MIL-PRF-26542/7B
First article inspection: FAT shall be performed by the supplier, after award of contract and prior to
production, at a location acceptable to the Government. First article inspection shall be performed
on sample units, which have been produced with equipment and procedures normally used in
production. Unless extended by the Government to other contracts or purchase orders, first article
approval is valid only on the contract or purchase order under which it is granted.
Sample size: Six (6) microphones shall be subjected to first article Inspection.
Inspection routine: The sample shall be subjected to the inspections specified in table I, in the order
shown. All sample units shall be subjected to the inspections of group I. The sample shall then be
divided equally into two sets of 3 (three) units each. One set shall be subjected to the inspections of
group II. The other set shall be subjected to the inspections of group III.
Failures: More than one failure in group I and any failure in group II or III shall be cause for refusal
to grant first article approval.
TABLE I. Parameter applicability.
First article
Group
Group
1/
A
B
Inspection
Group l
X
X
Visual and mechanical inspection
X
X
Sensitivity at ground level
X
Sensitivity at altitude
X
X
Frequency response at ground level
N/A
Frequency response at altitude
X
X
Impedance
N/A
Noise cancellation characteristics
N/A
Effect of external magnetic field
X
X
Stray magnetic field
X
X
Linearity
N/A
Talk-out
N/A
Dielectric withstanding voltage
X
Signal-to-noise
X
Distortion
X
X
Interchangeability
Group II
X
Thermal shock
X
Humidity
X
Drop
X
Pressure equalization
N/A
Explosive decompression
X
Salt fog
Group III
X
Vibration
N/A
Bounce
X
Altitude
X
Moisture barrier seal
N/A
Immersion
1/ See the associated requirement and method paragraphs within
sections 3 and 4 of MIL-PRF-26542, for the above inspections.
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