Allan C. Goetz

Qualitative assessment of smart skins and avionic/structures integration

Current military aircraft employ multiple single function antennas installed at different locations to provide communications, navigation and identification (CNI), electronic warfare and radar and weapon delivery in the .15 to 18 GHz frequency bands. The smart skins concept, wherein several antennas are integrated into one (or a few) multifunction apertures conformal to the outer geometry of the aircraft, promises considerable benefits. These include extended antenna coverage, efficient use of aircraft realestate, quick installation and replacement and structural weight savings. However, to realize these payoffs, several disparate technical and operational issues such as development of multifunction apertures, integration of the radiating elements and repackaging the electronics into load-bearing structure, antenna isolation and resource management, and tolerance to low velocity impact damage, need to be resolved. Potential payoffs and the technical challenges of smart skins implementation and avionics repackaging is discussed in quantized transitional states from black box avionics traditional packaging to structurally integrated avionics of the future. Qualitative assessments of related smart skin technologies and risk reduction approaches, which could transition the technology to current and future aircraft, are proposed, and preliminary cost estimates presented.

Application for smart skin technologies to the development of a conformal antenna installation in the vertical tail of a military aircraft

Recent developments in smart skins technology at Northrop Grumman have paved the way toward incorporating avionics communication functions, previously provided by blade antennas, into the vertical tail of a military aircraft. Radio frequency communication link ranges can be significantly improved by structurally integrating the antenna radiating element into the tail region. Excitation of the large vertical tail surface improves radiation efficiency in the VHF-FM, VHF-AM, and UHF frequency bands. Analysis shows use of the whole tail region as an antenna would provide the best gain and coverage, however, confining the antenna design to the end cap region alone, also significantly enhances performance compared to blade installations. Near term technology applications to retrofit aircraft with minimum perturbations to the existing tail design are therefore possible. Multidisciplinary aspects of the application approach are discussed under the subheadings (1) antenna design, (2) structures and materials, (3) manufacturing, and (4) weight assessment along with the resolution of key technical road blocks. Finally, recommendations for further work necessary to transition the application to a production aircraft are discussed.

Prototype testing and evaluation of a structurally integrated conformal antenna installation in the vertical tail of a military aircraft

Further proof-of-concept development for structurally integrating communication antennas in the vertical tail of a military aircraft at Northrop Grumman is presented. Bread board testing on a full scale dual tail aircraft mock-up of a structurally integrated multifunction tail tip antenna, in the VHF-FM, VHF-AM, and UHF-AM frequency regimes, has confirmed earlier simulation results, where it was suggested that smart skin installation electrical performance gain and radiation characteristics might compare favorable to conventional dorsal deck mounted blade installations. Scale model, and eventually full scale ground mock-up testing encouraged further development leading to fabrication of a preliminary flight test of a smart skin tip demonstration article. A low cost flight test program in the VHF SINCGARS band (30 to 88 MHz) has illustrated that structural integration, fabrication and manufacturing issues can be addressed for full feasibility with minimum penalties despite the hostile vibro-acoustic, moisture and electromagnetic environment. Salient features of the engineering technical design effort and recommendations for future concept development are discussed.