Wednesday, October 14, 2009

Rainy weather

It's been a soggy couple of days here in LA. Our first rain of the season has brought along with it predictions of mudslides in the fire-ravaged areas, although as I write this none have yet been reported.

Rainy weather often brings with it a flow change at LAX. We're usually west traffic because the prevailing winds are off the ocean, and normally stay west until the tailwind component exceeds ten knots. We informally call it the "three go-around" rule, meaning that we won't consider turning the airport around until the third arrival goes around. Despite having no go-arounds, we 'turned the boat' yesterday about mid-morning, when departing pilots started complaining about the 12-knot tailwind out of the east. After a lot of coordination between the tower, the tracon, and the center, the decision was made and LAX changed to east traffic. The rain began just an hour or so later. Here's how things looked before the rain began:

All the aircraft you can see here (with the exception of the ones at the gates) are departures for runway 7 Left; that's Southwest on short final for 7 Right.

Meanwhile: Looking out to the east, here it comes! This was taken maybe an hour before we saw rain on the window panes. The line of aircraft in the first shot was due to extra space required between each departure so there would be room for the pilots to deviate around this weather.

Ironically, once we were east, we had several go-arounds due to reduced visibility caused by the rain. Because of the dunes at the west end of the airport, better runway visibility is required for east arrivals than for those from the west. This is especially true for the north-side arrival runway, 6 Left, for which the ILS approach has higher minimums and requires a mile visibility. To illustrate (sort of), take a look at these two shots. The first is a JAL B747 on short final for 6L; the second is an Asiana B747 on short final for 6R:

Runway 6 Right is better, but that's normally used for the departures. While it is possible to depart off 6 Left, aircraft would then have to cross the arrival runway to get to the departure runway, and that would put them in the ILS critical area - meaning that the arrivals would not be guaranteed an uninterrupted ILS signal. Not to mention that 6 Left is our shortest runway: about a quarter-mile (roughly half a km for my international readers) shorter than 6 Right. Yet one more consideration is that the controllers have to plan way ahead for that 6 Left departure, as the turning point on taxiway E for 6 Left is over a quarter-mile prior to the entry point for 6 Right, and there's no easy way to get back to it once the aircraft has gone past it.

Besides all of that, the big deal about LAX going east is that it affects traffic throughout the LA basin. Everything tends to slow down a bit because we just don't do this very often, and the airport and airspace are not conducive to the same volume of traffic. The arrival and departure controllers in the tracon all have different airspace, with different runways, fixes, altitudes, and obstructions. While it's perhaps a bit simpler for the arrival guys since the finals extend out over the ocean (no ground obstructions to worry about), the departure controllers now have to contend with the ring of mountains that create the northern and eastern borders of the LA basin. Normally it's not a problem for them, as the heavy slow climbers can lumber out over the Pacific to gain altitude. When we're east, however, some of the long-haul heavies really struggle to get up over the terrain, which in places is less than twenty miles from the airport. Often we have to wait until the first heavy has made it out of the basin before we can roll the nest one. I've watched on the radar as the departure controller turns a slow-climber back and forth like switchbacks on a mountain hiking trail or a sailboat tacking into the wind. This is particularly a problem for north-bound departures.

Even the airport itself is optimized for west traffic. Runway exits that work fine during west operations are no help when we go east. There are a couple of taxiways that we virtually never use until we go east, when they suddenly become the preferred runway exits, namely H1, H3, and W:

As an aside, I was surprised at the difficulty in finding a current airport diagram on the web. It is available from the FAA and other sources as a PDF file, but I wanted a graphics format (jpg) to use here. Undoubtedly it's out there somewhere, but a quick search didn't find any current versions. There have been a number of changes at LAX in the last year or two, most of them associated with the addition of the taxiway between the south-side runways. After the construction was completed, we found that the original labels weren't working well, and so many were re-named. Anyway, the diagram above is, as of this date, the current airport diagram for LAX. I ended up printing out the PDF and then taking a picture of it for use here. As you can see by the dates on the bottom, stuff like this doesn't stay officially current for very long. For all sorts of pilot information about LAX, including links to the current airport diagram and approach plates, go to

Our first rain of the season was a great training opportunity. At present, LAX tower has a bit less than three dozen journeyman (journey person?) controllers - what we used to call 'FPLs' for Full Performance Level - and another dozen-plus in various stages of training. Since we are predominantly west traffic, some of those in training or freshly out of it have heard about east traffic but have never actually seen it - until now. Among them, we have one trainee whose first day was yesterday, several recently signed off on ground control (having never gotten to work east traffic while in training, including one of my ground trainees who just got signed off over the weekend), and our most-recently certified controller, who got signed off on Monday. It was pretty much non-stop training on all of the ground control positions all day, as everyone got to take a turn on each one. Lest I give the impression that safety was in any way possibly compromised, none of the 'newbies' was put on position without first getting to watch an experienced controller work it, and everyone got a quick refresher on east traffic procedures before taking position. Here is probably the best shot I got of training in progress:

Here are some other rainy-day shots. All were shot through the tower windows, as going out on the catwalk in this sort of weather is not especially prudent.

This is another shot of the Asiana B744 landing on 6 Right. Notice the spray thrown up by the reversers.

Earlier in the day, Qantas arrived on 6 Left in the A380.

Two shots of a Delta B752 showing the jet blast. In the first shot, just the left engine is running. In the second, both are running. The water spray effect loses something in still photographs, but you can still see it. It's also possible to see when an aircraft is taxiing on only one engine, as demonstrated by this Virgin America A320:

In this shot, I tried to show the area affected by jet blast behind an aircraft. Although it's hard to see (look at the disturbed surface of the water on the ground), the spray behind this Northwest B752 extends beyond the right edge of the shot all the way to the end of the alley.

Qantas 107 to JFK just airborne off 6 Right.

A couple of views of a Fedex MD11 departing off 7 Left for Memphis. The second shot would be pretty cool if not for the window shade ropes.

1 comment:

  1. Considering the pictures of the (largely imaginary) 747s, I'm surprised anyone was landing at all!