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Which Skydrol Types Are Used On Most Airliners?  
User currently offlineGrisee08 From United States of America, joined Mar 2013, 364 posts, RR: 0
Posted (1 year 6 months 1 week 2 days 8 hours ago) and read 6326 times:
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Hi everyone,

I know there are 3 different solutions, and 2 different types of Skydrol that are used today. What I am wondering is which type is most commonly used today, and if they are interchangeable?

I know there is:
Skydrol LD-4
Skydrol 500B-4
and
Skydrol 5 (which is apparently the newest formula)

Let's say I'm a mechanic (which I'm obviously not, since I am asking this question, and if I WERE a mechanic, you may not want to fly on any plane I work on lol), and I added hydraulic fluid, or changed it to an existing system. Let's say a Boeing 717 was using 500B-4; could I add LD-4 in there, or even put Skydrol 5 in? or would I have to completely drain the entire system of 500B-4 before I put LD-4 or 5 in there? I know for a fact that at least AirTran's 717s have stickers/decals on their engines that say "USE ONLY BP/EXXON TURBO OIL 2197." I know that oil is different (or is it), but the main question I need answered by you guys and gals that know more than me (lol) is about the hydraulic system.

P.S. If you could answer the oil question as well, it'd be a plus, but I'm mainly asking about Skydrol systems.

And sorry for being an annoying 20 questions machine here, but are there any modern airliners TODAY that DO NOT use Skydrol? (But some other brand/solution instead)

Thanks for any answers, and I appreciate the time YOU may have taken to read this. I hope it isn't too confusing lol.


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20 replies: All unread, jump to last
 
User currently offlineak907 From United States of America, joined Mar 2012, 42 posts, RR: 0
Reply 1, posted (1 year 6 months 1 week 2 days 7 hours ago) and read 6311 times:

LD-4 is most common. I think you have to drain the entire system to change the fluid, but that's it. No need to change seals and O-rings and such as if you were going from 5606 to Skydrol.

Oil is completely different than Skydrol.


User currently offlineB727LVR From United States of America, joined Jul 2008, 630 posts, RR: 0
Reply 2, posted (1 year 6 months 1 week 2 days 7 hours ago) and read 6301 times:

The aircraft I have worked on all have used 500B-4.

Quoting ak907 (Reply 1):
No need to change seals and O-rings and such as if you were going from 5606 to Skydrol.

Skydrol uses special O-rings due to the difference between it and 5606. If you use skydrol in a 5606 system, the skydrol will deteriorate the seals and o-rings, and will cause many headaches for mechanics.



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User currently offlineyeelep From United States of America, joined Apr 2011, 666 posts, RR: 0
Reply 3, posted (1 year 6 months 1 week 2 days 7 hours ago) and read 6288 times:

Along with the Skydrol's, there is also Exxon HyJet IV-a plus and Exxon HyJet V, all of which are phosphate ester based hydraulic fluids. I've only used Exxon HyJet IV-a plus.

Quoting Grisee08 (Thread starter):
Let's say a Boeing 717 was using 500B-4; could I add LD-4 in there, or even put Skydrol 5 in? or would I have to completely drain the entire system of 500B-4 before I put LD-4 or 5 in there?

You can only do what is allowed per the particular airlines approved maintenance program. At my airline we have to get engineering approval to mix different formulations even if they meet the same specifications, and then have to create a deferral to purge the system of the incorrect fluid and change filters.

Quoting Grisee08 (Thread starter):
I know for a fact that at least AirTran's 717s have stickers/decals on their engines that say "USE ONLY BP/EXXON TURBO OIL 2197." I know that oil is different (or is it)

Oil would be treated the same at my airline. We recently converted from Mobil 254 to Mobil Jet II, it required a drain/fill, filter change and re-placarding.


User currently offlineak907 From United States of America, joined Mar 2012, 42 posts, RR: 0
Reply 4, posted (1 year 6 months 1 week 2 days 7 hours ago) and read 6284 times:

Quoting B727LVR (Reply 2):
Skydrol uses special O-rings due to the difference between it and 5606. If you use skydrol in a 5606 system, the skydrol will deteriorate the seals and o-rings, and will cause many headaches for mechanics.

That's pretty much what I've said, but you worded it much better!

Also, what planes use the B-4 that you worked one?


User currently offlineB727LVR From United States of America, joined Jul 2008, 630 posts, RR: 0
Reply 5, posted (1 year 6 months 1 week 2 days 6 hours ago) and read 6273 times:

Quoting ak907 (Reply 4):
Also, what planes use the B-4 that you worked one?

The planes I have most recently work/worked on are the 737, DC9, and GIII, and in our lockers we only have B-4. The storage facilty I worked at, all we had was B-4, except for the skydrol gel (which is NASTY). I cant remember the name of the gel/jelly version of the skydrol off the top of my head. As for the type, it may be dependant on the operator to choose which type they want to use.



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User currently offline737tdi From United States of America, joined Sep 2007, 894 posts, RR: 1
Reply 6, posted (1 year 6 months 1 week 2 days ago) and read 6185 times:
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We use Exxon HyJet. As far as the gel goes it is only used as an assy. lube for packings/O rings.

User currently offlinedalmd88 From United States of America, joined Jul 2000, 2571 posts, RR: 14
Reply 7, posted (1 year 6 months 1 week 1 day 19 hours ago) and read 6149 times:

When we switched to HyJet is was done by topping off the systems. Same goes for changing engine oils. Top off and change the filter and sticker.

User currently offlinewingscrubber From UK - England, joined Sep 2001, 852 posts, RR: 0
Reply 8, posted (1 year 6 months 1 week 1 day 16 hours ago) and read 6117 times:

Acceptable fluids are usually dictated by the maintenance manual, however in some instances Skydrol 500B, LD4, HD4 and V are intermiscible, so are the red oils MIL-5606, 83282 and 87257.
500B is now obsolete for new design, 5606 ought to be too but Dassault still insists on using it.
Everything else on the drawing board is being designed for use with LD4, V or 87257.

Some seals designed for 500B don't cope with LD4 though, LD4 seals are peroxide cured, so a system designed for LD4 can probably accept 500B but not vice versa. In other words, a skydrol system might be backward compatible, but using a superseding fluid might not always be possible.

Cross-compatibility between the red oils and phosphate esters is an absolute no-no, but there are idiots who still try it from time to time, I've worked on at least one project where some folks thought they would be able to get away with it.

As for motor oils, these aren't a world away from ordinary hydraulic fluid. Non-aerospace hydraulic systems can get by with motor oil or kerosene sometimes (Boeing actually has a patent that pumps kerosene into the hydraulic system in an emergency) but flammability and temperature envelope concerns demand higher performance fluids for aircraft.

An aside, though, 'Royal Purple' motor oil is given its colour by phosphate anti-wear additive, which is similar to that found in skydrol.



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User currently offlineGrisee08 From United States of America, joined Mar 2013, 364 posts, RR: 0
Reply 9, posted (1 year 6 months 1 week 1 day 9 hours ago) and read 6045 times:
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Thanks for all the information, and answers. It provided a lot of insight. I was just curious, because I've always seen quarts and gallons of different Skydrol types sitting on carts on the ramps, and I've also seen quarts of oil just sitting around, and it always had me curious. I remember back when I was younger, I watched some mechanic put Aeroshell into a JT8D-9 with Southeast Airlines, and then I always saw cans of Exxon 2197 (2000) lying around AirTran's neck of the woods at my local airport. It was just so weird, because in my car, I use only one type of oil as well (Mobil 1).


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User currently offline737tdi From United States of America, joined Sep 2007, 894 posts, RR: 1
Reply 10, posted (1 year 6 months 1 week 23 hours ago) and read 5982 times:
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Quoting Grisee08 (Reply 9):
because in my car, I use only one type of oil as well (Mobil 1).




Just a note, a car and aircraft are two completely different critters. When you change the oil on your car that oil is going to stay in that engine until changed a few thousand miles later. On a aircraft engine (turbine) the oil is constantly reserviced on an almost daily basis. When I am called out for oil service on a CFM56-7 I will put between 5 and 8 qts. on just that one call. That is appx. a 20 to 30% replenishment (give or take). As you can see there is no reason to change the oil due to constant replenishment/replacement over multiple oil services.


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 11, posted (1 year 6 months 1 week 20 hours ago) and read 5973 times:

We've replaced 500B by LD4 as its lighter.
The http://www.skydrol.com/pages/ gives more details

As long as the specification is the same, it can be intermixed,else draining/flushing/refilling is called for.



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User currently offlinem1m2 From Canada, joined Dec 2011, 93 posts, RR: 0
Reply 12, posted (1 year 6 months 1 week 16 hours ago) and read 5959 times:

All I've ever seen at my work is Skydrol LD4, but I'm pretty sure that Hyjet is compatible as it says so on some of the reservoirs I've seen in systems. The seals used in Phosphate Ester systems are made from ethylene propylene. Not sure what exactly that is, but it works well with Skydrol.

Myself, I prefer 5606, but it's not used much anymore. It's much nicer to work with and doesn't dissolve paint, or rubber gloves! 5606 is still widely used in landing gear struts although I'm seeing that get replaced with something called Royco LGF (Landing Gear Fluid).

As for engine oil, I know that Mobil Jet II and Exxon 2380 are interchangeable although they look different. I have only seen Mobil Jet 254 used in one type of aircraft, but I'm sure it's much more common than I'm aware of. I thought it was a very odd looking oil, kinda the color of used 20W50!

As for the oil in a car/aircraft piston engine, that is designed to have a "film" effect to work with plain bearings. The synthetic oil used in turbine engines would not work in a piston engine. Turbine engines have ball/roller bearings onto which the oil is sprayed constantly and labyrinth seals which are sealed by air pressure. These seals are what allow the bulk of the oil that leaves the engine to escape past them. Of course, other types of seals are used where shafts pass externally out of the engine.


User currently offlineGrisee08 From United States of America, joined Mar 2013, 364 posts, RR: 0
Reply 13, posted (1 year 6 months 5 days 8 hours ago) and read 5815 times:
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Quoting 737tdi (Reply 10):
On a aircraft engine (turbine) the oil is constantly reserviced on an almost daily basis. When I am called out for oil service on a CFM56-7 I will put between 5 and 8 qts. on just that one call. That is appx. a 20 to 30% replenishment (give or take).

I certainly did not know this. I knew turbine engines went through oil, but I did not know they went through it that quickly. Thank you, kindly.

Quoting m1m2 (Reply 12):
or rubber gloves!

May I ask you to clarify "dissolve rubber gloves" If you are saying what I think you're saying, you are saying that skydrol eats through rubber gloves.  

Are there any AirTran, Midwest, Hawaiian, or TWA mechanics here (I will not use the word "former" who can tell me what was/is used on the 717? I have a 717 OJT Manual that was given to me by a friend from Alteon, and it shows/tells me LOADS of information, but not what kind of fluids are used/required? Except I already know for a fact that BP 2197 is used on the BR715s on AirTran But I just don't know what else is used where. (DC-9 information/JT8D info is a plus if anybody has that)



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User currently offlinem1m2 From Canada, joined Dec 2011, 93 posts, RR: 0
Reply 14, posted (1 year 6 months 5 days 8 hours ago) and read 5809 times:

Hi Grisee08, skydrol will make latex or nitrile gloves weaken to the point that you can't use them after about 30 minutes of use in the fluid. It doesn't "dissolve" them completely, but will make them about twice their normal size in 24 hours if you leave them soaking in Skydrol. I was just trying to show that it's a nasty fluid to work with, but it does it's job very well. Oh, one more note, you really don't want it in your eyes!

User currently offlineGrisee08 From United States of America, joined Mar 2013, 364 posts, RR: 0
Reply 15, posted (1 year 6 months 5 days 6 hours ago) and read 5803 times:
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Quoting m1m2 (Reply 14):

Hi there. I seem to remember that there was a problem among Mesaba's (NWA Jet Airlink) with hydraulic (skydrol) leaks that were penetrating the cabin and burned some passengers as the fluid was very hot. Am I correct on this, or no? It was so long ago, but I can't help but think about it from time to time. I think it was this forum I read about it, but I couldn't find it in the search.



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User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 16, posted (1 year 6 months 4 days 16 hours ago) and read 5745 times:

Quoting 737tdi (Reply 10):
When I am called out for oil service on a CFM56-7 I will put between 5 and 8 qts. on just that one c

Thats quite a lot.....how long was the flight......should be a qt approx an hour.



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User currently offlinem1m2 From Canada, joined Dec 2011, 93 posts, RR: 0
Reply 17, posted (1 year 6 months 4 days 16 hours ago) and read 5744 times:

It would have to be a very bad leak for something like that to occur. Usually, a small leak will produce a very fine mist (at 3000 psi). The Skydrol can get very hot in the system though, so it is possible. As an example, the overtemperature caution message for the CRJ comes on when the fluid reaches 96 Celsius. To put that into perspective, an ordinary household hot water tank is set to 60 degrees Celsius.

Not sure what type of aircraft you are referring to, so I wouldn't know which hydraulic lines are in the cabin. Usually, they are below the floor when/if they go into the cabin. I would guess that if skydrol got on passengers in the cabin, the "burning" they felt was from the chemical composition of the fluid, not from the temperature of it. Having said that, if you do come across a link to what you were referring to in your post, feel free to send it to me, I'd find it very interesting to read.


User currently offlineyeelep From United States of America, joined Apr 2011, 666 posts, RR: 0
Reply 18, posted (1 year 6 months 4 days 10 hours ago) and read 5731 times:

Quoting HAWK21M (Reply 16):
Quoting 737tdi (Reply 10):
When I am called out for oil service on a CFM56-7 I will put between 5 and 8 qts. on just that one c

Thats quite a lot.....how long was the flight......should be a qt approx an hour.

A quart an hour is excessive for a NG. Normal consumption is under .40 quarts an hour, with the ETOPS fleet at my airline its around .25 quarts per hour.


User currently offline737tdi From United States of America, joined Sep 2007, 894 posts, RR: 1
Reply 19, posted (1 year 6 months 3 days 20 hours ago) and read 5667 times:
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Quoting HAWK21M (Reply 16):
Thats quite a lot.....how long was the flight......should be a qt approx an hour.
Quoting yeelep (Reply 18):
A quart an hour is excessive for a NG. Normal consumption is under .40 quarts an hour, with the ETOPS fleet at my airline its around .25 quarts per hour.




Remember I work for an airline that flys an aircraft 8 to 10 legs a day, some less, some more. Sometimes that aircraft may overnight in ELP or LBB etc. These aircraft get no service overnight. First flight of the day back to DAL and we are filling some oil, heck these aircraft may have flown LGA, STL, OMA, SEA. Who knows? We do have contract maint. at these non-maintenance airports but they are only called if below limits. I am sure we are within specs. of oil usage but think about it. .5 qts. per hour +8 legs of 1.5 hours. Equals alot of oil.

If you look at your numbers and mine we are not far different. A 12 hour flight day would equal 6 qts. of oil. I have not even seen a brand new engine get that but I won't argue. It really does not matter.

My point was that oil is changed out on a turbine engine in just a little time.


User currently offlineGrisee08 From United States of America, joined Mar 2013, 364 posts, RR: 0
Reply 20, posted (1 year 6 months 3 days 5 hours ago) and read 5608 times:
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Quoting m1m2 (Reply 17):
Not sure what type of aircraft you are referring to

My apologies, I was referring to the ARJ-85. It was in 2005 I believe, but cannot remember exactly. I just remember the incident because of all the medical needs of the passengers who got it on their skin, clothes, and in their lungs and had to go to the hospital. I will try to find a link to the story if one still exists. I cant even remember if it was one incident, or a recurring problem, but I think it was just one incident.



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