GUY NORRIS / LOS ANGELES
Analytical model will help UCAV makers define requirements for air-to-air tanking
NASA has completed the initial phase of a flight-test programme using a modified Boeing F/A-18 aimed at developing analytical models for an automated aerial refuelling (AAR) system for unmanned air vehicles (UAV).
The flight-test phase cleared the full flight envelope of the F/A-18 equipped with a Sargent Fletcher in-flight refuelling pod. The envelope covered 175kt (320km/h) to 260kt at low altitudes and up to 290kt at higher altitudes, embracing most of the 180-300kt standard in-flight refuelling envelope within which UAVs, and specifically unmanned combat air vehicles (UCAVs), are expected to operate.
The next phase will involve recording the behaviour of the basket, hose and drogue by video cameras fitted to the two F/A-18s being used in the tests.
The work builds on the autonomous formation flight project flown on the same aircraft at NASA Dryden, California, in 2000-1, which showed that a 14% fuel saving could be achieved by precise station-keeping.
"As these are the same aircraft, they still have instrumented engines, so we will be able to measure thrust changes and infer drag changes due to the hose being out," says NASA Dryden AAR project manager Gerard Schkolnik. NASA plans to complete test flights in time to deliver a working analytical model by September.
This will be available to UCAV manufacturers, specifically Boeing and Northrop Grumman, to help define requirements for the AAR. "It will help them work out what the controller will need to look like, and whether it will need to control within a fraction of an inch or feet. This will drive sensor requirements so they will know if they need things such as high accuracy optical sensors or differential GPS," says Schkolnik.
Source: Flight International
