RDR - 8

Question 1

Describe the operation of IFF.

Answer 1

• The interrogator transmits a 1030MHz interrogation pulse.
• The transponder receives the interrogation pulse and
  transmits a 1090MHz response pulse.
• The response pulse from the transponder is received by
  the interrogator and decoded
• One wave transmission, hence longer range.

Question 2

List the use of different IFF modes

Answer 2

MODE 1 - General Identification:
* 2 Bit Code.
* 32 Codes Available.

MODE 2 - Personal Identification (Military)
* 4 Bit Code.
* 4096 Codes Available.

MODE 3 - Air Traffic Control Identification
* 4 Bit Code.
* 4096 Codes Available.
* Mode 3C Automatic Altitude Reporting.

MODE 4 - Military Encrypted. Outdated

Mode 5 – Cryptographic Military code. Replaced Mode 4

Mode S - referred to as the discrete address beacon system
– developed to reduce the workloads of both controllers
and pilots.
– used for airborne collision avoidance systems (ACAS),
including TCAS
– transmits a unique ‘squitter’ pulse every second, alerting
other aircraft of its presence.
– Does not rely on ground radar illumination to trigger the
transponder.

Question 3

State the emergency IFF mode 3 codes and their meanings.

Answer 3

MODE 3 CODE

7700 = AIRCRAFT EMERGENCY

7600 = COMMUNICATIONS FAILURE

7500 = UNLAWFUL INTERFERENCE

7400 = UNMANNED AERIAL VEHICLE LOST LINK

Question 4

Describe the operation of ADS-B.

Answer 4

Automatic Dependent Surveillance – Broadcast

Automatic : Requires no Pilot input or external interrogation

Dependant : Depends on accurate position from A/C data – GPS

Surveillance : Provides position, altitude, velocity and other data

Broadcast : Info is broadcasted twice every second

• Transmits twice every second
• Requires line of sight to transmits