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19AB67

TAIL FUEL FWD, then FUEL TEMP LO

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Hi folks,

 

again I am excited on PMDG's MD11's system depth... :Applause:

 

I am just cruising on my flight EHAM18L-KLM685-MMMX (passed YTS VOR heading OBK now)

and outside we have -73°C, TAT -45°C)

 

First I got the warning TAIL FUEL FWD and FUEL TEMP LO, so the fuel system put the rest of 400kg forward,

before it gets frozen to an unburnable block of useless weight!

 

Now I get FUEL TEMP LO again with the advice 'DESCEND TO WARMER ALTITUDE',

as the fuel temperatur falls also in the right wing tank from -37°C to -39°C

so I get down from FL360 to FL 340, but -69°C, TAT -39°C is still too cold.

Further down to FL320! Well, is it now 'warm' enough?

 

Uhh, with going down the aircraft thinks I started to descend and reduced the speed!

Let's fly faster! Manually 0.84M!

 

TAT goes up to -35°C... but the fuel sticks to -39°C...

Fuel consumption was down to about 2400kgs/h, now we consume rather 2650kgs/h

 

Ahh, and FUEL temp gets up to -38°C after a while.

 

(I remember BA38 with their STOL landing in EGLL...

https://en.wikipedia.org/wiki/British_Airways_Flight_38

Why did 'their' ice take effect only just before landing? )

 

Well, obviously I have to stay low at FL320 and wait until it gets warmer again...

 

Reading the SYSTEM pdf now, I see that the real thing supports COLD FUEL RECIRCulation to move the fuel around and keep it warm. I think it's fine that we cannot take advantage of that...

 

I stored the situation and test later, whether the engine will really stop due to clogged filters...

 

Ok, fuel temp -37°C again now, but I stay at FL320 a while. After STL it should get warmer again...

 

Have fun!

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Now I get FUEL TEMP LO again with the advice 'DESCEND TO WARMER ALTITUDE',

as the fuel temperatur falls also in the right wing tank from -37°C to -39°C

so I get down from FL360 to FL 340, but -69°C, TAT -39°C is still too cold.

Further down to FL320! Well, is it now 'warm' enough?

 

Depends. It could be warmer at FL210 but still too cold at FL320.

 

Ahh, and FUEL temp gets up to -38°C after a while.

 

The fuel temp is not going to increase with a snap of your finger. It's going to take a while.

 

I see that the real thing supports COLD FUEL RECIRCulation to move the fuel around and keep it warm. I think it's fine that we cannot take advantage of that...

 

The PMDG MD-11 will transfer fuel. Just like the real thing. Be warned though. If the fuel temp does not increase, the number two engine (not sure about the wing engines) will fail.

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It's going to take a while.

 

Yeah, it took a while to write my little story...

 

The PMDG MD-11 will transfer fuel.

 

... yup, but 'only' forward. No circulation I think.

 

Meanwhile I sneaked up to FL340, but to no avail: I have to go down again to FL320. (100nm to STL...)

What do real jockeys do in that situation? Also up and down?

 

Or are their flight plans exact enough to already know before take-off that they will fly low for a while?

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Judging from your temps you had the wrong fuel in the tanks, Jet A freezes like crazy, A1 is better and there is a 3rd fuel you can put on which is the fuel for the cold climates, I cannot recall its name but if you expect to fly in temps like that, you put that on the tanks.

As for the BA38 crash, their fuel oil heat exchanger got clogged by ice crystals that didn't melt, these were already in the fuel line, but a sudden demand for power broke them loose from the walls of the fuel line and the faulty design of the fuel oil heat exchanger got it clogged, as such the engines were stuck at close to idle thrust.

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Andreas,

 

If you fly a lot Stateside, this should help you a good bit in your altitude/temp planning:

http://aviationweather.gov/products/nws/all

(click the High button to see the temps at the higher altitudes)

 

If you're looking for wind and temp over the Oceans, the Flight Folder on that site has a bunch of resources:

http://aviationweather.gov/iffdp/ (H, in particular, for trans-Atlantic)

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Split it every two numbers (add the zero to the wind):

27|33|51

 

270 at 33, temp -51

(temps are assumed negative over FL240)

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Thanx again.

 

I just see that the true KLM685 takes a more Southern route

 

http://flightaware.com/live/flight/KLM685/history/20121109/1335Z/EHAM/MMMX

 

than published... for sure they want to avoid the freezing fuel... :lol:

 

BERGI UL602 SUPUR UL60 KOLAG UL60 OTBED UL26 PENIL UL70 BAGSO REVNU PIKIL 5700N 02000W 5900N 03000W 6000N 04000W 6000N 05000W 5900N 06000W LAKES YFM J480 YTS OMAGA TVC OBK STL J101 LIT LFK J101 IAH J29 PSX MAM OTOBA TMN AVSAR AVSAR2A

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Folks,

 

I am just flying back MMMX-KLM686-EHAM with the flight plan from flightaware:

 

RADAS J177 PSX J29 IAH J101 LIT J137 ARG ENL BVT GIJ KLANT YPP YZV REDBY CARPE 5400N 05000W 5600N 04000W 5700N 03000W 5700N 02000W SUNOT KESIX MIMKU UP6 REMSI UL603 LAMSO

 

... and again it is really cold (after passing YPP): -71°C, TAT -42°C, but now I see even

 

COLD FUEL RECIRC

 

being displayed! The wing temperature increases to -32°C.

 

BTW: When do OPUS implement the winds aloft feature??

 

Also I don't have the impression that the actual realisation always loads an approximate winds aloft:

The winds blew into my 'face' all the way up to YPP.

I terminated OPUS and restarted it again and get now 005°/55 from the left instead of 066°/53...

 

Well, anyway I go down to FL330 and hope for some boost over the Atlantic...

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Opus currently does not offer winds aloft... However it is going to implement winds aloft at a later date. Which kind of brings me to a question, what weather system is currently the best for winds aloft data?

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I bought OPUS because I thought their winds aloft is imminent... 8^(

 

So, still crossing the Atlantic, I terminated OPUS completely and get with the Jeppessen FSX weather now tail winds as expected.

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what weather system is currently the best for winds aloft data?

 

... and good question. If OPUS don't announce soon a date I'll get rid of OPUS.

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Why did 'their' ice take effect only just before landing?

Because it was a design flaw in the fuel/oil heat exchangers failing to adequately heat the fuel at low power (descent). When they throttled up for the approach phase, the ice that accumulated got sucked into the fuel pumps clogging them, and ultimately starved the engines of fuel.

 

http://en.wikipedia....9_February_2010

 

The Fuel/Oil Heat Exchangers, although compliant with the applicable certification requirements, was shown to be susceptible to restriction when presented with soft ice in a high concentration, with a fuel temperature that is below −10 °C and a fuel flow above flight idle.

Important, as they tried to suggest flying over Siberia was the cause, when in fact anything below -10 deg. C is sufficient (most places in the world).

 

Best regards,

Robin.

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