| Explaination:
The overall accuracy of Omega system is given as 1 nm during the day, 2 nm at night. Another VLF system is that known as Rho/Rho or Ranging system, or just VLF system. The principle is implemented by use of an accurate on-board atomic time standard which produces a timing pattern identical to the received signals. The necessary navigational data are derived from the comparison of the phase of the incoming signal with the time standard, one station giving one position line.
Several receivers capable of utilising these VLF signals are now on the market: a typical system would operate as follows. The airborne equipment consists of a flush-mounted aerial, receiver/computer, an atomic time standard, control head with all its sixteen buttons on the keyboard, a display head and a station indicator.
On switching on the equipment the station indicator lights up to indicate the stations being received. The receiver automatically selects the best stations for its operation. After around five minutes of warming up time from the
initial power supply, the atomic standard will have stabilised and a light signal will indicate that the system is ready to navigate. The computer is initially fed with the accurate start position and a continuous display of the present position is then maintained. Other types of display may be selected: distance to go, distance across, heading to a way point, ground speed, time to a way point and so forth. As the flight progresses the receiver will continue to adjust to the best incoming signals. Basically a very reliable system, it may lose signals when flying in cloud with high ice crystal content. Then the system will go in the DR mode but it will pick up from where it left off when stronger signals are received again. |
