Engineers are conducting sophisticated performance testing of F-35 Joint Strike Fighter (JSF) antennas at the AFRL Newport Research Facility, New York. Through an agreement with the F-35 Joint Program Office, engineers from Lockheed Martin and AFRL's Rome Research Site are collaborating on the test effort. Because antenna testing is occurring early in the aircraft development cycle, the team is using a model—a full-scale F-35 replica—to measure the installed performance of the aircraft's communications, navigation, identification, and electronic warfare antennas. The goal of this testing program is to optimize antenna performance and identify and correct antenna problems before the aircraft design is finalized and antenna system changes consequently become more difficult and expensive to incorporate.

A full-scale JSF model mounted on a pedestal at AFRL’s antenna research and measurement facility (photo courtesy of Captain Gabriel Mounce)
The JSF is a stealthy, supersonic, multirole fighter designed to replace a wide range of aging fighter and strike aircraft, including the US' AV-8B Harrier, A-10 Thunderbolt II, F-16 Fighting Falcon, and F/A-18 Hornet, along with the United Kingdom's Harrier GR.7 and Sea Harrier. Three variants derived from a common design will ensure the aircraft meets the performance needs of the Air Force (AF), Navy, and Marine Corps, as well as those of allied defense forces worldwide.

The Newport Research Facility, a worldclass antenna measurement facility that has been in existence for more than 30 years, is the only AF facility of its kind. The facility spans 2 hilltops and includes a total of 6 data collection locations and 10 measurement ranges. The 2 hills are separated by 1.5 miles and a 430-foot valley. Each hilltop houses transmit and receive equipment and heavy-duty, 3-axis aircraft pedestals. Engineers use the Newport facility to evaluate antennas and antenna systems in a "free space" environment, determine radiation pattern changes resulting from airframe effects, evaluate antenna-to-antenna system coupling, and support advanced antenna measurement technology development.

Mounting missiles, fuel tanks, or other types of equipment on the outside of an aircraft affects antenna patterns. In addition, new materials used in the construction of modern aircraft can alter antenna performance. A primary mission of the Newport Research Facility is to identify specific antenna effects and determine ways to minimize their impact on today's aircraft. The facility's aircraft pedestals allow engineers to test airframes at all rotational positions and at various pitch angles, thus offering a more comprehensive range of flight orientations than flight testing can provide (see figure). In only 8 minutes of range testing at the facility, engineers can obtain more antenna performance data than they could collect in 2 hours spent flying the future F-35.

Advance Technologies, Inc., located in Newport News, Virginia, designed and built the F-35 model to include features that capitalize on the test facility's unique measurement capabilities. The replica weighs just 8,500 lbs, and its interchangeable wing, fuselage, and tail components facilitate simulation of all three JSF variants. Rome Research Site fabrication personnel are manufacturing replicas of the F-35's external fuel tanks, weapons, and landing gear for the test program.

The AFRL/Lockheed Martin team began the test program by evaluating preproduction satellite communications, Global Positioning System, and ultra-high-frequency/ very-highfrequency communications antennas. Subsequent test phases will baseline production antenna performance on a clean aircraft configuration, with further testing efforts aimed at evaluating the impact of various external weapons configurations on aperture performance. Engineers will use the installed antennas to validate design, verify performance, reduce risk, and improve system performance modeling and simulation. Another benefit resulting from this testing will be a reduced number of F-35 flight tests required to verify avionics performance. Engineers will also use the existing model to measure antennato- antenna isolation to support F-35 radio frequency compatibility verification. Program personnel expect the testing to continue through 2008.

Capt Gabriel Mounce, of the Air Force Research Laboratory's Information Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at Reference document IF-H-05-05.

Air Force Research Laboratory Technology Horizons Magazine

This article first appeared in the October, 2005 issue of Air Force Research Laboratory Technology Horizons Magazine.

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