Precipitation static is a phenomenon that occurs on aircraft in flight. Friction between liquid water and the aircraft skin causes charge to build up. This can have two effects on the system , arcing and coronal discharge. The arcing often occurs between non-metallic components and metallic surfaces. Examples include, nose radome to structure below wind screen and engine inlets to personnel on ground after landing. The broadband noise from the spark can interfere with radio reception as well. The second effect is the corona which can occur along sharp edges, usually the trailing edge of the wings, horizontal, and vertical stabilizer. While the sparks may cause squelch breaks, only an annoyance, the corona can obscure radio reception. Interference with radio navigation aids can and has caused loss of vehicle and crew. To dissipate the charge build up static dischargers are positioned on the edges mentioned above. The discharges are often referred to as wicks. The wicks are just megaohm resistors protruding into the airflow. The controlled dissipation of charge does not produce the aforementioned effects.
_____________________________________________________ Jeff Bruce EME Engineer Raytheon Systems Co. (903) 457-4187 Electromagnetic Effects Fax: (903) 457-7640 Box 6056, CBN 024 [email protected] Greenville, TX 75403 The opinions expressed here are mine and not that of my employer. >---------- >From: Ing. Gert Gremmen[SMTP:[email protected]] >Sent: Friday, February 27, 1998 3:00 AM >To: '[email protected]' >Cc: 'EMC POST' (E-mail) >Subject: RE: Precipitation Static > >Hello Bruce > >Tell us someting about precipitation statics ! >== >CE-test, qualified testing, >Consultancy, Compliance tests for EMC and Electrical Safety >15 Great EMC-design tips available ! >Visit our site : http://www.cetest.nl >The Dutch Electronics Directory http://www.cetest.nl/electronics.htm >== > > >-----Oorspronkelijk bericht----- >Van: [email protected] [SMTP:[email protected]] >Verzonden: donderdag 26 februari 1998 17:29 >Aan: [email protected] >Onderwerp: Precipitation Static > >I realize this may be slightly out of scope for this group, but maybe >someone has experience in this matter. >I need to analyze how adding antennas to an aircraft will affect >p-static dissipation for the aircraft. Specifically I would like to >know how the number of dischargers required for a specific surface area >is determined. > >Any advice or references will be greatly appreciated. > >_____________________________________________________ >Jeff Bruce >EME Engineer Raytheon Systems Co. >(903) 457-4187 Electromagnetic Effects >Fax: (903) 457-7640 Box 6056, CBN 024 >[email protected] Greenville, TX 75403 > >The opinions expressed here are mine and not that of my employer. >
