Lube in Jet Engine

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4WD

4WD

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Questions for the turbine spinners - no, not LM2500's - but GE-90.
In Tokyo the other day - and a tech pulls up to a B772
He's in a man basket - and has a couple cases of Mobil synthetic. This guy poured bottles for a while.
(Gallon jugs maybe).
Questions:
What would the GE-90 engine hold? (Not a 115) ...
How much would they consume (13 hour flight in this case). ?
 
The pre-flight reading for sump quantity in the GE-90-94B is 22 Qts minimum for start. After start, it may read lower and there is no minimum quantity in flight, but there is a minimum requirement of 8 qts in the sump for takeoff. The sump can hold 34.4 qts. It's a dry sump (multiple scavenge pump) system. Normal consumption is 0.4 to 0.6 Qts per hour of flight.

Max continuous oil temp is 124C, but it can be up to 135C for 15 minutes. As in most jet engines, oil is cooled by fuel in a heat exchanger (which also warms the fuel, reducing the chance of paraffin formation). In this engine, there is an auxiliary oil cooler for the engine oil which uses generator oil to absorb the heat if needed.

Remarkably, the minimum oil pressure for this engine is 10 PSI. That's considerably lower than most jet engines.

That help?
 
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Originally Posted By: 4WD
Questions for the turbine spinners - no, not LM2500's - but GE-90.
In Tokyo the other day - and a tech pulls up to a B772
He's in a man basket - and has a couple cases of Mobil synthetic. This guy poured bottles for a while.
(Gallon jugs maybe).
Questions:
What would the GE-90 engine hold? (Not a 115) ...
How much would they consume (13 hour flight in this case). ?


Not sure about that particular airline's choice of oil. However, most modern turbine engines can use all of the commonly available turbine oils. Mobil Jet II is an older product that is very common and approved in nearly any engine. Mobil 254 is a more expensive, high temperature (HTS) gen III version of turbine oil. 254 (and other HTS turbine oils) is/are hard on seals and "O" rings, so it's use in older engines is generally frowned upon.

http://pds.exxonmobil.com/USA-English/Aviation/PDS/GLXXENAVIEMMobil_Jet_Oil_254.aspx

Most modern turbine engines use very little oil in flight. Also, the oil is typically not ever changed. It's not unusual to go 40-100 hours between adding oil on modern engines.

Turbine engines do not have piston rings or valve guides that can lead to oil consumption. The oil is pumped to bearings and scavenged from bearings via another pump. The labyrinth seals are pressurized with air, so it's very unlikely that any oil can overcome the air pressure and get through the seals.

The specification for modern turbine oils is: Mil-PRF-23699 (with a revision letter such as "F" or "G" after)

As you might expect, every once in a while, we see an engine that simply consumes a bit of oil. Most of the time, it's evident on the outside of the cowl. Either at the bottom, or by the breather outlet.
 
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Awesome - yes, I could see the Mobil and the SS jet on container (have seen around aircraft derivative gens) ... but could not read if 254 or not ...

Thanks for info ...
 
In my experience in both the P-3C and P-8A we did not ever go 40-100 hours without adding oil to either the Allison (now Rolls Royce) T56-14A turbo prop and CFM56-7 turbo fan engines. The T56 due to its age both leaked and consumed oil, we always used to joke that if there was no oil under them there was no oil in them. The consumption spec for the T56 was 1.4 quarts per flight hour, total capacity was 8.65 gallons. Most flights were much less than the maximum consumption rate allowed for, for an 8-10 hour flight I usually saw post flight oils between 0-2 quarts per engine, some were better than others and would go 2-3 flights without needing oil, most engined needed 1qt/10 flight hours. The CFM56 oil is measured in ounces and has a maximum consumption of 75.6 oz per flight hour, on my last P-8A flight we flew 3.5 hours and both engines needed exactly 32oz of oil on post flight. The CFM56 engine does not leak like the P-3's T56 does.
 
Is this what you used to see behind the big birds on takeoff?


I always thought it was because they were running rich since they were low and slow. I havent noticed it so much lately. Maybe the EPA isnt giving any form of transport a free pass.
 
Older engines smoke at any altitude, especially military, Some really old engines, like the J57 on old B-52s, had water injection during takeoff that really blackened the air.
 
Originally Posted By: mjoekingz28
I always thought it was because they were running rich since they were low and slow.


GTs don't get "rich" in the sense of an engine, as they are fuel limited due to blade temperatures.

If they actually ran at stoichiometric (like an engine), their life would be minutes.
 
Not sure everyone online would know GT - I'd take it as gas turbine such as GTG or MPG in the natural gas case ...
(Or dual - but gas as primary) ...
 
Originally Posted By: tom slick
Older engines smoke at any altitude, especially military, Some really old engines, like the J57 on old B-52s, had water injection during takeoff that really blackened the air.


Pretty cool watching the B-52s and KC-135s take off with water injection.
 
Originally Posted By: mjoekingz28
Is this what you used to see behind the big birds on takeoff?


I always thought it was because they were running rich since they were low and slow. I havent noticed it so much lately. Maybe the EPA isnt giving any form of transport a free pass.


It was the old combustor designs, they were not very efficient, add some water and they smoke even worse. Modern combustor designs, and more advanced metalurgy that allows higher temperatures has pretty much eliminated the smoke. I recall hearing GE starting to discuss cleaning up the emissions, including Nox at least 20 - 25 years ago.
 
Originally Posted By: Mr Nice
Originally Posted By: tom slick
Older engines smoke at any altitude, especially military, Some really old engines, like the J57 on old B-52s, had water injection during takeoff that really blackened the air.

Pretty cool watching the B-52s and KC-135s take off with water injection.


And 707s. I have this picture in my office:

 
Originally Posted By: JetStar
Originally Posted By: mjoekingz28
Is this what you used to see behind the big birds on takeoff?


I always thought it was because they were running rich since they were low and slow. I havent noticed it so much lately. Maybe the EPA isnt giving any form of transport a free pass.


It was the old combustor designs, they were not very efficient, add some water and they smoke even worse. Modern combustor designs, and more advanced metalurgy that allows higher temperatures has pretty much eliminated the smoke. I recall hearing GE starting to discuss cleaning up the emissions, including Nox at least 20 - 25 years ago.


The article linked here mentions that very thing:

P&W Growing Pains
 
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Oddly enough I can still remember the oil and hydraulic fluid we used to service aircraft with in the early 70s. Been 41 years. MIL-L-23699B and MIL-H-5606. Still remember my service number too. Can't seem to remember much else..
grin.gif
 
Originally Posted By: Shannow
Originally Posted By: mjoekingz28
I always thought it was because they were running rich since they were low and slow.


GTs don't get "rich" in the sense of an engine, as they are fuel limited due to blade temperatures.

If they actually ran at stoichiometric (like an engine), their life would be minutes.


At near full power, I agree. But with FADEC and lower power settings, I believe they can run near stoich, specially new powerplants not mechanically pressure controlled. Just a little rich of peak.
 
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Originally Posted By: 4WD
Awesome - yes, I could see the Mobil and the SS jet on container (have seen around aircraft derivative gens) ... but could not read if 254 or not ...

Thanks for info ...


Sounds like the Mobil Jet II logo. Sky-blue, red and white cans. Have to open with a can opener.
 
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