November 11, 2009
Feb. 15 - AOPA's Sweepstakes Bonanza suffered a small amount of skin damage because of surface corrosion during the 15 years it was hangared in Santa Maria, California. During the pre-purchase inspection, no structural corrosion was found. But skin corrosion was found under the assist step attachment bracket, along the belly skin overlap seam, and at the inboard end of flap cover fairing on the right side.
The corrosion was removed using mechanical means (as opposed to chemical) by using a sanding disk. After all the corrosion was removed, the depressions were blended into the surrounding metal, cleaned by an etching process, treated with a conversion coating, and primed. The purpose of the conversion coating is to give some chemical protection against further weathering and to provide a good surface for paint bonding.
If the depth of the corrosion is greater than 10 percent of the overall thickness of the metal skin, a repair over and above simple metal removal is needed. The 10 percent thickness is an industry rule-of-thumb for metal removal. Unfortunately, the corrosion had progressed further than 10 percent. This is not a lot of corrosion since the skins in the affected area are only .020-inch thick. After consulting with the technical representatives at Raytheon Aircraft, a simple repair was selected.
The repair consisted of cutting out the metal that had corroded beyond the 10 percent limit, splicing in a new piece of metal, and overlaying the surrounding area and the spliced-in section with a doubler of .032-inch thick aluminum. This repair not only removes any corrosion, it further strengthens the area. A good sheet metal craftsman will create and install a repair that melds into the surrounding structure. This repair is the last piece of the annual inspection.
The new Superior Air Parts Millennium engine has been installed along with the Tornado Alley turbonormalizer and a new McCauley propeller has been mounted. Engine operating parameters will be displayed with the latest in engine monitoring systems from JP Instruments. JPI's EDM-800 displays real time EGT/CHT and TIT, displays engine horsepower output, and is the engine monitor of choice at Tornado Alley Turbos. For further information on JPI products go to www.jpinstruments.com.
Next week we should have a flight test report as an AOPA Pilot editor gets checked out on operating the turbonormalizer installation. To get your copy of the operating instructions go to www.taturbo.com. After the checkout, our editor will fly the Bonanza to JA Air Center at DuPage Airport near Chicago for the avionics installation. For more information about JA Air Center, see the Web site www.jaair.com.
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