Jet engines leak like crazy. Nearly all oil is lost through operation by leaking past the no. 6 bearing in the turbine rear frame. This is the location of incredibly high heat and high difficulty in sealing. They don't use seals like on a car engine but rather they use a labyrinth seal that uses internal air pressure to literally blow the oil back into the scavenge sump.
There are three gearboxes that are potential oil leakers: inlet, transfer, and accessory drive module. Each of these gearboxes have shafts that can wear. They use carbon seals which do a great job of sealing but are very picky about being perfectly smooth. As wear creates gaps, oil leaks begin and increase exponentially over time.
And of course, the system is a dry sump design that mounts the oil tank on the side of the fan frame. The potential exists for servicing errors by ground support and the fact that this plane had a failure at this time duration makes it's quite possible that something was not done correctly back in Los Angeles.
I am curious to see if any information is brought forward on the cause of this problem. Rarely do companies share such data because it's bad for business but maybe someone with internal information can share when it's made available. All the speculation and it could turn out to be a faulty sensor.
Interesting, thanks.
I would not shut down any engine in flight , regardless how low the quantity shows, provided oil temp and pressure are o.k.
I would obviously advise dispatch and maintenance but keep it running.
Whether I diverted or not would depend on the discussion with maintenance ( assuming not flying over mountains, sorry, not doing that , depending how high, how far across ).
Yes, false warnings can happen. On the Airbus, to avoid this, they say we need two things before treating it as real low oil pressure ( red on the gauge plus another warning ). If we get just one, treat it as an indication problem.
Its like what Airbus says about Avionics smoke “warnings” - the pilot, not the warning, is considered more accurate and to totally ignore it unless backed up with PERCEPTIBLE smoke ( see, smell , not just a warning ). Lots of pilots do not understand that. If you do not understand things properly, you will end up putting the aircraft into electrical emergency configuration ( min stuff left ….limited Nav aids ) and making life more complicated than it should be.
Same with cargo smoke warning but you have no choice with that one in flight and must land ASAP because it could be real and pilots cannot obviously go down and check it out in flight. You will only know if it was real after landing ( or smoke, fire ) after inspected.
Air Transat had a cargo smoke warning, diverted ASAP to EWR , stopped on the runway for an inspection ( no smoke or fire , no hot spots so fire crew opened cargo door and saw smoke ) and then evacuated because smoke was seen coming out of cargo door when opened. Turned out it was smoke from the halon fire extinguishers, not from a fire. False smoke warning. Better safe than sorry, no choice but to divert.
Going off topic but , yes, false warnings can happen but it’s important for pilots to know what the manufacturer says to minimize going down the rabbit hole and complicating things in some cases.
know your aircraft, inside and out, and discuss with maintenance if time.
I am not second guessing the united crew. Just talking about false warnings/cautions for discussion as some may find the discussion interesting. I have no clue what they experienced on that United flight. I am very curious to find out.
