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sddjd

Fuel temp low & oil temp/press event

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Just wondering if anyone has comment or insight on a corner into which I flew myself yesterday  :blush:

 

I was roughly mid-route JFK-HKG overnight when I received the "fuel temp low" warning.  New to me, I looked up its meaning and some suggested resolutions (CDU was set to warn at -38).  I was cruising at that time pre-step and so was "only" at 33k.  I dropped to 300 and increased speed to just below max allowed.  The warning remained lit through the duration of the flight.

 

Upon descending into HKG at approximately 180agl the left engine oil temp spiked into the red; didn't slowly climb, it jumped.  As I pulled up checklists the same warning appeared for the right engine.  FF appeared normal, though simultaneously I received low pressure indicators for the left tanks.

 

While I was still trying to make sense of these warnings oil pressure in both engines dropped, followed shortly thereafter by shutdowns/failures in both within sight of the airport.  

 

At that point, not wanting to end my flight in the drink I reset all failures and continued.  I tend towards long overwater and polar flights, but this is a first. My question is whether I created my own little disaster by failing to solve the fuel temp issue, or if the double oil/engine issue might have been a program crash (FSX had been running a LONG time at that point).  I can't imagine the odds of such a thing happening without user error.  Might my left tanks have finally frozen, the single heat exchanger on that side (vs two on the right) being the reason it began there...?

 

Not using saved states, etc, FYI. Was certainly jarring to have the rug pulled out in such a fashion.   B)


Dan Dominik                                                                           

"I thought you said your dog does not bite....
                                                                That's not my dog."

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Not using saved states, etc, FYI.

 

So you load with the engines running then?


Kyle Rodgers

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Yes, engines running.  Generally I start a fresh FSX session (default flight, default MS aircraft, then move to origin and load 777). 

 

I've since been reading up on low fuel temps; a Boeing paper notes that descent to altitudes as low as 250 may be necessary (assuming no polar temp inversion).  Could be I went into this unprepared with an incorrect fuel type and let my tanks turn to slush, then solid...? 

 

Still not sure why that would lead to an oil temp spike instead of a flameout, but what a sim!


Dan Dominik                                                                           

"I thought you said your dog does not bite....
                                                                That's not my dog."

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Yes, engines running.  Generally I start a fresh FSX session (default flight, default MS aircraft, then move to origin and load 777). 

 

I've since been reading up on low fuel temps; a Boeing paper notes that descent to altitudes as low as 250 may be necessary (assuming no polar temp inversion).  Could be I went into this unprepared with an incorrect fuel type and let my tanks turn to slush, then solid...? 

 

Still not sure why that would lead to an oil temp spike instead of a flameout, but what a sim!

 

I doubt its modeled but the Fuel is heated in the main fuel/oil heat exchanger on the gearbox, if the cooler matrix get clogged the oil temp will rise as the scavenge oil hasnt been cooled! Does it happen in the sim...who knows!

 

Dan.


Boeing777_Banner_Pilot.jpg

 

Dan Davies

AMM GE90, GP7200 CFM56 RB211

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I've had this issue about 4 or 5 times now, during descent oil pressure starts dropping and the temp starts climbing rapidly, if you don't routinely increase and decrease the thrust then both engines will flame-out pretty quickly. I'm almost certain it's a bug and not a feature unless there's something obscure I'm missing to do with engine management. Thought SP1 would fix it but it just happened to me again and disabling service based failures made no difference.

The issues I think it could be -

1) Loading a saved flight, I usually leave air con and grd pwr attached when i save my flight. PMDG did mention something to do with panel states and sp1 on a post somewhere here but i followed those instructions and deleted my panel states so I should be sweet, right?

2) Leaving the flight paused (at TOD) for a long duration.

3) Using autostart, havent tried manually putting the fuel on yet.

4) FsPassengers conflict

Going to do another flight now and load a new flight with a default aircraft and then switch to 777, also going to load default C&D panel state. I'll probably still auto start as i really doubt it's the issue and it is rather convenient.

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Well did the return flight from OMDB to EGLL and it was fine, oil temp and press did get what seemed a bit extreme looking at the gauges (~67 and ~32 respectively) but I don't know what they're normally supposed to be during descent so who knows lol, I should start writing them down to compare. So either it could be that loading a new flight with a default aircraft, then switching to 777 and loading C&D panel state fixed it, or it was never going to happen again last flight and I was just overly worried that the readings would keep getting more extreme as they did when the bug actually was present.  I saved my "gate" panel state this time and next time will try loading the saved flight and applying that and see what happens, but if it doesn't happen again looks like they actually did fix it lol. Mind you this time I didn't pause the flight or have service based failures enabled so yeah, alotta variables lol.

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