US-450K Series 2

Airspeed measurement principle of US-450K

The US-450K works by measuring the difference between total pressure and static pressure. These pressures are supplied to the instrument from the aircraft pitot-static system, typically through separate pressure lines connected to a pitot tube such as PVD-6M or an equivalent approved source. Total pressure acts on the sensitive manometric capsule, while static pressure is applied to the instrument case cavity. The pressure difference creates movement of the capsule, and this movement is transmitted through a mechanical linkage to the pointer.

Cockpit speed indication on US-450K Series 2

The indicator scale shows airspeed in kilometers per hour. The Series 2 execution covers the helicopter airspeed range up to the specified maximum value and is intended for normal cockpit reading during flight. On twin-pilot helicopters, two airspeed indicators may be installed, one on the captain’s instrument panel and one on the co-pilot’s panel. In such layouts, they may be connected to duplicated pitot-static circuits to improve flight safety and provide independent speed reference for both pilots.

US-450K with pitot-static pressure lines

The correct operation of the US-450K depends not only on the instrument itself, but also on the pitot-static system. Blocked pressure lines, leakage, moisture, incorrect connection of total or static pressure, or a damaged pitot tube can cause wrong airspeed indication. For this reason, troubleshooting should include both the indicator and the pneumatic system. A mechanically serviceable instrument will still show incorrect values if the pressure source is not reliable or if the lines are contaminated or leaking.

Scale lighting and Series 2 execution

The US-450K Series 2 may use a luminous coating or temporary light compound on the scale for reading in low-light conditions with cockpit lighting or ultraviolet illumination, depending on execution and aircraft documentation. This is important when replacing the instrument, because similar airspeed indicators may differ by scale design, lighting execution, series, markings or compatibility with the aircraft panel. The exact series and designation should therefore be checked before procurement, especially when replacing an installed unit on a helicopter.

Maintenance and inspection of US-450K

During maintenance, the US-450K is checked for pointer smoothness, scale readability, glass condition, housing condition, pressure fitting integrity and absence of pointer sticking. The instrument should respond smoothly to pressure changes, without excessive oscillation or uneven movement. The pitot-static connections must also be checked for tightness and correct connection. For aviation supply, the passport or label, condition, storage history, series, verification status and compatibility with the aircraft cockpit layout should be confirmed before installation.