MIL-PRF-87260B(USAF)
6.5.5 Lot.
Fifteen machine runs of product.
6.6 Classes.
The class distinction noted in the specification is intended to separate the available products by
their ability to dissipate static electricity at low fuel temperatures. Testing has indicated that
below the low temperature fuel limits stated (Class 1 is +10°F and Class 2 is -25°F) the material
may accumulate excessive static charge when impinged by high velocity fuel and as such may
result in discharge and vapor ignition. This in itself is not a safety problem for single point
refueling since the foam suppresses the resulting explosion internally; however, in the case
where over the wing (gravity) type refueling is used, then a potential hazardous situation exists
to refueling personnel and equipment since the fuel vapor can be ignited as it exits the filler
opening. Requirements for interchangeability of products are as follows:
a. Class 2 products are interchangeable (substitutable) for Class 1 materials; however,
only if it is the same grade (example: Grade I for Grade I and Grade II for Grade II).
b. Class 1 products are not interchangeable for Class 2 materials unless it is determined
that the low temperature requirements can be waived or gravity refueling is restricted to
emergency operations.
6.7 Installation guidelines for reticulated foam in aircraft fuel tanks and dry bays.
Guidelines for the proper design, fabrication, and installation of various reticulated foams can be
found in SAE AIR 4170.
6.8 Service life.
The service life of the foam under this military specification begins on the date of foam
manufacture. Service life limitation is a cumulative effect of its storage life exposure and its
exposures in aircraft fuel tanks. Service life for foam baffles are also dependent upon how often
the foam is removed and replaced in an aircraft. Although it is anticipated that foams under this
specification will have a long, useful service life, determination of the practical limit of the
service life by vigilant periodic inspection and testing, is the responsibility of each aircraft's
maintenance and engineering organizations.
6.9 Fabricated parts.
Fabricated foam parts will be free of contaminates, specifically lint and debris.
6.10 Air deionizer.
An available source for the model 2U500 air deionizer specified in 4.5.14 is Amstat Industries,
Inc., 3012 N. Lake Terrace, Glenview IL 60026-1335, phone 1-800-783-9999, web site
6.11 Marker identifier.
Suggested markers to be considered for testing are as follows:
a. Diagraph GP-X, Diagraph Marking & Stenciling Products Group, 5307 Meadowland
Parkway, Marion IL 62959, phone 1-800-521-3047, web site https://www.diagraphmsp.com/ or
equivalent.
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