Litre Meter Press Release

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UK flowmeter specialist Litre Meter ( has introduced a range of fuel flow meters from Austrian manufacturer KRAL which can help airline operators and developers ensure the safety of their aircraft and control testing costs.

Major overhauls are carried out regularly during which aircraft are literally taken apart and every system, instrument and component is checked on a test stand.

LufthansaAt German airline Lufthansa, KRAL Volumeter flowmeters – available from UK distributor Litre Meter – are used as part of the test system to check the flow of hydraulic fluid on servo valves and the various cylinders operating flaps and landing gear. These are safety critical functions of the aircraft during take off, landing and in flight.

During testing the servo valves are actuated with a 0-20 milliamps (mA) signal and must allow a precisely defined volume of hydraulic fluid to pass. Flow over the current range is monitored and additional checks are made by measuring any leakage from hydraulic cylinders.

KRAL meters are also used to measure flow in hydraulic pumps and motors in the return stroke and under pressure. To test them the pumps are brought up to operating speed by a drive mechanism then flow and discharge pressures are measured. Discharge pressure is then built up to 200 bar and the meters monitor the flow of the hydraulic fluid to check if the correct flow rate is achieved.

The specialist KRAL Volumeter flow meters now offered by Litre Meter work virtually independently of viscosity and work accurately within Luthansa’s test stand viscosity range of between 3mm2/s and 10mm2/s. This means that fluids of varying viscosity can be tested without recalibrating the meters each time – which is both time consuming and costly.

Alan Christie of Litre Meter said: “There are strong economic and safety arguments for regular safety overhauls of aircraft. An essential starting point is having an accurate measurement of hydraulic flows in safety critical elements of the craft including the hydraulics that operate the servo valves, flaps and landing gear.

“Due to the high measuring performance of Kral Volumeters, test bench operators can achieve extremely accurate results under test in a number of applications.”