Surveillance Flashcards
What is Surveillance ?
● It is the ability to reliably detect key flight attributes such as position, level and intent.
● Types of surveillance :
○ Dependent.
○ Independent.
○ Co-operative.
Procedural Surveillance (Dependent)
● Procedural control is a method of providing Air Traffic Control services without the use of radar.
● Pilots report their position using a voice channel (HF, VHF)
● It is slow, cumbersome & exposed to human error.
● It relies on the pilot/aircraft navigation capability
Primary Radar Surveillance (Independent)
● A Surveillance system in which a radar is used to detect and spot targets.
● Radar measures the position of aircraft.
● It allows smaller separation standards.
● Typically used in busy terminal areas
Secondary Radar Surveillance (Co-operative)
● A Radar system measures position of aircraft (range & azimuth) but also requests additional information from the aircraft.
● Secondary Surveillance Radar depends on targets equipped with a transponder to downlink altitude.
● They are also more accurate
Principle of Operation
● The airborne system consists of a controller, a receiver/transmitter and a small L-band antenna mounted on the underside of the aircraft.
● The transponder works by the ground equipment sending out a special interrogation signal asking all aircraft “who they are”.
● The airborne transponder picks up the signal and automatically sends back a strong pulsed signal in reply.
● The reply signal is computed into distance and direction, in addition to a pressure altitude when using Mode C.
● This information is then displayed on the air traffic controller’s scope.
➢ NOTE: The pressure altitude readout is provided by an encoding internal pressure altimeter (blind encoder)－one that is independent of the aircraft altimeter
Phraseology and Use
● The interrogations signals from the ground radar are
➢ Mode A asks for identification/squawk code (provides position information only)
➢ Mode C asks for identification/squawk code and altitude information (provides position and aircraft pressure altitude). Uses a encoded altimeter.
➢ Mode S asks for unique signature, altitude, and limited data
Mode S
● Mode S is a more recent development for transponders giving controllers a significant increase in the available information and they know exactly which aircraft it is that is being interrogated.
➢ This gives the advantage of helping reduce the loads placed on the heavily used VHF channels.
● Along with performing all the functions of Mode A and C transponders, Mode S transponders also have a data link capability.
➢ Are also an integral component of all TCAS II/ACAS II installations.
● Airworthiness approval must be obtained by Canadian aircraft operators who install Mode S transponders
● Transponder phraseology used by ATC
➢ Squawk (code) － Operate the transponder on the specified code
➢ Squawk ident － Push the IDENT button (positively identifies your aircraft on the scanning screen). If there is more than one aircraft squawking the same code, such as 1200 ATC may ask an aircraft to squawk IDENT
➢ Squawk standby － Switch transponder to standby position
➢ Stop squawk － Switch off transponder
● Transponder mode switch four positions
➢ OFF － Transponder is off
➢ STBY － Used for warm-up and whenever ALT readout is not required
➢ ON － Provides position information only
➢ ALT － Provides position and altitude information to ATC There is also an IDENT button
Transponder Codes
● The transponder can be set to different codes which help the controllers identify different aircraft.
➢ 1000: IFR if no code is assigned below 18 000 feet ASL.
➢ 1200: VFR if no code is assigned at or below 12 500 feet ASL.
➢ 1400: VFR if no code is assigned above 12 500 feet ASL.
➢ 2000: IFR if no code is assigned at or above 18 000 feet ASL
● 7500: Unlawful interference (hijack)
○ Selecting 7500 and then 7700 indicates the situation is desperate and you are requesting armed intervention
Transponder Code When Leaving Controlled Airspace
● A pilot instructed to squawk a discrete code should not adjust their assigned transponder code when informed that radar or surveillance service is terminated.
● Don’t change to 1200 when leaving controlled airspace unless you are told to “squawk VFR or 1200”.
● Since your code is tagged by ATC, they can follow your registration/type as the flight progresses
Benefits of ADS-B
● Real-time ADS-B is used now for Air Traffic Control.
● It reduces costs, and lessens harmful effects on the environment.
● ADS-B equipped aircraft will be subject to reduced separation standards, allowing more aircraft to operate at optimum levels.
● The accuracy is unaffected by the range to the aircraft as in the case of radar.
Principle of Operation
● An aircraft with ADS-B capability determines its position using GPS.
● The Mode S transponder then broadcasts that position at rapid intervals, along with identity, altitude and velocity information.
● Dedicated ADS-B ground stations can receive the broadcasts and relay the information to air traffic control for precise tracking of the aircraft.
● Other proximate aircraft can also receive the broadcasts.
Equipment Onboard for ADS-B
- A WAAS GPS receiver to supply position data to your transponder or transceiver.
- A Mode S Extended Squitter Transponder
ADS-B Functions
● Two ADS-B functions :
○ ADS-B Out
○ ADS-B In
● If an aircraft is able to broadcast its information, it has “ADS-B Out” capability.
● If it is able to receive information from other aircraft and ground stations, it has “ADS-B In” capability
ADS-B In
● ADS-B In receives the transmissions from ADS-B Out equipped aircraft within radio range.
● ADS-B In is Line-Of-Sight to ADS-B Out sources and requires a screen in the cockpit to display the traffic information received by ADS-B In.
● 1090 ES ADS-B In doesn’t receive weather.
● Since ADS-B In equipment is not mandated, it does not require certification and can be portable.
● With a compatible flight display, an aircraft equipped with 978 MHz UAT ADS-B In equipment shows: other aircraft, other vehicles, terrain, and weather information
