Other Radio and Radar Aids Flashcards
VHF Direction Finding DF Steers
● VHF Direction Finding service (know as VDF steer) is intended to provide directional assistance to a pilot who may be unsure of their location.
➢ Information about the aircraft’s location is obtained by a tower or FSS using the radio signal that is transmitted by the aircraft.
➢ Heading indicators should not be reset without advising the DF operator once service is being provided.
● Information on airports that have VDF is found in the CFS and on the VNC.
➢ There are only a few left, as of this filming.
➢ A service that is and has been replaced by radar
● How does it work?
➢ The controller asks the pilot to “transmit for bearing” and the pilot then makes a transmission of at least 5 seconds in length – usually by saying the registration slowly.
➢ The controller would then know where you are from the station.
➢ The process would then be repeated as the aircraft comes closer to the station.
● As mentioned, DF steers are slowly being removed from service
Primary Surveillance Radar (PSR)
● Displays reflected radio signals from contacts like aircraft and weather without requiring any information from the aircraft
Secondary Surveillance Radar (SSR)
● Requires a reply from a transponder, known as interrogation, to determine the aircraft’s range
RNAV
● Area Navigation (RNAV) can be defined as a method of navigation that permits aircraft operation on any desired course within the coverage of the station-referenced navigation.
● Direct to means no airways required.
● RNAV was developed to provide more lateral freedom and thus more complete use of available airspace
RNAV Advantages
● This method of navigation does not require a track directly to or from any specific radio navigation aid, and has three principal applications:
1. A route structure can be organized between any given departure and arrival point to reduce flight distance and traffic separation;
2. Aircraft can be flown into terminal areas on varied pre-programmed arrival and departure paths to expedite traffic flow; and
3. Instrument approaches can be developed and certified at certain airports, without local instrument landing aids at that airport.
RNAV Systems
● The CDI (Course Deviation Indicator) for RNAV shows distance off track in nautical miles.
➢ Remember–VOR and ADF show degrees, not miles off!
● Navigation systems which provide a RNAV capability include:
➢ Multiple VOR / DME stations
➢ GNSS / GPS
➢ Inertial Navigation Systems (INS) or Inertial Reference Systems (IRS)
VOR / DME
● A common type of general aviation RNAV system is the Track-Line Computer (TLC), based on azimuth and distance information from a VORTAC
● It is also called the RHO-THETA system.
● With the track-line computer the pilot effectively moves or offsets the VOR/DME to any desired location if it is within reception range.
● This “phantom station” is created by setting the distance (RHO) and the bearing (THETA) of the waypoint from a convenient VOR/DME in the appropriate windows of the waypoint selector.
● A series of these “phantom stations” or waypoints make up an RNAV route
Inertial Navigation Systems
● Inertial Navigation Systems (INS) are completely self-contained and independent of ground based navigation aids. ○ In other words, these systems are built in to the aircraft itself
● After being supplied with initial position information it is capable of updating with accurate displays of position, attitude, and Heading
● The INS can calculate the track and the distance between two points, while also displaying course error, ETA, ground speed, and wind information.
● It can also provide guidance and steering information for the pilot’s instruments.
● The core of the system consists of the inertial platform, the interior accelerometers, and a computer
● The platform senses the movement of the aircraft over the ground, which contains two gyroscopes.
● These maintain their orientation in space while the accelerometers sense all direction changes and rate of movement.
● The information from the accelerometers and gyroscopes is sent to the computer, which corrects the track to allow for such factors as the rotation of the earth, the drift of the aircraft, speed, and rate of turn.
● The aircraft’s attitude instruments may also be linked to the inertial platform.
● The accuracy of the INS is dependent on the accuracy of the initial position information programmed into the system.
● Therefore, system alignment before flight is very important
● Accuracy is very high initially following alignment and decays with time at the rate of about 1 to 2 NM per hour.
● Position updates can be accomplished in flight using ground based references with manual input or by automatic update using multiple DME or VOR inputs
