Fabio Miguez

Hi Carl, I bumped into this topic, and I have an answer, so This happens because of the jet stream. You probably know this already, but it's a "belt" of winds that travel all the way around the world. There are two of them, one in the Northern Hemisphere, the other in the South. They always travel on an Easterly direction. They're also relatively narrow, which means you have to be heading East and be right over one of them to benefit from it. The shortest route from Dubai to Seattle is a polar one that flies almost over the North Pole, see it here: http://www.gcmap.com/mapui?P=OMDB-ksea which is what Emirates flies when going that way. But on the way back, they deliberately pick a longer route (by about 800nm!). This route, though, lies almost entirely inside the jet stream, which they "surf" halfway around the world, and arrive there almost a full hour earlier than the polar route. That's quicker, which also means less fuel. Thank you NASA for your weather satellites .

Hey Wes, just checking in to see if you got any results from your tests...? Thanks!

Wes, I'm aware of the friction energy transfer, I actually had to do that in real life once . I wasn't aware it's not possible to transfer fuel from wings to center tank in the 777. My own "type rating" program is still being designed, I'm merging the real training program of two different airlines, and designing the training flight sessions still, so my technical knowledge on this airframe is close to nil at the moment. Thanks for sharing!

Hi Wes, I read here that the MD-11 had fuel freeze simulated, and so the 777 might have it too. If it does, then my question stands. Also, another intriguing behavior that PMDG might have modeled, considering their attention to detail, is the possibility of transferring fuel from the wings to the center tanks, where the surface area in contact with an external surface, such as the skin of the aircraft, is lowered. This is most effective, evidently, to slow the cooling of the fuel, as opposed to reverting it. We have an upcoming group flight from Dubai to Los Angeles. My last flight through this route, which is polar, got the fuel very cold, but not enough to set off the FUEL TEMP LOW caution (-37º C by default in the FMC), and that was a 15h42m flight. We'll see what the weather gods bring this time. And good thing there's a good ENSB scenery, you never know when you're going to have that failure at the worst possible time... Looking forward to some more info.

I am writing a guide on Polar Operations for Skywards Virtual (we emulate Emirates Airlines), and in the topic of fuel freezing, the real Emirates has company policy depending on the type of fuel you use, Jet-A or Jet-A1, due to their different freezing temperatures (already covered here in this forum in a number of messages). What I have been unable to find out is if PMDG has built in functionality for these two types or not. I.e. perhaps changing the fuel freezing temperature in the FMC changes the fuel freeze logic behind the scenes. That would be an interesting way to add such flexibility. Or they've modeled their fuel freeze around Jet A only, which is fine too. But I'm looking for confirmation one way or another, so our guidance can be accurate. Thanks in advance, Fabio Miguez Sorry for the double message, but I got a "Request failed due to server maintenance or busy" prompt after hitting submit, so posted again thinking the first one hadn't gone through. Please delete both of these posts.

I am writing a guide on Polar Operations for Skywards Virtual (we emulate Emirates Airlines), and in the topic of fuel freezing, the real Emirates has company policy depending on the type of fuel you use, Jet A or Jet A1, due to their different freezing temperatures (already covered here in this forum in a number of messages). What I have been unable to find out is if PMDG has built in functionality for these two types or not. I.e. perhaps changing the fuel freezing temperature in the FMC changes the fuel freeze logic behind the scenes. That would be an interesting way to add such flexibility. Or they've modeled their fuel freeze around Jet A only, which is fine too. But I'm looking for confirmation one way or another, so our guidance can be accurate. Thanks in advance, Fabio Miguez

Hello Richard, It's dictated by duty time, not distance (although the latter certainly dictates the former ). Different country/authorities have differing regulations, but they're similar. Here's a summary of the FAA regs. Best regards, Fabio Miguez