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MIL-PRF-87257 Hydraulic Fluid, Fire Resistant; Low Temperature, Synthetic Hydrocarbon Base, Aircraft And MissileThis specification describes the characteristics and provides the requirements for a synthetic hydrocarbon base hydraulic fluid for use in the -54??C to +200??C temperature range in aircraft and missile hydraulic systems. This hydraulic fluid is identified by NATO Code No. H-538 \(see 6.5\).

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MIL-PRF-87257B

TABLE III. Conformance tests.

Test Method

Inspection

Test Limit

FED-STD-

ASTM

791

Acid number, mg KOH/g

0.20 max

D 664

API Gravity

See table I

D 287

Color of finished fluid

See table I

D 1500

Evaporation loss (6.5 hours @135�C), weight percent

20 max

D 972

Flash point, �C

160 min

D 92

Foaming characteristics @ 24�C

See table I

D 892

Foaming tendency, ml

65 max

(volume at end of 5-minute blowing period)

Complete

Foam stability, ml

collapse

(volume at end of 10-minute settling period)

D 4172

Four-ball, use test condition A, scar diameter, mm

1 kg load

0.21 max

10 kg load

0.30 max

40kg load

0.65 max

3458

Low temperature stability, 72 hours @ -54�C �1�C

See table I

Particulate contamination

3012

See table II

Particle count

1.0 max

D4898

Gravimetric analysis, mg/100 ml

Pour point, �C

-60 min

D 97 or

D 5949

Viscosity, mm2/sec

D 445

6.7 min

@ 40�C

2.0 min

@ 100�C

550 max

@ -40�C

Viscosity stability @ -54�C mm2/sec

D 2532

2500 max

3 hours

100 max

Water content, parts per million

D 6304