Condensed moisture from ingressed humid air was responsible for inducing corrosion within the aft radar antenna from an RAAF P-3C Orion maritime surveillance aircraft. The results of laboratory examination have shown that corrosion in the antenna was caused by the presence of moisture which may have entered the waveguide due to failure of the seals. Condensation of the water vapour, caused by variation in temperature and pressure, as the aircraft cycled between low and high altitude, would have produced a thin film of moisture on the surface of the waveguide which would act as an electrolyte and ultimately cause corrosion. The change in conditions was most likely too rapid for the desiccant to have time to absorb the moisture. Porosity in the silver-plating of a flexible waveguide allowed moisture to penetrate to the brass substrate and cause dezincification. The moisture also corroded some of the 6061 aluminum alloy waveguides leading to production of white corrosion product. An investigation determined that moisture ingress occurred at a waveguide flange, possibly from the failure of a seal. Recommended corrective actions include a dry nitrogen gas purge after disassembly of any part of the waveguide system. It is also recommended that the waveguide flanges be inspected regularly with particular attention given to the condition of the 'O'-rings and the grease.
Corrosion of an aircraft radar antenna waveguide
Korrosion einer Luftfahrt-Wellenleiter-Radarantenne
Engineering Failure Analysis ; 9 , 4 ; 423-434
2002
12 Seiten, 10 Bilder, 2 Tabellen, 7 Quellen
Article (Journal)
English
Luftfahrt , Radarantenne , Wellenleiterantenne , elektronisches Gerät , Messing , metallischer Überzug , Silber , Aluminiumlegierung , Feuchtigkeit , örtliche Korrosion , Entzinken , Korrosionsversuch , Natriumchlorid , Polarisationskurve , Rasterelektronenmikroskopie , Porosität , energiedispersive Spektrometrie , Kupferzinklegierung , Aluminiummagnesiumsiliciumlegierung
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