Hi everyone,I have just completed (sort of...) one of the most interesting simulated flights of my life! I was flying from Taipei to Anchorage using last weeks real world weather (I was going to do it last Sunday-flying EVA606) but just off the East coast of Russia, approaching the Bering Strait, I noticed the temperature had fallen from around -35C to -62C! This was clearly a rather sudden drop in temperature, because my fuel, at this point was at a perfectly reasonable temperature of -36C, but not being stupid, I knew this was going to fall. Being only about four hours into my flight, I had just watched the sun rise, and because my fuel load was heavy, the pumps had reconfigured themselves to circulate the fuel around the system, to help maintain its temperature. Obviously this only slows down the cooling, so I knew I needed to descend to a lower altitude, as suggested by the EAD, but on my descent (to FL250 from FL350-clearly I needed to descend a long way) the fuel temperature fell to -41C, and when it had been here for a few minutes, the inherent gelling, led to an engine flameout in the no. 1, followed by the no. 3. After this I had to descend to 10,000, partly because the temperature, even here was about -50C and also because the plane didn't come close to maintaining this altitude on one engine, although even here the aircraft failed to maintain altitude, and the temperature was still -38C. The fuel was only warming very slowly, and several minutes later, the no. 2 died as well. This meant I was now flying a drift-down, and getting very worried, having programmed a diversion to UHMM and printed out an approach chart. The problem was that I was at 7000' and 215nm from the airport, obviously this was unfeasible, but it was still the nearest field. When I reached 5000', with the ADG deployed, and APU running the temperature had warmed to -28C, and fortunately a restart was possible in all engines, in the end I did make it to UHMM (although I did face another problem, Microsoft failed to integrate an ILS beam into this airport, which made the approach difficult, having had to design my own NDB approach, based on an ILS chart!).Sorry for being long-winded above, but what I want to ask is, how do the professionals do it? I can tell you that 7000' was the highest altitude above -36C around here, and it needs to be that warm to prevent fuel gelling, but surely pilots don't cross oceans this low, hence I ask, in these conditions, are planes grounded, or do they really fly that low?ThanksCharlie Reed

The MD11 doesn't have fuel heaters like on the MD80 series planes. The only prevention is the automatic transfer around of the fuel between the various tanks to warm it. Of course, that way can only slow down the freezing. In real life there are some procedures, like descending to warmer altitudes. Another thing you need to know is that during long cold flight during winter, the planes are loaded with a special type of fuel that have a lower freezing point respect the normal JET A (freezing temp -40°C). It's the so called JET B fuel, with a much lower freezing temperature, like -55°C. But JET B fuel is dangerous for various reasons, so it's rarely used in real life. Another type of fuel is the JET A1, which has a lower freezing temp. than the A type (A1, -47°C).JET A is only used in the USA, and in the other parts of the world the JET A1 type is the standard fuel for any commercial turbine plane.As i know, in very cold places like the zones over the Pole the JET B fuel is used to prevent freezing. I suggest you to set JET B as the fuel on the MD11 when flying in those cold zones. And also, to prevent the freeze of the fuel descending before to reach the freezing temperature, in this way you can come to warmer altitudes in time, excluding the flame-outs.In our PMDG MD11 you can set the type of fuel into the INIT 3 page, where you also set the REFUEL quantity on the CDU. (and you will see also the freezing point for the specific type of fuel you have selected)Cheers,

Hi,Thanks very much for you response, I guess I should have had a better look through the manual (it's probably in there somewhere). I'll try that next time, I cross the Atlantic far more regularly, but the coldest I've ever seen that is -42C at FL350, but from their I got down quickly enough so that not even a "FUEL TEMP LOW" warning occurred. I guess I just wasn't ready for what The Bering Strait had to throw at me, and having only done preflight to the extent of a flight plan, charts and a load-sheet, I hadn't bothered checking the METAR, or downloaded some weather charts.Anyway, I look forward to repeating the flight tomorrow, perhaps with the latest weather and some charts (bearing in mind I don't have a WX radar) I'll have more success.Charlie Reed

Me too, never seen temperatures below -45°C in flight...but i never flown over the Pole except for some trans-atlantic flight with real weather between Europe and USA. But with a full loaded MD11 is difficult to reach very high altitudes before starting the Atlantic crossing, so i never came to colder levels in those flights.Set JET B fuel on the INIT page and everything will be good.Cheers,

Hi everyone,I have just completed (sort of...) one of the most interesting simulated flights of my life! I was flying from Taipei to Anchorage using last weeks real world weather (I was going to do it last Sunday-flying EVA606) but just off the East coast of Russia, approaching the Bering Strait, I noticed the temperature had fallen from around -35C to -62C! This was clearly a rather sudden drop in temperature, because my fuel, at this point was at a perfectly reasonable temperature of -36C, but not being stupid, I knew this was going to fall. Being only about four hours into my flight, I had just watched the sun rise, and because my fuel load was heavy, the pumps had reconfigured themselves to circulate the fuel around the system, to help maintain its temperature. Obviously this only slows down the cooling, so I knew I needed to descend to a lower altitude, as suggested by the EAD, but on my descent (to FL250 from FL350-clearly I needed to descend a long way) the fuel temperature fell to -41C, and when it had been here for a few minutes, the inherent gelling, led to an engine flameout in the no. 1, followed by the no. 3. After this I had to descend to 10,000, partly because the temperature, even here was about -50C and also because the plane didn't come close to maintaining this altitude on one engine, although even here the aircraft failed to maintain altitude, and the temperature was still -38C. The fuel was only warming very slowly, and several minutes later, the no. 2 died as well. This meant I was now flying a drift-down, and getting very worried, having programmed a diversion to UHMM and printed out an approach chart. The problem was that I was at 7000' and 215nm from the airport, obviously this was unfeasible, but it was still the nearest field. When I reached 5000', with the ADG deployed, and APU running the temperature had warmed to -28C, and fortunately a restart was possible in all engines, in the end I did make it to UHMM (although I did face another problem, Microsoft failed to integrate an ILS beam into this airport, which made the approach difficult, having had to design my own NDB approach, based on an ILS chart!).Sorry for being long-winded above, but what I want to ask is, how do the professionals do it? I can tell you that 7000' was the highest altitude above -36C around here, and it needs to be that warm to prevent fuel gelling, but surely pilots don't cross oceans this low, hence I ask, in these conditions, are planes grounded, or do they really fly that low?ThanksCharlie Reed

this could be interesting for you:http://www.boeing.com/commercial/aeromagazine/aero_16/polar_route_ops.pdf

this could be interesting for you:http://www.boeing.co...r_route_ops.pdf

Thank you very much for this document, I found it really helpful and quite an interesting read, just out of interest, does anyone know how to change the fuel type in the PMDG 747?Charlie Reed