Which mode in the AN/TPX-42A Secondary Surveillance Radar has the highest priority in the interlace sequence?

• A. Mode 1
• B. Mode 2
• C. Mode 3/A
• D. Mode C

Answer: (C)

In the context of the AN/TPX-42A Secondary Surveillance Radar, Mode 3/A is considered to have the highest priority in the interlace sequence. This is due to the essential role that Mode 3/A plays in air traffic control and identification processes. Mode 3/A transmits a four-digit code that helps to identify aircraft within controlled airspace and is fundamental for maintaining situational awareness and ensuring safety in air operations.

When an air traffic controller requests information about an aircraft, Mode 3/A responses are prioritized to quickly provide this crucial identification data. This prioritization facilitates efficient tracking and management of air traffic, allowing controllers to make better-informed decisions based on the information retrieved from this mode.

Other modes such as Mode 1, Mode 2, and Mode C serve specific functions and are important, but they do not hold the same level of priority in the sequence as Mode 3/A. Mode 1 is typically used for military purposes, Mode 2 is for aircraft operating under certain conditions, and Mode C provides altitude reporting. These modes have distinct applications, but their urgencies in the interlace sequence are lower compared to the critical nature of the information provided by Mode 3/A. Thus, Mode 3/A is