Tuesday, November 9, 2010

Too Good?

The pattern in Pocatello was all ours, which was good. Strong south winds meant that runway 17 was in use, and that traffic patterns were pretty distorted. I was flying with a student, and we had calculated the crosswind component; it was waaay beyond his current skill level. The tailwind meant a quick downwind leg, but he was keeping up.

A Mooney taxied for departure on 17 to stay in the pattern. Now there would be two of us in the pattern, which is not usually a problem. Then a Skyhawk taxied for departure. I recognized the pilot's voice: a good friend who is also one of the most skilled pilots I know. He asked to depart runway 21; the crosswind was not pushing his skill level. But notice that the departure paths for 17 and 21 intersect...

"Oh, no," I thought, "this could get interesting."

The tower had us fly runway heading off 17 to make room for the Skyhawk departure just as the Mooney using 17 called "Ready." When the tower cleared the Skyhawk for takeoff, the Mooney thought that he was cleared. The tower stopped him quickly, but the frequency was tied up while everyone straightened this out.

And now we were flying toward high terrain. I wished I had brought my Garmin so my student could watch the "Terrain" window pop up with the big red X's denoting where we were going to hit the mountains.

The tower cleared us to start a left crosswind as soon as the 21 departure was airborne. Whoops! We didn't have enough of a wind correction, and our square crosswind leg was really a diagonal to the midfield point on the downwind. This put us directly over the departing traffic, and I asked my student to fly behind it.

Worse, the departing Skyhawk was headed northeast, right through our downwind. So we got to do a 360 to let it out.

Once the Skyhawk was high enough, ATC cleared the Mooney to go. Now we had three airplanes pointed at the same piece of sky. The Mooney's pattern was distorted by the wind, too, and he ended up following us too closely and had to go around.

When things get interesting it's worth examining the chain of events that got us there. You can't really blame the Skyhawk pilot; when he called and requested 21 he had no way to know that there were airplanes in the pattern for 17.

You can blame me a little bit for not flying a square crosswind; that would have saved us the 360.

You can blame the Mooney a little for mishearing the radio call, and poor planning in the pattern, but the wind was an extenuating factor.

But you can blame the tower a lot. With two airplanes in the pattern for 17 the proper reply to anyone requesting 21 is "Unable."

Now somebody might insist on using 21 for length reasons, but then there will be a delay. This reminds me of a story from many years ago. I was in the jumpseat of an Airbus 320 departing Boston. It was the FO's leg. "We're 4000 pounds too heavy for runway 4L," he declared. There were 15 airplanes taxiing to 4L and 15 more on final to 4R.

"What do you want to do?" the Captain asked.

"We need to use 15R." Runway 15R crosses both 4L and 4R.

"OK," the Captain replied, maybe rolling his eyes just a little bit. And we taxied to 15R. We weren't going anywhere with all of that crossing traffic, and the FO was jumping out of his seat, shaking his fist at the tower, and yelling "It's not that busy here!" The Captain just smiled. By the time we were cleared for takeoff, we had burned so much fuel that we would have been light enough for 4L.

Back in Pocatello we had another option: if the Skhawk had done a left downwind departure before turning north the runway 17 traffic would have been able to continue in right closed traffic.

But nobody thought of that at the time.



At November 10, 2010 at 5:54 AM , Anonymous AFP said...

It sounds like this provided your student with some terrific real-world experience. Even if he wasn't the one at the controls, I'm sure he learned alot from the experience and the post flight debriefing.

Thanks for sharing the story with us.


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