March 2003 - American Bonanza Society

alancing the surfaces after they've painted them.Ruddervator balance on Bonanzas is super-critical. andI've seen more than one set leave the paint shop out of balanceand unable to be balanced correctly because the painter putone or two many coats of paint on them.I f you see a paint job that is about a year old Ulat appearsto have had a little woml crawling around under the paint onthe ruddervators, RUN! Do not walk away. You are about to beattacked by the voracious and deadly Iilliworm'CORROSION IN AVIONICSFinall y, on to corrosion in avionics. Back in the ABSarchives somewhere there is a story of mine about buying usedavionics. In it was a sad tale of a Bonanza pilot who bought acomplete stack of King KX-IS5 navcoms, a transponder, anaudio panel and two nav indicators (one with glideslope) outof Trade-A-Plalle at a ridiculously low price.Upon receipt of the goods, and upon further investigation(after the money was gone. of course), it was learned that theavionics package had taken a tumble off an oil rig in a helicopter,landing in the salty gul f. 0 amount or brand of corrosioninhibitor could save them. Let the buyer beware.Corrosion from leaky windshieldsAnother source of avionics corrosion is a leaking windshield.Perhaps it doesn't leak at rest, only when the airplaneis airborne and ram air is pushing water into the stack. Whenthe airplane does come to rest in the hot sun, the avionics istreated to a humidified steam bath'Most of our later model Bonanzas and Barons have theirradio stack cooled by an electrical cooling fan . If yours isn 't. Ihighly recommend that you invest in one. A cooling fan is oneof the most effective and least costly means of preserving theli fe of your avionic s.Many older Bonanzas/Barons have a "cooling scoop"mounted on one side of the cabin to use ram air to cool theavionics. Properly installed. this scoop will lead to a Pentiumchamber, designed to sepamte water from air, then to the avionicsstac k. What 's wrong with that arrangement is that they don'talways sepamte the water from the air, such as in heavy rain.And, until the airplane is airbome, they don't get enough ram airto cool anything. Just get the@#$%Acooling fan!Corrosion under antenna padsAgain in previous articles. I have ment ioned corrosionunder antenna mounting pads. Most antenna manufacturersship their products with a rubber or neoprene pad to mountbetween the antenna base and the airplane skin. Some shopsuse this pad and other shops don·t. I'm ambivalent on whetherto use the pad; it depends on what kind of antenna it is. Forthe most part, I don 't use it , because I want the antenna to havea ground path to the airframe.Whether or not the shop uses the pad, what's most impor-tant is whether they use a bead of good-quality silicone sealaround the base of the antenna when they are done.Unfortunately. there is no silicone seal that will stand up tosummer sun for very many years.At least every annual you (or your mechanic, your avionicsshop or somebody) should inspect the bases of all yourantennas, top and borlom, to see that the silicone beads are intact.If any are cracked, it is a simple job to run a new bead of silicone(clear or colored, your choice) around the base of the antenna.Do you want min squirting between your antenna base and yourairplane skin in fli ght? Do you want it to live there?Corrosion in connectorsPin connectors and B C connectors are another areawhere corrosion can cause big problems. Here, [ have successfully used Corrosion-X or ACF-50 10 SlOp the beginningsof corrosion, and have not had it degrade avionics perfomlance.The best procedure. though, is to tie the connectors insuch a way that slipstream or water or dirt (as in under thecabin) does not get into the connectors. This is a simple thingto do using wire ties or even old-fashioned string, but I haveseen far too many connections dangling under the floorboardsor in the tail cones of airplanes.Speaking of dangling. I think I' ll wind this up for thismonth . See ya.~Jim Hughes is the chief pilot, corporate aviation of Embry-Riddle AeronauticalUniversify. flying a Citalion II. He also heads Markeling and Professional Services.a consulting firm specializing in flight test Dnd avionics Integration. HIS ratmgsmclude both on ATP and on A&P mechanICS license, with a long list of type ralingsfrom Boeings to Sikorsky helicopters. He has more than 21,000 hours,including over 3,000 hours in Bonanzas, Barons, Dukes Dnd King Airs.•• . . . .. ••••• • • •• •• • • •.. . .- ••••••• • • .... • -...ABS March 2003Page 7737