Northrop Grumman and TRW's Avionics Systems division are planning further test flights of a "smart-skin" antenna system which has been flown for the first time on NASA Dryden's McDonnell Douglas F-18 Systems Research Aircraft (SRA) at Edwards AFB, California.

Early results from the tests of the antenna, embedded in a specially built tip mounted on the SRA's right vertical fin, show a fivefold increase in voice-communication range with a "substantial" improvement in radio-transmission quality compared to the conventional-blade antenna.

The development, sponsored by the US Air Force's Wright Laboratory, was dependent on recent breakthroughs in thermoset composite and core-material technology, which allow the actual skin of the tail to act as the antenna. The new materials combine low-loss, high-conductivity, electrical properties which stimulate surface current flow, along with high strength to withstand twin-tail buffet loads.

During two flight tests of the antenna, NASA pilots flew circular patterns of about 18km (10nm) in diameter, while flight-test engineers transmitted signals from the aircraft's radios at 33Mhz and 65Mhz to Edwards. The aircraft was flown at bank angles of 0 degrees, 15 degrees and 30 degrees to evaluate range, gain and radiation patterns of the smart- skin and conventional-blade antennas. The patterns were flown at distances of 32km and 56km from the ground-receiving station. The smart skin demonstrated a 15-25dB improvement in signal-to-noise ratio at the lower frequency.

The USAF believes that smart-skin antennas could not only enhance voice communications and navigation, but also reduce aircraft structural weight by anything from 115kg to 450kg because of a 65% reduction in airframe structural cutouts. It could also improve maintainability, as well as reducing drag and radar signature.

Source: Flight International