MIL-DTL-287J
6. NOTES
(This section contains information of a general or explanatory nature which may be helpful, but is not mandatory.)
6.1 Intended use. Twistable and non-twistable, flexible waveguide assemblies are intended for operation in the
microwave region of the spectrum, to facilitate complex installations, provide for misalignments, and permit relative
motion between connected components. They have satisfactory electrical as well as mechanical characteristics to
supplement rigid waveguide assemblies.
6.2 Acquisition requirements. Acquisition documents must specify the following:
a. Title, number, and date of this specification.
b. Title, number, and date of applicable specification sheet and the complete part number.
c. Inspection of commercial packaging.
d. Levels of preservation and packing required (see 5.1).
e. Special marking, if required.
6.3 Military uniqueness. The waveguide assemblies herein specified are military unique because they must
function within and withstand for prolonged periods harsh worldwide military unique environments. Commercial
electronic components are not designed to withstand such extreme environmental conditions and would experience
catastrophic failure. The flexure and twist requirements are beyond the capability of commercial grade components.
Nonstandard units would not be compatible with fielded systems whose replacement would be costly.
6.4 First article inspection. Invitations for bids should provide that the government reserves the right to waive the
requirement for first article samples from bidders offering products which have been previously acquired or tested by
the Government, and that bidders offering such products who wish to rely on such production or tests must furnish
evidence with the bid that prior Government approval is presently appropriate for the pending acquisition.
6.5 Definitions. For the purpose of this specification, the following definitions apply:
6.5.1 Twistable and non-twistable, flexible waveguide assemblies. A twistable or non-twistable, flexible
waveguide assembly consists of a section of twistable or non-twistable, flexible waveguide with all associated fittings
attached thereto and which mates electrically and mechanically with a matched standard rectangular or ridged
waveguide. A twistable assembly is capable of withstanding bending, tensile, compressive, or torsional stresses
without causing mechanical damage or causing the electrical properties to exceed the values specified (see 3.1). A
non-twistable assembly is capable of withstanding bending, tensile, or compressive stresses without causing
mechanical damage or causing the electrical properties to exceed the values specified (see 3.1).
6.5.2 Relaxed position. An assembly is in the relaxed position when it is restrained only by a horizontal surface
on which it rests subject to no stress except that imposed by gravity.
6.5.3 Minimum centerline (CL) bending radius. The minimum centerline bending radius is the specified radius
measured to the centerline of the assembly to which an assembly can be bent in the appropriate plane and under
appropriate conditions without causing mechanical damage or causing electrical properties to exceed the values
specified (see 3.1).
6.5.4 E-plane. The E-plane is a plane perpendicular to the wide faces of the waveguide and parallel to the
narrow faces for rectangular waveguides.
6.5.5 H-plane. The H-plane is a plane perpendicular to the narrow faces of the waveguide and parallel to the
wide faces for rectangular waveguides.
6.5.6 Flexure. Flexure is the number of cycles through which an assembly can be bent without causing
mechanical damage or causing the electrical properties to exceed the values specified (see 3.1).
6.5.7 Axial twist. Axial twist is the maximum angle through which one flange of an assembly of a given length
can be rotated with respect to the other flange without causing mechanical damage or causing the electrical
properties to exceed the values specified (see 3.1). Axial twist is measured in degrees per foot.
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