Scenes from the shop floor

The engine finally came off my plane earlier this week, and it should be on its way to Halifax today for a complete teardown and inspection after my lightning strike in July. I snapped a few cell-phone pictures while I was in the shop.

Bent propellers from a gear-up landing.

The first photo shows the propellers from a twin that was forced to do a gear-up landing after both the regular and manual gear extension failed — without the gear, the spinning propellers hit the pavement on landing. The pilot was smart enough to land the plane normally rather than trying to slow down and stop the props first — the props aren’t pretty, but the pilot’s unhurt and the plane, despite some damage, will fly again (hopefully before late fall).

Engine front view.

The second is a front view of my magic magnetic engine, with the propeller and cowling removed. If you’re not used to looking at airplane engines (because, say, you rent planes that have only tiny oil-filler doors), the first thing you should note are the huge cylinders, compared to what you’d find in a car engine. Personally, I’m a bit concerned with what looks like damage on the prop spinner plate (I hadn’t noticed it when I was taking the picture).

Engine accessories.

The third is a view of the accessory drive on the back of the engine — there are various attachments there to allow the engine to spin things that, well, are supposed to spin, as well as room for other toys. The white thing in the middle is the oil filter, which gets replaced with every 50-hour oil change. One of the first things a new private owner-pilot learns is how to cut the safety wire, remove an old oil filter, cut the filter open to look for metal, attach a new filter, and safety wire it. On my plane, it’s possible do all of that without even taking off the cowling.

The dark thing just to the right of and slightly lower than the oil filter is the right magneto, which spins around to generate power for the spark plugs — there is a wire from the magneto going to one plug on each of the four cylinders (the left magneto also has a wire to a separate plug in each of the cylinders, for redundancy). Magnetos are maintenance hogs, and sometimes need to be rebuilt every few hundred hours, but fortunately the costs are not too high.

The grey, red, black, and white thing to the right of and slightly above the oil filter is the vacuum pump, which spins around to create suction to drive the gyros in the attitude indicator and heading indicator. Dry pumps like this one last 1,000 hours on average, but can fail at any time; even worse, unlike most parts, they give no warning — they go from 100% to 0% in a split second. Fortunately, I cannot find a single case of a fatal crash due to a vacuum pump failure in IMC on a fixed-gear plane flying IFR (the drag of the gear makes the plane easier to control), but there are many cases for retractables. Note to self: after losing vacuum pump in a retractable-gear plane, step #1 is lower the gear.

Carburetor and data plate.

Here’s a close-up picture of the engine’s data plate (still can’t read it, though), and the carburetor. You know that my O-320 engine has a carburetor because of the bare “O-” prefix; if it were fuel injected, it would have an “IO-” prefix. Airplane engines almost universally use updraft carburetors, mounted underneath the crankcase — I’m not sure if there’s a good mechanical reason for that, other than avoiding having a hump sticking up in the middle of the top of the cowling. The throttle lever in the cabin pulls a wire around a series of pullies to a control on the other side of the carb (as does the mixture lever, I think). For some reason, the carburetor is much cleaner-looking than the rest of the engine.

That’s it for now. I’ve been up twice in a rental Cessna 172 to keep current, and hope to be flying my own plane again before the end of September.

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About David Megginson

Scholar, tech guy, Canuck, open-source/data/information zealot, urban pedestrian, language geek, tea drinker, pater familias, red tory, amateur musician, private pilot.
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4 Responses to Scenes from the shop floor

  1. Jared says:

    You should have them show you how they repitch a prop… it’s highly scientific procedure that involves a huge wrench.

  2. Rick Wilson says:

    Oooooouch. That prop twist looked painful. ;)

  3. Paul says:

    David,

    I surprised people gave you a pass on the vacuum / retractible gear / IMC failure thingy. I think we’re going to see more with the SR-20 / SR-22s running around. I think you can say most are retracts though. Here are a couple:

    MIA98FA045 12/24/1997 N12172 Cessna 172 Raleigh-Durham NC Fatal Personal
    ATL91FA067 03/18/1991 N2871H Piper PA 28 Hamilton NC Fatal Business

    BTW – the carb isn’t always on the bottom. In a few oddball aircraft, the cylinders are, or were on the bottom. But, I think an updraft carb setup makes it easier to streamline the cowling. I’ve heard people say that it’s safer to put the carb on the bottom, because when you overdo the throttle pump and get raw gas going, it just drains away. I’m not sure I think so, though.

    Great blog, BTW

    Paul – N9002F

  4. david says:

    Thanks for the comment, Paul, and thanks especially for the two accident references. They’re interesting reading, and I plan to make a separate post about them.

    The SR-20 and SR-22 are all electric, I think (even the standby gyros).

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