Comms (14-05-18) Flashcards
What is the range of HF comms and why?
Very long range due to the refraction properties in the ionosphere.
Leads to a clarity trade off.
What is the frequency band of HF comms?
2-22MHz
What is the frequency band of VHF comms?
118 - 137MHz
What is the frequency band for NAVAIDs?
108 - 118MHz
What is SELCAL?
A system used to allow ATC to indicate that they are trying to contact an A/C
When does SELCAL have to be checked/changed?
On first contact with a new ATC
What is SATCOM?
Satellite communications operated by INMARSAT via 4 geostationary satellites giving covereage between 80degN - 80degS
What are ACARS?
Aircraft Communication Addressing and Reporting System
VHF data link that automatically passes info about engine and Nav data within organisation.
What is CPDLC?
Controller Pilot DataLink Comms
Uses ACARS to pass ATC clearances and communications to the crew via FMS
What is VDF?
VHF direction finding.
When using VDF, what is variation and when is it applied?
Variation is the difference between mag and true north and it is applied at the station.
What did old VDF systems use?
adcock aerials and sense aerials
What do modern VDF systems use?
Array of vertical dipoles all connected to a central receiver.
What are the classification of VDF systems?
By accuracy:
Class A - +/- 2deg
Class B - +/- 5deg
Class C - +/- 10deg
Class D - >+/- 10deg
What is the emergency frequency?
121.5MHz
What does the approach procedure code QDM mean?
Follow A/C mag heading to station.
What does the approach procedure code QDR mean?
Follow mag bearing from station (reciprocal to QDM)
What does the approach procedure code QUJ mean?
Follow true track to station. (true to union jack)
What does the approach procedure code QTE mean?
Follow true bearing from station (reciprocal to QUJ)
What are the errors associated with VDF?
Ground reflected waves (vertical plane) - causing destructive interference
Multipath error (horizontal plane) - causing destructive interference
Cone of confusion
Synchronous transmissions - 2 A/C transmitting at once
Intervening high ground
Super-refraction; sub-refraction; sporadic E
