The U.S. Navy (USN) is seeking innovative solutions through the Small Business Innovation Research (SBIR) program to develop an Aerial Refueling Latch Indicator, a critical device for unmanned aerial refueling operations. The objective is to create a low-power, compact sensor that can confirm a secure latch between the refueling probe and drogue, addressing safety risks associated with unmanned systems where visual confirmation is insufficient. This technology is vital for ensuring efficient fuel transfer and preventing spillage during aerial refueling missions, particularly as the Navy integrates unmanned aircraft into its fleet. Interested parties should note that the solicitation is set to open on January 8, 2025, with applications due by February 5, 2025, and can find more information at the provided source link.

## Description

The U.S. Navy (USN) uses the probe and drogue style of aerial refueling. This involves a receiver aircraft maneuvering its probe tip into the coupling portion of a refueling drogue that flies on the end of a refueling hose. Once in the coupling, the probe is pushed into the coupling until a latch occurs. This latching provides a retaining force holding the drogue onto the probe, keeping the fuel valve open, and allowing fuel to flow to the receiver. Maintaining a positive latch is critical to ensuring fuel flow and preventing fuel spillage. Currently, with manned aviation, the receiver pilot visually confirms the drogue stays latched onto the probe by looking for excess movement, positive fuel flow, and no leakage. As unmanned receivers come into the fleet, a visual indication will not be enough to confirm latch. Sometimes, a soft contact occurs where the drogue is in the right position (visually looks OK), but is not fully seated, that results in fuel leakage, or a drogue coming unseated. This would present a safety risk to the unmanned receiver. A device must be developed that can be used as a sensor to provide input to an unmanned receiver to confirm positive latch, or to alert when the nozzle becomes unseated. This device by design will have to be very low power, and have a very small form factor, to fit inside either the probe nozzle, or the refueling coupling/drogue. It will need to be powered by either existing aircraft power on the receiver, or by on board power generation on the refueling drogue/coupling. No power can be run down the hose. It must be extremely damage tolerant as the refueling mission involves the collision of the refueling probe with the drogue at up to 15 ft/s. It must have some means of providing the indication to the receiver aircraft.The probe nozzle used by the Navy conforms to MIL-N-25161 [Ref 1]. MIL-PRF-81975 is the specification for the MA-3 coupling that the refueling nozzle mates with [Ref 2]. MS-24356 gives the basic nozzle dimensions [Ref 4].

## Objective

Develop a prototype sensing system that can positively identify when a refueling drogue is securely latched onto the refueling probe.

## Phase I

Develop and refine initial design concepts that converge on a final prototype design. Assemble system requirements and complete a preliminary prototype design to the extent that the USN can determine technical feasibility. Implement the design in a CAD software of choice. It is expected that some level of bench/breadboard testing will be completed to evaluate technology solutions and justify the preliminary design. A final report shall address requirements generation, lab testing completed and document the prototype design. The system design shall allow for easy adaptation to the current aerial refueling hardware.The Phase I Option, if exercised, will continue the prototype design refinement and prepare for system level demonstration and validation in Phase II.

## Phase II

Produce a full up prototype design and prototype full up system hardware/software. Throughout Phase II, requirements will be reassessed against original design assumptions and a requirements document will be produced outlining path to full system qualification. Component level testing shall be conducted on actual hardware and software, and ultimately, a system level test will be conducted to demonstrate and validate the system meets the requirements. It is expected that GFE hardware in the form of a refueling coupling and refueling nozzle will be provided to awardees.The robustness of the system must be considered so that the vendor can capitalize on any developmental flight opportunities that might exist.

## Phase III: Dual Use Applications

Update and finalize system design based on system level testing and conduct full qualification testing. This product is intended to transfer to the USN via the MQ-25 and/or PMA-201 Aerial refueling store. With multiple commercial aerial refueling companies in the market, this system would have commercial viability as well.

Aerial Refueling Latch Indicator

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