The U.S. Air Force Research Laboratory (AFRL) is kicking off the second phase of its automated aerial refueling (AAR) program to demonstrate the capability to refuel unmanned aircraft in flight.

AFRL is looking for an integrator to conduct AAR Phase II, which will develop and demonstrate the capability for U.S Air Force-style boom and receptacle refueling of unmanned aerial vehicles (UAVs). U.S. Navy-style probe and drogue refueling will not be demonstrated.

Scheduled to run from late fiscal 2008-2012, at an estimated cost of $49 million, the program will build on Phase I, which demonstrated a proof-of-concept AAR capability using a single-channel relative navigation system based on the Precision Global Positioning System (PGPS).

In Phase I, a Calspan-operated Learjet acting as a surrogate UAV demonstrated the entire refueling operation, but did not make contact with the boom of the KC-135 tanker. Phase II will culminate in a wet contact between the tanker and a manned surrogate.

Phase II will involve two spirals. In Spiral 1, according to AFRL presolicitation documents, the selected integrator will take the government-furnished, single-channel AAR system from Phase I and develop a multichannel PGPS relative navigation system and automated flight control system (FCS).

The Spiral 1 system will use dual-redundant Tactical Targeting Network Technology wideband datalinks to connect the PGPS systems in the tanker and receiver. Using outputs from the relative navigation system, the redundant FCS will control the receiver aircraft during aerial refueling, including rendezvous with the tanker, station-keeping, repositioning, separation and contingencies.

A version of the Spiral 1 system will be installed in a receptacle-equipped military aircraft, likely an F-16, that will act as the surrogate UAV for flight-tests in fiscal 2010 and 2001.

Under Spiral 2, meanwhile, the Phase II integrator will study a “sensor-augmented” AAR relative navigation system able to operate in environments where GPS is degraded or denied.

The overall goal is to have the AAR system ready to enter system development and demonstration at the end of Phase II. A likely first platform for the system is the Next Generation Bomber, which will be designed to operate unmanned as well as manned.

Photo: DoD