Thursday, September 21, 2006

End of summer break, back to school

I started the Instruments class at the A&P school last night. This one should be every bit as interesting as the sheet metal structures class I took in the spring. It's two five-hour classes a week, same as list time, so it's definitely going to have a severe impact on my free time, but it looks like it will make up for that by being quite interesting.

Last night was more or less review for most of the class given that four of the five students are either licensed pilots or very nearly so, and the 5th guy has a background in naval aviation. The program is a part 147 school, which when boiled down means the curriculum is very structured, and despite the fact that every student in the room knows what an altimeter or airspeed indicator does, we have to go through the motions of assuming no one in the room has ever seen either of them before. That part goes quickly, though, as the expectation that there will be clarifying questions from the students is virtually nil. As with all of these classes I've had so far, though, no matter how familiar the subject matter is, there is always something more to learn. In last night's discussion of altimeters, airspeed indicators, and VSIs there were more than a few very subtle details provided that went beyond what we were taught as fledgling pilots. A five hour lecture is a looonnnnngggg lecture, so the periodic emergence of a nugget of new info was extremely welcome.

As the class progresses, it will get even more interesting because we will have the opportunity to do some lab work. Next Monday, for example, we've been instructed to bring a flashlight, side cutters, and a flat file. The flashlight will be used as we tour the flight deck of the old FedEx Boeing 727 that was recently donated to the school. The cutters and file will be used to craft a brass screwdriver that we will then use to swing magnetic compasses. As I found in the sheet metal class, the A&P curriculum eerily shadows my real-world needs: since I moved the mag compass to a different spot in my panel to make room for the Anywhere Map PDA, it has indicated quite a few degrees in error. I swung the compass in the Tampico once, but I did it without the benefit of any formal training. I'll soon know what I did right and what I may have done wrong back then, and will quickly apply that knowledge to my current problem.

It's a new teacher (to me, anyway) this time around, and he has an interesting teaching style. Rather than write a list of flight instruments on the board to discuss, he has the class see how complete of a list we can generate. Now and then he'll throw in a little factoid and challenge us to say why this or that is the case. For example, last night as he was talking about altimeters he threw out the fact that they are usually mounted using brass bolts. "Why is that?" Well, I took a guess at it. Mind you, I know that brass is used to mount things like the mag compass to avoid magnetic interference that could affect the accuracy of the compass. But he was asking about the altimeter, and we had just talked about its inherent delicacy. I offered up the opinion that a brass mounting bolt would be softer than the metal of the altimeter's case and would thus not provide sufficient torque to warp the case. BZZZZTTTT - wrong answer! It was still the magnetic interference issue. Oh well, sez I, that's what I get for not taking the obvious answer. Every class needs a smart ass, and I have long played that role. And of course, as we all know there are no smart donkeys in the circus because nobody likes a smart ass.

We also spent a lot of time talking about the pitot-static system and perusing the FAA regs that govern inspections and currency of same. Because the A&P school does not assume that any given student will ultimately work only on small GA planes, the discussion also includes the far more complex systems of airliners and other very high performance planes. This is all fertile ground to me as my exposure to transport-quality turbine planes has been relatively minimal, unless you count my time in the Air Force working on SR-71s and RF-4Cs, or the handful of times I flew in the NetJets birds.


  1. What? The altimeter has magnetic issues? Or the altimeter screws are near the compass?

  2. I think his point was that brass mounting screws are used for all of the intruments to avoid introducing errors to the mag compass, whether said instruments were in close proximity to the mag compass or not. Why that came up in the context of the altimeter, I'm not sure. That's what threw me off - nothing all that unique about the altimeter when it comes to mounting.