408 

14 CFR Ch. I (1–1–19 Edition) 

Pt. 25, App. F 

Part IV—Test Method To Determine the Heat 

Release Rate From Cabin Materials Exposed 
to Radiant Heat. 

(a) 

Summary of Method. 

Three or more 

specimens representing the completed air-
craft component are tested. Each test speci-
men is injected into an environmental cham-
ber through which a constant flow of air 
passes. The specimen’s exposure is deter-
mined by a radiant heat source adjusted to 
produce, on the specimen, the desired total 
heat flux of 3.5 W/cm

2

. The specimen is tested 

with the exposed surface vertical. Combus-
tion is initiated by piloted ignition. The 
combustion products leaving the chamber 
are monitored in order to calculate the re-
lease rate of heat. 

(b) 

Apparatus. 

The Ohio State University 

(OSU) rate of heat release apparatus, as de-
scribed below, is used. This is a modified 
version of the rate of heat release apparatus 
standardized by the American Society of 
Testing and Materials (ASTM), ASTM E–906. 

(1) This apparatus is shown in Figures 1A 

and 1B of this part IV. All exterior surfaces 
of the apparatus, except the holding cham-
ber, must be insulated with 1 inch (25 mm) 
thick, low density, high temperature, fiber-
glass board insulation. A gasketed door, 
through which the sample injection rod 
slides, must be used to form an airtight clo-
sure on the specimen hold chamber. 

(2) 

Thermopile. 

The temperature difference 

between the air entering the environmental 
chamber and that leaving must be monitored 
by a thermopile having five hot, and five 
cold, 24-guage Chromel-Alumel junctions. 
The hot junctions must be spaced across the 
top of the exhaust stack, .38 inches (10 mm) 
below the top of the chimney. The 
thermocouples must have a .050 

±

.010 inch 

(1.3 

±

.3mm) diameter, ball-type, welded tip. 

One thermocouple must be located in the 
geometric center, with the other four located 
1.18 inch (30 mm) from the center along the 
diagonal toward each of the corners (Figure 
5 of this part IV). The cold junctions must be 
located in the pan below the lower air dis-
tribution plate (see paragraph (b)(4) of this 
part IV). Thermopile hot junctions must be 
cleared of soot deposits as needed to main-
tain the calibrated sensitivity. 

(3) 

Radiation Source. 

A radiant heat source 

incorporating four Type LL silicon carbide 
elements, 20 inches (508 mm) long by .63 inch 
(16 mm) O.D., must be used, as shown in Fig-
ures 2A and 2B of this part IV. The heat 
source must have a nominal resistance of 1.4 
ohms and be capable of generating a flux up 
to 100 kW/m

2

. The silicone carbide elements 

must be mounted in the stainless steel panel 
box by inserting them through .63 inch (16 
mm) holes in .03 inch (1 mm) thick ceramic 
fiber or calcium-silicate millboard. Loca-
tions of the holes in the pads and stainless 
steel cover plates are shown in Figure 2B of 

this part IV. The truncated diamond-shaped 
mask of .042 

±

.002 inch (1.07 

±

.05mm) stainless 

steel must be added to provide uniform heat 
flux density over the area occupied by the 
vertical sample. 

(4) 

Air Distribution System. 

The air entering 

the environmental chamber must be distrib-
uted by a .25 inch (6.3 mm) thick aluminum 
plate having eight No. 4 drill-holes, located 2 
inches (51 mm) from sides on 4 inch (102 mm) 
centers, mounted at the base of the environ-
mental chamber. A second plate of 18 guage 
stainless steel having 120, evenly spaced, No. 
28 drill holes must be mounted 6 inches (152 
mm) above the aluminum plate. A well-regu-
lated air supply is required. The air-supply 
manifold at the base of the pyramidal sec-
tion must have 48, evenly spaced, No. 26 drill 
holes located .38 inch (10 mm) from the inner 
edge of the manifold, resulting in an airflow 
split of approximately three to one within 
the apparatus. 

(5) 

Exhaust Stack. 

An exhaust stack, 5.25 

× 

2.75 inches (133 

× 

70 mm) in cross section, and 

10 inches (254 mm) long, fabricated from 28 
guage stainless steel must be mounted on 
the outlet of the pyramidal section. A. 1.0 

× 

3.0 inch (25 

× 

76 mm) baffle plate of .018 

±

.002 

inch (.50 

±

.05 mm) stainless steel must be 

centered inside the stack, perpendicular to 
the air flow, 3 inches (76 mm) above the base 
of the stack. 

(6) 

Specimen Holders. 

(i) The specimen must 

be tested in a vertical orientation. The speci-
men holder (Figure 3 of this part IV) must 
incorporate a frame that touches the speci-
men (which is wrapped with aluminum foil 
as required by paragraph (d)(3) of this Part) 
along only the .25 inch (6 mm) perimeter. A 
‘‘V’’ shaped spring is used to hold the assem-
bly together. A detachable .50 

× 

50 

× 

5.91 inch 

(12 

× 

12 

× 

150 mm) drip pan and two .020 inch 

(.5 mm) stainless steel wires (as shown in 
Figure 3 of this part IV) must be used for 
testing materials prone to melting and drip-
ping. The positioning of the spring and frame 
may be changed to accommodate different 
specimen thicknesses by inserting the re-
taining rod in different holes on the speci-
men holder. 

(ii) Since the radiation shield described in 

ASTM E–906 is not used, a guide pin must be 
added to the injection mechanism. This fits 
into a slotted metal plate on the injection 
mechanism outside of the holding chamber. 
It can be used to provide accurate posi-
tioning of the specimen face after injection. 
The front surface of the specimen must be 3.9 
inches (100 mm) from the closed radiation 
doors after injection. 

(iii) The specimen holder clips onto the 

mounted bracket (Figure 3 of this part IV). 
The mounting bracket must be attached to 
the injection rod by three screws that pass 
through a wide-area washer welded onto a 

1

⁄

2

- 

inch (13 mm) nut. The end of the injection 
rod must be threaded to screw into the nut, 

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