Friday, December 01, 2006

Wall of iPods

Time and geograpy are tyrannical.

Technology makes it obvious.

In order to make required arrival times in the US, a veritable wall of aircraft launch from a dozen Asian airfields within a fairly short time span. Since the shortest distance between two points on Earth is a curve where the surface and a plane defined by the departure, destination, and Earth's center intersect, all these aircraft end up boring holes through five tracks lying along a 240 mile wide band running from Japan to Alaska.

Adding to the synchronicity, all large transport category aircraft are designed to operate within a fairly narrow speed range, from about .80 to .85 Mach.

There's nothing particularly new in all this, but GPS and advanced altimetry have made it all something of a spectacle.

Before GPS, inertial navigation systems, which rely on accelerometers to measure accelerations to calculate velocity, got the job done, but with a fair amount of "smear." Without fixed ground references, the black line on the chart was more notional than factual; hence, the sixty mile spacing between tracks. With GPS, everyone is Right On The Line, leading to walls of airplanes stepped from FL290 (29,000') to about FL370, moving like a school of single minded fish.

Adding to the spectacle, advances in altimetry (primarily in, IIRC, controlling for compressibility errors at altitude) have allowed relaxing altitude separation above FL270 from 2,000 feet to 1,000.*

All of which means that scenes like this are, despite the size of the sky, not the least uncommon:


A couple hours later, over western Alaska, we finally caught up:


*Before GPS and advanced altimetry, getting on the wrong route, or the wrong altitude on the right route, was, due smear, extremely unlikely to have a tragic outcome. Now, given the wrong kind of error and the precision of modern navigation, a mid-air collision would be nearly certain. Reverting to manual heading control was required to get an up-sun side view.

6 Comments:

Blogger Peter Burnet said...

Wow and wow. That is mind-bogglingly impressive and beautiful. But look, you idiots, we wanted Playstation 3's and Nintendo Wii's.

Once again, the miracles of science misapprehend real human needs.

December 02, 2006 3:45 AM  
Blogger David said...

That first photo is obviously faked. It shows a distinct curvature of the Earth, despite the fact that the Earth is flat.

December 02, 2006 7:00 AM  
Blogger Harry Eagar said...

Do you radio over to say, 'I'm overtaking you' or 'Howdy'?

Or do the airships just pass in the night?

A local businessman died yesterday. He was involved in what was then (maybe still) the most expensive hotel in the world. When it opened, I had a tour, and the developer was bragging that it included 42 kinds of stone from 41 countries, which he had 'had flown in.'

I couldn't believe it. 'Surely you had it sent by barge.'

'O yes, of course. By barge.'

A few years later, after he went bust to the tune of about $300 million, there was a sale of leftover building materials from the hotel. I went out of curiosity.

Damned if there weren't crates of Italian marble with the PAR AVION stickers still on them.

December 02, 2006 7:18 AM  
Blogger Duck said...

It took me awhile to figure out what was so unusual about your first photo, until I realized the context - that it was an unusual viewpoint from the cockpit of a regularly scheduled comercial aircraft. Context is everything.

If I chucked it all to live in the isolation of the Alaskan wilderness, I'd be pretty pissed to find out that I was living under an international air transport freeway. Sometimes people would rather side with time and geography.

December 02, 2006 10:08 AM  
Blogger Hey Skipper said...

Peter:

The title occurred to me when I recalled an overheard conversation in Anchorage flight ops. The freight coordinator was seriously faffing over getting a load of iPods somewhere on time.


Harry:

Do you radio over to say, 'I'm overtaking you' or 'Howdy'?

No, because of this niggling thing called "radio discipline."

In a previous life, we would have "chattermarks." That would allow guys to tell another airplane to go, say, "Cheap Suit" and he would know to come up 129.95, which would most likely not be getting used locally, then we could communicate whatever nefarious scheme had overcome our better judgment.

This is an alien concept in the big airplane world.

David:

... despite the fact that the Earth is flat.

That got a laugh.

Huh? What? You were serious?


I'd be pretty pissed to find out that I was living under an international air transport freeway.

It is decidedly odd. Anchorage, as cities go, is pretty small. And it is surrounded by a whole bunch of heck-all.

Despite that, a couple times a day, the airport practically sags under the onslaught of jumbo jets, as the cargo ramp becomes chock-a-block with 747s and MD-11s.

December 03, 2006 2:24 AM  
Blogger Harry Eagar said...

Hmmm. Next big quake to hit Anchorage (like '64), sell Wal-mart short.

December 03, 2006 10:50 AM  

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