ECN-91B

ECN-91B in the aircraft fuel system

The ECN-91B is an aircraft electric centrifugal fuel pump designed to transfer aviation fuel from external or additional fuel tanks into the service tank. It is used in fuel systems of helicopters and aircraft where fuel must be moved from tank sections to the main supply circuit. On Mi-8 / Mi-17 helicopters, the pump helps transfer kerosene from the left and right external tanks into the central service tank, from where fuel is further supplied to the engines through the standard fuel feed system.

Fuel transfer function of ECN-91B

The main role of the ECN-91B is to provide stable fuel transfer from auxiliary tank volume to the service tank. The pump creates the required flow and outlet pressure to move fuel through the aircraft fuel lines. It is not an engine high-pressure fuel pump; it works as a transfer / booster pump within the aircraft fuel system. Correct operation of the ECN-91B is important for full fuel use from external tanks and for maintaining the required fuel level in the service tank during flight.

In-tank installation of ECN-91B

The ECN-91B is installed directly inside the fuel tank as a submerged pump. On Mi-8 / Mi-17 helicopters, two pumps are typically installed: one in the lower part of the left external tank and one in the lower part of the right external tank. The pump is mounted through a flange opening, sealed with a sealing ring and fixed by a clamping element or bolts depending on tank design. This installation keeps the pump close to the fuel volume and allows the pumped kerosene to cool the electric motor during operation.

Monoblock construction of ECN-91B

The ECN-91B is built as a compact monoblock unit combining a centrifugal pump section and a DC electric motor. The drive motor is MP-100S-2S. The pump has a cylindrical body and is designed for installation in limited tank space. During operation, the electric motor rotates the centrifugal pumping element and moves fuel into the outlet line. Since the pump operates submerged in aviation kerosene, the condition of the housing, electrical insulation, connector, sealing area and inlet section is important for safe and stable operation.

Cooling and operation of ECN-91B in aviation kerosene

The ECN-91B operates while fully immersed in fuel. The pumped aviation kerosene cools the motor and supports normal thermal operation of the pump. Operation without fuel or with a low fuel level can lead to overheating, abnormal current consumption or mechanical wear. During maintenance, the pump should be checked for free rotation, fuel delivery, outlet pressure, current consumption and housing condition. Any contamination in the tank or blockage at the inlet can reduce pump performance and affect the fuel transfer rate.

ECN-91B aircraft application

The ECN-91B is used on Mi-8, Mi-17 and Mi-24 helicopters, and also on aircraft such as Su-25, Su-27, Yak-40 and Tu-134 depending on the fuel system configuration. On helicopters, it is commonly associated with external tank fuel transfer. On fixed-wing aircraft, it may be installed in wing or fuselage tanks as a transfer or booster pump according to the specific fuel system layout. Before replacement, the exact aircraft modification, installation point and technical documentation should be checked.

Supply and checking of ECN-91B

For supply, the pump should be requested by its full designation: ECN-91B / ЭЦН-91Б. It is also useful to specify the aircraft type, required condition and available documentation. Before installation, the unit should be checked electrically and hydraulically: supply voltage, current draw, motor operation, delivery rate, outlet pressure, connector condition and flange sealing must be verified. For aircraft use, documentation and test results are important, especially for units supplied from storage or after repair.

Product Type: Aircraft electric centrifugal fuel transfer pump
Designation: ECN-91B
Alternative Designations: ЭЦН-91Б; ECN-91B
Function: Transfer of fuel from external / additional tanks into the service tank
Application / Where Used: Aircraft and helicopter fuel systems
System / Installation Area: In-tank fuel transfer system
Part of System / Included in Set: Fuel transfer circuit from external or auxiliary tanks to service tank
Compatible Aircraft / Equipment: Mi-8, Mi-17, Mi-24, Su-25, Su-27, Yak-40, Tu-134 depending on aircraft configuration
Pump Type: Submersible / in-tank electric centrifugal pump
Construction: Monoblock cylindrical unit with centrifugal pump and DC electric motor
Drive Motor: MP-100S-2S DC electric motor
Working Medium: Aviation fuel / kerosene grades T-1, TS-1, T-2, RT
Fuel Flow Rate: 3800 L/h
Outlet Pressure / Head: 4800 mmHg / approx. 0.64–0.65 kgf/cm²
Supply Voltage: 27 V DC
Current Consumption: Not more than 8.5 A
Operating Mode: Continuous
Typical Installation on Mi-8 / Mi-17: One pump in each external tank, mounted in the lower part of the left and right external tanks
Mounting Type: Flange-mounted in-tank installation with sealing ring and clamping fixation
Overall Dimensions: 225 mm length × Ø90 mm diameter
Weight: 2.7 kg
Inspection / Testing: Electrical check, current consumption check, rotation check, flow rate check, outlet pressure verification, connector, flange and housing inspection

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