A-037-1A

A-037-1A transceiver in the A-037 Variant 11 set

The A-037-1A is the primary transmitting and receiving unit of the A-037 radio altimeter set, Variant 11. It measures true aircraft height above land, water or rough terrain and sends altitude data to cockpit indicators and related onboard systems. The unit is installed on fixed-wing aircraft and helicopters, including Mi-8, Mi-17 and Mi-171 series helicopters, depending on aircraft configuration. The A-037-1A is not a cockpit indicator; it is the electronic measuring block that forms the core of the radio altimeter system.

Operating principle of the A-037-1A

The A-037-1A operates as a continuous-wave radar with frequency modulation. The unit transmits a radio-frequency signal toward the surface below the aircraft, receives the reflected return and processes the signal difference to determine true altitude in real time. This method gives the aircraft actual clearance above the surface below it, not barometric altitude. The measured value is then used by the pointer indicator, low-altitude warning circuit and other connected aircraft systems, depending on the installed configuration.

Altitude measurement range of A-037-1A

For the A-037-1A version, the operating altitude range is specified as 20 to 300 meters. This makes the unit suitable for low-altitude flight profiles where accurate terrain or water clearance information is required. The system supports continuous altitude indication and warning logic within its operating envelope. Although some related A-037 units may have different altitude ranges, the A-037-1A should be selected and supplied according to its own variant data and the A-037 Variant 11 documentation.

Indication, warning and fault output

In the A-037 radio altimeter system, the A-037-1A provides data for continuous altitude display on a pointer indicator. The system can also generate a low-altitude warning when the aircraft descends below a preset threshold. Depending on aircraft configuration, this warning may be visual and aural. If the system detects a malfunction, loses radar contact with the surface, or operates outside the valid height range, a fault indication appears on the cockpit indicator scale. This tells the crew that the displayed altitude should not be relied on.

Electronic structure and construction of A-037-1A

The A-037-1A includes receiving, transmitting, signal-processing and monitoring circuits. The unit housing is metallic and has a perforated U-shaped top cover. Manual access points for “1RS” and “2RS” adjustments are provided on the block. The transceiver is mounted on standard frame fixtures and connects to the aircraft wiring through the rear connector Ш1-1. Since the unit is the electronic core of the altimeter set, its condition affects indication, warning output and system reliability.

A-037-1A on Mi-8, Mi-17 and Mi-171 helicopters

The A-037-1A may be used on Mi-8, Mi-17 and Mi-171 series helicopters, as well as other aircraft platforms equipped with the A-037 Variant 11 radio altimeter set. On helicopters, radio altitude data are important during approach, landing, hover, descent, external-load work, flight over water and terrain-clearance monitoring. Exact applicability must be confirmed by helicopter modification, installed equipment list, wiring diagram and the aircraft’s radio altimeter documentation.

Installation, service and supply of A-037-1A

The A-037-1A must be operated and maintained according to aircraft documentation and A-037 radio altimeter technical requirements. Before installation, the unit should be checked for condition, passport, service history, connector integrity, completeness, mounting compatibility and test status. When troubleshooting, the full system should be checked: transceiver, antennas, coaxial lines, cockpit indicator, warning circuits, power supply and interconnecting cables. For procurement, the full designation A-037-1A should be stated clearly.

Product Name: Radio Altimeter Transceiver
Part Number: A-037-1A
Product Type: Radar altitude measuring unit / transmitting-receiving unit
Function: Measurement of true altitude above ground, water or rough terrain
Operating Principle: Continuous-wave radar with frequency modulation
System Application: A-037 radio altimeter set, Variant 11
Operating Altitude Range: 20–300 m
Residual Altitude H₀: 7.2 m
Measurement Error, 95%, H1/H3 Outputs up to 20 m: ±0.6 + 0.05·H
Measurement Error, 95%, Above 60 m: ±0.6 + 0.05·H
Analog Indication Error, 0–20 m: ±2 m
Calibration Error on K-5 Delay Line, H1/H3 Analog Outputs: ±(0.3 + 0.03·H)
Indicator Calibration Error: ±0.05·H
Overall Sensitivity on K-5 Line: ≥87 dB
Altitude Pulse Outputs, 1RS / 2RS: 5–750 m
Danger-Altitude Signal Error, 0–20 m: ±1 m
Danger-Altitude Signal Error Above 20 m: ±2 m
Aural Signal Duration: 3–9 s
Indicator Backlight: White / red
Control-Mode Altitude Indication: 15 ±2 m
Power Consumption from 115 V, 400 Hz Supply: Up to 10 VA
Power Consumption from 27 V DC Supply: Up to 30 W
Unit Mass: 6.8 ±0.3 kg
Installation / Mounting: Standard frame fixtures; rear connector Ш1-1
Adjustment Access Points: “1RS” and “2RS”
Typical Installation Platforms: Mi-8, Mi-17, Mi-171 helicopters and other aircraft on request
Condition: As applicable
Alternate Designations: A-037-1A; A037-1A; A 037 1A; A-037-1A transceiver
Documentation: Product passport and operation manual

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