Please advise on OIL TEMPS

[DERG]

I see the T972 ran at about 180C normal cruise.
Max temp allowed is 196C on this engine.

Please advise what your machines run at.
Does not matter what type, or how old or new.
Thank you in advance.

[dixi188]

DERG.

I first thought a T972 might be a piston engine or some obscure eastern invention and nearly passed by. Google came up with RR Trent 972.
There are so many abbreviations in aviation, it would help to put a bit more in your post.

My A/C is Airbus A300-B4 and the GE CF6-50C2 normally runs at 80 to 100 C with limits of 160 C continuous and 175 C transient for 15 mins.

Hope this helps.

[con-pilot]

There is no way on God's earth that I will ever again be invloved with a thread on oil and aircraft. Never.

[DERG]

Yes.. indeed I beg your pardon Dixi. Thats exactly the information I was looking for. As far as I was aware before the Qantas/A380 incident that 150C was pretty much tops.

The NTSB has published a preliminary report about the incident and it cleary shows a 180C constant temp on this T972 engine. Further reading revealed a max of 196C. It also has a print out record of "oil chemistry".

My suspicion is that Rolls Royce have robbed cold air from the cooling sysytem to get more thrust out the engine. I am not sure if all these RB211 series engines...they have three main discs with one contra-rotating...run at a higher oil temp then GE-P&W. Are all Rolls Royce engines running at 180C at cruise?

All I am asking here is what is normal oil temp for your aircraft and your engine. Of course there will be locations within the engine where the oil runs at its hottest but the normal guage reading is of interest to me. Thanks for your help.

[barit1]

There is no way on God's earth that I will ever again be invloved with a thread on oil and aircraft. Never.

Not even with a DC-3?? :}

[DERG]

Will you PLEASE stop injecting my threads with your fatuous remarks!
Get the F out of my business and STAY OUT.

[lomapaseo]

DERG

This is an open forum even the thread starter does not own a thread.

I'll delete my response of you'll delete yours :)

[CAAAD]

DERG The engine will have demonstrated max oil temps etc during endurance testing prior to certification. Cooling will also have been demonstrated to the Regulator's satisfaction.

Are you suggesting that RR have changed the values subsequent to certification?

But before comparing with other engine manufacturers you need to be sure that the temperature is measured at the same place so as to compare apples with apples.

The RB211 535E4 has a max oil temp of 177 deg C, the 524is 100 deg C. But 535 is measured at scavenge return, 524 at outlet from oil pressure pump ie after cooling.

So I am not surprised that oil technology etc has moved on since the 535 so as to be able to cope with a very modest temperature increase.

Oil temperature is specified on the Engine Type Certificate Data Sheets which are easily available online. Well, the CAA ones are, EASA not so easy. FAA probably easy.

[barit1]

Come on, DERG, mine was a friendly poke at c-p, paranthetical to 'your' thread - it should be like water off a duck's back to you. :=

[DERG]

Barit old boy I can barely read enough to type these days so if you have something to add about what you did with that test machine you used to tout around please tell me. That thing must have had some temp guages on it. If not then STFU. What your dad did in WW2 has no bearing on what you did with your career.

Caad Thank you. Of couase I am NOT suggesting RR fraudulently offered false data. They may be incompetent engineers and pass the odd buff envelope around when soliciting business with foreigners....but data fraud NO!

"Oil temperature is specified on the Engine Type Certificate Data Sheets which are easily available online. Well, the CAA ones are, EASA not so easy. FAA probably easy."

Oh really?

The issue is that any oil will begin to vapourise above 150C. This is a valid question of interest and I would be grateful if the more generous members of this forum would tell me what they see on their guages.

[bearfoil]

One envisions an oiling system that relies on "Aeration" (misting) might contribute to heat induced "Vaporisation?? Coking? There is that "de-aeration" Tray........ One step past "foaming" ?? IMO.

[DERG]

Bear: the foaming happens when oil gets mixed with water either water liquid OR water vapour. Only time it ever foams. I have found my reading spectacles I can now type:ok:

I have yet to encounter any machine that uses oil vapour to achieve lubrication or cooling. I am aware there is a whole new section of science called nanotechnology but I cannot see the oil vapour being used in the technology we are using (publically in civil use) today.

If oil does vapourise it is past it's usefulness and it gives of a flamable gas and leaves a hard carbon residue caled "coking". Bear I know you follow the A-380 thread and it is this gas that upset the computer control of the engine causing the spline wear.

In this thread I am seeking to know what the guys are seeing on their temp guages in day to day operation. No more than that. It may well be that all RR turbines run with the oil around 180C. This adds up when you realise they have THREE turbine sections as opposed to the TWO in GE products.

All repilies very welcome. Barit1 if you can remember what your whirlygig oil temps ran at then please advise.

[CAAAD]

DERG - If oil vapourises at 150degC, why is the scavenge oil temp of the RB211 535, just about the most reliable gas turbine in existence set at 177degC?

I'm leaving this sideshow now because I prefer a civilised exchange of views. Your views on the integrity of RR are not shared.

[DERG]

The 469 passengers on the Qantas 380 that had the explode will also have questions regarding the integrity of Rolls Royce.

The avaition has its fair share of "yes" men unfortunately and probably more than most.

You are no loss Caad.

[SinglePilotCaptain]

On the space shuttle we use a special oil that will not boil off at normal temperatures....we have a special indicator as well.....

[CAAAD]

DERG - Yes, I'm sure I won't be missed, But

WHAT ABOUT THE 535 OIL TEMPERATURE

Sorry to shout, but you really are a bit irritating

[DERG]

Oil vapourizes above 150C...fact. Prove to me it does not!

Maybe RR units go through a hell of a lot of top oil. No one is counting how many top up tins are poured in because no has to record these additions. Not sure if they even issued the A-380 with an "away pack" to use in top ups.

If oil tecnology had moved on the T970 series would not be in the mess we find it.

Seems to me RR think they are minor deities. They are allowed to product test using the public.

They think they can have THREE turbine discs running and expect the oil to be able to handle a 50% increase in frictional load and temperature.

Moreover they are paranoid about taking bypass air to cool the oil. All in all I get the impression they are in this business cause they always have been. They have leagacy rights to over ride basic physics.

[stevef]

No one is counting how many top up tins are poured in because no has to record these additions.
That's interesting... every freight/public transport aircraft I've worked on had a Tech Log in which all oil/fuel uplifts were recorded.

[763 jock]

B757 with RB211-535E4 engines. Cruise oil temps (off the EICAS) are rarely in three digits. They use a little bit of oil, but powerplant engineers monitor uplifts. If it gets excessive, shop visit time.

[KBPsen]

Oil vapourizes above 150C...fact. It is not a fact, it is you talking nonsense.

A standard oil such as Jet Oil II has a flash point of 270°C. If you don't know what flash point means Google it. After 6.5 hours at 204°C, 3% will have been lost through evaporation.

For Jet Oil 254 the evaporation loss is even less.

Mobil Jet Oil II data sheet (http://www.exxonmobil.com/USA-English/Aviation/PDS/GLXXENAVIEMMobil_Jet_Oil_II.aspx)

You are also talking nonsense when claiming oil replenishment is not recorded. It most certainly is, as anyone who operates or maintains aircraft will know.

[KUMOOZ]

While not knowing this engine initimately it is usual for RR engines oil to be cooled by cold fuel with the heat exchange also warming the fuel.
I may be wrong but your post no4 about 'robbing cool air' is probably completely wrong..now what is your point exactly? :ugh:

[lomapaseo]

I may be wrong but your post no4 about 'robbing cool air' is probably completely wrong..now what is your point exactly? :ugh:

quite a few threads that wander into the technical side of things have newbie posters who post questions to confirm the answer to an already made up mind. Sometimes you might notice this when hidden in the text is the "given that you are still be beating your wife"

Or worse yet when the answers don't come in the way that they have expected they try and divert the subject rather than listen and learn.

[KBPsen]

Yes, it is almost more than one can bear.

[bearfoil]

Try the gym, Bench Press should do it.

[KBPsen]

Conjecture and substituting facts with opinions doesn't carry much weight. Neither does being tetchy. All in all, it's much like the Emperor; Much huffing and puffing and strutting about, while actually being nothing more than bare.

[bearfoil]

KUMOOZ

Oil cooling is indeed accomplished at the Fuel Oil Heat Exchanger.

It is the cooler of preference, though there is also An Air Cooler for engine and gearbox Oil. The FOHE is bypassed at Cruise and Descent in favor of the Air Cooler.

There is no provision for Fuel Heating via the FOHE. It has been piggybacked by the AD on TRENT 700 installed on the 777. The manual I have leaves that function out of the Operator's handbook. The GE90 does include a reference to Fuel Heating in its OM. For what its worth.

bear

[Brian Abraham]

DERG = ssg = johns? Strange similarities.

[Turbine D]

The GP7200 runs an oil temperature of 163℃ at the oil outlet, with transient operations of 177℃ limited to 20 minutes for comparison purposes to the Trent 900.

Indeed, lubricating oil is cooled using fuel from the wings during takeoff and climb.

There is also a minimum oil temperature that must be reached prior to takeoff.

Turbine D

[barit1]

DERG asked me about my experience in test cell ops. I have located the TCDS, and scavenge temp limits are: 160C continuous, 170C 5 minutes.

I never recorded oil temps - my focus was aero/thermo parameters, and I had my hands full with that. The local throttle jockeys took care of the mechanical numbers, but in several hundred hours of aggressive operation, they never had a oil temp problem on my engines. :)

[DERG]

"B757 with RB211-535E4 engines. Cruise oil temps (off the EICAS) are rarely in three digits. They use a little bit of oil, but powerplant engineers monitor uplifts. If it gets excessive, shop visit time."

Thank you for this post. This is the info I am seeking.

What do I want to know? Some of us are wondering just WTF is going on with this T970 series and the "RR total care" contract. Just how is the oil top up recorded, YES how and where... and who looks at the record. Do you see the issue here? If the only people overseeing the engine are RR then clearly an operator has little control over the equipment used. Moreover the operator may be taking risks that are unacceprtable.

Turbine D thank you that helps.
Brian.. I have never used other screen names.
Bear..thank you..complex but constructive.
Lomapeso..oh yes..we know your classification well..you need a nanny on the shop floor in case you trip and fall. You are stardust, you are golden.

KBP If you have the inclination go get a litre of turbine oil and heat it up on a domestic cooker. If you can measure the temp at 150C. See what happens above 150C. There is no danger involved in this home experiment. But you may be surprised.

SteveF: I am damn sure the A388 of Lufthansa had this record, I am also sure that Singapore had it. But I am uncertain if Qantas had it. I am not saying Qantas was negligent in not having a hard copy paper record. What I am saying is that under the RR Total Care programme they may well have been led to believe they did not require one.

As I requested I would be grateful what the guys are seeing in daily use on their oil temp guages. The 180C running temp of the T972 as used in this A388 seems a lot higher than any other engine in civil aviation.

All replies welcome.

[no-hoper]

There is no Air/Oil Cooler on the Trent 900.Only a Fuel/Oil Heat Exchanger is installed.The GP 7200 has got both devices.RR and EA using Air/Oil Cooler for VFG Oil.

[DERG]

what is this please?

[no-hoper]

VFG is a Variable Frequency Generator mounted on the accessory gearbox.It supplies 115V AC with a frequency between 370 to 770 Hz related to the engine speed.

[barit1]

One source I have informs me that the GE90 oil temp is measured at the supply side, not scavenge, and thus runs somewhat cooler on the readout.

Be careful in comparing apples to apples! :=

[KBPsen]

DERG,

I don't need to heat anything on a cooker to know what will happen. Even if I did, I would not be surprised by the result.

1 litre of oil heated to 200°C would have lost 3% mass after 6.5 hours.

End of story.

[spannersatcx]

TRENT 700 installed on the 777
Would that be anything like the Trent 700 on the A330?

[DERG]

Thank you for the replies so far.

KBPsen Sure at standard temp and pressure, but the jet engines don't work at std temps and pressures. Back in 1971 I studied Kelvin's Gas Laws. I am sure you did too. You are not thick, I can tell.

Barit: excellent point YES.

no-hoper: thank you, please feel free to add to this thread. This Trent oil temperature issue fascinates.

spannersatcz..nice screen name! That is exactly what I want to know too!

Additional comments. GE/PandW/EA recently issued a notice to check oil lines for coking and fractures as a consequence of the Qantas incident on the A-388.

The RR Trent has more bearing surface area to cool than EA products. We know that the running temp of the Trent 972 is 180C. We have been told that the running temps of GE/GA/Pand W engines is less.

Would be grateful if others could please advise what temps they are seeing in day to day use in a/c they fly.

[Lonewolf_50]

DERG:
MIL-PRF-7808 is a lubricating oil that must meet the following spec: Flash point 210° C (~ 410° F). I appreciate that an ambient pressure less than atmospheric would likely induce a flash to vapor at lower temps.

But lubricating oil in a jet engine is a fluid / liquid, under pressure.

Why do you feel that a fluid under pressure will flash?

I guess my question to you is: at what point when operating at cruise altitude do you believe that the lubricating oil is operating at ambient (20K feet, 30K feet 35K feet) pressures? The oil system remains under positive pressure, and contained ... or it leaks and sprays oil and you run out post haste and the issue of "flash" is far less than it is oil starvation.

I'll bite.

How is the application of Kelvin' Gas Laws utile in our discussion of oil properties when we are discussing a closed fluid circulating system under positive pressure? Is it your position that the lube is sprayed/applied by the system, before scavenge, to components that are operating at ambient pressure for the altitude? :confused:

Happy to understand your point better, if you'll elaborate a bit.

Thanks.

[DERG]

Thanks for your reply. Everytime I try to log on to this site I get like 5/6 refusals so if I don't get back and reply you prolly will guess that I am onto an embarrasing scent. Too close to the truth for the well being of RR plc.

"Flash point 210° C (~ 410° F). I appreciate that an ambient pressure less than atmospheric would likely induce a flash to vapor at lower temps." Thanks for that info. The bearing chamber that RR uses is unique and patented. It uses pressure differentials to work as designed. So YES reduced pressure/partial vacuum lowe flash point. We know the T972 ran at 180C cruise so a spontaneous ignition inside the chamber is within probablilty. So the oil temp only has to rise about 9% to attain that unstable state at one atmosphere pressure.

"But lubricating oil in a jet engine is a fluid / liquid, under pressure." Not in this case it ain't. Especially if a pipe was fractured as the ATSB has identified.


"I guess my question to you is: at what point when operating at cruise altitude do you believe that the lubricating oil is operating at ambient (20K feet, 30K feet 35K feet) pressures? The oil system remains under positive pressure, and contained ... or it leaks and sprays oil and you run out post haste and the issue of "flash" is far less than it is oil starvation."

This happened at about 5K feet I think under about 85% load on TO. There is evidence that a lot of these T970s had oil leaks. The basic principal of by pass jet propulsion demands controlled pressures and are independent of outside air pressure. This is not the case with ambient temperatures at TO thrusts.

Kelvin Gas Pressure Law. Any liquid unless at absolute zero temp has an atmosphere just above the liquid state. This depends on both temp and pressure and is governed by a gas contsant value which I forget..ahem..I was 17 when I did this stuff.

Using the Kelvin laws I believe that the 9% temp leeway preventing a spontaneous combustion is not only possible but likely. Throw in a fractured oil pipe and a few places where the oil has accumulated and bingo you have an explosion.

I have to say if that 210C flash point is correct I want to know just WTF this company are seeking to achieve with this engine design.

[Turbine D]

DERG

An items not noted, as of yet, in your thread relative to oil temperature:

It is called "soak back". Soak back occurs when the engine is shut down and the oil coating the walls of the sump or in the tubing is heated above normal operational conditions verses if the engine was running and oil was flowing. It happens to sumps, tubing and bearing locations in very close proximity to hot components such as the frame between the HPT rotor and the IPT rotor. "Soak back" is a factor in the design of sumps and the location of the oil lines, but it is still probably the leading cause of the formation and build up of coke.

Turbine D

[DERG]

Yes Turbine D, thanks for your reply. I believe that the design of this engine has reduced the mass and increased the energy transfer to such an extent that there is not enough mass in the parts to effectively absorb the waste heat.

Of course this why Qantas chose the T970 engine to achieve greater payloads. As it happened the failure occured when the a/c was not heavily laden and under a reduced TO power setting.

And to quote Rolls Royce verbatim "High in power, yet low in mass." Of course the way to prevent this is to provide auxillary oil pumping after the engine has been shut down to keep the oil flowing and prevent the coking.

But of course if the surfaces are so hot to instantly carbonise the oil under normal use, say in 95% load in TO, there is little to stop this happening. Reading back through the thread an earlier poster stated that 270C was the flash point and not the 210C noted later.