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 10 Yellow value on engine screen (Read 2880 times)
OfirVanunu
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Yellow value on engine screen
Sep 28th, 2019 at 10:55am
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Hello everyone !
When I fly with the 757 after something like 11000 feet I get a yellow value where the "oil temp" and it shows 29 in yellow.

Does anyone know why this is happening?

Attached is a picture of the problem


  

2019-9-28_13-47-22-540.jpg ( 302 KB | 166 Downloads )
2019-9-28_13-47-22-540.jpg
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Markoz
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Re: Yellow value on engine screen
Reply #1 - Sep 28th, 2019 at 4:27pm
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Are the Engine Anti-Ice Switches ON?
  

Mark Fletcher



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OfirVanunu
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Re: Yellow value on engine screen
Reply #2 - Sep 29th, 2019 at 1:32pm
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No
That's the problem?
  
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Markoz
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Re: Yellow value on engine screen
Reply #3 - Sep 30th, 2019 at 3:03am
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I don't know if that is the problem, but I think that if the outside temperature is very low (as in subzero) when you reach 11000 feet, it would explain why the oil temp is so low (29).
  

Mark Fletcher



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OfirVanunu
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Re: Yellow value on engine screen
Reply #4 - Sep 30th, 2019 at 8:06am
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Ok, thank you!
I will check that
  
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jbirdsal
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Re: Yellow value on engine screen
Reply #5 - Apr 2nd, 2020 at 12:52am
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Gentlemen:

+1 on this, with B757-300 RB535E4B version in P3d v4.5.

Occurs on climbout with TAT well above freezing and eng a/i off, although engine anti-ice would have no effect on oil temps.  Engine anti-ice directs high pressure bleed air to the nacelle lip/inlet cowl; it does not heat the fan, hot section, or accessory section -- thus, it would not touch the oil system at any point. 

On a similar note, low ambient temp would be insufficient to drive oil temp down to 29*c on a running engine.  Engine oil temps were confirmed at above 50*c prior to application of takeoff power, iaw Engine Start Procedure vol III pg.33.

Symptom is per screenshot by OP.

Cheers,

Jason
  
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jbirdsal
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Re: Yellow value on engine screen
Reply #6 - Apr 2nd, 2020 at 1:37am
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Oil temps for the 757-300 seem to atrophy as speed increases, behaving almost as one would expect a CHT gauge to read.  The temps indicate yellow at 11000 because that is when -- considering acceleration above 10000 -- IAS picks up enough to drive the temps into the yellow. 

This behavior is consistent across  both 757-300 models (PW and RB), however the PW is consistently 10* warmer than the RB so it does not "go yellow", despite the temperature atrophy with speed increase.

This behavior is not consistent with the actual aircraft, and thus I strongly suspect a bug at work here.

I have not tested with the 757-200 series yet.  Will try that later.

Cheers,

Jason
  
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jbirdsal
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Re: Yellow value on engine screen
Reply #7 - Apr 2nd, 2020 at 12:47pm
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B757-200 exhibits the same behavior, although the temperature is high enough that you do not get a yellow temp caution.
  
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Markoz
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Re: Yellow value on engine screen
Reply #8 - Apr 3rd, 2020 at 2:53am
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jbirdsal wrote on Apr 2nd, 2020 at 1:37am:
This behavior is not consistent with the actual aircraft, and thus I strongly suspect a bug at work here.
This could be a case of it being a copy of code from the RB models to the PW models, but seeing as the 757-200PW is the Base model, I suspect it's more a case of incorrect coding - both the PW's, and RB's, are using the same, or a very similar coding. If that's the case, I guess we could call it a bug.
  

Mark Fletcher



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aburek
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Re: Yellow value on engine screen
Reply #9 - Apr 8th, 2020 at 2:17pm
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On Pratt engines the digital readouts change from white to yellow when the temperature increases above 163°. When the oil temperature exceeds 177° the readouts are red.
  

Allan Burek
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jbirdsal
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Re: Yellow value on engine screen
Reply #10 - Apr 12th, 2020 at 10:41pm
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Gentlemen:

Perhaps I should clarify -- my main point here is not the color, but the behavior.  Oil temperature is cooling with an increase in indicated airspeed, as one would expect from an air-cooled system (I referenced CHT as the airflow correlates too strongly with a decrease in temperature for even an air-cooled oil system). 

The 757 oil system is cooled via a fuel/oil heat exchanger on the downstream side from the reservoir prior to the engine; fuel is the 'heatsink', not airstream.  Having the oil temp cool as airspeed increases is not consistent with how the system behaves on this aircraft.

Attached file was taken from my EFB at FL410, TAT -22*C.  Would've been about .80 Mach.  Compare these numbers against the two-digit numbers you'll get at cruise and climb in the simulator version.  Unfortunately I can't legally capture climbout screens -- even from the EFB -- below sterile cockpit altitude.  Suffice to say that prohibition against advancing power until temps have risen to 50*C is consistent with RW practice, and that the temps tend to rise to what you're seeing in the pic, and stay there, without a whole lot of variance. 

This pic is from a PW-engined 757-200.

Cheers,

Jason
  

IMG_0969.JPG ( 127 KB | 135 Downloads )
IMG_0969.JPG
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Captain Sim
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Re: Yellow value on engine screen
Reply #11 - Apr 13th, 2020 at 4:15pm
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jbirdsal wrote on Apr 12th, 2020 at 10:41pm:
my main point here is not the color, but the behavior.

What/when exactly we should change in the code? Thanks.
  
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jbirdsal
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Re: Yellow value on engine screen
Reply #12 - Apr 16th, 2020 at 2:58pm
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Gentlemen:

Captain Sim wrote on Apr 13th, 2020 at 4:15pm:
What/when exactly we should change in the code? Thanks.


I guess it depends on what you want it to do.  If your focus is solely on normal operations (no abnormals or emergency procedures) you could probably hard-code the temps to rise from ambient temps at engine start to stabilize 125* to 145* and just stay there until engine shutdown.  Number are an estimate -- I'll pay more attention to trends on my next rotation but, the global airline situation being what it is, that may be some time in the future yet.

Regarding abnormals or emergencies, you may still be able to get away with a hard coded trend.  In 12 years of flying these engines (PW, that is) I have never had a high oil temp issue.  Waiting to advance the power until the temp rises out of the yellow is normal in winter; waiting for takeoff power until 50*c is also normal; but no high temp issues.  It is such an unlikely occurrence that there isn't even an EICAS message for oil temperature, only X ENG OIL PRESS for pressure.

Regarding the oil temperature reading -- the system takes the readout (as I understand it) on the return line from the engine to the reservoir.  This is on the opposite "side" of the system from the fuel/oil heat exchanger.  Thus, any variance you would want to program into the oil temp would be most directly related to engine power and engine power alone.  That said, running the engine at full rated power for 5 minutes should not be enough to cause an oil overtemp...

Hope this helps.  As I am not a programmer, I'm not really sure how to help translate RW behavior into code. 

Cheers,

Jason

  
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Captain Sim
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Re: Yellow value on engine screen
Reply #13 - Apr 18th, 2020 at 2:12pm
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jbirdsal wrote on Apr 16th, 2020 at 2:58pm:
As I am not a programmer, I'm not really sure how to help translate RW behavior into code.

Thanks, we'll see what we can do.
  
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