Global Hawk on the test pad

Posted on: May. 25th, 2006 || Source: dcmilitary.com | E-mail Article | Print Article

Global Hawk on the test pad

For the next few weeks, a large and unusual aircraft will be undergoing tests at the NAWCAD T&E facilities here. It is the Navy's newest Unmanned Air System (UAS), the Global Hawk Maritime Demonstrator (GHMD). With its distinct "V" tail, bulbous nose, and the wingspan of a Boeing 737, this fully autonomous aircraft can take off, perform surveillance and reconnaissance missions, and land with just a few clicks of a mouse. The GHMD is undergoing testing at the Naval Electromagnetic Radiation Facility (NERF), just one of the many advanced facilities at the Air Combat Environment Test and Evaluation Facility/Electromagnetic Environmental Effects complex. These facilities are operated and maintained to provide complex test services in support of manned and unmanned systems by the Integrated Battlespace Simulation Test (IBST) department in the T&E competency.

Before the GHMD arrived here, the IBST department's Electromagnetic Compatibility (EMC) branch was tasked by PMA-263's Unmanned Air Systems Center of Excellence to evaluate the aircraft for susceptibility to potential interference problems. The NAVAIR flight clearance process requires that aircraft demonstrate operational suitability of their installed systems and subsystems when exposed to high intensity radiated fields. The goal is to identify susceptibilities to radio frequency (RF) emissions from various sites located in and around Global Hawk's new main operating base at Patuxent River to prevent potential mishaps. The uniqueness of the autonomous Global Hawk created many T&E challenges for the GHMD test engineers and technicians.

The challenges, some as simple as designing custom cooling fixtures to allow the avionics to run for extended test periods on the ground; and some as complex as fooling the flight computers into thinking they are engaged in safe flight so test data can be taken on the ground, took more than a year and a half of detailed preparation. Planning and executing tests of fully autonomous aircraft is one of the most demanding tasks the EMC branch has encountered as a test facility. The Global Hawk's autonomous software is designed to keep the aircraft safe, and to keep the surrounding area safe in the event of a system failure. These features make testing difficult because when these same types of conditions are replicated on the ground, the aircraft goes into a mode that makes it very difficult to take data...it shuts down.

"The software defined what we could or could not do with the aircraft and forced us to think outside the box for test planning to obtain meaningful results. The GHMD test team had to ask themselves what could potentially impact the aircraft's safe flight for take offs and landings at Pax River up to the 2,000-foot flight-level. They needed to make sure that it was not susceptible to emitters located in and around operating runways, taxiways and the airfield. The team could not take any chances damaging the aircraft and identified weaknesses in the aircraft by exposing it to increasingly harmful RF field levels until the criteria field levels were reached," said Paul Achtellik, EMC project engineer. During these tests, the command and control (C2) link with the aircraft is emulated via a laptop PC, called a Vehicle Test Controller, or through a launch and recovery element located near hangar 101. The GHMD test team had to recognize and contend with potential "runaway" computers and servos as well as the RF hazards to the C2 systems. These were all safety-of-test considerations, further complicating the test planning because the onboard autonomous software has total control of all aircraft functions, not a human.

Through advanced planning and hard work, the test team ensures that all tests conducted will result in safe evaluations of the GHMD. The team includes IBST's EMC and Electromagnetic Effects branches, PMA-263's GHMD air vehicle team, and Northrop Grumman GHMD industry partners. Advanced and innovative T&E methods developed at NAWCAD for UAS' and other fully autonomous systems tests will increase in importance as the battlefield transitions to more autonomous technology.

NAVAIR will continue to lead the way in safe test methods as complex sensor payloads are added to support new missions, as systems increase in their autonomy, as interoperability with other platforms and networks become more critical and as innovative new roles for UAS' emerge to support the warfighter.
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