Trent engine oil loss question
 

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.

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

PDR

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.

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.

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....

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.

Oil Loss or Indication Loss?
 

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

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.

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.

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.

RMC you are describing a loss of oil quantity indication.

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.

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.

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.

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.

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.

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.

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

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.

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"