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-   -   Not necessarily life threatening but could ruin your day (https://vansairforce.net/community/showthread.php?t=4737)

qdu000 12-26-2005 07:46 AM

Not necessarily life threatening but could ruin your day
 
This bulletin is for Cirrus Aircraft, but it also applies to pilots/owners of Van's aircraft.
It happened to me, I was going to a flyin at Abilene Texas. The flyin activities were at the NW end of the airport, the control tower had me land on 17L, abut a half a mile from where I wanted to go. It was my first X/C after my 40hrs of flight testing. It was also the longest runway.
Taxing back I inadverently rode the brakes, about 100yards from the activities the left brake failed. I managed to get parked on the the grass. Upon inspection the wheel pant was very hot, and scoarched a little. After it cooled I tried to add fluid but the "O" ring would not contain the fluid. Before flying home I had to remove the wheel pant, brake calaper, and replace the "O" ring.
Fortunately there was no fire.

CIRRUS TO ISSUE SB ON BRAKE OVERHEATING, FIRES
Cirrus Design plans to issue a Service Bulletin on all its aircraft in
response to a spate of brake fires (the most recent of which occurred
Dec. 9) that have caused serious damage to at least five aircraft. The
SB will call for the installation of color-changing temperature
sensors on the brake components so that pilots can tell -- during the
preflight -- if the brakes have been previously overheated. Cirrus
spokesman Ian Bentley said overheating can cause failure of an O-ring.
Failure of the O-ring allows flammable brake fluid to leak onto
potentially hot parts. If they're hot enough, the brake fluid ignites
and causes a stubborn fire that can really make a mess of a low-wing
plastic airplane.
http://www.avweb.com/eletter/archive...ll.html#191252

IMPROPER BRAKE USE TO BLAME, SAYS CIRRUS
Bentley said Cirrus has studied the incidents extensively and
determined there are no design or equipment faults at work, and for
Cirrus this leaves only "operator error" as the cause. Unlike many
aircraft pilots may be transitioning from, Cirruses have a free
castering nosewheel and are steered only with differential braking,
plus some positive or negative contribution from the rudder (dependant
on relative wind). Bentley said some pilots may have a tendency to
overuse the brakes to compensate for excessive power settings or may
simply be riding the brakes. Last June, the company e-mailed all its
customers (click here for a pdf version) with an owner service
advisory that warned them not to overtax the brakes, which Cirrus also
says are more than adequate for an airplane with the performance and
weight of a Cirrus.
http://www.avweb.com/eletter/archive...ll.html#191253

COMPANY LOOKS AT PREVENTION FIRST
Bentley said Cirrus is doing everything it can to prevent
brake-related fires. "We do take these things very seriously," he
said. In most cases, he said, the fires have occurred on club or
rental aircraft that see a lot of different pilots (the most recent
incident was an exception). Cirrus believes the heat sensors will be
most beneficial in those cases because they'll give pilots an
indication of whether the brakes have been abused by those before
them. And, although Cirrus says the factory-installed brakes are a
common installation on aircraft of similar size and exceed design
standards, the company will be offering -- as retrofit kits only --
higher-capacity brakes.
http://www.avweb.com/eletter/archive...ll.html#191254

gmcjetpilot 12-26-2005 10:04 AM

Lession learned again again
 
Thanks for the report. It is a good reminder. This happens more often than you think and nothing new or unique to Cirrus. Brake fires do happen to RV's and other planes all the time. Composite gear legs may be worse than steel from a heat and fire stand point but know or 3 RV wheel/brake fires. Many times its pilot technique that causes fires. The other issue is the OLD obsolete fluid we use for brake fluid in our planes, which should be phased out, at least for new planes.

A Gentleman flew around the world in a RV-8. He wrote about his trip in a multi part article/story in recent issues of the RVator. He had a massive brake/wheel fire. I read about a Piper retract (Arrow/Saratoga?) having a tire/brake fire. The Piper pilot taxied with high power, dragging brakes until one main burst into fire. The plane was a complete loss.

Here are pictures a another RV brake fire (from a broken aluminum brake line):
http://www.matronics.com/photoshare/...om.07.02.2005/ (scroll down)


FLUID: Give your self a chance. The old red brake fluid (MIL-H-8606) has been around for over 60 years and no one uses it except the GA community. In fact I understand the GA manufactures are not using it anymore. Airlines, commercial and military all have stopped using MIL-H-8606 long ago, which IS VERY FLAMMABLE. It has a low flash point and burns furiously once started. I don't know why any home-builder would use the stuff except that its easy to get. There are more modern fluids that are much safer. So next condition inspection consider switching to a modern synthetic hydraulic fluid.

This is a snip, para phrase from a thread going at another list.

If you are going to use brake fluid consider using MIL-H-83282, which is much better than the old standard red MIL-H-5606. MIL-H-83282 is synthetic hydrocarbon based. Flash point, fire point, and spontaneous ignition temperature of MIL-H-83282 is far superior and exceeds that of MIL-H-5606. MIL-H-83282 fluid extinguishes itself when the external source of flame or heat is removed. Hydraulic fluid MIL-H-83282 is compatible with all materials used in systems presently using MIL-H-5606. It maybe combined with MIL-H-5606 with the adverse effect of reduction of its fire-resistant properties. (So a flush is recommended when switching fluids but small contamination of -5606 is not critical.) Airlines and military do NOT use -5606, which was developed in the 1930's or 40's. MIL-H-83282 or similar fluids are required in military aircraft and airliners. (In fact a turbo prop commuter airliner was service incorrectly with -5606 and resulted in a hydraulic in-flight fire, fed by -5606 and subsequent loss of aircraft, crew and passengers. The aircraft was only to be service with MIL-H-83282.)

There is no down side to -83282 except that it is only available in a min of gallon size, and common GA suppliers (ACS) do not always carry -83282. However it is not impossible to buy and I am sure most large jet maintenance bases/FBO's have it available and will be happy to sell you a pint or qt. The cost is not much greater and the protection from fire is, so much better there really is no agreement. THE OLD MIL-H-5606 IS TOO FLAMMABLE. If builders start to insist on MIL-H-83282, Van's and other suppliers will start to carry it I am sure.


Braking Technique: They way they teach you at the airlines is if taxi speed it too high, brake to check your speed to a very low taxi speed and release the brakes COMPLETLY. If the taxi speed builds, allow the speed to build with the brakes OFF (completely) and than check speed again, back to a low taxi speed, of course followed by compete releasing of the brakes. (no riding). Repeat as needed. Dragging the brakes continuously is a sure way to heat it up. Add the old flammable -5606 to the hot brakes and you may have an ugly surprise.


George

wingtime 12-26-2005 04:04 PM

Sillycone?
 
What about using a 100% Silicone racing type brake fluid insted of 5606?

osxuser 12-26-2005 10:02 PM

I have to disagree on the fluid, good idea in principal, but lack of general availablity and the correct seals makes it unwise in my view. The vast majority of the time using 5606 is just fine. In my 4 years of working as an A&P, i've never seen a brake fire. Its kinda rare in my view, not something i'd lose sleep over.

Ironflight 12-26-2005 10:16 PM

What's different about the RV's?
 
It's interesting the read differnt web forums and resources for different aircraft types, and find out what the "hot" buttons are.

I'd been a Grumman owner for almost 25 years, and they are steered on the ground exclusively with brakes - yet can I can remember not a single discussion on brake fires!

Now, Valve wobble test on 320 and 360 Lycomings, that is a whole 'nuther ball of wax! I wonder what it is about our RV-mounted Lyc's that's so different that it never gets mentioned ?:rolleyes:

Seriously, I have to wonder what is different about the RV brake system that has lead to several overheats and fires - is it the 5" wheels? Or the closer-cowled wheel pants? I have no idea - would love to hear some ideas!

Paul

az_gila 12-26-2005 11:11 PM

Quote:

Originally Posted by Ironflight
I'd been a Grumman owner for almost 25 years, and they are steered on the ground exclusively with brakes - yet can I can remember not a single discussion on brake fires!
Paul

Paul... as a fellow Grumman owner I remember some discussion. quick search of the Grumman archive found:-
N81307 - AA-5B - destroyed by a brake fire in N.C. in 1997 - use of the canopy cover was not enough to put out the fire.

It can happen to Grummans, but perhaps less often due to bigger brakes/wheels...

gil in Tucson

randylervold 07-13-2006 05:31 PM

MIL-PRF-83282 compatibility
 
Does anyone know if 83282 is fully backward compatible with aircraft brake systems where 5606 is normally specified? The reason I ask is that I just bought a power brake system bleeder from ATS and right in the instructions it says to switch in the pump's internal seals with the supplied EPDM if using an ester-based synthetic fluid, which 83282 is. So, it occured to me that if the bleeder seals weren't compatible what about the brake system seals, both caliper and master cylinder (Cleveland and Matco)?

For those in search of MIL-PRF-83282, it is available from www.aci-lubes.com. It is available in quarts, but only in a case of 24. You can buy a gallon for $18. + shipping though, not bad. Heck, I'll put the whole gallon in my new bleeder and then let my pals use it.

avpro56 07-13-2006 09:04 PM

Quote:

Originally Posted by randylervold
Does anyone know if 83282 is fully backward compatible with aircraft brake systems where 5606 is normally specified? The reason I ask is that I just bought a power brake system bleeder from ATS and right in the instructions it says to switch in the pump's internal seals with the supplied EPDM if using an ester-based synthetic fluid, which 83282 is. So, it occured to me that if the bleeder seals weren't compatible what about the brake system seals, both caliper and master cylinder (Cleveland and Matco)?

For those in search of MIL-PRF-83282, it is available from www.aci-lubes.com. It is available in quarts, but only in a case of 24. You can buy a gallon for $18. + shipping though, not bad. Heck, I'll put the whole gallon in my new bleeder and then let my pals use it.

Randy:

It's no secrect that Mil 5606 is not very good stuff. As it turns out the Cleveland piston seal for the 30-9 caliper is an ordinary MS28775-218 nitrile o-ring. Nitrile's temperature rating is - 65F to +275 F. A caliper seal with a 275F temp limit is below automotive standards, but that's another story. Changing your caliper seals to Viton seals might be a good idea because Cleaveland uses ordinary nitrile seals. If you have Robby Grove brake calipers it would not surprise me if he used the higher temerature Viton seals during their manufacture.

Cleveland specifies that either Mil-H-5606 or Mil-H-83282 as acceptable. Mil-H-83282 was created because the military was tired of setting it's airplanes on fire. Mil-H-5606 is the standard red hydraulic fluid sold by Spruce, Wicks, Chief, etc.

It is a petroleum base, and it has a very low flash point. The Mil-H-83282 is also red, and compatible with 5606 fluid as well as seals created for 5606. However, it is a synthetic, with much higher flash and burn points, and is self-extinguishing when removed from the ignition source.

You can download complete specs for Aeroshell Fluid 41 (Mil-H-5606) and Aeroshell Fluid 31 (Mil-H-83282) at:

http://193.113.209.166/aeroshell/aer...ulicfluids.pdf

See page two where changeover from 5606 to 83282 is discussed, the answer you seek is there. The two fluids are conpletely compatible. 83282 is often referred to as 5 digit fluid, whille 5606 is called 4 digit fluid. (a simple way to avoid lots of numbers for us 50 something year old airplane types) Note the flash points of the two fluids. Aeroshell 41 is 104 C, which is only 219 F. Aeroshell 31 is 237 C, or 458 F.

The simple solution is to simply drain the system and install Mil-H-83238 fluid with no need to change seals. (except if you want better high temp Viton seals as noted above) You're also OK if you have to someday top off the fluid in some out of the way place with 5606 becuase it's all you could find.

Spruce does not sell Mil-H-83238 fluid, but several other distribtors do.

Hope this helps and see you at Oshkosh!

Jon Ross
RV-8 N207RV
A&P IA, EAA Tech Counselor

randylervold 07-13-2006 11:19 PM

Wow, thanks Jon! Know a good source off hand for the Viton o-rings? I've heard good things about them from other builders as well.

No OSH this year for me, next year I'll fly the -3 back. Good luck in the race!

Best,

RV6_flyer 07-14-2006 06:19 AM

Brake fires do happen on RVs.

http://members3.clubphoto.com/_cgi-b...97-2ca0&trans=

Lets see if my photo insert works.

A photo album of what was found after the fire is:photo of RV-8 brake fire


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