Engine prob on B737

[FRying]

Say your B737-500 is having a major but intermittent oil leak on one of its engines, causing big spills on the tarmac. Mechs simply cannot spot the cause nor the origin as the leak only happens after a fairly long flight. However, they still need to add at least 3 quarts after most 2-3 hour flights. You're told you can still go ahead as oil level and vanishing speed are always within tolerance.

What would you do as a pilot knowing you have no access to any maintenance manual ? Keep going ? Ground the airplane ?

Thx

I forgot to add I need very well backed replies as this is a real issue. I do not have sufficient tools to build constructive arguments. thx

[PilotsPal]

You might get a speedier response if you try this topic in the Tech Log forum. Perhaps Engineers & Technicians might have a view too.

[LME (GOD)]

The maintenance manual will state specific limits for allowable oil consumption. this figure is usuall quoted as quarts or pints per hour. If it is a repeat write up the are obliged to sign off the defect as in limts per amm 7x-xx-xx. Do not accept a sign off as eng run carried out no leaks evident. Ask to see a copy of the mm and work out the oil consumption per flt hour from the uplifts in the tech log. Irregardless if it is in limits or not, you are within your rights to refuse an aircraft, especially for a defet such as this. Oil leaks never get better. hope this helps

[lomapaseo]

We all have to work within the rules to maintain our certificates. Your questions are no different than a passengers questions of your competency.

In this case from what you wrote it seems that a qualified mechanic did perform an assessment and presumably worked within the guidelines in the maintenance manual.

Under this circumstance your concern should be generalized and kicked upstairs for procedural review.

Of course you also have the right and the responsibility to to form judgements based on your manuals, but be careful that these judgements are not perceived as punitive in nature.

[PeePeerune]

is it def an oil leak, and from where......



eng, idg/csd, starter?????

not a simple answer to this one really.

unusual for a 73 too.

p.s any chance of knowing operator??

[FRying]

Impossible to know where the leak was originating from as mechanics were not able to spot the origin themselves (amazing I find !...)

That's why, in doubt, I thought a conservatory measure was more appropriate : I don't know the cause so I'm not going vs I don't know the cause so I can afford to go.

I thank you very much for your interest.

[On standby]

Not sure of the answer but would someone at Boeing have the info'?

Why not check their website to see if there is anyway you can get an indication from them?

[GotTheTshirt]

These kind of problems are never easy.
All you can do on the ground is check for leaks while its running.
Not much help when the problem occurs after some time and possible affected by altitude.
The MM has Fault isolation section which provide the logical steps and the engineers will have already gone through that.
The only other point is you say there is a pool of oil under the engine. It should be possible to see where that is coming from but it may will be from a collector drain which several different areas are drained into one.
As mentioned the MM will have a maximum consumption per hour and that can be monitored.
The other thing that can affect it is altitude so the flights when it happens should be checked for this and power settings.

Been down this road and its sometimes a long one:)

[Tallbloke]

p.s any chance of knowing operator??
When the original post was from FRying?

[FRying]

Tallbloke, this post is dating back to yesterday. I'd rather not giving out the name of airline involved.

Talking to several people, this problems seems to be happening fairly "frequently". I assume there is no straight response to this type trouble.

Thanks.

[used2flyboeing]

CALL 1-206-544-7500 BOEING RAPID RESPONSE CENTER ..& TALK TO ONE OF THEIE MECHANICS .. SHOULDNT COST YOU ANYTHING EITHER ..

[Continuous Ignition]

Depending on which of the collector drains its coming from it could be many sources..

I just completed the factory course at GE on the CFM-56-3 motor and one problem the instructor informed us about was a leak that came from the starter pad drain tube but when the seal was replaced or starter pulled, there was no evidence of leakage.

But what many in the field didn't know is the accessory pad above (going from memory here and I'm getting a little long in the tooth so bear with me) the starter actually has a small drain port that bleeds into the starters drain and both use the same tube.

So it would appear that its the starter pad leaking.. You pull the starter and no oil in the sump area. But oil still leaking from that tube. One of those things that make you go "Hmmmmm"

Anyway maybe a long shot but something to check out. I'll consult my CD's and notes from the class and report back later.

[spannersatcx]

Impossible to know where the leak was originating from as mechanics were not able to spot the origin themselves (amazing I find !...)

If only it was always that easy!

Not 737 related but just to give you some idea that it's not always that straight forward.

I recently had an a/c arrive on stand, shut down, did the normal checks and we had to put a lot more than normal uplift of oil into an IDG/CSD, there was also a write up in the log about IDG/CSD oil temp etc, gets hot when there isn't a lot left in there.

Now a visible check didn't reveal any obvious leaks. OK, not a problem, ran the engine up still no leaks, strange, still have seen it before when a previous base has not topped up or checked the oil levels. Then after about 10 mins after shutting down the engine, a large puddle of oil appeared under the said engine. Very strange, had a look still couldn't see any leaks, topped it up and when through the same scenario. Lo and behold after 10 mins oil coming out again. Found where the leak was and sorted it, it was actually coming from a joint on the generator. So what was happening? Once the engine was run up and the oil in the CSD/IDG became pressurised there was no leak at all, once the pressure dissipated then the leak became apparent.

I've also seen similar things with hydraulic leaks, a/c arrives there's been a drop in oil qty, you can find the area that is soaked in hydraulic fluid, can you find the leak when pressurising the system, can you heck. But once the pressure is dissippated and the hydraulic lines relax it becomes apparent that it is a low pressure leak from a quick release coupling that seals itself when pressurised because the line straigtens itself and seals better than when unpressurised it sags down slightly opening the joint.

So the moral is although it seems quite obvious that there is a leak it's not always so obvious where it originates.

I would say that any maintenance organisation that is worth it's salt will be on top of it and monitoring the uplifts and once it reaches the stage where the consumption limit is reached the a/c would then be taken out of service. Not that there is any commercial consideration or pressure involve........ha!:ugh:

[A pair with balance]

The leak could well be the fwd sump drain. On the cfm56-3 the fwd sump has an overboard drain which will normaly never be used,it sits at 6 oclock on the fan frame and looks like a boss with a hole, ie no drain line to it.The idea behind it, is in a normal eng, air across the labirenth seals of the fwd sump is of a higher value than the oil pressure within the sump. So air goes in and the oil stays in. But if the lab' seals are worn or tear then the balance can be lost. This is rare and usualy shows with a decent,the oil floods the seal due to a/c attitude,air pressure being low with idle set and the scavange system running slower. Oil leaves the sump into the sump shroud and o/board via the drain. Symtems oil loss, wet cowls but no leak on the grd with a level attitude.fault isolation is to bag the drain with a plastic bottle that has a hole at the top so to allow venting(air is always comming out of this drain so will blow up and pop a bag) fly and check.No luck,bag all drains fly and check.No luck engineers chalking powder and dust the casings, check. Good luck.

[mrcabbage]

Had a similar problem on a BA 737-400 and a Lufthansa -500. The BA Aircraft was leaking from the Tacho Generator cover plate due to an internal seal failure. This is on the rear RHS of the engine at about the 7 oclock position looking aft. The Lufthansa had an overfilled VSCF.

[LEM]

What would you do as a pilot knowing you have no access to any maintenance manual ? Keep going ? Ground the airplane ?

I would keep going, after they reply to my entry in the techlog.

Nowadays we are used to almost perfection, and get alarmed for the slightest sign of imperfection.

It's not your duty to argue with engineers if they officially make appropriates entries in the techlog.

If the oil consumption is within limits, then it's within limits.

When I started in Africa flying (also) a DC3, I trusted my experienced sudaf engineer over these grounds...

You fly, and if you have an eng failure, please don't disconnect the autopilot, just trim the rudder! :E

LEM

[morroccomole]

FRying: as a member of th eflight deck community, you would not be expected to have access to maint manuals. The engineers when they sign off your entry as checked and found to be within mm limits should alwayd actually give the mm reference, not just a bland statement. For 737-300 they are:

71-00-00 p241 - 242

I. Oil Consumption Limits
S 842-053-C00
(1) Normal oil consumption is less than
0.4 U.S. quarts/hour or
0.1 U.S. gallons/hour (0.38 liters/hour).

S 842-054-C00
(2) If you find increased oil consumption that meets the conditions that follow, you must find the cause and take corrective action; do the engine oil trouble shooting procedure (AMM 71-00-44/101):
(a) Oil consumption that shows a gradually increasing trend.
(b) Oil consumption that shows a sudden step increase.
(c) Oil consumption that is more than
0.8 U.S. quarts/hour or
0.2 U.S. gallons/hour (0.76 liters/hour).

S 842-055-C00
(3) Oil consumption must not be more than a maximum of
1.6 U.S. quarts/hour or
0.4 U.S. gallons/hour (1.5 liters/hour).

So it seems that your hypothetical 737-500 is probably within the MM71-00-00 p241-242 limit.
There is however something that does cloud the issue. The above figures are for CONSUMPTION, ie the engine is 'burning' or 'drinking' the oil. The puddle on the floor and wet cowlings suggest you have a leak. Leakage limits are given in MM 71-71-00 p601 onward, but these refer to leak rates from individual drains and it seems the engineers in your case cannot find anything coming from drains?

Anyawy, moral of the story is if the engineer has quoted chapter and verse with regard to mm refs, be happy to believe him. If he jut says 'within mm limits' ask to see the limit as he surely has checked it and will have it to hand?

[ManaAdaSystem]

CFM 56 engines do not leak. If it does, there is something wrong.

I do not consider an oil leak a consumption issue. I know there are limitations when it comes to leaks (from the different drains), normally x number of drops pr minute.

My own procedures are as follows:

If there is a small leak, I'll enter it in the log, and the engineer must sign it off as within limits, checked, no leak found, or whatever. I will monitor the engine for the remaining sectors. The information will then be available to the next crew if they bother to check the log for the previous flight(s).

If there is a pool of oil under the engine, I'm not going before it is fixed. Simple as that. They can throw manuals and limitations at me all they want, I don't care. If management pilots have any objections, then they can take the dodgy engine on the night ETOPS, over water, flight themselves. Not likely, as you never see them on those flights will perfect aircraft either.

Each and every time I spot a leak, I'm told "Its normal", or "the engine will always discard some oil during shut down", or "we spilled some oil when we topped it up", or something to that effect. And every time I have refused the aircraft, they have found something wrong with it.

The crew on that MD-80 (some years ago) that blew one engine on take off, killing some passengers, also spotted an oil leak under the "bad" engine. I believe they were charged with man slaughter after that accident.

I work with engineering, but with caution.

[IFixPlanes]

ManaAdaSystem (Greetings withheld)

...They can throw manuals and limitations at me all they want, I don't care...I am glad that 99.9% of the pilots i work with are not so arrogant.
They do their learned job (like you) and they signed responsible for it. Don´t tell them how to work as well as they don´t tell you how to fly.

...I work with engineering, but with caution...I must work with pilots that have that attitude but i dislike them.

Ingo

[ManaAdaSystem]

No need to be offended IFP.

Would you sign off an engine with a 30 inch diameter pool of oil under it? You can't see any leaks, so it's within limits?

You know well it's my right to refuse an aircraft if I'm not happy with it. It doesn't happen very often, but in the case above, I did.

It's about safety, not arrogance.

[IFixPlanes]

Hi ManaAdaSystem

Yes it is your right to refuse an aircraft you are not happy with, but when an engineer sign it you have to accept the delay code 65. :eek:

Some examples out of AMM(737NG):
...In very cold weather (outside air temperature less than -4 degrees F (-20 degrees C)), leaks from the drain can occur on an engine that does not operate or during an engine start. These leaks are not unusual, and should stop after the engine operates at minimum idle for 5 minutes...
-------------------------------
or:
Aft Sump (Overboard Drain)
NOTE:
Oil traces at the bottom of exhaust plug, the exhaust sleeve and the turbine rear frame is usual. Oil coking at the flame arrestor and on the rear cover is usual.
NOTE:
An oil puddle in the exhaust plug is usual. After engine dry or wet motoring, a large oil puddle in the exhaust plug is usual.
...
Serviceable limit:
1) After an engine shutdown only, there is not more than 60 cc/hr (20 drops per minute).
( after 2,5 hours you have 0,15 liter of oil which can produce a 30 inch diameter pool of oil)
-------------------------------
or ...
-------------------------------
So if I do a test run and there is no leak I sign it.
Seals at the engine are designed to withheld fluids under pressure. If there is no pressure they could leak.
Therefore every task to identify the leak starts with a idle run or even with a part power run.
But I must say, that I didn´t sign off anything blind according AMM. When the AMM says OK but my experience (or should I say feeling) say NO, I decide for safety. I think that every engineer must have backbend* to say NO!
Safety must be the first choice without splitting hairs. So everyone is doing his job.

Ingo
*(I just translate the German wording "Rückrad" witch means that you stay at your opinion even when it is against the policy)

[LEM]

You don't mess with Ingo.

:ok:

[prop jocket]

I have no engine experience on 737's to speak of, but the talk of pad seals and so on above sounds reminiscent of the cement mixer technology found in the JT9 accessory gearbox.

Whenever we had a problem like this on one of those engines we'd perform a breather pressure check to find which of the carbon seals or mount pad seals was the culprit. It usually turned out to be more than one. Is such a thing as a breather pressure check possible on 737s?

That said, the only time a JT9 wasn't leaking was when the oil tank was empty.