726V

Starting fuel supply by the 726V pump

The main function of the 726V is to deliver fuel at the required pressure during engine or APU start. During the start sequence, the pump feeds the starting fuel circuit so that fuel can enter the combustion chamber and form a combustible mixture for ignition. Stable pressure in this short operating phase is important. If the pump does not produce the required outlet pressure, start may be delayed, unstable or unsuccessful. For AI-9V applications, the pump is factory-adjusted for operation within the APU starting system.

726V operation with the AI-9V auxiliary power unit

On helicopters equipped with the AI-9V APU, the 726V works according to the start cycle logic. It is energized for a limited time, delivers fuel to the starting circuit and then switches off after the required phase of the sequence. The unit is designed for repeated short-time operation, not for continuous fuel delivery. This operating mode must be respected during testing and maintenance, because excessive running time can overload the electric motor and affect pump life.

Electric drive of the 726V pump

The 726V is equipped with a DC electric motor, such as the D-102TF Series 2 according to the supplied data. The motor operates from the aircraft 27 V DC network and drives the pump section directly, without an electromagnetic clutch. The nominal motor power is 63.5 W, and the rotational speed is 4000 rpm. During inspection, the electric motor, wiring, connector, current behavior and short-time operating response should be checked together with the hydraulic output of the pump.

Fuel and pressure characteristics of 726V

The 726V is designed to work with TS-1 aviation kerosene. The specified outlet pressure is 3 ±0.5 kgf/cm², which is required for the starting fuel circuit. Drain leakage must remain low, with the supplied reference value not more than 0.5 cm³/h. These parameters are important for start reliability and fire safety. During maintenance, technicians should check outlet pressure, leakage, tightness of fittings, pump body condition and any signs of fuel seepage after storage or operation.

Short-time operating mode of 726V

The 726V works in a repeated short-time mode. One operating cycle should not exceed 15 seconds according to the supplied data. This operating limit is tied to the function of the unit: it is intended to support the starting phase, not to run continuously. Bench testing should therefore follow the approved timing and cooling intervals. Running the pump for too long can distort test results, overheat the motor or cause unnecessary wear.

Supply condition and aircraft use of 726V

The 726V belongs to aircraft technical inventory and may be supplied as new / first category from storage, repaired stock, overhauled stock or serviceable stock depending on availability. For aircraft installation, the unit should be checked by documentation, pressure output, leakage, electrical operation and compliance with the AI-9V starting system requirements. The pump should be identified by the full designation 726V / 726В, because similar starting fuel pumps may differ by motor, pressure adjustment or aircraft application.