VAR-30MK Series 4

Vertical speed measurement on VAR-30MK

The instrument measures vertical speed through changes in atmospheric pressure. When the aircraft climbs or descends, static pressure changes. The sensitive capsule and the instrument case receive this pressure with different timing because one path is restricted through a calibrated capillary. This creates a temporary pressure difference proportional to the rate of altitude change. The capsule deformation is transmitted through a mechanical linkage to the pointer. The result is a simple, fully mechanical indication of climb or descent rate without electronic signal processing.

VAR-30MK connection to static pressure system

The VAR-30MK is connected to the aircraft static pressure system. Correct indication depends not only on the instrument itself, but also on the condition of the static pressure line, fittings and the cleanliness of the capillary path. Leaks, moisture, blockage or incorrect connection can make the pointer slow, unstable or inaccurate. For this reason, troubleshooting should include both the variometer and the aircraft pressure system. A serviceable indicator will not work correctly if the static pressure supply is contaminated or not tight.

Series 4 cockpit scale execution

The Series 4 execution is adapted for cockpit use with red night lighting. The “K” index indicates red-light compatible execution. Digits, scale marks and the pointer are finished with a special white enamel or temporary light compound, depending on production and documentation, so the instrument remains readable under red cockpit illumination. This detail matters when replacing the instrument, because similar VAR-30M / VAR-30MK indicators may differ by scale execution, lighting compatibility, series, markings and maintenance documentation.

Application on Mi-8 / Mi-17 helicopters

On Mi-8, Mi-17 and Mi-171 helicopters, the VAR-30MK Series 4 is used as a basic flight instrument for monitoring vertical movement. It helps the crew control climb and descent rate during takeoff, approach, landing and en-route altitude changes. On helicopters, vertical-speed indication is especially useful because small altitude changes can happen quickly during low-speed flight, hover transitions and descent planning. The instrument is usually mounted on the pilots’ instrument panel in a position suitable for direct reading during flight.

Inspection and maintenance of VAR-30MK

The VAR-30MK is a precision mechanical aircraft instrument. During maintenance, technicians normally check pointer zero position, smoothness of pointer movement, indication error, leak tightness, case condition, glass, scale readability and pressure fittings. The instrument should not show excessive pointer sticking, lag or unstable return to zero. Calibration, sealing and test procedures are performed according to the applicable technical specifications and maintenance manual. For supply, passport, label, series, condition, storage history and verification status should be confirmed before installation.