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B-757 Red Landing Gear Fluid

Posted: Mon May 31, 2004 11:10 am
by goboeing
I saw this picture and read the caption:


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Photo © Dean Barnes - AirTeamImages



"Look closely at the far landing gear. That red "ribbon" had me thinking it was some defraction artifact or similar at first glance...but on closer inspection it looks very much like a fluid leak of some sort."

The 5606 hydraulic fluid on general aviation planes is red. Do transport category aircraft have a similar colored fluid around the landing gear for brakes or movement?

Nick

RE: B-757 Red Landing Gear Fluid

Posted: Mon May 31, 2004 11:24 am
by dl757md
Goboeing

Most Boeing landing gear struts are serviced with 5606. It looks like the strut fluid is coming from the oil recharging valve.

Dl757md

RE: B-757 Red Landing Gear Fluid

Posted: Mon May 31, 2004 11:47 am
by Yikes!
Agreed. Nothing to do with brakes. The high-pressure systems use Skydrol or equivalent, a hi-pressure hydraulic fluid. MIL5606 doesn't need to withstand the pressures/temperatures of high pressure systems.

Yikes!

BTW - very observant photographer!

RE: B-757 Red Landing Gear Fluid

Posted: Mon May 31, 2004 1:56 pm
by LineMechQX
I agree with the other two posts, MIL-H-5606 hyd fluid(red) is used for strut servicing. And on large aircraft Skydrol(bright purple) is used for hyd. systems. However they are both perfectly capable Hydraulic fluids, the main difference being 5606 burns, and Skydrol will not support a flame no matter what you do to it. Skydrol is used in large planes with a lot of fluid because if a fire were to break out the last thing you want is 3000 psi of "5606 fuel" to be dumping itself on the fire. However Skydrol has its draw backs, it sucks to work around, burns skin on contact (not real burns just irritation), the worst place to have it is in the eyes, makes you go blind till you get it out, it also peels paints and melts plastic quite readily. So 5606 is often used in its place when large quantities aren't required, such as LG struts or HTCS (Hydraulic Torque Compensation Systems) on the PW150's on the Q400's.
That fluid looks to be coming from where I would expect the Nitrogen servicing point to be on that gear, never having worked on a 757. Should be plenty more fluid where that's coming from on landing at his destination. Of course that brings up an interesting question I haven't had answered yet, what happens when a plane lands on one or more "flat" struts? Especially a plane of that size. I would assume it would make for a somewhat rough landing. Anyone know?

RE: B-757 Red Landing Gear Fluid

Posted: Mon May 31, 2004 3:28 pm
by dl757md
Linemechqx

Great stuff on the properties and uses of 5606 and Skydrol. Ever tried mineral oil from a drug store to relieve the burn when you get it in your eyes. Works great. Eyes are still red as hell but at least you can open it and it doesn't hurt anymore. Make sure you use an unopened bottle though, mineral oil makes a great pitri dish and can give you a bad eye infection.

On a 57 you service the nitrogen on top of the strut. The oil recharging valve is on the inboard side of the strut about where you see the fluid stream coming from in the pic.

As for landing with a flat strut on a 57, I don't know first hand but pilots have told me it's very uncomfortable. It can really tear up the inside of the strut as well.

Dl757md

RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 12:10 am
by chdmcmanus
Are most operators still using Mil-H-5606 or have they switched to Mil-H-83282?

ChD

RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 12:39 am
by MrFord
That's a great discussion  Smile

But, as I can see, there is no fluid loss here.
This is only the red roof of the white building that's showing blurred because of the jet blast hehe.

RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 2:13 am
by 411A
Skydrol will indeed support combustion under the right conditions, ie: very fine high pressure misting combined with a high enough heat source.
Extensive tests conducted after the SaudiArabian Lockheed TriStar accident (RUH) in 1980 proved this quite conclusively.

RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 3:15 am
by MD11Engineer
Actually our 757 AMM says to use Mil-H-5606 mixed with a stuff called Lubricol for filling the struts, Lubricol is some oil containing graphite / molybdenium disuphide for better lubrication. As an alternative you can use Royco SSF (Shock Strut Fluid), which contains these lubricants already premixed and is black in colour.

Jan

RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 9:51 am
by dl757md
Mr Ford

Keen eyes. I think you are right. Does anybody have any pics of this area that show the building undistorted?

Dl757md

RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 9:59 am
by greasespot
We no longer use 5606......We now use Royco SSF since we switched to that we have not had weeping oleos on our gavel A/C in a while. I was told that this stuff has something that causes the strut o-rings to swell slightly and seal better. It is a clear to yellowish fluid. I wish I could remember the mil spec.

GS

RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 1:31 pm
by MrFord
DL757MD,

I foud that one, check out at the upper left corner :


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Photo © Dean Barnes - AirTeamImages


RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 2:25 pm
by dl757md
MrFord

Great detective work! I sure was fooled.

Thanks
Dl757md

RE: B-757 Red Landing Gear Fluid

Posted: Tue Jun 01, 2004 3:04 pm
by T prop
This brings up another question. The gear is a certain length and N2 pressure keeps it extended when the gear is off the ground. The gear well is designed so the extended gear fits into the well. On a large aircraft such as the 757, would a strut losing its charge completely possibly allow the gear to compress itself, or change position in the well after it's retracted? On Dash 8 nose gear at least, this could be a problem. I know of at least one incident where a nose gear hung up in the well because of this. I've never heard of this happening on a large aircraft.

T prop.

RE: B-757 Red Landing Gear Fluid

Posted: Wed Jun 02, 2004 1:45 am
by 747Teach
Goboeing: Some of the very first 747's did indeed have Skydrol in their struts. This was because the struts were connected to the ship's No. 1 and 4 hydraulic systems through a load leveling system. The load leveling system was designed to pump the struts up and down in order to keep the aircraft level laterally while moving on uneven taxi ways. It was an option, and few if any aircraft were equipped with the system much after the 20th or so airframe, as taxi ways were rapidly improved, and the system just wasn't needed. I worked on some of these aircraft at TWA, and have in fact put 5606 or Skydrol into the struts, depending on the strut. TWA had removed the load leveling system, but continued to use the seals compatible with Skydrol in those struts that were originally manufactured for them. We also operated some later model 747's that had only 5606 struts. As you can imagine, it was very important to pay attention to the maintenance manual and placards to insure the struts were serviced with the correct fluid. Regards,

RE: B-757 Red Landing Gear Fluid

Posted: Wed Jun 02, 2004 9:39 am
by Jetfixer75
WN has switched over from 5606 to CastrolAero 40, which has Lubrizol already in it. No need for mixing anymore, although 5606 is still an acceptable substitute.

RE: B-757 Red Landing Gear Fluid

Posted: Sun Jun 06, 2004 8:14 am
by NZ1
Ha ha, I was fooled too, then I thought, you wouldn't even see a 5606 leak from the diatance the photo was taken would you? The schrader valve isn't exactly huge in diameter, and at best would be a quarter inch steam if that.

By the way, NZ use Royco (black fluid) in their struts. Easier to use the premixed stuff.

Regards
NZ1

RE: B-757 Red Landing Gear Fluid

Posted: Mon Jun 07, 2004 2:16 am
by MD11Engineer
The Schrader valve has exactly the same diameter as a normal car tire valve (I use those yellow caps on my car).

Jan

RE: B-757 Red Landing Gear Fluid

Posted: Mon Jun 07, 2004 4:23 pm
by SkydrolBoy
Dl757md,

We use Olive Oil at my work and seems to do a good job after hydraulic fluid in your eyes, but I'm sure mineral oil does the same job. We've never had a problem with anyone getting an eye infection after using it, maybe you should give it a try.

Skydrolboy