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Black Tar Substance Over Inside Of Cowl  
User currently offlineCALTECH From Poland, joined May 2007, 2223 posts, RR: 26
Posted (1 year 2 months 17 hours ago) and read 3540 times:

Has a hydraulic pump failure recently, and there was this black tar like substance dripping all over the inside of the cowl. It looked just like tar. Seemed as though it might have been Skydrol and engine oil mixing a bit under heat and pressure, it did smell burnt, and then created this tar. Has anyone else run into this ? Never remember seeing this before.


UNITED We Stand
15 replies: All unread, jump to last
 
User currently offlinefr8mech From United States of America, joined Sep 2005, 5400 posts, RR: 14
Reply 1, posted (1 year 2 months 17 hours ago) and read 3513 times:

The top breaks off in chunks and the under layer is gooey? It's burned Skydrol (or equivalent).

It's hard to clean. There is a commercially available cleaner, but the name escapes me.

As I recall, we have replaced engines because of this contamination. Apparently, the residue can cause damage to the engine case after repeated exposure to high heat.



When seconds count...the police are minutes away.
User currently offlineatlamt From United States of America, joined Sep 2001, 240 posts, RR: 3
Reply 2, posted (1 year 2 months 7 hours ago) and read 3349 times:

I think the cleaner you are thinking of is call skykleen.


Fwd to MCO and Placard
User currently offlinefr8mech From United States of America, joined Sep 2005, 5400 posts, RR: 14
Reply 3, posted (1 year 1 month 4 weeks 1 day 21 hours ago) and read 3189 times:

Quoting atlamt (Reply 2):
I think the cleaner you are thinking of is call skykleen.

That's the stuff.



When seconds count...the police are minutes away.
User currently offlineCALTECH From Poland, joined May 2007, 2223 posts, RR: 26
Reply 4, posted (1 year 1 month 4 weeks 1 day 18 hours ago) and read 3124 times:

All of the substance was very runny. And a lot of it. Should have taken a pic. Never saw this amount before. Ran a 737 B system down, hyd pump failed. No crust, all of it was like hot tar. Very plastic.


UNITED We Stand
User currently offlinefr8mech From United States of America, joined Sep 2005, 5400 posts, RR: 14
Reply 5, posted (1 year 1 month 4 weeks 1 day 18 hours ago) and read 3118 times:

Quoting CALTECH (Reply 4):
All of the substance was very runny. And a lot of it. Should have taken a pic. Never saw this amount before. Ran a 737 B system down, hyd pump failed. No crust, all of it was like hot tar. Very plastic.

Yeah, it's Skydrol that has been exposed to very high heat. The crust tends to form in the cooler areas. We had a B747 come in one night that had the stuff dripping out the bottom of the cowl. The leak was at the pylon disconnect. The Skydrol had left a trail all the way down the case and had chewed up the ablative coating on lower parts of the T/R halves. What a mess.



When seconds count...the police are minutes away.
User currently offlineCALTECH From Poland, joined May 2007, 2223 posts, RR: 26
Reply 6, posted (1 year 1 month 4 weeks 1 day 17 hours ago) and read 3109 times:

Never saw burnt phosphate ester in that amount before.


UNITED We Stand
User currently offlinefr8mech From United States of America, joined Sep 2005, 5400 posts, RR: 14
Reply 7, posted (1 year 1 month 4 weeks 1 day 17 hours ago) and read 3087 times:

Quoting CALTECH (Reply 6):
Never saw burnt phosphate ester in that amount before.



I've seen a lot of hydraulic leaks on engines, in the past. But, the tar-like appearance is fairly recent, so far as I can recall. Say, 5 years or so.

I wonder if there has been a formulation change...



When seconds count...the police are minutes away.
User currently offlineCALTECH From Poland, joined May 2007, 2223 posts, RR: 26
Reply 8, posted (1 year 1 month 3 weeks 6 days 3 hours ago) and read 2729 times:

Quoting fr8mech (Reply 7):
wonder if there has been a formulation change...
http://skydrol.com/pages/aircraft.asp

Now starting to notice the black substance all the aircraft. From the slats seems to be pretty bad. Noticing it on the engine in a few places.



UNITED We Stand
User currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 9, posted (1 year 1 month 3 weeks 4 days 21 hours ago) and read 2581 times:

I presume by your wordings it was an EDP.....was the pumps not switched off when the LOP warnings appeared.


Think of the brighter side!
User currently offlineCALTECH From Poland, joined May 2007, 2223 posts, RR: 26
Reply 10, posted (1 year 1 month 3 weeks 3 days 13 hours ago) and read 2454 times:

Quoting CALTECH (Reply 8):
Now starting to notice the black substance all the aircraft. From the slats seems to be pretty bad. Noticing it on the engine in a few places.

That should read, starting to see the black substance on many aircraft in different areas on the airplanes.

Quoting HAWK21M (Reply 9):
I presume by your wordings it was an EDP.....was the pumps not switched off when the LOP warnings appeared.

Yes, it was a EDP and it failed, and yes it was switched off before the reservoir leaked down to zero. Then they ran the slats down for landing which lost the rest of the fluid.



UNITED We Stand
User currently offlinesancho99504 From United States of America, joined Dec 2005, 570 posts, RR: 0
Reply 11, posted (1 year 1 month 3 weeks 3 days 3 hours ago) and read 2377 times:

Quoting CALTECH (Reply 8):

When I left DL in 2008, we received all but 737-700 and 777-200's at my station and I notice the tar looking substance streaking down the belly just behind the MLG doors on the 757 and 767, and on the elevators, rudders, flaps and ailerons, but never on the slats. On the CRJ-200 we received daily, it only had it on the rudder hinges.....Is Skydrol bad for the fuselage and wing skin like it is for the for the engine case?



kill 'em all and let God sort 'em out-USMC
User currently offlineCALTECH From Poland, joined May 2007, 2223 posts, RR: 26
Reply 12, posted (1 year 1 month 3 weeks 1 day 2 hours ago) and read 2190 times:

Quoting sancho99504 (Reply 11):
When I left DL in 2008, we received all but 737-700 and 777-200's at my station and I notice the tar looking substance streaking down the belly just behind the MLG doors on the 757 and 767, and on the elevators, rudders, flaps and ailerons, but never on the slats

Top of the wing behind the slats,...


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Quoting sancho99504 (Reply 11):
Is Skydrol bad for the fuselage and wing skin like it is for the for the engine case?

Not really for the metal of the engine case, as said above, but the ablative coating. Now on some of the bigger engines, such as 757 Rolls-Royce RB-211s, you do not want anything, not even water, to get on the Fan Case kevlar wraps.But it doesn't hurt the metal.

Do not believe Skydrol hurts aluminum at all. Don't get it on your tires though.

Think this low density hydraulic fluid is dirtier than the old skydrol. Old stuff seemed to strip the paint, this newer composition just seems to leave a black sticky residue.



UNITED We Stand
User currently offlinebikerthai From United States of America, joined Apr 2010, 2106 posts, RR: 4
Reply 13, posted (1 year 1 month 3 weeks 19 hours ago) and read 2155 times:

So are you all referring to skydrol in the generic term? or what I consider Skydol, the original stuff?

I thought that the original Skydrol, the real bad stuff, is not used any more except in the Military.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineCALTECH From Poland, joined May 2007, 2223 posts, RR: 26
Reply 14, posted (1 year 1 month 3 weeks 18 hours ago) and read 2151 times:

It still is just as nasty as anything that has come before. In this incident where it was all over the engine cowl, to hear a 50+ year old Tech scream like a kid tells the story. Burns the eyes just as good as the old Skydrol did.


UNITED We Stand
User currently offlineyeelep From United States of America, joined Apr 2011, 654 posts, RR: 0
Reply 15, posted (1 year 1 month 3 weeks 17 hours ago) and read 2141 times:

CALTECH, what fluid are you guys using? We've being using Hy-jet IV-A plus for eons and have always had leakage issues, especially the early build -700 and -900's. Its a very well known issue on the 737NG, check out 737-SL-29-095-A for a decent overview.

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