quintic

I was checking the UA89 flight status today, and found it flying eastbound. I though it is used to be westbound transpacific flight. Is it common? How does the airline/pilot decide which way to fly?

Kacee

He sticks his thumb out the window to see which way the wind is blowing

g46r

It's actually northbound over the pole. Depending on how the wind alot is blowing on that day, the initial heading out of EWR is often slightly to the east. (Wind aloft between 40N-65N lattitude can be very strong west to east, particularly in the winter months).

One example EWR-PVG flight a few years ago:

Kacee

That is a really cool image. Much more accurate at showing the polar route than what you get from a Mercator projector (such as is used by FlightAware and similar websites).

g46r

You can see wind aloft forecast here.

mherdeg

That's a beautiful image. My wife the space physicist adds a note that they will adjust the polar route depending on the space weather forecast. (Too much solar wind activity of the wrong type could lead to crew being unable to legally fly for the rest of the year.)

PV_Premier

per today's flight aware route, more "southerly" than usual, but it did split the strait between Greenland and Iceland, so it will probably top out at about 80N latitude for this trip.

http://flightaware.com/live/flight/U...710Z/KEWR/ZBAA

astroflyer

Not to take this on a tangent, but I think this is partly correct and partly incorrect. Yes, if the solar weather is severe, they will adjust or curtail polar routes (the magnetic fields near the poles provide much less protection from cosmic rays than near the equator). However, they explicitly do NOT track crew radiation exposure. I think it's a "See no evil, hear no evil" sort of situation. If they did track exposure, there's the possibility that all sort of US radiation-worker laws might apply. Generally, these rules only apply to exposure to radiation from radioactive sources, equipment, and reactions and never to cosmic radiation. Also some complicated rules apply to when a worked is "declared pregnant" as some rather stringent limits come into play. If a woman doesn't declare her pregnancy, she could look like Demi Moore on the cover of Vanity Fair, and no one can say anything.

mdpdjx

What a beautiful image. It provides a very good way to visualize the flight pattern.

LaserSailor

One of the funniest career moves in my life was trying to explain this to a EU corporate entity

JDT1955

That's about as far south as I've seen this flight go (when it goes to the "right" of the pole), over 1000 extra miles than the great circle route. Must have been SOME winds!

At certain times to the year, the direction of this flight can actually affect how much I sleep. When it goes "left", it seems like a daytime flight, and I try to stay up the whole way (at most a postprandial nap), whereas going east makes it more of an overnight flight, and I sack in for 6+ hours. Irrational, yes, but there you have it!

mherdeg

Wow, the regulatory stuff here is fascinating, thanks for the insight.

I'll trust you 100% here — my source is an expert on the physics but not the law!

astroflyer

Before moving to astrophysics I did nuclear engineering. Who knows, I might know your wife professionally