IDG oil purpose

[pensador]

Hello ! There was the controversy between a first officer and a checker about the IDG oil purpose (Airbus*). Does anyone have any info about the IDG construction? Thanks in advance!

[411A]

There was the controversy between a first officer and a checker about the IDG oil purpose ...

Cooling and lubrication.

[Capt Pit Bull]

Couldn't comment on the airbus specifically, but IDG oil systems exist for lubrication and cooling.

pb

[Intruder]

I believe the IDG has a constant-speed, variable-displacement hydraulic pump as the drive component. th oil is the working fluid for the drive/pump.

[Tinwacker]

IDG cooling and lubrication as the previous posts stated..
For your info an extract from A330 Trent IDG system:

The oil enters the IDG at the opposite side of the drive end and is ported to:
- the differential gear,
- input seal,
- charge pump,
- generator stator and rotor.

The oil supplied to the differential gear is also used to spray cool the PMG stator and lube the disconnect spline.
The input housing has rectangular grooves cut around the main generator stator core in which oil flows to cool the stator and maintain a lower IDG surface temperature.
The charge pump draws in the oil flow at its suction port and intensifies its pressure.

The charge oil is then used:
- as a motive flow in the hydraulic and control system,
- for cooling and lubrication of the hydraulic parts.

The oil entering the rotor is distributed for cooling at level of:
- the exciter and main generator rotors,
- exciter and main generator windings,
- the diodes.

This oil used is then either ported directly to the de-aerator or leaked to the IDG sump where it is scavenged and pumped to the de-aerator. The oil is de-aerated and then ported to the supply pump.
There it runs through the filter into the external system lines for cooling if required.

Hope that wasn't too heavy for my first written test:ok:
hands still hot & clammy!!

TW

[SNS3Guppy]

The IDG uses oil for more than just cooling and lubrication. It functions much like an automatic transmission which is governed for speed. The function of oil certainly is critical for both lubrication and for cooling, but it's also critical to the function of the IDG itself, and works in much the same way as transmission fluid in an automatic transaxle on your car.

[Tinwacker]

You are correct of course its prime function is within the operation and control of the IDG/CSD variable swash plate and being pumped by the pistons a la automatique....to ensure a constand output speed to the generator - whence the heat generation is built up then for the oil to do its next function of cooling while all the time lubricating the moving bits....

The charge oil is then used:
- as a motive flow in the hydraulic and control system,
- for cooling and lubrication of the hydraulic parts.

Remember not to overfill the oil system as this will also cause overheating of the IDG/CSD as the frothed up oil struggles to move round the cooling system.

For once too mush oil is not good.....

[qwertyuiop]

I have had this conversation with a couple of young FO's recently. In very simple terms the oil is there to lubricate the IDG. The oil gets hot as does any other gearbox oil and this heat is used to heat the fuel or you could say the fuel cools the oil. They both go through a fuel/oil heat exchanger and benefit.

I believe the 330 glider had high IDG oil temp due to lack of fuel through the intercooler.

[TopBunk]

To be honest, who gives a ****.

All this bollox about niff naff and trivia. Modern aircraft will tell you what's wrong - they don't (nor do the manufacturer's) expect you to know what value a valve opens at etc, but to follow the ECAM/EICAS drills and continue.

Trying to think beyond that is pointless.

I hasten to add that I think that this is part of the dumbing down of the profession and that I would wish it otherwise, but at the end of the day, if you don't follow the above, you open yourself to criticism and much more in a court of law; conversely, if you follow the manufacturers directives, you protect yourself.

[SNS3Guppy]

To be honest, who gives a ****.

All this bollox about niff naff and trivia. Modern aircraft will tell you what's wrong - they don't (nor do the manufacturer's) expect you to know what value a valve opens at etc, but to follow the ECAM/EICAS drills and continue.

Trying to think beyond that is pointless.


That's not the single most ignorant comment I've ever read here, but it's very close.

You think systems knowledge and understanding is ridiculous, then?

I'm alive thanks to systems knowledge and understanding, several times over.

I'm very familiar with the school of thought that suggests one need no nothing beyond annunciators and ECAM messages...but I also strongly disagree. I don't think you can ever know enough about your airplane.

I also strongly believe that one who enters the forum asking an honest question deserves to get an honest answer, and not ridicule for asking.

[FLEXPWR]

I have to agree with Guppy,

I strongly believe that knowing your systems beyond the basic minimum required rises the level of awareness and safety. More than once have I found myself in situations where checklists would not apply, and systems knowledge and understanding helped me find a sound solution.

As one of the greatest once put it:

"I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit. [...] I never flew an airplane then that I didn't know more about the systems than the guy that invented it, and that'll keep you alive."

— General Chuck Yeager

But what does he know about flying, right? :}

Ever heard too little knowledge is a dangerous thing?


Flex

[TopBunk]

SNS3Guppy

You could at least have acknowledged the next part:

I hasten to add that I think that this is part of the dumbing down of the profession and that I would wish it otherwise

Regards

[pensador]

everybody, thanks a lot!!!! So! the IDG disconnectios leads to very serious aftereffect for the aircraft (judge by guarded pushbutton on the overhead panel). What consumers will be off in that case?

[smudgethecat]

Worth bearing in mind pensador once you disconnect the IDG in flight it can only be reconnected on the ground, (hence the guarded switch)

[muduckace]

I have to admit alot of the replies are a bit long winded and useless information for pilots. Understanding the IDG oil purpose is no more complicated than asking what the purpose of having oil and coolant in your car's piston engine.

This thread needs to be moved if it is for the purpose of discussing the inner workings of an IDG.

Don't get me wrong I am for anyone seeking knowledge, just stating the tech log that should be titled "aircraft ops, procedures and anomilies" due to the great majority of the content is not the correct place for this discussion.

The MOD's will hopefully pick up on this.

[FLEXPWR]

Errr...Mud... I thought this was THE place to discuss technical matters...Not trying to make a point, but where do you suggest this thread be moved to?

Is there a "supertech techie" forum in Pprune I haven't noticed?

So far I have myself learned a lot from this subject, and would welcome anyone to continue the contribution. I come to visit the tech log forum many times a week for just that reason: learn more about a specific aircraft system, an operating procedure or a design study.

If I missed something in the understanding of this forum, anyone welcome to shed some light on my ignorance.

Flex

[SNS3Guppy]

You could at least have acknowledged the next part:



I could have done or said a lot of things, actually...but as it's my thoughts and my words...you'll have to speak for yourself, and let me speak for me. That okay with you?

I have to admit alot of the replies are a bit long winded and useless information for pilots. Understanding the IDG oil purpose is no more complicated than asking what the purpose of having oil and coolant in your car's piston engine.


In your opinion, perhaps. You're a mechanic and not a pilot, correct? Regardless, systems knowledge is hardly wasted information.

You might think a pilot knowing that a generator or CSD/IDG unit is made largely of magnesium might be of little interest or use. I disagree. Knowing that you may end up with an uncontrollable class D metal fire out there on the wing or pylon is a wonderful motivator for making a decision on a generator speed problem.

[muduckace]

General systems information is great for the tech log, as far as technical information it seems to be dominated by the procedural tech. as applies to FCOM questions as to system operation. The detail listed above referring to the inner workings of components that have not reasonable position to operating an aircraft and the published responses to system failures or anomalies need not be published here.

Pilots in my opinion who wish or have the desire to gain knowledge beyond the above would be better served posting said questions in the..

http://www.pprune.org/engineers-technicians-22/

thread.

I in no way discourage this, I just do not see other than arguments over issues pertaining to procedure or question of validity to be posted here. As an AMT I value sharing any information I can supply to those who have the curiosity to understand the aircraft they are operating.

I have operated in that gray area as a "maintenance rep" or flight mechanic often influencing pilot's decisions based on my knowledge safely. I miss this interaction I had as being a part of the crew. I proactivly share as much information as I can as a line/avionics tech advising pilots on rectified problems prior to block out as I can now as I understand your/their position better than most.

I respect allot of older pilots who grew in an environment of less regulation and more common sense. The days of the PFE are about gone now, those guys were an asset to the flight deck.

Like I said those days are gone and most would be better served addressing systems issues that can not be answered by a procedure to the above link.

Just the same I monitor pilot threads ask questions and interact for my love of aviation. Avionics being my current focus, it is a great resource in staying sharp in my field.

[muduckace]

You might think a pilot knowing that a generator or CSD/IDG unit is made largely of magnesium might be of little interest or use. I disagree. Knowing that you may end up with an uncontrollable class D metal fire out there on the wing or pylon is a wonderful motivator for making a decision on a generator speed problem.


Not much of a discussion, I am sure all commercial aircraft you have operated have a generator disconnect button if not automated and fire warning. Both scenarios are covered in the flight manual and there is not a damb thing else you can do about a melting IDG or CSD and/or generator other than landing at the nearest airport.

[SNS3Guppy]

Not much of a discussion, I am sure all commercial aircraft you have operated have a generator disconnect button if not automated and fire warning.


You'd be wrong about that. Not all aircraft have the capability of disconnecting the CSD or IDG, and not all aircraft incorporate one. Certainly not all aircraft I've flown had a fire warning capability, or even an overheat indication, and on some aircraft the frequency of false fire warnings far exceeds those of actual fires by a very wide margin.

For that matter, knowing that a 90 degree turn may extinguish the fire light and permit continuing the mission because one understands that the fire detector in the nacelle is triggered by sunlight or a reflection off the ground may mean a big difference in the way the pilot acts in the cockpit.

One may not have an opportunity to land at the nearest, and shutting the engine down may be the only choice.

During a cockpit fire several years ago, systems knowledge made the difference beween surviving (and saving the aircraft), and not. I was single pilot, single seat, without autopilot of course, in a cockpit full of smoke in an unstable airplane. No way to consult, or run checklists. System knowledge and an intimate procedures familiarity not only enabled a safe, rapid landing, but stopping a departure of control once on the ground, when it started.

I'm sure many posters can provide personal examples of the import of systems knowledge. The foolhardy will suggest there's no need to know one's systems. As I said before, I believe it's one of the single most ignorant statements one can make, here or anywhere.

What you don't know can kill you.

I'll give you a light airplane example. Very simple systems, very common airplane...but if you follow the AFM procedure, not only do you very nearly guarantee an engine failure, but you will create an unrecoverable one, most of the time. The Cessna 206, or any 200 series single engine Cessna (save for the 208) for that matter, is susceptible to fuel flow fluctuation. A knowledge of the fuel system and the way the fuel flow works will quickly reveal the reason why the book procedure of applying fuel boost, switching tanks, and adjusting the mixture, is the wrong course of action. A pilot who knows the systems on that airplane, admittedly simple, will switch tanks first while retarding the throttle...and in nearly every case immediately restore power...then go for the boost pump and mixture (if necessary)...and THEN refer to the checklist.

I've had enough personal experiences with knowing systems and it paying off to have a very sure belief in the principle that one can't know enough about one's airplane. One may not be able to control every aspect, but just as situational awareness is not only a good idea (but a critical one) when flying, knowing the full landscape and the reason procedures are performed is much more than important. Knowing your airplane may very well save your life.

Ask Al Haynes and crew about systems knowledge and following book procedure with respect to UAL 232 in Sioux City. There may very well come a day when you find events which aren't cut and dried enough to be found in your procedures.

Systems knowledge was most likely a critical element in the demise of the crew and passengers aboard Payne Stewart's LR35 some years ago...a crew familiar with one emergency pressurization system in the airplane...but not the early one. They never had a chance to run a checklist, and they never will. We can go on all day...but failure to know your systems is not only professional, but is done at the risk to your own life and those of your passengers and crew, the reputation of your employer, and the safety of those below you.

Don't know the airplane? Very bad idea.

I in no way discourage this, I just do not see other than arguments over issues pertaining to procedure or question of validity to be posted here. As an AMT I value sharing any information I can supply to those who have the curiosity to understand the aircraft they are operating.


As a mechanic/engineer/inspector, so do I.

This is a valid forum for sharing those observations. The original poster enquired about the operation and workings of the IDG, with specific emphasis to the fluid contained therein. This is a technical question. It is not simply a forum for pilots to ask questions about performance or instrument procedures. It's a t-e-c-h-n-i-c-a-l forum. I don't do avionics beyond operating them and the most elemental trouble shooting before I call someone like yourself. Accordingly, I'm not particularly qualified to discuss them, and generally don't. You're able to do that. We have people here who deal in performance engineering, and are very qualified experts in that field...they frequently address those questions here. Each poster has his or her particular area of expertise, and when a question involves a technical aspect, asking it here is hardly out of line.

As you haven't contributed to the threat materially or answered the original poster's question (or the issues developed thereafter), perhaps this thread is not for you. This does not mean that addressing the poster's question with systems information (even as basic and elemental as it's been) is wrong...just that you're out of place.

Of course, if you're here to preach that systems knowledge isn't important for pilots, especially if you're not a pilot...then you're already out of place.

Understanding the IDG oil purpose is no more complicated than asking what the purpose of having oil and coolant in your car's piston engine.


Again, that might be true if IDG oil only served the purpose of cooling and lubrication...but it doesn't. It's the magic that makes the IDG do what it does...and a much better comparison is to an automatic transmission, than a motor. In fact it is a transmission...which makes it a nearly perfect comparison, whereas the IDG is nothing at all like an internal combustion motor...which is part of the reason that it's got it's own oil supply in most cases, separate from the engine...just like a...transmission.

Go figure.

[mutt]

SNS3Guppy..... Can i suggest that you read TopBunks original message again. I believe that you might have taken him up incorrectly. :ok:

Mutt

[john_tullamarine]

General systems information is great for the tech log

As a note, we don't control the nature of tech discussion in Tech Log. So long as the thread is vaguely Tech in nature, at least, it is fine. The filtering system relies on those who aren't interested not reading the thread ...

Some questions may get a "better" technical answer in the Engineers' Forum but that is not the point. As I see it, the main and underlying aim of Tech Log is the educational value for those coming up behind us old pharts ...

Those who seek the black and white of the maintainers' point of view are always free to frequent and/or post in the Engineers' Forum.

[SNS3Guppy]

Can i suggest that you read TopBunks original message again. I believe that you might have taken him up incorrectly.


Mutt, I read it correctly the first time; however, I disagree with his comments, hence my own.

[TheChitterneFlyer]

Just to add my 'two-penneth'... the CSD oil cooler is actually an air exchange cooler and not a fuel/oil exchange cooler. You're confusing the engine oil system with that of the CSD Oil Cooling System. The engine oil is cooled by fuel; or conversely, the fuel is heated by the engine oil system. Which makes more sense don't you think? If the CSD was disconnected it wouldn't then provide any heating to the fuel system!

Just a retired Flight Engineer's perspective... it would appear that you flying chaps could do with a little technical expertise up there. You see what happens when we let you loose on your own!

Happy days... now, where's my Gin & Tonic?

TCF

[Microburst2002]

IDGs must be treated with respect.

A few years ago we had IDG temp advisories in the ECAM, or where they apparently spurious intermittent cautions? Anyway, after those everything was normal. We wrote it in the Tech Log. It occurred again in the flight next day and I asked the engineers. They said the IDG was OK and that they had refilled with oil. They checked again and everything was OK. Again they refilled.
In the first occurrence I asked the captain if we should disconnet the IDG. In the second occurrence I strongly suggested the captain to do it. He decided not to. He did not want to lose a GEN.
Later on I asked the engineers if oil consumption was normal and they said it wasn't. "So IDG is not OK" I replied. But they did all checks and it was OK.

A few days later the whole engine was lost during cruise because of the IDG. The crew was unable to disconnect it with the pushbutton and it did a mess in the gear box.

So if your IDGs are drinking oil like kosacks drink vodka... beware!

[compressor stall]

CFMs for the oil cooling by the fuel...

The fuel recirculation system returns the warm fuel from the fuel cooled IDG oil cooler to the wing tank. The FADEC stops the recirculation system if:
- the fuel temperature increases to a high level
- the fuel flow rate to the engine is at a high level
- the engines have a gravity fuel feed only
- the fuel level in the wing tanks is low
- the fuel goes into a vent surge tank.

There is also a thermocouple in the IDG limiting the oil coming in thought the cooler that's temperature dependant. I seem to recall between 70-85°C it's open, but can't find the reference at the moment though

[grounded27]

IDGs must be treated with respect.

A few years ago we had IDG temp advisories in the ECAM, or where they apparently spurious intermittent cautions? Anyway, after those everything was normal. We wrote it in the Tech Log. It occurred again in the flight next day and I asked the engineers. They said the IDG was OK and that they had refilled with oil. They checked again and everything was OK. Again they refilled.
In the first occurrence I asked the captain if we should disconnet the IDG. In the second occurrence I strongly suggested the captain to do it. He decided not to. He did not want to lose a GEN.
Later on I asked the engineers if oil consumption was normal and they said it wasn't. "So IDG is not OK" I replied. But they did all checks and it was OK.

A few days later the whole engine was lost during cruise because of the IDG. The crew was unable to disconnect it with the pushbutton and it did a mess in the gear box.

So if your IDGs are drinking oil like kosacks drink vodka... beware!


Sounds like you had a gearbox issue, hard to diagnose, not much tech support on this from the mfgr's often. They don't expect it to ever happen!?! The LAME's most likely did their job's by the book!

[Down...2 greens]

On a related topic: on the A320 (CFM engines) the IDG oil is cooled by fuel under certain conditions (e.g. low thrust). Is any cooling provided at other times? I had an idea there was also a fan air heat exchanger, but can't find any mention of it in the current manuals.

[grounded27]

That's not the single most ignorant comment I've ever read here, but it's very close.

You think systems knowledge and understanding is ridiculous, then?

I'm alive thanks to systems knowledge and understanding, several times over.

I'm very familiar with the school of thought that suggests one need no nothing beyond annunciators and ECAM messages...but I also strongly disagree. I don't think you can ever know enough about your airplane.

I also strongly believe that one who enters the forum asking an honest question deserves to get an honest answer, and not ridicule for asking.

No one should be ridiculed for asking a question. I think though the diverse answers above are all clear but both elaborate and concise. If I was tasked with operating an engine witn a CSD/IDG I would want to know why if given an abnormal indication it may fail (usually low oil quantity) but more importantly how to react, tasked with troubleshooting the more common IDG It's inner workings may be more helpfull. Once off wing the details of it's failure are more important in helping to look for the reason it failed. Everyone envolved has a different function, the guy who break's the machine down has little care about a simple "fail" indication, The guy who see's the fail light should not concern himself with the inner workings when he has an aircraft to fly, only react as the manufacturer and company tells him to. Too much thought can be dangerous, knowledge is an asset.

[bcgallacher]

IDG cooling is more usually Air/oil - the increase in temperature on a disconnected IDG or CSD is caused by heat soak from the still running engine,there being no oil circulation on the dead IDG.

[HAWK21M]

Cooling.Lubrication.Heat transfer.

[FE Hoppy]

THE CSD part of an IDG uses the oil as a hydraulic fluid to drive a hydraulic motor the output of which is summed with the geared rotation to maintain a constant output speed to the generator.

Can you obtain an ATP these days with no knowledge of CSDs?

The oil is also used for the cooling and lubrication of the entire device.