Trent engine oil loss question

[RMC]

On my initial course I was told the Trent was certified to run at full thrust with a complete loss of INDICATED engine oil.If it happened all we needed to do was continue to check oil pressure and temperature and as long as these did not change we could continue to destination. I understand there have been numerous nstances of oil loss on Trent and Rb211 and this procedure is approved ( not sure how it is different from the Quantas 380 uncontained failure). I am interested to know though
- how many Trent oil loss incidents there have been
- how long the oil loss takes.

Our company does not have a procedure for monitoring secondary instruments ( oil quantity, pressure and temperature on the basis that " if it becomes critical the aircraft will tell us"

Apart from basic airmanship my argument is that in an engine which seems to have a greater than average number of oil leaks maybe it is not a bad idea to monitor oil quantity so you know before say you start an Oceanic segment you may have a developing oil problem.

If the oil leaks are instantaneous ( burst seal etc) this argument is not as convincing.

Any support or otherwise for either side of the argument would be appreciated.

[PDR1]

How do you monitor the pressure and temperature of an absence of oil?

PDR

[Exup]

I hope you mean loss of oil qty indication ( or fault), then as with a number of engines you can monitor oil px & temp but as previously stated if it is a genuine total oil loss there will be no px indication to monitor.

[RMC]

The scenario is a genuine loss of oil....indications range from 4 to 0 (quarts?) ...normal around 12.

The RR guy said that even with an indication of zero in the tank there would be oil in and around the bearings, seals and at the oil pressure transducer.

[Togue]

Ask the RR guy about complete loss of fuel.

I guess he'll tell you to keep flying because there's still fuel in the lines....

[lomapaseo]

Well where did the oil go?

I would rather it spilled out the nacelle drains than worry about it cooking something in the turbine innards. I'm sure that any written words on this available to the crew consider solid experience and understanding.

[No Fly Zone]

Just because one CAN do it does not mean that one SHOULD do it.

[RMC]

Hey Toggle,

Trent Oil Capacity
Nominal total oil system capacity (78.2 imp pints)
Nominal oil tank capacity (41.0 imp pints)
Usable oil (including effect of attitude) minimum (27.1 imp pints).

Typical Aircraft FUEL tank capacity 235,000 imperial pints
Unusable fuel (190 imperial pints)
Fuel feed pipe capacity (350 imperial pints)

Could you give these ratios some thought :rolleyes:

There is more than one cause of oil loss apparently...bearing seals is one I know about.

[Exup]

If you have gone from 12 to 0 & it is a genuine oil loss there will be nothing around the pressure tx. For the pressure tx to work it requires a sealed system, if the system is not sealed no pressure will build up. If you still have good oil pressure the primary cause would be qty indication fault. As good as modern engines are they don't work that well with out oil pressure.

[RMC]

Ex up...you are right it was a total loss of indicated oil....there was however enough oil to pressurise and cool the bearings and no pressure loss at all. We need a Trent / RB 211 specialist to explain what does sound counter intuitive. Any subsequent change in oil pressure requires an immediate divert....in the BA case the 787 Dumped indicated oil over St Johns and continued ( being monitored very closely) to Houston with no change in pressure or temperature boroscoped in Texas....no damage.

[yotty]

RMC you are describing a loss of oil quantity indication.

[RMC]

Hi Yotti,
I know to non RB 211 people ( of which I was one until recently) it sounds like a loss of quantity indication....but the seal failed and much oil was sprayed into the atmosphere.

[Exup]

I don't know how to put this more simply, no oil, engine destroyed, everybody dies, basic understanding of how mechanical systems work. If you can use an engine with out oil why put it in there in the first place. Loss of oil indication is a different thing. If you do not understand these basic principles there is no hope.

[tdracer]

RMC, yotty is absolutely correct - what you are referring to is a loss of oil quantity indication. Oil Quantity Indication is not the most robust signal in the world (sometimes the float sinks), so typical QRH instructions are to monitor oil pressure and oil temperature and operate the engine normally as long as pressure and temperature remain within normal limits. IF oil pressure and/or temperature are outside normal ranges, immediate shutdown.
Basically, if the oil quantity is really zero, the pressure will rapidly decrease and the temperature rapidly increase outside normal limits within a minute or two - and if you don't shut down the engine a serious, perhaps catastrophic, engine failure is guaranteed.

In short, operating any turbine without oil is a recipe for disaster - there have been several uncontained failures of Rolls engines when lubrication problems resulted in bearing/shaft failures.

[RMC]

Ex up, read the post! It does not say No engine oil....it says no indicated oil. Just like you don't have full engine oil if you dip your car when it is running....much of the oil is elsewhere. total system capacity 78.2 imp pints.....oil tank (where the indication would be measured) 41 imperial pints. The Trent is certified to operate in the cruise at full thrust for several hours in this minimal oil configuration.
Td...I mentioned one of the uncontained failures in the original post. There is a history of Trent oil loss...some are dramatic.....in most cases the flight continues. What I am looking for is rate of oil loss from someone who has experienced this...or an incident reference.

[tdracer]

On my initial course I was told the Trent was certified to run at full thrust with a complete loss of engine oil.If it happened all we needed to do was continue to check oil pressure and temperature and as lond as these did not change we could continue to destination.
.

RMC, your original post... NO engine will run for any length of time with a "complete loss of engine oil". Either you've misrepresented what was given in your initial course, or the course is dangerously wrong.

I've not worked the Trent in 20 years, but most engine oil tanks have a couple quarts left when the gauge reads zero - so if it's a slow leak you can keep running for a while with "zero indication", even if the quantity is valid. But the oil pump feeds from the bottom of the oil tank - as soon as the pump starts sucking vapor instead of oil, the oil pressure will start fluctuating and you have a serious problem - all of that oil left in the system is no longer pressurized and won't be doing what it's designed to do.

[InSoMnIaC]

RMC if you are talking about loss of Oil indication it is not the same as an oil qty indicator showing zero due to oil leaking and only a minimum quantity remaining.

[lomapaseo]

I'm uncomfortable with folks predicting catastrophes from simple loss of oil.

Tis true that even if a small quantity (not always detectable) finds its way to where it can overheat and light off, shaft rotor disk failure may result (certainly not catastrophic but biggies nevertheless). The more likely scenario is that bearings overheat and get smaller. This forces the engine rotors to find other bearings for support over time and as this progresses vibration is going to be felt along with blade tips rubbing resulting in EGT increasing. By this time you should be pulling it back to idle to extend its life as needed.

I would have thought by now that somebody would have delved into the early L1011 incident

[CCA]

Had it on a 744 RB211-524G across the pacific, oil quantity slowly dropped to zero monitored T & P kept engine running. After landing and shut down the oil level increased & upon inspection oil had dumped everywhere over the cowl.

It was filled up again & flew one sector (15hours) approved to home base, episide repeated on return and gearbox changed.

Oh and we didnt die from 0 oil quantity indication nor did the engine explode.

RR* oil is held in the gearbox not in an oil tank like P&W and GE, its just a design difference. Different design different rules.

* There are probably RR engines with oil tanks and should the tank quantity drop to zero then a shutdown is required.

More recently a gearbox had a crack RR confirmed fill it up, it'll lose it during takeoff and climb but as long as the oil in the system keeps the Ts & Ps satisfactory then its ok to keep the engine running.

[RogerGliding]

See this post http://www.pprune.org/6205197-post1142.html in the Concorde thread.
To quote the book, "Up to the late 1980's the tunnel's portals were obscured by massive steel doors, built a little in front of the stonework and supported by a frame. These where constructed as an anti-blast measure by Rolls Royce in 1968, who used the tunnel for destructive tests on the Olympus engine for Concorde. They ran an engine without oil, expecting it to blow up within 20 minutes or so, but in the event it laster for well over two hours !. The tunnel's use for this purpose was only over a few days, planning permission having been sought from Shepton Mallet RDC as a matter of course, in case an explosion caused a change in the local topography"

[yotty]

I think I've got it now. When there is a slow leak in the system it causes a reduce oil level in the reservoir/gearbox (which is where the oil level sensor is). The remaining oil is still "transiting through" the reservoir/gearbox but not hanging around long enough to give a meaningful reading. Thus the lubrication system is still operating with a much reduced indicated oil level. So it's really a case of "partial oil loss" as clearly with a total oil loss there would be no oil to lubricate the bearings at all. I wouldn't expect the situation to last that long,eventually the oil would leak away to a point where lubrication would end. this ties up neatly with RMC's statement "Our company does not have a procedure for monitoring secondary instruments ( oil quantity, pressure and temperature on the basis that " if it becomes critical the aircraft will tell us" :ok:

[RMC]

Thanks CCA, that was what I was looking for so your partial oil loss was not instantaneous and would have been picked up by bringing up the secondary instruments display. On the Trent 800 this low quantity indication does not pop up until almost 75% of INDICATED oil has gone ( although that still leaves just over 40 imperial pints, a little over 50% of the TOTAL SYSTEM oil).
Really interested to hear how many others have had a similar experience to CCA AND / or any references which show how many times this has happened. Read that the Trent 900 had 15 oil leaks in one year.....but no indication how much oil was lost in these cases.

[Exup]

I have just read your post again, now that you have Edited it to read no indicated oil from its original total loss of oil you are correct. Rather than asking me to read the post maybe get it correct in the first place.

[yotty]

No harm done though Exup eh? It just proves that the Drivers and the Engineers need to be ever vigilant and use the correct terminology, how often can a single word change the context of a situation completely? :cool:

[RMC]

Ex up, The clarification was necessary, however are you happy that this is not an indication problem...it is an indication that most of the oil has leaked out?

[riff_raff]

I believe R-R Trent engines are similar to most other large turbofan engines with respect to their lube oil system. The engine bearing chambers are scavenged by a shaft driven pump located in the EMAD gearbox, which is mounted to the lower section of the fan case. After the scavenged oil is de-aerated, it is returned to the oil tank. The Trent oil tank is separate from the EMAD gearbox housing and is mounted higher up on the fan case. It is the gray thing just to the right of the large vertical yellow cylinder in this picture (https://upload.wikimedia.org/wikipedia/commons/d/d2/Airbus_Lagard%C3%A8re_-_Trent_900_engine_MSN100_%286%29.JPG).

The engine oil feed is provided by a shaft driven pressure pump located in the EMAD gearbox. The pressure pump is fed from the oil tank. The pressurized oil passes thru a filter and heat exchanger before being distributed to the engine bearings/gears/splines/carbon face seals, EMAD bearings/gears/splines/shaft seals, etc.

The oil level sensor is located in the oil tank, but even if a properly functioning oil level sensor indicates zero oil level in the tank, there can still be a fair amount of oil still circulating through the system. It will just be in the form of an air/oil mixture. If we consider that a primary function of lube oil flow is to provide cooling of engine bearings, then even having an air/oil mist sprayed from the lube jets onto the bearings can help significantly. The rolling element shaft bearings in a turbofan engine are very high performance devices, and would quickly fail due to scuffing with a total absence of lube oil.

As for the pressure and temperature sensors in the lube oil circuit, they are calibrated for liquid oil flow. If the oil tank level was essentially zero, but the scavenge and pressure pumps continued to operate, there would still be some compressed air & oil mist flowing thru the circuit which would be detected by the pressure sensor. However, the pressure of an air/oil mixture coming from the pressure pump would be much lower than a flow of liquid oil.

A large turbofan engine like the Trent has some capability to continue operating for a brief period with loss of lube oil. But it could not operate for extended periods at full power with a loss of lube oil.

[underfire]

Must be a British thing! Look at Triumph motorcycles!
(they leaked so much the entire frame was filled with oil, you knew you had a buffer when checking the frame oil, because it could be completely gone, and still enough oil in the engine crankcase and transmission to run the beast, and yes, engine and transmission oil were the same)

[Capt Quentin McHale]

CCA,


"RR* oil is held in the gearbox not in an oil tank". Close, but no banana. Assuming you are talking about the RB211-524G engine, it does in fact have an oil tank which is integral to and attached onto the front face of the High Speed External Gearbox at about the 6 to 8 o'clock position.


Many, many moons ago, a wise old flight instructor said to me...."know your aeroplane, but KNOW it's systems" and I have lived by that creed ever since. Anytime I see an engine cowl open with engineers under it, or engineers working in general, I join them and ask questions.


McHale. :)

[tdracer]

Must be a British thing! Look at Triumph motorcycles!
(they leaked so much the entire frame was filled with oil, you knew you had a buffer when checking the frame oil, because it could be completely gone, and still enough oil in the engine crankcase and transmission to run the beast, and yes, engine and transmission oil were the same)

Smoke Theory of Electricity - The Compass Adjuster (http://thecompassadjuster.com/education/resources/smoke-theory-of-electricity.html)

Positive ground depends upon proper circuit functioning, the transmission of negative ions by retention of the visible spectral manifestation known as "smoke". Smoke is the thing that makes electrical circuits work; we know this to be true because every time one lets the smoke out of the electrical system, it stops working. This can be verified repeatedly through empirical testing.

When, for example, the smoke escapes from an electrical component (i.e., say, a Lucas voltage regulator), it will be observed that the component stops working. The function of the wire harness is to carry the smoke from one device to another; when the wire harness "springs a leak", and lets all the smoke out of the system, nothing works afterwards. Starter motors were frowned upon in British Automobiles for some time, largely because they consume large quantities of smoke, requiring very large wires.

It has been noted that Lucas components are possibly more prone to electrical leakage than Bosch or generic Japanese electrics. Experts point out that this is because Lucas is British and all things British leak. British engines leak oil, shock absorbers, hydraulic forks and disk brakes leak fluid, British tires leak air and the British defense establishment leaks secrets...so, naturally, British electronics leak smoke.

(Author Unknown ):D:D:D

[riff_raff]

Cap'n-

There are some R-R commercial turbofan engines that have a lube oil tank integral with the EMAD gearbox housing. The BR710 is one such engine. If you look at this picture (https://upload.wikimedia.org/wikipedia/commons/a/aa/Engine_BR710-2.jpg), the structure just to the lower right of the fan containment ring is the lube oil tank (the part with the ID plate attached to it). It is an integral part of the EMAD gearbox housing casting.

I am intimately familiar with this particular housing casting since I designed it back in 1993. Rolls-Royce wanted the EMAD gearbox main housing casting to be single piece with an integral tank and piping to minimize the potential for leaks and maximize reliability. The downside of this approach was the high cost of manufacturing such a very complex casting.

[Capt Quentin McHale]

riff raff,


Many thanks for the info. I was merely pointing out to CCA that said engine does in fact have an oil tank.


McHale. :) :ok:

[riff_raff]

Cap'n-

Gotcha. Every turbofan engine I know of does indeed have at least one lube oil tank somewhere. In fact, I believe there are some engines that have two separate lube oil tanks. A primary tank located integral with the EMAD gearbox, and a supplementary tank remote from the EMAD. The remote tank is used to replenish the primary tank if it experiences a loss of oil.