spaschal on DSK3GDR082PROD with CFR

Federal Aviation Administration, DOT

Pt. 25, App. F

and a .020 inch (5.1 mm) thick wide area
washer must be held between two 1-2-inch (13
mm) nuts that are adjusted to tightly cover
the hole in the radiation doors through
which the injection rod or calibration calorimeter pass.
(7) Calorimeter. A total-flux type calorimeter must be mounted in the center of a
1-2-inch Kaowool  - M -  board inserted in the
sample holder to measure the total heat flux.
The calorimeter must have a view angle of
180 degrees and be calibrated for incident
flux. The calorimeter calibration must be acceptable to the Administrator.
(8) Pilot-Flame Positions. Pilot ignition of
the specimen must be accomplished by simultaneously exposing the specimen to a
lower pilot burner and an upper pilot burner,
as described in paragraph (b)(8)(i) and
(b)(8)(ii) or (b)(8)(iii) of this part IV, respectively. Since intermittent pilot flame extinguishment for more than 3 seconds would invalidate the test results, a spark ignitor may
be installed to ensure that the lower pilot
burner remains lighted.
(i) Lower Pilot Burner. The pilot-flame tubing must be .25 inch (6.3 mm) O.D., .03 inch
(0.8mm) wall, stainless steel tubing. A mixture of 120 cm3/min. of methane and 850 cm3/
min. of air must be fed to the lower pilot
flame burner. The normal position of the end
of the pilot burner tubing is .40 inch (10 mm)
from and perpendicular to the exposed
vertical surface of the specimen. The centerline at the outlet of the burner tubing must
intersect the vertical centerline of the sample at a point .20 inch (5 mm) above the lower
exposed edge of the specimen.
(ii) Standard Three-Hole Upper Pilot Burner.
The pilot burner must be a straight length of
.25 inch (6.3 mm) O.D., .03 inch (0.8 mm) wall,
stainless steel tubing that is 14 inches (360
mm) long. One end of the tubing must be
closed, and three No. 40 drill holes must be
drilled into the tubing, 2.38 inch (60 mm)
apart, for gas ports, all radiating in the same
direction. The first hole must be .19 inch (5
mm) from the closed end of the tubing. The
tube must be positioned .75 inch (19 mm)
above and .75 inch (19 mm) behind the exposed upper edge of the specimen. The middle hole must be in the vertical plane perpendicular to the exposed surface of the specimen which passes through its vertical centerline and must be pointed toward the radiation source. The gas supplied to the burner
must be methane and must be adjusted to
produce flame lengths of 1 inch (25 mm).
(iii) Optional Fourteen-Hole Upper Pilot
Burner. This burner may be used in lieu of
the standard three-hole burner described in
paragraph (b)(8)(ii) of this part IV. The pilot
burner must be a straight length of .25 inch
(6.3 mm) O.D., .03 inch (0.8 mm) wall, stainless steel tubing that is 15.75 inches (400 mm)
long. One end of the tubing must be closed,
and 14 No. 59 drill holes must be drilled into

the tubing, .50 inch (13 mm) apart, for gas
ports, all radiating in the same direction.
The first hole must be .50 inch (13 mm) from
the closed end of the tubing. The tube must
be positioned above the specimen holder so
that the holes are placed above the specimen
as shown in Figure 1B of this part IV. The
fuel supplied to the burner must be methane
mixed with air in a ratio of approximately
50/50 by volume. The total gas flow must be
adjusted to produce flame lengths of 1 inch
(25 mm). When the gas/air ratio and the flow
rate are properly adjusted, approximately .25
inch (6 mm) of the flame length appears yellow in color.
(c) Calibration of Equipment - (1) Heat Release Rate. A calibration burner, as shown in
Figure 4, must be placed over the end of the
lower pilot flame tubing using a gas tight
connection. The flow of gas to the pilot
flame must be at least 99 percent methane
and must be accurately metered. Prior to
usage, the wet test meter must be properly
leveled and filled with distilled water to the
tip of the internal pointer while no gas is
flowing. Ambient temperature and pressure
of the water are based on the internal wet
test meter temperature. A baseline flow rate
of approximately 1 liter/min. must be set and
increased to higher preset flows of 4, 6, 8, 6
and 4 liters/min. Immediately prior to recording methane flow rates, a flow rate of 8
liters/min. must be used for 2 minutes to precondition the chamber. This is not recorded
as part of calibration. The rate must be determined by using a stopwatch to time a
complete revolution of the wet test meter for
both the baseline and higher flow, with the
flow returned to baseline before changing to
the next higher flow. The thermopile baseline voltage must be measured. The gas flow
to the burner must be increased to the higher preset flow and allowed to burn for 2.0
minutes, and the thermopile voltage must be
measured. The sequence must be repeated
until all five values have been determined.
The average of the five values must be used
as the calibration factor. The procedure
must be repeated if the percent relative
standard deviation is greater than 5 percent.
Calculations are shown in paragraph (f) of
this part IV.
(2) Flux Uniformity. Uniformity of flux over
the specimen must be checked periodically
and after each heating element change to determine if it is within acceptable limits of
plus or minus 5 percent.
(3) As noted in paragraph (b)(2) of this part
IV, thermopile hot junctions must be cleared
of soot deposits as needed to maintain the
calibrated sensitivity.
(d) Preparation of Test Specimens. (1) The
test specimens must be representative of the
aircraft component in regard to materials
and construction methods. The standard size
for the test specimens is 5.91 Section.03  5.91 Section.03
inches (149 Section1  149 Section1 mm). The thickness of

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