Билет №34
1). Ground Direction Finding. Ground stations with the facility of taking a bearing of an aircraft from that aircraft’s transmissions are shown in the relevant section of the AIP. Users are advised that bearing information will only be given when conditions are satisfactory; furthermore a number of facilities are shown as “not available for en-route navigations”. Worldwide such services may be provide in the MF and HF bands but in most countries it operates in the VHF and UHF bands only. As civil aircraft do not use UHF, effectively ground direction finding is limited to VHF.
2). Night Effect - revers to problems that occurs when sky waves are received from the tuned NDB. ADF is designed to use only the vertically polarized ground wave and communication by the sky wave will cause bearing errors and wandering of the ADF needle.
3). At what Frequency operate ADF. ADF equipment senses incoming radio waves as they arrive at the aircraft and measures their direction relative to the nose of the aircraft. The direction of the radio wave may be shown on a RBI or displayed on an indicator orientated with magnetic heading, known as a RMI. On the RMI, the ADF indication is the magnetic bearing TO the source of the radio waves. This bearing is referred to as the QDM. Frequency Bands – LF and MF. Frequencies- 190 kHz to 1750 kHz (most commonly 200-500kHz).
Билет №35
1.) VOR is an acronym for VHF Omnidirectional Range, also known as OMNI. Because it operates in the VHF band, it is not affected by many of the problems associated with ADF such static interference and night effect. It is similar to ADF in that is provides the bearing of the aircraft TO or FROM a transmitter at a known ground position. However whereas ADF equipment measures the direction of the radio wave when it arrives at the aircraft, the VOR airborne receiver decodes from the radio wave its direction when it left the ground transmitter.
2). Phase Difference - the phase difference is the angular difference between the corresponding points on the waveform and is measurable provided the two signals have a common frequency.
3). At what Frequency operate NDB - frequency surface wave range increases as frequency decreases because attenuation is reduced. 190 kHz to 1750 kHz (most commonly 200-500 kHz).
Билет №36
1). Radio Magnetic Indicator - the RMI is alternative indicator for VOR and ADF. For both VOR and ADF bearings, the orientation of the pointer is determined by relative bearing but the reading of the pointer when taken against the compass card is magnetic bearing to the aid (QDM). The compass card rotates to show magnetic heading against the index at the top. As the card must be driven, the RMI requires an electrical input of heading such as that provided by a gyro – magnetic compass.
2). Tracking by RMI - If the aircraft is on track between NDBs or VORs, the pointers on the RMI will be aligned. It can be readily seen from the RMI on which side of track the aircraft is located.
3). At what Frequency operate Ground Direction Finding - the frequencies to be used are in the AIP. An aircraft can call a VDF station and request true or magnetic bearings as follows:
QTE – the aircraft’s true bearing from the station
QUJ - the aircraft’s true track to the station
QDR – the aircraft’s magnetic bearing from the station
QDM - the aircraft’s magnetic track to the station