VIAVI PSD737-1 Fuel Quantity Interface Unit for Boeing 737-700 & 737-800 Aircraft

The VIAVI PSD737-1 Fuel Quantity Interface Unit is used during maintenance and troubleshooting of the Boeing 737 fuel quantity indicating system (FQIS). It provides a safe and accurate interface between the aircraft fuel system and the PSD60-2R fuel quantity test set. This allows technicians to measure and simulate fuel system capacitance without disturbing installed components. The unit supports both line and hangar maintenance activities.

The PSD737-1 is designed specifically for Boeing 737 aircraft, including the B737-700 and B737-800 variants. It interfaces with the left-wing, right-wing, and center fuel tank systems. Compatibility is based on aircraft equipped with AC capacitive fuel quantity systems. Always refer to the Aircraft Maintenance Manual (AMM) to confirm applicability for specific configurations.

The PSD737-1 connects between the aircraft fuel system and the PSD60-2R AC fuel capacitance test set. Once connected, it allows the PSD60-2R to measure total tank capacitance, individual fuel probes, and compensator values. This setup enables accurate testing, simulation, and calibration of the fuel quantity indicating system. The interface unit ensures proper signal routing and system protection during testing.

Fuel quantity systems use AC capacitance, which requires precise, aircraft-specific connections for accurate testing. An interface unit, such as the PSD737-1, ensures correct electrical connections without damaging probes, wiring, or indicators. It also simplifies access to multiple tanks and test points. Using the correct interface helps maintain compliance with OEM testing procedures.

Yes, the PSD737-1 is approved for use with fuel present in the tanks when operated with the PSD60-2R test set. This allows technicians to perform live system measurements and diagnostics without draining fuel. Testing with fuel present can help identify real-world system behavior. All procedures should follow the applicable maintenance manual and safety guidelines.

The PSD737-1 supports fuel probe capacitance measurement, compensator simulation, total tank capacitance measurement, and system calibration testing. It also enables insulation resistance and wiring integrity checks when used with the PSD60-2R. These tests help verify system accuracy and troubleshoot faults. The interface unit supports both functional testing and fault isolation.

The PSD737-1 supports both calibration and troubleshooting tasks. It allows technicians to simulate known capacitance values for indicator calibration. At the same time, it enables detailed analysis of probes, compensators, and wiring to locate faults. This dual capability makes it useful throughout the maintenance lifecycle.

No, the PSD737-1 does not replace installed fuel probes or compensators. Instead, it allows technicians to simulate or measure their electrical characteristics during testing. This avoids unnecessary component removal and reduces troubleshooting time. It is strictly a diagnostic interface, not a replacement part.

By providing a direct, aircraft-specific interface, the PSD737-1 reduces setup time and minimizes wiring errors during testing. Technicians can quickly access test points for all fuel tanks without needing to disassemble components. This speeds up diagnostics and reduces aircraft downtime. Efficient testing supports faster return to service.

Yes, the PSD737-1 is suitable for both line maintenance and scheduled hangar inspections. Its portable design supports on-wing testing, while its accuracy meets the needs of deeper troubleshooting during heavy maintenance visits. This versatility makes it valuable across multiple maintenance environments. Proper handling and storage help maintain long-term reliability.

The PSD737-1 itself does not typically require standalone calibration, as it functions as a passive interface unit. Calibration requirements are associated with the PSD60-2R test set. However, the interface unit should be periodically inspected for connector integrity and cable condition. Damaged connectors or wiring can affect test accuracy.

The PSD737-1 carries NSN 4920-01-473-6663, which supports standardized identification and procurement. This is especially useful for military, government, and large fleet operators. An NSN helps streamline ordering, inventory control, and documentation. It also supports traceability within regulated maintenance environments.