ARK-UD

ARK-UD homing on emergency beacons

The main task of ARK-UD is to guide the search aircraft or helicopter toward a radio beacon using automatic bearing indication. The system provides continuous circular direction indication and allows the crew to fly toward transmitters operating with quartz frequency stabilization. When the aircraft passes over the beacon, the course indication changes by 180 degrees, giving the crew a clear sign that the source has been overflown. This function is important in rescue work because the aircraft may need to narrow the search area quickly and confirm the exact location of the emergency transmitter.

Signal identification through the ARK-UD system

ARK-UD is not limited to blind bearing indication. The crew can identify the operating beacon or radio station by listening to its signal in the headset. This is necessary because in a search area there may be several signals, interference sources, or transmitters operating on nearby channels. Audio identification helps confirm that the aircraft is being guided to the correct source. Depending on the aircraft installation, received signal information and bearing data may be displayed through common cockpit navigation indicators, while sound indication is provided through the onboard communication / headset system.

Operating modes of ARK-UD

The ARK-UD has several operating modes for different beacon signal types. Wide-band mode is used for continuous-emission beacons where wider reception is needed. Narrow-band mode is used for continuous-emission beacons when a more selective reception channel is required. Pulse mode is intended for impulse-type radio beacons. The control panel also includes an RPK mode, described as a radio semi-compass mode for indicating the side of the radio station relative to the aircraft longitudinal axis, although this mode may not be used on certain aircraft installations.

ARK-UD frequency channels and beacon types

The ARK-UD operates on fixed VHF channels and a UHF channel used for emergency and search radio systems. The VHF channel set includes frequencies used by aviation rescue and beacon equipment, while the UHF channel covers the 243.0 MHz emergency frequency. This channel structure makes the system suitable for working with both continuous and pulsed emergency transmitters. For a crew performing a search task, this is more practical than a general-purpose receiver, because the channels and operating modes are organized around the signals expected from emergency beacons.

Equipment set and aircraft installation of ARK-UD

The ARK-UD is a distributed aircraft radio system, not a single cockpit instrument. The antenna block and antenna amplifier are installed in the lower fuselage area. The receiving and direction-finding equipment includes the receiver unit, direction-finder unit, built-in test generator and distribution box, usually installed on an equipment rack. The control panel is placed on the navigator’s instrument panel or in the cockpit area depending on aircraft layout. A switching box is installed in the radio compartment, and a mechanical transition unit is used to connect the radio compass with the course indicator.

Aircraft application and supply of ARK-UD

ARK-UD equipment is used on search aircraft and helicopters, including platforms such as An-26, Mi-8, Mi-24 and Mi-26 depending on configuration. In these aircraft, it works as part of the search-navigation equipment set and can be connected to common course or radio-magnetic indicators. For procurement, it is important to define whether the requirement is for a complete set or only for a separate block: control panel, antenna unit, receiver / direction-finder unit, switching box, built-in test generator, amplifier or mechanical transition unit. Completeness and documentation should be checked before shipment.