Monday, September 17, 2012

This is Why We Walk Around the Airplane

A while ago I posted a discussion of how to change the oil in a Cessna 182. On the list of items to be gathered in preparation for changing the oil I included "a helper." The helper becomes very useful when it's time to wrangle the lower cowl.

About a week ago it was time, indeed past time, to change the oil in N631S. I'd accumulated about 56 hours since the last change and it was getting to be important to get to the job. But my usual helper was out of town on travel, and my backup helper was not feeling well. So I decided to see if I could change the oil "solo" – and in the event, it did not prove terribly difficult.

I removed the upper cowl and loosened the quarter-turn Cleco fasteners on the right side of the lower cowl. Then I disconnected the cowl flap control cable from the right cowl flap. This gave me access through the cowl flap opening to the quick-drain fitting on the bottom of the crankcase. Without too much difficulty I was able to slip a 1" vinyl hose over the quick drain and open it to allow the used oil to drain. (The resulting lash-up appears at left.) And while the oil drained, I replaced the filter and safety wire in the normal way.

I don't expect to make this my standard procedure for oil changes, because it doesn't provide an opportunity to give the lower parts of the powerplant a thorough inspection. But in the circumstances (no helper) it worked well.

Feeling rather satisfied with myself, I re-secured the lower cowl and replaced the upper cowl. The latter needed the usual amount of persuasion but after a few minutes it dropped into place and I finished up, closed the hangar, and went home.

About 0600 the following Monday morning I arrived back at the airport, for my weekly trip to Connecticut. I stowed my bag and briefcase and began to do my pre-flight inspection. Of course I use a checklist, but I also like to take a step back and just look at the airplane. And when I looked at the right side of the upper cowl, this is what I saw:

As you can see, the whole row of Cleco fasteners that fasten the right side of the upper cowl to the lower were not secured. As I finished the oil change, I'd gotten the right side of the upper cowl seated, walked around to wrestle the left side into place, secured the Clecos on that side and then declared myself finished.

And that is why you always walk around the airplane. If I'd not bothered with a good pre-flight walk-around, would the upper cowl have come adrift during the takeoff roll? I don't know and have absolutely no interest in finding out. This highlights a second reason to do the oil-change with a helper if one can be had – a second pair of eyes greatly increases the probability of trapping boneheaded errors.