Aircraft Hydraulic System Maintenance

[toolguy]

I am putting together a list of maintenance tips on maintaining aircraft hydraulic systems for a magazine article and would like to hear about what works and what does not. For example: when performing flight control checks on the ground, verify flight control inputs with hand signals to the cockpt and verify each control is moving in correct response to the input. Never run your hand along high pressure hydraulic lines checking for pinhole leaks, the high pressure can cut through the skin before you feel the pain. Or if you would like to share how you or your fellow engineers/ technicians have averted a problem due to a thorough ground check. My thoughts are that complacency is easy to set in with hydraulic actuators being very reliable and we should not let our guard down. All responses will be kept confidential unless otherwise agreed. Thanks for your help!

[fescalised portion]

From my own experience, you wouldn't need to get near a pinhole leak in a pressurised hydraulic line with your hand before you discovered where it was coming from. There would be a choking/blinding mist in the immediate vicinity, that, unless you were wearing the appropriete clothing/equipment, would for sure, stop you from getting anywhere near it until the pressure was dissipated.

Hydraulic fluid, typically manufactured by Monsato and called Skydrol and is a purple coloured synthetic phosphate/esther(sp.) based fluid(used on large transport type A/C). Is particularly unforgiving when it enters you eyes. It is extremely painful and has a burning sensation that can last for what seems like an age. It can be neutralised with a saline eye-wash bottle or if that is not available then milk will also work.

Basically, you have to be extremely safety-conscious when you are working with this fluid, even just getting it on your hands can bite you in the harris if you are not careful, a small rub of the eye will give you at least 10 minutes of pain! Eye protection is a must, and gloves are also recommended.....Although it will destroy/distort most latex/rubber types within a short while which really hinders your work.

Just my 2 cents worth.....

[Lost_luggage34]

I would certainly echo the comments re. Skydrol and eyes as previously mentioned.

[Krystal n chips]

Toolguy------just curious here as to whom your target audience is for the magazine please ? Whilst I am all in favour of education and expanding skills and safety issues, most, if not all of the examples you have offered surely relate to basic training for engineers do they not ? Thus they should already be familiar with the maintenance procedures prior to encountering them in the course of their work.

Please be aware that I am not being pedantic here--just curious as I said.

Best of luck in your endeavours though

[toolguy]

Krystal n chips,

I try to focus my writing to two different skill levels: the senior engineer/technician who may be in a position to mentor the newly trained, and the newly trained looking for guidance and advice. There is no substitute for experience, and unfortunately not all with experience are willing to share. Many senior technicians have learned lessons the hard way and feel that the next generation should learn that way too, I am trying to help collect and share helpful information to those who truly want to help teach and learn.

[WJman]

I could add a few cold weather points from here in the North.
Overservicing can be an issue here. If an a/c spends the night at the gate in -30 the volume drops a bit. We have had some people service the system to full in the morning, Once the a/c and fluid is warm the expansion makes for an overserviced system. On the 737NG's we had instances of the overserviced system leaking and causing fumes in the air con system.
I would also add making sure the system is properly depresessurized before working on it. Both that the pumps are off and that head pressure is removed. I have seen many newbies think a system is depressurized when only the pumps are off.
Maybe a little point on lubricating "O" rings with a little fluid before installation in a hydraulic system could help a new guy out.
The possibility of cross contamination when servicing a/c from the same hydraulic container. I don't know about you guy's but here many 727 operator's supply 5 gallon buckets to service the system and these are used on all the a/c in the fleet. It could have contamination implications.
Hope some of this helps, good luck.

[eng123]

Wise words indeed ASFKAP.

[IFixPlanes]

When you have changed parts in the hydraulic system it is sometimes difficult to clean the fittings so accurately that the leak check is without doubt. Use denatured alcohol (Spirit) to clean the area. Spill it over the suspected parts and wait until it is evaporated.
Leak checks are much easier now.

[g4phil]

Here is the link to the Skydrol Safety Information Sheet:

http://domino.solutia.com/solutia/sm...56ab0007035dd/$FILE/English.pdf