MIL-H-5605 vs MIL-PRF-83282 1

[Ethan Ng]

Hi,

As reported in various literature and from your conversion above, both MIL-STD Hydraulic are compatible and miscible, and that 83282 is designed to replace 5606. I'm looking at replacing the MIL-H-5606D on the Helicopter type that i work on, with MIL-PRF-83282, because somehow, that Helicopter uses both types of hydraulic. Weird..anyway, to effect the change, i can either drain the existing MIL-H-5606 and flush the system to purge out all existing MIL-H-5606, or i can just top up the existing MIL-H-5605 with MIL-PRF-83282. For the latter, i read that when you mix the two, there is a reduction of the fire-resistant properties of the now-mixed hydraulic fluid. Question is, is there a unit of measure of fire-resistant property? Is fire-resistant property, the same as flammability?

Thanks in advance for your answers!

Regards

Ethan

 

[verymadmac]

As I recall one of the principle reasons for the development of MIL-PRF-83282 was because they needed a fluid that unlike 5606 wasn't flammable. Changing the fluid from 5606 to 83282 is a modification that will require approval.

If the helicopter uses both, there is a specific reason and until that reason is determined reliably one shouldn't progress any farther (this is one of those apparently really simple modifications that's going to suck up at least a month of an engineers life).

 

[WKTaylor]

Ethan... verymadmac has provided very valuable precautionary advice. Proceed with great CAUTION!

This 'modification' could entail a significant flight test program also.

Low and high temp properties of oils can vary a lot.

Most applicable seal rubbers are highly compatible with hydrocarbon base and synthetic hydrocarbon base oils.

My acft replaced all MIL-PRF-5606 hydraulic oil with MIL-PRF-87257 [lower service temp capable oil] on an attrition basis starting a long time ago. This was done with a lot of prior lab analysis, formal flight test [drain 100% OR mix-in with attrition] and in-service testing with a few designated acft.

NOTE/odd info.

One of our FMS operators did NOT transition to 87257 and has continued to use 5606... for their 'own confidential reasons'.

Oil that has been in-service many years may and has accumulated wear and moisture contaminates... in a 'small system'... may easily justify 100% drain/replace.



Regards, Wil Taylor

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