Aircraft Hydraulic Fluids

[gconaty]

Hi

Before i get shot off the moderators i apologise for posting 2 threads next to each other.

My question is about aircraft hydraulic fluids. What types of hydraulic fluids ar ein use today? I have 3 main types in my notes those being Castor Based, Mineral Based and Synthetic Ester Based fluid. Do aircraft still use petroleum based fluid? I thought they were taken out years ago due to their high flamability but am not too sure. Also, another quick question, does anyone knwo what type of hydraulic fluid is used in light aircraft and what different properties light aircraft hydraulic systems require compared to the properties required by larger commercial aircrat.

Thank you for your time

[Kanga767]

Most light aircraft run MIL-H-5606, mineral oil. only 2000 psi.

Metros run MIL-H-83282 at 2000 psi, i think there is some fire retardant properties. there's probably a few more on this one I imagine.

of course then we go to Skydrol.... Smallest airframes I know are Dash-8s and some bizjets. Other aircraft in their category are happy to use 5606.

K

[gconaty]

Thank you. Are there any websites which explain these types of hydraulic fluid? I am writing an assignemnt on hydraulif fluids but have only got the properties of the three types of fluids i mentioned and jnot descriptions of where they are used etc...

[Pimp Daddy]

Skydrol tastes nicer than 5606

[gas path]

Skydrol also stings more when you get it in your eyes than 5606

[Nopax,thanx]

Basically two common types of fluid. Petroleum based (MIL-H-5606) which is red in colour (dyed for identification) Explosive in a mist, which is how a lot of hyd leaks manifest themselves. So, in the fifties, Phosphate Ester (Skydrol) was introduced for commercial aircraft. The military don't seem bothered by possible explosions..... so Skydrol's not commonly used by them.

One of the best sources of info on hydraulics in general is the US Navy - they have some very clear and concise manuals.

This is quite useful;

http://www.tpub.com/content/aviation.../14018_178.htm

[gconaty]

Ok thank you for your help

As i stated before i was given 3 main types for the assignment those being:

1. Caster Based (not sure of the name)
2. Minerla Based (not sure of the name)
3. Synthetic Ester Based (Skydrol)

Are these the mian three types used?

thank you

[Nopax,thanx]

The castor based fluid is not in common use - it was used in stuff like light aircraft brakes many years ago. I think it was dyed blue, although I could be wrong there; it may be alcohol-based fluids that are blue dyed.

Technical study books still refer to it because they've never got around to changing the subject matter. It's there more as a historical reference than anything else.

So basically, you've got just two types.

If you want a good training and reference source, I found the ATP series of books very helpful.

http://www.atp.com/

[allthatglitters]

"Skydrol also stings more when you get it in your eyes than 5606"
I have been reliably informed it stings even more when you get Skydrol or Exxon Hyjet on your wedding tackle!

Try http://www.skydrol.com/pages/default.asp

Why not try using a search engine, like Google with the spec numbers eg. MIL-H-5606, this one turned up an American Gov docs on aviation type hyd fluids.

[Nopax,thanx]

I have been reliably informed it stings even more when you get Skydrol or Exxon Hyjet on your wedding tackle!

Indeed it does! Over many years of working on with hydraulic systems, I was fortunate enough to never get any sprayed on me...but a Skydrol mist is horrible, gets in your throat and eyes and you cannot do anything but get out of the way.

If you wash NEARLY all of the Skydrol off your hands and then go to the Men's room, the residual fluid on your hands gives a warm glow to your bits.....

.....quite pleasant really!

[daruka]

Castor Oil

Keep a bottle of Castor oil in your tool box ,,,,,instant relief for Skydrol......

Milk also works but spoils quickly in toolbox...:-))

[BigJETS]

I believe Skydrol also burns when atomized--and gives off phosgene.

[Orville]

I recall seeing a training video around 30 years ago giving a sales pitch on Skydrol and its properties. This was true propaganda put out by Monsato ( manufacturers) they showed an engineer drop his cigerette into a tray of oil, and after retrieving it continuing to smoke it. Another clip showed an engineer( stunt man) dropping a contact lense into a tray of oil, he picked it up and put it straight back into his eye, never flinched a muscle.

I wonder where these engineers(?) are now, possibly moved on to that great hangar in the sky.

Of interest to your studies is that any oil has the potential for fire, when any of these oils are released through a pin hole in a hyd. system of 3000psi an ignition source is all that is needed. My belief is that the Airbus A380 will incorporate systems as high as 4000psi.

More details on these oils can be source if you do a search through 'MSDS' specs and safety precautions.

[KwikPhix]

Most light aircraft run MIL-H-5606, mineral oil. only 2000 psi.

The commercial a/c type that i work on uses this oil in the hyd systems at a normal working pressure of approx 3,000 psi. (Aeroshell Fluid 41 ). I have also worked on a Mil A/C that uses this oil at 287 bar ( approx 4,000 psi ), It was called OM15 on the Mil A/C.

HTH.