COLD and quiet day before the inauguration

Planes tied down at the airport were moved into hangers to make room for incoming fly-ins. The temperature was well below freezing. The wind picked up to 12 knots with peak gusts at 22 knots. I wanted to fly, but I wanted to stay warm and safe too.

So what does a student do? Well, we spent a little time preparing for my first country. The rest of the time we spent looking at some plane engines (a Piper Malibu and a Piper Warrior ). Why not get a little education on the systems that power the plane?

It was cool to contrast the two engines. In this case, the little Piper Warrior was a small four cylinder aspirated engine. The Malibu has a six cylinder fuel injected engine with a constant speed propeller. So here is a run down of things I learned in no particular order.

Magnetos:
* Both planes have two magnetos, as one would expect, and both have keys (unlike the dual engine cousins). This is important, because the key, in the 'off' position grounds out BOTH P-leads attached to the magnetos. If one of those P-leads breaks (it is thin wire...they break!), then simply turning the key to 'off' does not shutdown the engine. This is one good reason to cut the mixture when shutting down the engine. No gas, no run!
* Aptly name, the magnetos are left and right, on the left and right of the plane from the pilot's perspective and directly tied to the the 'left' and 'right' on the ignition switch. Turn the key to left, that grounds out the RIGHT magneto, and vice versa.
* When starting the engine (yes with the key) ONLY the left magneto is operating (assuming the ground is working). The reason is quite simple. Engine timing of a four cycle engine is such that the spark ignites when the piston is close to but not at the apex of its climb to the cylinder head. This is called ignition timing (remember hearing something to the effect of 20 degrees of top dead center in My Cousin Vinny? Sure you did). When the engine runs really slow (as in starting), ignition can happen to soon. So the left magneto has a impulse coupling (a spring loaded device) to alter the timing during ignition.
* Now here is where it gets interesting (well, if you are into this stuff). If you look at the wires to the spark plugs from the magnetos, you will notice the right wires go to the top (two, three) plugs on the right cylinders and the bottom plugs on the left cylinders. The left is in reverse. This is key (heh...foreshadowing;-). When priming the engine, the primer dumps gas into the cylinder head. The primer tube looks like a small fuel injection line. As you might guess, too much priming results in too much gas hanging out at the bottom part of the cylinder (cylinders are horizontal to the ground). This means the bottom spark plugs may get too much fuel and ground out. So, when starting, often times only the two LEFT cylinders will begin working because the LEFT magnetos provide the spark for the top left spark plugs. Now, Lycoming is not stupid. They often provide primers for only a subset of cylinders (skipping one or two on the right). This insures that some right cylinders are not flooded, pulling the gas from the carburateur. Once the ignition goes to BOTH, the top RIGHT spark plugs start igniting gas and then engine stops sputtering around.
* Fuel injection does not use primers. Fuel is injected into the cylinders. However, they do have an air pressure system that dumps air into the cylinders from the intake manifold. This serves the usual purpose as expected. In addition, these tubes maintain a fairly constant pressure in the cylinder so gas does not back up through the fuel lines.
* Turbochargers found on carburateur engines are driven by exhaust gases to turn a turbine. The turbine's primary function is to help maintain pressure within the carburateur, allowing the plane to fly at higher altitudes. The Warrior did not have one of these. It did however air conditioning. How convenient!

Ahh...so much more to tell. I will provide another post in a day or so. Spoilers: Not all planes have EGT thermometers on all the exhaust pipes. There are some easy ways to tell if there is a leak in the exhaust pipes. It is just plane stupid the use the throttle to dump fuel into the carburateur unless the purpose is to burn out the air intake.