Atkins Column

Hello SPA,

It is time to get our equipment ready for the 2003 flying season. Our stuff has been languishing in storage through the winter and should be given a thorough check before committing aviation.

The first item on the agenda should be batteries. It is a good idea to cycle batteries at least three times to make sure that they deliver rated capacity. Every battery that I have ever checked delivered slightly more than its rated capacity. Usually from 25 to 50 mils more. Any battery that delivers less than rated capacity is suspect, even if it only falls slightly short, and should be replaced.

The wiring harness should be checked for abrasion or other damage. The switch harness should probably be replaced if it is over a year old and has been flown a lot. I have lost three airplanes to switch harnesses failure over the years. The receiver antenna should be checked for abrasion where it exits the fuselage. All wiring should be checked for the dread black wire disease and general condition. A vibration of 10,000 cycles per minute can do serious damage to servo leads.

The control linkages need careful scrutiny. Be sure that all metal clevises have a jam nut and that the jam nut is tight. A loose nut will allow the clevis to move on the threaded rod until the threads wear to the point where the clevis can be pulled from the rod. Not a good thing on elevators or ailerons. I use HAYES clevises for this reason. The cable in pull-pull systems should be checked for fraying.

Give the servo mount system a close look. When wooden servo trays or rails are used, the glue joints should be closely inspected. A firm landing will cause the fuselage to deflect, and servo tray or rail glue joints seem to be the first to fail. While you are looking at the servo area, be sure that servo movement is smooth and linear, with no dead spots or jumpiness.

Check all engine mounting bolts and prop nut and make sure that everything is secure.

Check the engine bearings for smoothness. Rock the prop back and forth slowly and see if you can feel any roughness in the bearings. Any tiny roughness that you feel, the gritty kind, means that the bearing will be shedding more and more metal particles as run time increases. These metal particles will circulate through the engine, and everything that happens as a result thereof will be BAD. If in doubt, change the bearing. It beats the heck out of replacing an engine. 90% of the mechanical trouble I have ever had with engines has been due to bearings. The problem is not always rust. The engines of today are delivering enormous power at relatively low RPM. This combination beats bearings to death.

Give the airframe an inspection for any undetected damage, and you are ready to fly.

Good luck. See you at the field.

Tom