) and the secondary signal 90 seconds later. These systems, coupled with dead reckoning techniques and the E6B, work well for slower aircraft and are low cost. In the 1950s, VOR was coupled with Distance Measuring Systems (DME) which used two pulse pairs of fixed duration and separation for calculating distance from a DME station. Soon, LORAN systems, inertial navigation systems and others were available for aviation use.

Pilots, as much as they may disagree, are human. They are quite capable of making mistakes and mistakes in navigation can be deadly. When computer systems became small enough and light enough that they could be economically fitted to aircraft one of their first applications was in navigation. The Flight Management System (FMS) was first approved for use on the Boeing 767. Sperry Flight Systems created a computer that used a database of the VOR/DME systems so that it could monitor several at one point and calculate a location. It also incorporated LORAN and inertial navigation systems and a rudimentary vertical navigation (VNAV) system for calculating climbs and descents taking into account aircraft weight and fuel consumption.

Since then, FMS has grown in capability to where it is now. Today’s FMS is tied to engine FADEC systems, autopilot systems, communication system, GPS and other nav systems, and databases of aircraft performance attributes. With all of this information, the FMS can be programmed with a flight plan and guide the aircraft through an entire flight and let the pilot know exactly where the aircraft is at, where it is heading, how long it will take to get there, how much fuel will be consumed, and if his wife has found out about his mistress.

These systems provide reliable and accurate position and flight planning information. Hopefully, though, the pilot still knows how to use his E6B should the system fail.

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2 comments to Flight Computers

  • Wolfie

    On the subject of navigation, how does a high tech mine detection ship miss a rather large underwater obstruction?
    Too much reliance on technology,and not enough human interaction.

  • highmileage_v1

    Sure beats using an abacus. The new flight management systems have basically turned aircraft into fully automated devices that only require occasional pilot input. We are reaching the point where flight profiles are going to be so demanding that a human cannot fly them. Time to fly a kite instead.

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