5606/?

[Eeubanks]

so curious which 5606, A,B, C lmnop, ???
is there enough difference to warrant one over another?

[DrDave]

Hi:

I just researched all of this. The 5606 is a mineral based fluid. 5606 is a 1940's mineral based fluid that is being replaced by a newer retrocompatible fluid. The new spec is 83282. The best way to go is Shell Fluid 31. this is synthetic based product that is compatible with 5606. It has a much higher flame temperature.

I sent a new sample of fluid 31 for oil analysis with particle count. It certainly meets the spec of "super clean." I also sampled the existing 5606 fluid. The lab found the 5606 fluid that was in the system to be contaminated and the particle count was high. I'm flushing Fluid 31 through the whole system.

Dave

[cessnadriver]

Hello.
My 2 cents about MIL-H-5605. I also research this. Here is what I found. According to a hydraulic fluid expert:
MIL-H-83282 can be mixed with 5606 to improve the flame resistance BUT it can only contain not more 50%. The new hydraulic (83282) CAN NOT be used straight in older aircraft due to incompatibility of the O-rings. The reason I searched this out because I bought about 20 gallons of the new fluid to flush out my Skymaster thinking I could use straight 83282 after flushing. but found out after purchasing the new stuff I COULD NOT!
BILLS

[DrDave]

Originally Posted by cessnadriver

Hello.
My 2 cents about MIL-H-5605. I also research this. Here is what I found. According to a hydraulic fluid expert:
MIL-H-83282 can be mixed with 5606 to improve the flame resistance BUT it can only contain not more 50%. The new hydraulic (83282) CAN NOT be used straight in older aircraft due to incompatibility of the O-rings. The reason I searched this out because I bought about 20 gallons of the new fluid to flush out my Skymaster thinking I could use straight 83282 after flushing. but found out after purchasing the new stuff I COULD NOT!
BILLS

Having read this I went back to the spec sheets on the various fluids. I found nothing describing a partial mix being acceptable and a full-strength changover unacceptable. The specific language from Shell regarding 31 and 41 and other fluids is complete compatibility. I have to question the fluid experts sources of his information. The changover instructions simply say to drain the 5606 and refill with a 83282 fluid such as 31. At this point I don't find the "expert"(s) opinion credible.

[cessnadriver]

Dr. Dave I'm not arguing with you I just stated the facts as I know them. If someone uses straight MIL-H-83282 they will have problems with leaks past the O-rings the stuff is not compatible with old materials used in manufacturing the O-rings. Another example is I was a Hydraulic Repairer in the US Army during the late 1970's and the Army switched all the Chinook helicopters from 5606 to 83282 which by the way took about 100 gallons to flush and refill. Afterwards there were problems with the seal/O-rings leaking.FYI.
BILLS