ATPL Radio Navigation - Class 11: Secondary Surveillance Radar.

Summary

This video explains the workings of Secondary Surveillance Radar (SSR), an advanced system used in air traffic control for tracking aircraft. SSR functions by sending interrogation signals from the ground to aircraft transponders, which respond with vital information like location, altitude, and unique identification codes. The video details the different modes of transponders (Mode A, Mode C, and Mode S), each with varying levels of complexity and functionality. It also covers emergency codes, collision avoidance systems, and potential errors in SSR, highlighting its crucial role in aviation safety and efficient airspace management.

Takeaways

• 😀 SSR (Secondary Surveillance Radar) is an advanced radar system used by air traffic control to safely guide aircraft in the sky, working in conjunction with primary radar.
• 😀 SSR operates by sending an interrogation signal from the ground, and the aircraft's transponder responds with data such as identification and altitude.
• 😀 SSR transponders work on two key frequencies: 1030 MHz for the interrogation signal from the ground and 1090 MHz for the aircraft's response.
• 😀 Mode A is the most basic SSR mode, providing a four-digit squawk code for aircraft identification. There are 4,096 unique codes.
• 😀 Mode C transponders include both a squawk code (like Mode A) and an altitude readout for the aircraft, measured with pressure altimeter settings.
• 😀 Mode S is the most advanced SSR mode, with a unique 24-bit address for each aircraft, allowing for selective interrogation and the transmission of more detailed data (e.g., speed, heading, call sign).
• 😀 Mode S also enables TCAS (Traffic Collision and Avoidance System), allowing aircraft to communicate and avoid collisions by adjusting their altitudes.
• 😀 Emergency squawk codes like 7500 (hijack), 7600 (communication failure), and 7700 (general emergency) help controllers quickly identify and respond to critical situations.
• 😀 Fruiting occurs when two ground stations receive the same signal from an aircraft, causing confusion in identifying the aircraft's location.
• 😀 Garbing happens when two aircraft are aligned on the same bearing, and their responses overlap, leading to incorrect distance data.
• 😀 Mode S improves the reliability of SSR by resolving issues like fruiting and garbing, thanks to its unique identification code and more precise data transmission.

Q & A

What is Secondary Surveillance Radar (SSR) used for in air traffic control?

SSR is used to help air traffic controllers track and guide aircraft more efficiently by sending an interrogation signal from the ground and receiving a response from the aircraft. It provides more detailed data compared to primary radar.

How does Secondary Surveillance Radar differ from Primary Radar?

Unlike primary radar, SSR only sends signals in one direction, reducing the chance of erroneous reflections. SSR also allows for more detailed data to be transmitted, such as altitude and specific aircraft information.

What is a squawk code in SSR, and how is it used?

A squawk code is a four-digit code sent by an aircraft’s transponder in Mode A, used for aircraft identification. These codes are assigned by air traffic controllers or set automatically in emergency situations.

What is the significance of the emergency squawk codes (7500, 7600, 7700)?

Emergency squawk codes help air traffic controllers quickly identify the nature of an emergency. For example, 7500 signals a hijack, 7600 indicates a radio failure, and 7700 denotes a general emergency.

How does Mode C improve on Mode A in SSR?

Mode C adds altitude information to the transponder’s response, allowing air traffic controllers to track not only the position but also the altitude of an aircraft, which helps ensure correct altitude assignments.

What is the unique feature of Mode S transponders?

Mode S transponders have a unique 24-bit address, allowing for over 16 million possible codes, enabling selective interrogations. They can provide detailed data like speed, heading, aircraft registration, and altitude.

What role does the 'ident' function in a transponder serve?

The 'ident' function allows the pilot to trigger a unique pulse that helps air traffic controllers quickly locate the aircraft on radar, especially useful when an aircraft enters or leaves an airspace.

What is the Traffic Collision and Avoidance System (TCAS) and how does it work?

TCAS is a system where transponders in nearby aircraft share flight data. If a collision risk is detected, TCAS will suggest a climb or descent maneuver to the pilots to avoid a collision.

What are the errors 'fruiting' and 'garbing' in the SSR system, and how are they mitigated?

Fruiting occurs when two ground stations receive responses from the same aircraft, causing confusion in bearing and distance data. Garbing happens when two aircraft are aligned along the same bearing, leading to overlapping responses. Mode S mitigates these issues with its unique identification system.

How does Mode S improve the reliability of SSR compared to Mode A and C?

Mode S improves reliability by providing a unique identification code for each aircraft, allowing for more accurate tracking and reducing errors such as fruiting and garbing. It also enables more detailed information to be transmitted, such as vertical speed and aircraft registration.