Why do we preflight?

Before Flight

Before Flight

So Adam and I have carefully planned our flight to Ryan Field, Arizona. We have an oxygen system, plotted flight plan, information about the airport we’re headed to, and information about airports along the way. We have snacks packed, liters and liters of water, and even a bunch of “Brief Relief” units. (Those are little plastic bags with gel at the bottom. The same gel that is in Pampers, which turns liquid into more gel. So you pee in the bag and there’s no sloshing or leaking to worry about. You seal it and put it in a trash bag. Seems to be entirely a male sport.)

Because we wanted to leave early enough that we had a margin for exploration and any minor difficulties we parked the plane at HHR (Hawthorne) rather than SMO (Santa Monica) or TOA (Torrance). Both TOA and SMO have curfews and Notice to Airmen (NOTAMs) against early morning departures on weekend mornings. So Rudy and I flew down to HHR and Adam collected us before we met Sharalyn for dinner. We all slept at Adam & Sharalyn’s house and in the morning Adam and packed up and drove to the airport. (Nell and Dexter were in Boston, enjoy temperatures of twenty degrees.)

We were going to be in the plane for four hours. And we were planning on heading up to the top of the air space we are allowed to fly in. (You can’t fly higher than 18,000ft unless you have filed, and are flying, an instrument flight plan.) While Adam worked on strapping the oxygen bottle to the back of the co-pilot’s seat, and started putting the waypoints for our course into the navigation system, I walked around the plane doing a very thorough pre-flight inspection.

On the Piper Cherokee we learned to fly in, there were more things to look at. You were meant to examine every rivit, in fact. There were four antenna. The Diamond has two, one on top of the fuselage and one below. There are no rivets. Most of the control surfaces have only a couple of connections, and there are just a few nuts to look over. Still, when I draw it out I can spend fifteen minutes walking around the perimeter of the plan wiggling things, poking things, peering into openings. You don’t get a chance to do it after takeoff, so I like to really look at everything.

Everything looked good. The oil level has been holding at six quarts since we had it changed, so they clearly caught a little leak. The last step is to drain a bit of fuel out of three fuel sumps to make sure no water or other containments have made it into the tanks. There’s a sump at the low point in the left tank, the center of the plane (where the fuel lines lead toward the engine), and at the low point in the right tank. I started at the left. Good. Center: good. Left: what the hell?

The sort of aviation fuel, AvGas, we use is a light blue tint. That’s 100 octane, low-lead. AvGas which is much lower octane (80) is pink. When you mix the two together you get a clear fluid. So I was confused when I drained a beaker full of pink liquid out of the right sump. Adam looked at it. We smelled it. It didn’t really smell like AvGas. I tossed it on the ground and drained another tester tube full. Same thing. Damn. It sure looked like we had a tank full of bad fuel. The wrong sort, or a tank of contaminated correct sort, it was hard to tell. But we weren’t going to fly for four hours with that tank as part of the equation, we knew that.

Despondent, we called Hawthorne Ground Control, received a clearance through the VFR mini-route over LAX to Santa Monica and took off. (We flew on the left tank. We could have flown for two hours easily on that tank. It took fifteen minutes to fly up to Santa Monica.) Even with the bad news of the trip being cancelled and, possibly, a tremendous hassle ahead of us (drain twenty gallons out of the tank? rinse it out with the correct gas and re-fill?), the climb up over Hawthorne and the 405 freeway was amazing. It was just a wonderful day to be in the sky. Scattered clouds here and there, but mostly a great view of the Pacific Ocean.

We flew over LAX and landed at SMO. I let the plane float down the runway all the way to American Flyers, the place that fuels the plane on the field. Adam thought we should admonish them on the Unicom radio frequency (“Hey, what did you fuel the plane with?”) but I thought that was too impolite. I was glad we didn’t.

We taxied to their hanger, shut down and hopped out. Adam went in and brought out one of their instructors (one that we had on a Cessna flight, in fact). Brian, the CFI, looked at the beaker and said, “I don’t know, it doesn’t look like jet fuel.” We drained more. He said, “It couldn’t be us that fueled it wrong, because we don’t have jet fuel on the truck.” We kept draining it and looking at it.

Then the guy who ran the truck sniffed it, poked it, and squinted at it. “Doesn’t look like any sort of fuel to me,” he said.

Brian nodded, sniffed again and said, “That’s true. I think it’s water. I don’t know why it’s pink, but I think it’s water. Keep draining.” So we kept draining. (Actually, Adam kept draining. That early in the morning getting under the plane and smelling gasoline can churn my stomach a bit.) It took fifteen minutes of draining and dumping, but we finally got a bit of blue. There was a half dozen people standing around by then. Someone looked at the fuel filler caps and suggested that the gasket on the right side might not be as snug a fit as the left side. Since we had a heavy downpour on Friday it made sense that some rainwater was forced in by the filler cap.

We probably drained a quart of water out of the right tank. While the fuel truck was topping off the tanks we talked about water in the fuel with one of the other CFI’s. He said that their mechanic had to testify in an aviation accident case about the amount of fuel you had to have in the tank before it would actually stop the engine. He said, “A lot. Turns out it’s a whole lot. More than a gallon.” As we did another pre-flight inspection and drained blue AvGas from each of the sumps and climbed in, I thought about that. It made sense. Once the plane is in flight there’s a lot of vibration and sloshing of the tanks. The fuel is fed from the lowest point in the tank, and the water is heavier than the AvGas, but it is probably difficult to get pure water. So the big four cylinder engine is banging around and one cylinder gulps some water. There’s a misfire, probably just a dead cycle on that cylinder, a bunch of steam goes out with the exhaust and then it is rolling on to the next cycle.

I don’t understand pilots who skip the pre-flight inspection. It seems like the time to catch things like water in the fuel tank. Things that might make it a little too exciting up in the air. There are just oodles of accidents in the accident database which are simply things missed on preflight inspection (leaving the physical control lock in place on the control yoke is the one that always sticks in my mind; the lock has a huge red metal flap that says remove before flight, and it is right in front of the pilot’s face).

About Colin Summers

I am an architect, programmer, private pilot, husband and father. A couple of those I am good at.
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