Next week at this time I will have completed my Oral and Practical exams for my Powerplant license. As you might imagine, much of time is currently devoted to studying. I am feeling pretty confident about the oral portion of the exam, except for the parts about fuel metering in carbureted engines.
About that – did you know that there’s a type of carburetor that operates on the same principle as your toilet tank? It’s called a float carburetor, and, much like your toilet tank has a float ball that’s linked to a valve that will shut off the flow of water to your toilet bowl when the float reaches a certain level, the carb has vaguely kidney-shaped (or, for some motorcycles and the like, toilet-seat-shaped – hahahaha!) floats that are linked to a valve that will restrict or shut off flow of fuel to the engine when the floats reach a certain level. Who knew that aviation borrowed technology from plumbing?
Carburetors aside, the part of the exam I’m most concerned about is the Practical portion. This is where I demonstrate that I actually learned how to work on airplanes during the last 20 months. It’s up to the examiner to decide exactly what I’ll be doing, so I don’t know exactly what the exam will entail, but, from the prep guide, here’s a sampling:
- Time a magneto to a reciprocating engine
- Using a wiring diagram and a multi-meter, troubleshoot an electrical fault on an airplane
- Safety wire fasteners in a series so that the wire keeps them from unscrewing
- Starting with plain tubing and various fittings, fabricate the tubing and fasteners together to be able to withstand thousands of foot-pounds of hydraulic pressure (the pictures are from my practice sessions a couple of weeks ago)
- Use some fancy measuring tools to figure out if a crankshaft is bent, and if so, how much
- Use a multi-meter to measure the resistance, current and voltage drop and check the continuity of various circuits
- Run up an engine and check for proper idling and magneto switch operation
- Grind valves to the proper measurements
- And, many more!
I’m a little terrified about the practical aspect of of the exam. Since I don’t have an airplane at my house, I have to rely on book knowledge for preparation. Well, that and 20 months of training. We have done all the above activities in class, so studying is mostly a matter of reviewing the techniques and making sure I remember all the steps and potential gotchas.
It’s hard to believe how much has happened since that fateful day when I decided to leave Microsoft. Now the rubber hits the road (or the tarmac, if you will). I’m not just an aviation dilettante any more – I’m about to be an actual mechanic! Whoo hoo! But, also, EEEEEKKKK!