Aircraft brake fluid?

[Dutch]

Just throwing it out there.
what is the difference between automotive type one transmission fluid and aircraft brake fluid? The brake fluid is kind of a pain to get & seems to to look the same to me. I'm sure there is a difference. Could someone clue me in. Dutch

[Tom Waid]

I believe This (http://www.aircraftspruce.com/catalog/lgpages/hydfluid5606qt.php?clickkey=2364154) is what you need.



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[Av8r_Sed]

Dutch, see this previous string: http://www.teamkitfox.com/Forums/showthread.php?t=4341

Answer: Some use ATF, most prefer to stick with aviation grade 5606H. Either should be compatible with synthetic rubber seals.

[n85ae]

You could probably put Marvel Mystery oil in there, and it would work fine
(plus smell good) ... I don't think these brake systems are that picky to be
honest, as long as the seals don't melt ...

Jeff

[cgruby]

Unless you're a chemical engineer, I wouldn't want to guess what's compatible with the seals in your brake system. Use 5606 as it's called for and you won't have any problems.

As much as I've been using lately, I just bought a gallon from Aircraft Spruce and it should last me a lifetime.

Cheers,

[Dutch]

Thank's for all the replies. The reason I brought it up, is that I suspected it is like a lot of other things, In that it is the same cheap beer in an other bottle. I fear that when the word aircraft appears anywhere on the label,it usually costs 3 times as much.Dutch

[PapuaPilot]

There are definitely areas we cans save $ on building our planes, but this wouldn't be one that I would choose. Brakes are one of the things I want to work properly with out any doubts. You don't want you brakes to fail at an inopportune moment, especially if the third wheel happens to be at the back of your plane.

Aircraft Spruce has a quart of Philips brand 5606 for less than $7. That should be enough to do your entire brake system. It's not worth the $4 you MIGHT save here.

[Paul Z]

I concur Phil, especially with the third wheel is where it belongs. You could have some serious :eek: aaaw cr@@ moments!

[jiott]

Just FYI, the 5606 is different than ATF fluid: The 5606 is a high quality mineral based hydraulic fluid. ATF is also a mineral based fluid with different additives for automatic transmissions, such as friction modifiers for the clutches, but some times is also used as a hydraulic fluid. It is just not optimized for hydraulic use as the 5606 is.

[cgruby]

A little late on the reply, but I was just looking through the MATCO specs and they indeed do authorize DOT 5 brake fluid. All others are not usable due to incompatibility with the seals.

[PapuaPilot]

I haven't heard of DOT-5 so I did a quick search for it online. NAPA Auto doesn't show it. Then I checked Amazon and found it. DOT-5 is a synthetic brake fluid and it looks like the price would be around $12 for 12 oz. That is 5x more expensive than 5606 from Aircraft Spruce.

[Paul Z]

I use DOT 5 on my Triumph TR6, it is tough on paint.

[jtpitkin06]

The MSDS for 5606H lists it as

Distillates (petroleum), hydrotreated light naphthenic

Whatever that is it sounds nasty.

The MSDS for ATF lists it as

highly refined mineral oil

I'd probably wash my hands in ATF without worrying.

DOT-3 is a mixture of Glycol and Glycol Ethers. Not alcohol. Don't breathe the fumes unless you want to go to sleep, permanently.

DOT-5 is Polydimethylsiloxane... Huh???? Some art of silicone. Unpronounceable but it doesn't kill rats.

As for substituting one fluid for another by definition we are experimental aviators. But that's not the real issue here. Neither is cost.

The real issue is availability. So you fly into a small GA airport and your brake goes flat due to a slow leak and lack of fluid. You ask around and most line boys will give you a blank stare when you ask for "MIL SPEC 5606H"

Last I checked there were only two outlets for Aircraft Spruce and they are not open on Sundays.

Scour your airport after 6 PM on a weekend and see if you can find 5606, and really, I don't know of anyone that carries a spare pint of hydraulic fluid in their airplane.

But a trip to the local Wal-Mart will be successful in a search for "brake fluid". DOT 3 is everywhere. DOT 5 is a bit hard to find. My local Autozone and Oreilly's do not carry it, but the New Holland tractor dealer does.

Both DOT-3 and -5 have some nasty habits of eating some seals and paint. ATF is easy on paint and seals but I have no clue as to how it resists the high temps in brake pucks. My Case 480 backhoe uses general purpose hydraulic oil for the brakes and a placard warns against using DOT -3. go figure...

I think the simple test is to put some chosen fluid into a jar with some old brake seals and set it on the shelf for a month. What the hey... You may find that Wesson oil is the answer.

John

[cgruby]

Dot 5 is used in Harley Davidson motorcycles, so you should be able to find it there. "MIL SPEC 5606H" is pretty much the standard hydraulic fluid used in a lot of airplanes, so I would think it would be plentiful around any maintenance facility.

[jiott]

Yes 5606 is not that hard to find. I find it in most all aircraft maintenance and supply dealers in the Portland area. It is also available in many tractor supply houses since it is often used in mobile equipment hydraulic systems, especially in colder climates (it is lower viscosity than most common hydraulic fluids). It is almost exclusively used in military and civilian aircraft hydraulic systems where a mineral oil is called for rather than a synthetic. It is known as military "red oil". Very high quality and not much different than ATF fluid in toxicity. I am a retired hydraulic engineer and worked with the stuff for many years. It is NOT compatible with brake system seals designed for DOT 3 fluid, not sure about DOT 5, but would carefully check first. The 5606 is not hard on paint like most brake fluids. It is flammable at hi temps which is why it is not used in cars where brakes are generally used harder and hotter than most airplanes. I would stick with what the aircraft/brake manufacturer specifies.

[jrevens]

The standard mineral based fluid, 5606H, is usually readily available at any airport with any kind of maintenance facilities, and can usually be found even at small airports. Many of my friends have a quart of the stuff in their hangars. It's just very common, and that's one of the reasons to probably use it instead of one of the automotive fluids, even if your o-rings & seals are compatible with them. One potential improved substitute for some of us is Royco 782 (Mil-PRF-83282). It has a 440 deg. F. flashpoint (vs. 220 for mineral base hydraulic oil). It's readily available from Aircraft Spruce & others. It pretty much eliminates the risk of brake fires. This oil is 100% compatible and mixable with standard mineral based oil and our standard brake seals; however, any more than 5% mineral oil mixed in will compromise the fire resistant feature. You can use Viton seals in the brake calipers instead of the commonly used Buna-N also - they remain intact to very high temperatures.

Years ago I had a friend whose brake on one wheel jammed and was dragging a little (he for some reason ignored it), and in taxiing just a couple of hundred yards had a brake fire that traveled up the brake line and gear leg, and caused major damage to the airplane before he could put it out.

[jtpitkin06]

Most of the places I fly to for a $100 hamburger in east Texas do not have maintenance. Even here at KGVT with a big defense contractor (L3)on the airport there is no GA maintenance. The city owned terminal operated by L3 sells fuel only. That means no fluids, no oils, no oxygen, nuttin' honey. Run what you you brung. If you break something, you're screwed. You have to bring in your own A&P and pay travel time.

The reason I have a supply of 5606 is I needed some and no one on the airport had it. After calling other airports that had maintenance and striking out I ordered some from ACS. The Cessna Service Center at Dallas Addison did have some if I brought my plane in for servicing, but they wouldn't sell me a pint to top off my reservoir as the owner operator.

While 5606 may be common in some parts of the country, around these parts it's like trying to find a good anchovy milk shake.

That's why good ol' tractor fluid is looking better all the time.

Again, it's all about availability.

John in Greenvilleburgtown aerofield.

[TahoeTim]

This sums it up for me.

From the Grove website:

Hydraulic Fluids

All Grove brake systems incorporate Buna-N (Nitrile) O-Ring seals that are compatible with MIL-H-5606 hydraulic fluid which has been the aircraft industry standard for many years.

MIL-H-5606 hydraulic is a mineral-oil based fluid with excellent operating properties over a temperature range of -65°F to 274°F. A major deficiency of MIL-H-5606 is its high degree of flammability. Because of this, the commercial aircraft industry has developed and uses hydraulic systems based on phosphate-ester based hydraulic fluids. However, these fluids ARE NOT compatible with MIL-H-5606 or its systems.

The military led the way in developing a more flame resistant hydraulic fluid that is compatible and miscible with MIL-H-5606. As a result, a synthetic-hydrocarbon based fluid MIL-H-83282 (now MIL-PRF-83282) was developed which is superior to MIL-H-5606 (now MIL-PRF-5606) in fire resistant properties, but lacks good qualities in low temperature viscosity.

More recently MIL-PRF 87257 was introduced in order to address the concerns over the low temperature viscosity weakness of MIL-PRF-83282.

Bottom Line: MIL-H-5606 has been replaced with MIL-PRF-83282 and MIL-PRF-87257. Each of these fluids, and their associated systems, are compatible and miscible with each other. You can mix any combination and/or amount of these fluids together without any ill effects.

If, and/or when, you change over from MIL-H-5606 you can either:
1. drain your hydraulic system and refill with MIL-PRF-83282 or MIL-PRF-87257, or
2. merely top off the reservoir with MIL-PRF-83282 or MIL-PRF-87257 as needed.
Both methods have been used with great success with no reported problems.

[jrevens]

This sums it up for me.

From the Grove website:

Hydraulic Fluids


...The military led the way in developing a more flame resistant hydraulic fluid that is compatible and miscible with MIL-H-5606. As a result, a synthetic-hydrocarbon based fluid MIL-H-83282 (now MIL-PRF-83282) was developed which is superior to MIL-H-5606 (now MIL-PRF-5606) in fire resistant properties, but lacks good qualities in low temperature viscosity.

More recently MIL-PRF 87257 was introduced in order to address the concerns over the low temperature viscosity weakness of MIL-PRF-83282.

Bottom Line: MIL-H-5606 has been replaced with MIL-PRF-83282 and MIL-PRF-87257. Each of these fluids, and their associated systems, are compatible and miscible with each other. You can mix any combination and/or amount of these fluids together without any ill effects.

If, and/or when, you change over from MIL-H-5606 you can either:
1. drain your hydraulic system and refill with MIL-PRF-83282 or MIL-PRF-87257, or
2. merely top off the reservoir with MIL-PRF-83282 or MIL-PRF-87257 as needed.
Both methods have been used with great success with no reported problems.

Thanks Tim... I didn't know about the low temperature issue. I've never had any discernible issues with it (we do occasionally get a little cold around here), but I will get a quart of the new stuff for the Kitfox.

John P... If you need some brake fluid, come on up to Colorado. It's very available here. ;)