Fuel systems

Fuel systems

In the last 25 years, Secondo Mona has made and consolidated the step from equipment supplier to system partner of the airframers, with the design and development of fuel systems for trainers and fighters, business jets and commuters, helicopters and UAVs.

Secondo Mona technical contribution typically starts with the study and design of the whole fuel system architecture and of each single equipment (pumps, valves, probes, control units, gauging, hoses and tanks) in accordance with technical specification from the airframer and close collaboration with the customer; Secondo Mona follows with the development of prototypes and qualification tests, at equipment and subsystem level, up to system verification before entering series production.

Equipment are purposely in-house designed (pumps, valves, probes, control units, refuel systems etc.) or carefully specified to subcontractors (hoses, bladder tanks, temperature/pressure sensors etc.) to provide uncompromised tailored solutions to customers’ needs.

Integrated assemblies

Where required by the application, and following a constant trend in systems supply, Secondo Mona can offer integrated assemblies (pre-tested at kit level if needed), also to facilitate installation and removal at aircraft/helicopter level.

Examples are Integrated Sump Flanges (with Pumps, probes and Valves) for helicopters or Feeding and Transfer Assemblies (Pumps and Ejectors) for fixed wing application.

The picture shows a fuel collector box (30 sec negative g) with two centrifugal DC booster pumps and four transfer ejectors, featuring also self-suction path, designed for a civil tiltrotor; polymer hoses and a bidirectional pump complete the kit.

Fuel pumps

Secondo Mona boasts a long tradition in the design and manufacturing of Pumps (115 V AC, 28 and 270 V DC), both of the centrifugal and volumetric types. Each pump, while offering high reliability as well as DO160G and AC25.981-1D full verified compliance, show full compatibility with 100% SAFs and, where needed, features peculiar characteristics to fulfill specific application needs, like: reinforced plastic housing and impellers, carbon polymer bearings, vapor separating impellers, flanged canister with removable pump module, double inlets or inverted flight canisters, integrated flow-pressure or health sensor, independent high-impedance start signal, wet triple layer explosion-proof wire conduit, bidirectional command and/or stepped controls.

Fuel ejectors

Jet pumps are lightweight booster or transfer devices, energized by fuel pressure tapped from engine or electrical pumps, with no moving parts. Secondo Mona has developed a proprietary design code, to ensure adequate tailoring to motive pressure, grant best efficiency and positively avoid cavitation. Large use of techno polymers sides the usual light alloy for main bodies, while nozzles are typically light alloy for transfer and CRES for booster ejectors.
Secondo Mona customizes body design to ease and comply with peculiar aircraft installation, offering fully submerged as well as dry in-line installation, or bulkhead mounting at frames and tank walls.

Refuel and defuel subsystems

Secondo Mona offers several types of Pressure Refuel and Defuel Sub-Systems, either electrically or hydraulically piloted.

PRDS, when not part of a complete Fuel System supply, are specifically tailored to adapt to existing conveyance and fuel management of each peculiar application.

From single point Adapter to Refuel/Defuel Valves (solenoid and/or hydraulically operated), from Level Sensors to Safety Vent and Overflow Valves, each component is carefully selected or purposely designed to fit any peculiar applications.

Fuel indication systems

Secondo Mona develops and produces AC25-981-1D compliant Fuel Quantity Indication Systems, for fixed and rotary wing application, complemented – where required by Customers – by Signal Conditioners, and Protection Boxes.

Gauging Probes are of the capacitive, active, type and typically with digital output, based however on a simple electronic hardware design and without any embedded SW. Units may be designed for either submerged installation or for flange tank mounting; they can include segregated discrete level sensors, temperature sensors and integrated compensator.

Fuel management units and panels

Fuel Control Units and Panels are based on microcontroller families with a well-established maturity, integrating a subset of simple peripheral as defined by the EASA CM – SWCEH – 001.  SW is developed in house following DO178C guidelines. Units are designed to acquire gauging probes and perform on-board fuel quantity calculation (based, where advisable and available, also on inertial pitch and roll); if low level sensors are acquired, boxes are mechanically divided in segregated areas, to ensure independency. Data acquired, including fuel equipment status, are provided via digital bus to aircraft avionics.

Electrical shut-off valves

DC Motor operated shut-off valves are composed by two modules: the ball valve and the electrical actuator, held together by a “V” clamp band, for easy replacement of the actuator, without requiring  removal of the valve. Valves are often integrated in specially designed manifolds, or featuring bulkhead designs, to enable installation of the hydraulic section inside the tank, while actuator is mounted in dry bay.

Solenoid operated (or piloted) valves are either designed for safe fully submerged installation or dry (in-line) installation outside tank; solenoids are specifically conceived by Secondo Mona: complete valves might thus be of the normally open (power to close) or normally closed (power to open) type. Typical applications of solenoid operated valves include refueling, defueling, jettison, transfer control, draining.

Fuel control valves

Secondo Mona Fuel System Supply is often completed by several types of flow and air control valves, such as:

  • Non-Return Valves,
  • Drain and Dump Valves,
  • Flapper Valves,
  • Air/No-Fuel valves,
  • discrete level switches and level sensors.

Where requested, Secondo Mona contribution to Fuel System supply extends also to flexible tanks, conveyance tubing and wet cables.