Data Links Flashcards
Types of Datalinks
● Like most everything in the world today, having the ability to access data and communicate are critical necessities in the aviation world.
● In order to accomplish this, we have many “traditional” ways to do this.
○ Radio
○ Radar
● In this presentation, we will take a look at some of the newer technologies that we are using to accomplish this.
○ CPDLC: Controller Pilot Data Link Communications
○ XM Satellite Weather
○ Mode S Transponders
○ ADS-B
CPDLC
● CPDLC: Controller Pilot Data Link Communications
○ This is a lot like text messaging between ATC and pilots.
○ It is used to help alleviate frequency congestion.
○ This method can use satellite (INMARSAT) or ground stations to send and receive the texts.
○ They are sent and received via the FMS
● FMS sends position, speed, altitude and other flight parameters to ATC (and/or company operations).
● ATC instructions and clearances can also be sent directly to the FMS.
Messages Arrives
● Chime
“ATC” message alert on Upper Display Unit
● There are Two major CPDLC systems:
-Future Air Navigation System (FANS-A, FANS-1/A)
* developed by Airbus and Boeing
* ACARS (Aircraft Communications and Addressing Reporting System) based.
* mostly used on oceanic routes (INMARSAT)
-ICAO Doc 9705 ATN/CPDLC
* European
XM Satellite Weather
● Through XM we can have METARs, TAFs, NEXRAD, Lightning, and more directly overlaid on our Jeppesen and topographic map databases.
● This is accomplished through two S-band geostationary satellites positioned over the east and west coasts.
● Together, they deliver seamless and near real-time coverage at any altitude across continental North America.
Mode S Transponders
● Mode S (Selective) transponders help avoid over-interrogation.
○ Each mode S transponder has a unique 24 bit code.
○ This means that a transponder will only reply to interrogations directly addressed to it.
○ The reply contains mode A, mode C, and 24 bit code.
○ The reply also contains a GPS position
Mode S & TCAS
● It is important to remember that a TCAS equipped
aircraft requires a mode S transponder.
● The level of protection TCAS gives us is going to depend
on the transponder of the other aircraft.
○ No transponder = No protection
○ Mode A = Traffic Alert (TA) only
○ Mode C = Uncoordinated Resolution Advisory (RA)
○ Mode S = Coordinated RA
ICAO 24-bit address
● All modern aircraft are assigned a unique ICAO 24-bit address or (informally) Mode-S “hex code” upon national registration.
○ This address becomes a part of the aircraft’s Certificate of Registration.
● Normally, the address is never changed.
○ However, the transponders are reprogrammable.
○ Occasionally they are moved from one aircraft to another (presumably for operational or cost purposes).
○ This will be done by by maintenance and by changing the appropriate entry in the aircraft’s FMS system
Automatic Dependent Surveillance – Broadcast (ADS-B)
● With this system, an aircraft will use GNSS information (such as GPS, Galileo, etc) to find its position.
○ The Mode S transponder then broadcasts the position, altitude, heading, speed to both a ground station and to other mode S transponders.
○ The other Mode S transponders will receive the information from the transmitting airplane.
○ Of course, they too, will be finding their positions and broadcasting it through their Mode S transponders.
○ The ground station will further back this up by relaying their data from all aircraft and to ATC
“ADS-B”
“ADS-B”
- Automatic - requires no operator intervention
- Dependent -depends on aircraft equipment
- Surveillance - provides position data
- Broadcast – sends data without interrogation
Advantages over RADAR
● Inexpensive technology.
○ Smaller footprint and power requirements.
● Viable for remote locations
● More accurate over longer distances
● Aircraft can be seen behind mountains.
○ And clear on down to the ground!
