A-034-4-3

Extended altitude range of the A-034-4-3

The A-034-4-3 belongs to the A-034-4 family of radio-altimeter indicators. Its main distinguishing feature is the extended indication range up to 1500 meters. Other indicators in the same family may use 300 m, 700 m or 750 m scales, but this version is intended for aircraft that require radio-altitude awareness over a wider operating envelope. The instrument keeps the same general pointer-indicator logic while using a scale layout adapted to higher values. This makes it useful where the crew still needs radio-altitude reference above the usual low-height zone.

Scale layout on the A-034-4-3 indicator

The scale of the A-034-4-3 is divided into several zones with different resolution. From 0 to 20 meters, the division is 5 meters. From 20 to 100 meters, the division changes to 10 meters. From 100 to 1500 meters, the scale uses 100-meter divisions. This is a practical compromise for an extended-range radio-altimeter indicator. The lower part remains readable for near-ground operation, while the upper range gives the crew broader altitude awareness without making the dial overloaded with too many marks.

Danger altitude setting on the A-034-4-3

The A-034-4-3 includes a danger altitude setting sector and an integrated warning lamp. The crew can set a selected warning height on the instrument. When the aircraft descends to the selected value, the warning output activates and draws attention to the unsafe altitude condition. This feature is important because the pilot should not have to constantly compare the pointer with the scale during a busy phase of flight. The warning function gives a separate visual cue when the aircraft approaches the preset radio-height limit.

TEST function and blinker indication of A-034-4-3

The indicator has a TEST push button for cockpit verification of the radio altimeter indication channel. When the A-037 system is operating correctly, pressing TEST should move the pointer to the reference mark. If the pointer does not respond, or if the system cannot provide valid altitude information, the drop-out blinker flag appears on the display. The blinker is a direct warning that the indication is not reliable. In maintenance, this check helps separate normal indication from a possible fault in the indicator, wiring, transceiver, antennas or power circuits.

A-034-4-3 with A-037 transceivers and antennas

The A-034-4-3 works with A-037 radio altimeter equipment, including A-037-1 series transceivers and system antennas. Compatible transceiver versions may include A-037-1A, A-037-1B, A-037-1V and A-037-1G, depending on the aircraft configuration and documentation. The radio altimeter operates in the 4200–4400 MHz frequency band at system level. The indicator itself is only one cockpit element of the complete set, so any replacement or troubleshooting should be made with reference to the full A-037 configuration installed on the aircraft.

Installation and supply of A-034-4-3

The A-034-4-3 is mounted on the cockpit instrument panel and should be selected by exact designation, not only by appearance. Indicators in the A-034-4 family can look similar while having different ranges, scales, markings and system variants. Before installation, the unit should be checked for pointer movement, scale readability, TEST response, blinker operation, connector condition, mounting integrity and documentation. When ordering, it is worth specifying that the required item is the 1500 m scale version for the A-037 radio altimeter system.

Related instruments: A-034-4-18, A-034-4-11, A-034-4-8. These links are grouped by function and system context and do not indicate interchangeability.