Tuesday, September 26, 2023

American Carrier Strike Groups: An Electronic Perspective (Part 4 of 5)

B. Kamalanath is a technical writer. He is also a research scholar, pursuing Ph.D in military technology

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Once aircraft are lined for landing, these are transferred to approach and landing controllers, that help the pilots in landing the aircraft. During high-intensity air operations aircraft come and land every 30 seconds. For this, a radar called marshalling radar is used, which is the air-traffic control radar.

Marshalling radar. The marshalling radar AN/SPN-43 is a 2D air-surveillance S-Band (2GHz-4GHz) radar, dedicated for air-traffic control. It is used for vectoring carrier-bound aircraft into final approach for landing. It also acts as a back-up, short-range, air-search radar for air-defence operations. It provides azimuth and range of detected aircraft from 80.5km (50 miles) to a minimum range of 229m (250 yards), at altitudes from radar horizon to 9144m (30,000 feet).

The radar has an inbuilt Identify Friend or Foe (IFF) system. The radar display console displays all echoes in the area of responsibility in the form of blips. But how can individual aircraft be set apart from these blips? For this, a system called Direct Altitude and Identity Readout (DAIR) is used to identify the aircraft.

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DAIR. DAIR is a highly-automated beacon and radar-tracking system. It is used for identifying incoming aircraft and operates as a sort of back-end for marshalling operations, whereas the radar operates as the front-end. Every American combat aircraft has a transponder. This transponder is queried by DAIR through AN/SPN-43 radar.

These transponders give their identity and altitude of the aircraft to DAIR through AN/SPN-43 radar. Then, DAIR superimposes this data as alphanumerals over the blips of corresponding aircraft appearing on display consoles. So mere anonymous blips are replaced by names and their altitudes. This system is also capable of processing and superimposing flight plans, geographic reference points and map lines for enhancing mission planning.

Marshalling radar-DAIR combo is a high-precision system enabling controllers to track every aircraft effectively. Through their consoles, air-traffic controllers can interact with DAIR for tracking a particular aircraft’s flight. Then they give instructions for the pilot through separate communication channels that exist between air-traffic controllers and pilots. They line up aircraft in a queue for landing and then transfer the control to the landing controllers.

In CATCC, there are many personnel, each handling a specific controlling and monitoring task dealing with outbound aircraft, incoming aircraft, landing aircraft, civilian and neutral flights, unidentified blips and the like.

Fig. 25: FA-18 combat aircraft on the carrier approaching land at dusk (centreline lights are visible and a tiny green spot on the left side is FLOLS)
Fig. 26: AN/SPN-41 radars highlighted (the top-left highlighted section is the LSO station)

Landing: the mortal challenge
For any pilot, landing his aircraft smoothly is a challenge. But normal pilots come nowhere near their naval counterparts. Naval pilots have to land their aircraft on a moving aircraft carrier, which is the supreme challenge comprising layers of challenges for a pilot’s airmanship because of the landing procedure. So naval pilots are considered a special breed among pilots.

Normally, an aircraft after landing runs over the runway, sheds off the enormous momentum, slows down and stops. But the flight-deck of a carrier is not even one-tenth the length of a runway. So the aircraft has to be arrested and trapped to stop its momentum. All aircraft belonging to carriers have a hook, known as a tail hook, beneath their tails. During landing, pilots touch the runway such that the hook snags a thick arresting cable present on the flight deck. The pilot has an error margin of just centimetres. If missed, the pilot increases power, takes off and makes another attempt.

Now comes the next aspect of the challenge—the runway is not only short but also unstable. It pitches up/down and rolls left/right. The pilot has to land guessing how the runway will move and then land, accordingly. The pilot has to guess that in just fractions of a second. During landing, the pilot first aligns the aircraft to the centreline of the runway from an altitude and gradually descends at a constant speed in a shallow angle; it is called approach. In the meantime, if the flight-deck pitches up, the pilot nudges the throttle to increase speed and hence altitude, and vice-versa. Similarly, if the carrier yaws, the pilot adjusts the aircraft, accordingly, and may have to make more than 100 such adjustments during the approach.

Further, landing at night time on a very short runway of a minimally-lit carrier, which is pitching, rolling, yawing and sliding, is nerve shattering and a mortal challenge. An error caused due to the pilot’s judgement may cost not only his or her life but many other lives and also many aircraft.


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