NARRATOR: Welcome to the William J. Hughes
Technical Center of the Federal Aviation Administration,
the nations premier aviation research,
development, test, and evaluation facility
and recognized international leader
in shaping the future of aviation.
The Technical Center is at the forefront of the FAA's challenge
to continually enhance
and insure the safety and security of the flying public.
Set within the beautiful New Jersey pinelands,
among the many complex laboratories and test facilities
is the home of the Fire Safety Branch.
The full-scale fire test facility, completed in 1980,
is the largest aircraft fire testing laboratory in the world.
The facility allows for the conduct of realistic fire tests
under controlled conditions.
The research conducted in this facility
has lead to the implementation of many new safety standards,
including fire-resistant seats and interior surfaces,
heat-resistant evacuation slides,
floor proximity lighting,
fire-resistant cargo compartments
and most recently,
burn-through-resistant insulation.
Comprised of a dedicated group of engineers,
technicians, and computer science specialists,
the Fire Safety Branch personnel investigate
and research a variety of safety related areas,
including fuel tank flammability,
hidden area fire protection, and halon replacement.
On November 26, 1984, a federal aviation regulation
concerning the flammability of aircraft seat cushions
went into effect.
The regulation addresses one of the major areas of concern
in a fire onboard an aircraft,
the flammable urethane cushion material used in aircraft seats.
The technical background for this rule
was obtained through full-scale fire tests conducted at
the Federal Aviation Administration Technical Center
using a surplus Air Force C-133 cargo aircraft
as the primary test article.
This test aircraft was configured to resemble
a wide-body aircraft
to simulate conditions in a real post-crash fire scenario.
Baseline tests were conducted with the interior furnished
with carpet, side wall panels,
stowage bins, and ceiling materials
which were exposed to a large exterior pool fire
through an opening in the fuselage,
such as would occur if an exit door
was inadvertently opened or the fuselage ruptured.
These baseline tests established that severe thermal radiation
would easily penetrate the outer seat
upholstery and involve
the relatively large mass of urethane foam in the fire.
Burning urethane foam hastens the spread of flame
and produces large quantities of smoke,
combustible gases, and toxic gases such as carbon monoxide,
hydrogen chloride, and hydrogen cyanide.
The result of accident investigations
and the experimental fire tests have demonstrated
this involvement of foam cushion material
is a dominant factor in the spread of fire hazards
inside the cabin of a burning aircraft.
To reduce the hazards associated with burning urethane foam,
the options were to replace the urethane foam
with more fire-resistant foam materials,
which appeared to be impractical at that time,
or to protect the urethane foam with fire-blocking layers.
The fire-blocking layer concept
involves the use of a thin layer
of highly fire-resistant material
to completely encapsulate
and protect the urethane foam core seat cushion material
from involvement in the fire.
This layer of fire-resistant material
delays the onset of ignition
and retards the involvement of the foam core in the fire.
Some blocking layers are thin layers of foam
that are glued onto the urethane.
Other types include woven cloths,
felt, and aluminized materials.
Full-scale fire tests were conducted
using the fire-blocking layer technique.
The results of these tests are reported
in DOT/FAA/CT-83/43 titled
"AIRCRAFT SEAT FIRE BLOCKING LAYERS;
EFFECTIVENESS AND BENEFITS UNDER VARIOUS SCENARIOS."
These tests compared standard,
unprotected seats to fire-blocked seats
to measure the difference in burn characteristics over time.
The difference can be seen graphically
in a side-by-side comparison after only 1 minute of burning.
After 2 minutes, the unprotected seat on the left
is almost totally consumed in flames,
while the fire-blocked seat on the right
appears to remain intact
and only minor burning is evident.
After 3 minutes, the seat on the left
is almost completely consumed.
Note the burning puddle under the seat formed
by melted urethane,
creating yet another avenue for the spread of the fire.
The fire-blocked seat on the right appears to be
basically intact
with no fire damage to the foam cushion,
and the fire is almost out.
An important phase of the program
was the development of a fire test method for evaluation
and certification of seat cushions
using a modified 2 gallon per hour kerosene burner.
The test subjects the seat test sample to temperature
and heat flux levels typical of full-scale cabin fires,
and is far more realistic
and severe than the Bunsen burner test
previously required by federal aviation regulations
for seat cushion materials.
Proposed criteria for material acceptance are based
on the percentage weight loss of the seat test sample,
and flames spread across the sample during the test.
While the bulk of the background testing was conducted
with cushions assembled
using blocking layer construction,
the regulation does not require
that seat cushions be constructed that way.
Rather, it proposes objective standards of performance
for seat cushions
so that other concepts can be used
without the need for regulatory amendment.
Fire-hardened foams are one such example
which meet the flammability requirement
without the aid of a blocking layer.
The established criteria for performing
the tests are as follows.
One, at least three seat test samples
consisting of one vertical cushion assembly
and one horizontal cushion assembly must be tested.
Two, if a cushion is constructed with a fire-blocking material,
the fire-blocking material
must completely enclose the cushion foam core material.
If a cushion is constructed with more than one type
of blocking layer,
individual tests must be conducted
with each type of blocking layer
completely encapsulating the cushion.
Three, each seat test sample tested must be fabricated
using the principle components and assembly processes
(representative seams and closures)
intended for use in the production articles.
The principle components include foam core,
flotation material,
fire-blocking material, if used, and dress covering.
If a different material combination
is used for the production
back cushion than the production bottom cushion,
both material combinations must be tested independently
as a complete seat test sample.
Four, the horizontal cushion assembly
must be 18 inches wide by 20 inches deep by 4 inches thick,
exclusive of fabric closures and seam overlaps.
And the vertical cushion assembly must be 18 inches wide
by 25 inches high by 2 inches thick,
exclusive of fabric closures and seam overlap.
All dimensions are plus 0 or minus 0.125 inches.
Tests should be conducted under a ventilation hood.
It should be noted that this test procedure
may involve hazardous materials, smoke and toxic gases.
It is the responsibility of the test conductor
to ensure proper safety precautions.
The test sample apparatus includes the seat test sample
mounting frame and drip pan.
The sample apparatus must have the capability of moving
away from the stationary burner during warm-up.
Fabricate the sample mounting frame for the seat test sample
from 1-by-1-by-0.125-inch steel angle,
and 1-by-0.125-inch steel flat stock.
The test sample mounting frame is used for mounting
the seat test sample horizontal and vertical assemblies.
The dimensions listed for the test frame
are all inside measurements.
The frame's upright section,
used for mounting the vertical assembly,
must be 33 plus or minus 0.125 inches high,
and 18.125 plus or minus 0.125 inches wide.
The frame's bottom section,
used for mounting the horizontal assembly,
must be 18.125 plus or minus 0.125 inches wide,
and 22.125 plus or minus 0.125 inches long.
The vertical and horizontal mounting surfaces
should have two supporting braces made
from 1-by-0.125-inch steel flat stock.
The center lines of the flat stock braces are 6 plus or minus
0.125 inches measured from the outer edges
of the steel angle on the left
and right sides of the frame.
Four legs fabricated from 1-by-1-by-0.125-inch steel angle
and 12 plus or minus 0.125 inches tall
are located below the four corners
of the horizontal assembly mounting section of the frame.
All connecting joints of the stand are welded
and the flat stock components are butt welded.
The position of the test sample mounting frame relative
to the burner cone
during testing must be positioned as shown.
The test sample frame must have the capability of being moved
away from the stationary burner during warm-up.
The minimum distance between the burner cone and test sample
during warm-up is 36 inches.
Test samples must be secured to the test frame
to prevent movement during testing.
The number of restraints used during testing will depend upon
the type of material used for the test sample dress covering.
A formed stainless steel rod must be used to secure
the vertical cushion assembly to the sample frame.
The rod restraint is uninsulated,
solid, 0.125 inches in diameter,
and is located 1.5 plus or minus 0.5 inches
from the top surface of the vertical cushion assembly
as it sits in the sample test frame.
No additional restraints should be used
for fabric dress covered samples.
Due to leather dress covers' tendency to shrink away
from the flame during testing,
both the vertical and horizontal cushion
assemblies require formed rod restraints,
securing the assemblies to the sample test frame.
The rods must be uninsulated,
solid stainless steel measuring 0.125 inches in diameter.
Two rods must be used to restrain the vertical assembly,
and are located 1.5 plus or minus 0.5 inches from the top
and bottom surfaces of the vertical cushion assembly
as it sits in the sample test frame.
The larger rod restraint must be used to secure
the horizontal cushion assembly,
and is located along the center line of the horizontal cushion
in parallel with the direction of the burner
so as not to impede the burner flame.
The test apparatus must include a suitable drip pan lined
with aluminum foil with the less reflective side facing up.
The drip pan must be located at the bottom of the test sample
mounting frame legs,
at least 12 inches or more below the portion of the test sample
mounting frame that supports the horizontal cushion assembly.
The burner is a gun-type using a pressurized sprayed fuel charge
in conjunction with a ducted air source
to produce the burner flames.
An interchangeable screw-in fuel nozzle is used to produce
the conically shaped fuel charge
from a pressurized fuel source.
A pressurized air source controlled via a regulated
sonic nozzle supplies the combustion air.
The combustion air is ducted through a cylindrical draft tube
containing a series of defusing vanes.
There are several types of internal vanes
used to diffuse the combustion air.
The diffused combustion air will mix with the sprayed fuel charge
in a bell-shaped combustion cone.
The fuel air charge is then ignited by a high voltage
spark plug positioned in the burner cone.
Flame characteristics can be adjusted slightly
by varying the pressure of the regulated air
into the sonic nozzle.
Air pressure must remain within the specified tolerance range
as explained later in this video.
The burner housing is comprised of three main sections --
the draft tube, the coupling, and the back section.
The draft tube is constructed of 4-inch inner diameter mild seam
steel tubing with a wall thickness of 0.125 inches.
The length of the draft tube is 15 inches
with 3 inches of the tube inserted into the coupling,
resulting in a coupling-to-tip end of draft tube
distance of 12 inches.
The coupling is constructed of 4.25-inch inner diameter
mild seam steel tubing
that is 4 inches long with an outer diameter of 4.5 inches.
Three setscrew holes are 120 degrees apart
and are drilled 1 inch in from the edge
to hold the draft tube in place.
The coupling has two mounting brackets welded to the sides
for easy mounting and adjustment.
The back section is made of the same 4-inch tubing
as the draft tube,
but is 6 inches long with 1 inch inserted into the coupling
and welded in place.
A back plate is constructed of a 0.25-inch steel plate
cut into a 4.25-inch-diameter circle
to cap the back section,
with holes for the air inlet and fuel inlet.
A 1.50-inch national pipe thread pipe nipple
is cut to a length of 2.90 inches
and welded into the recessed cut on the center of the back plate.
The NexGen burner airflow is regulated with a sonic nozzle
which will deliver a constant mass flow rate
depending on the supplied inlet air pressure.
The nozzle is constructed from stainless steel
with 1-inch NPT male thread ends.
The throat diameter must be 0.25 inches,
which will deliver a mass flow rate
in standard cubic feet per minute
as a function of inlet pressure in pounds per square inch gauge
using the following equation.
Mass flow rate equals 0.89 times the inlet pressure plus 12.43.
The exact inlet air pressure, and hence mass flow rate,
will be test method specific
and is described in the respective chapter.
The nozzle that the FAA has used to develop the NexGen burner
is manufactured by Fox Venturi Products of Dover, New Jersey,
and is identified by part number 612021-8.
The air pressure regulator is critical to maintaining
the stability of the airflow supplied to the burner.
The regulator should have 1-inch NPT female connections,
at least one pressure tap for measurement of outlet pressure
and should regulate over the range
at which the burner is normally operated.
The regulator must also maintain the desired pressure
for the duration of a test.
A suitable regulator is available from Grainger,
item number 4ZM10,
manufactured by SPEEDAIRE, with an adjustment range of 5
to 125 pounds per square inch.
Another suitable regulator is available from MSC Industrial,
part number 73535627, manufactured by Parker,
model R119-08CGM2
with an adjustment range of 2 to 125 pounds per square inch.
The air pressure measured just prior to the sonic nozzle
is critical to the proper mass flow rate of air
through the sonic nozzle.
The pressure gauge or transducer
must have NIST traceable certification
with a plus or minus 2 percent accuracy or less.
Digital gauges capable of reading in increments
of 1 pound per square inch
or less are recommended if a pressure transducer is not used.
Should an analog gauge be used, it should be glycerin-filled
to reduce needle flutter
and have a dial that is easily read.
The gauge or transducer must also have a working range
appropriately suited for the range
of air pressures typically used during tests.
A suitable digital gauge is supplied
by OMEGA Engineering, part number DPG1001B-100G.
A suitable analog gauge is supplied by McMaster-Carr,
part number 4053K23 with a 0
to 60 pounds per square inch pressure range.
A suitable pressure transducer is supplied by
OMEGA Engineering, part number PX329-100G5V.
An airflow muffler is used to reduce the high frequency noise
created by the air expanding from the sonic nozzle throat.
The 2.625-inch outside diameter muffler
has 1.5-inch NPT female thread connections,
an overall length of 12 inches,
and has no internal baffles or tubes.
A suitable muffler is supplied by McMaster-Carr,
part number 5889K73.
Low pressure drop polyurethane foam
must be used to further reduce
the noise issuing from the burner.
The foam can be cut into a cylinder 3 inches in diameter
by 12 inches long,
and should have a density of 1.20
to 1.50 pounds per cubic foot
with a porosity of 20 plus or minus 2 pores per inch.
It is necessary to affix two pieces of safety wire
to the muffler's internal steel mesh at the outlet end
to prevent the foam cylinder
from moving out of position into the burner housing.
The two wires should be arranged perpendicular
to each other in a cross pattern.
The male outlet of the sonic nozzle connects to
a female to male hex bushing measuring 1-inch NPT female
to 1.5-inch male bushing.
The hex bushing male outlet connects to the intake side
of the muffler via a schedule 40 standard wall
1.5-inch NPT female
to 1.5-inch NPT male 90-degree street elbow.
The temperature of the inlet air measured at the sonic nozzle
must be maintained at 50 plus or minus 10 degrees
Fahrenheit for the duration of a test.
This can be achieved by constructing a heat
exchange system as described later in this video.
The stator and turbulator are used to deflect
and diffuse the airflow within the sonic burner.
Three-dimensional drawing files can be used
to fabricate the components on a computer
numerical controlled CNC milling machine.
These files can be downloaded from the fire safety website.
The stator is a four vane internal component
that creates a swirling of internal airflow
and aligns the fuel tube
with the center axis of the draft tube.
The stator is 4 inches in diameter
and should have a snug fit when placed inside the draft tube.
A suitable stator is supplied by MARLIN Engineering,
part number ME1513-3,
The turbulator is a 4-inch diameter component
for air swirling placed in the end of the draft tube.
The center hole is 2.75 inches in diameter.
A suitable turbulator is supplied by MARLIN Engineering,
part number ME1512-1.
The stator slides onto the fuel tube.
It is oriented in the proper direction
and is locked into place
with a setscrew located at the 12 o'clock position.
The turbulator is placed on the end of the draft tube
with the notch located at the 6 o'clock position.
The typical configuration positions the face of the stator
approximately 2.6875 inches from the exit plane
of the turbulator.
Exact positioning of the stator and turbulator will be explained
in the preparation of apparatus section of this video.
A method of fuel pressurization is required
to deliver the proper amount of fuel
to the spray nozzle for consistent atomization.
The delivered fuel pressure is typically in the range of 100
to 120 pounds per square inch,
and must maintain the desired pressure
for the duration of a test.
A suitable method of fuel pressurization
is a pressurized fuel tank.
Alternatively, a fuel pump may be used provided
it can maintain the required pressure for the duration
of a test with minimal fluctuation
so as to maintain 2 gallons per hour
plus or minus 0.1 gallon per hour.
Fuel pressure should be adjustable
to establish the pressure required
to produce 2.0 gallons per hour
plus or minus 0.1 gallon per hour from the fuel nozzle
during the fuel flow calibration procedure.
During burner operation,
the fuel pressure at the burner inlet
must not fluctuate more than plus or minus
2 pounds per square inch
from the established fuel pressure
obtained during the fuel flow calibration procedure.
Heat transfer from the pump must not cause the fuel temperature
to exceed the tolerance of 42 degrees Fahrenheit,
plus or minus 10 degrees Fahrenheit,
as measured at the burner fuel inlet.
A fuel pressure vessel, or tank,
such as McMaster-Carr part number 1584K7,
with a 15 gallon capacity, measuring 12 inches in diameter
by 33 inches tall, can be used to contain the fuel.
The tank has various fittings on the top, bottom, and sides
to allow for connection of pipe fittings
for filling, discharging, fuel quantity level,
pressure measurement, pressurization, and venting.
Nitrogen is used to pressurize the head space of the fuel tank.
Solenoids or manual valves can be used to start
and stop the flow of fuel, nitrogen, and vent gas.
The head space gas pressure is controlled
by a precision regulator,
and monitored using a fuel pressure gauge or transducer.
A high-pressure translucent tube
can be used for indicating the fuel level in the tank.
A suitable pressure gauge or transducer
must be used to monitor the pressure inside the fuel tank,
which is critical for establishing the proper
flow of fuel into the fuel nozzle.
The pressure gauge or transducer
must have NIST traceable certification
with a plus or minus 2 percent accuracy or less.
If a pressure transducer is not used,
digital gauges capable of reading in increments
of 1 pound per square inch or less are recommended.
If an analog gauge is used, it should be glycerin-filled
to reduce needle flutter
and have an easily readable dial.
The gauge must also have a working range
appropriately suited for the range of fuel pressures
typically used during tests.
A suitable digital gauge is supplied by OMEGA Engineering,
part number DPG1001B-500G.
A suitable analog gauge is supplied by McMaster-Carr,
part number 4053K23 with a 0 to 160 pounds
per square inch pressure range.
A suitable pressure transducer
is supplied by OMEGA Engineering,
part number PX329-150G5V.
The fuel entering the burner fuel tube
must be maintained at a temperature range of 42
plus or minus 10 degrees Fahrenheit
for the duration of a test.
This could be achieved by constructing
a heat exchange system as described later in this video.
The fuel tube in the sonic burner
is designed to allow both the fuel nozzle
and the airflow to be aligned with the axis of the draft tube.
This is accomplished by creating two bends in the section
of the fuel tube that enters the back of the burner.
The tube is constructed from schedule 80, thick wall,
0.125-inch steel pipe
with an outside diameter of 0.405 inches,
an inside diameter of 0.215 inches,
and a wall thickness of 0.095 inches.
The tube is cut to a length of approximately 21.5 inches.
A section of the outer wall is removed on a lathe
to fit the tube through the keyless bushing
that holds the tube in place.
The outer diameter of the fuel tube is reduced to approximately
0.3750 inches for a length of 4 inches at one end.
The tube is then shaped with a pipe bender
according to the dimensions in the drawing.
A die is used to thread both ends of the tube with 1/8-inch
NPT pipe threads.
Heavy-duty 0.004-inch-thick thread seal tape
is wrapped on the fuel tube threads to prevent fuel leakage.
A 1.375-inch-long brass fuel nozzle adapter is threaded
onto the front end of the fuel tube
where the fuel nozzle is attached.
A keyless bushing, Fenner Drives part number 6202109,
is used to hold the back end of the fuel tube in place.
A pipe fitting is attached to the back end of the fuel tube
to connect the pressurized fuel system to the fuel tube.
The fuel nozzle for the sonic burner should be
an 80-degree solid
conical spray pattern oil burner nozzle.
The rated flow rate provided by the manufacturer is achieved
when applying 100 pounds per square inch pressure
to the nozzle.
If a different flow rate is desired,
the pressure can be adjusted
accordingly to achieve a wide range of flow rates.
In general, the flow rate is related to the pressure
by the following equation.
The desired flow rate equals the rated flow rate
times the square root of the desired pressure divided
by the rated pressure.
In which F sub D is the desired flow rate,
F sub R is the rated flow rate.
P sub D is the desired pressure
and P sub R is the rated pressure,
typically 100 pounds per square inch.
For example, a 5.5-gallon-per-hour-rated nozzle
is operated at 120 pounds per square inch,
producing a flow rate of 6.0 gallons per hour.
A Delavan 80-degree, 2.0 gallon per hour B-type spray nozzle
has been found suitable for this application.
The fuel nozzle adapter is a brass fitting
1.375 inches in length
with an 1/8-inch NPT thread on the inlet side,
and a 0.5625-inch 24 unified fine thread
where the nozzle attaches.
Use jet fuel Jet A, JP-8, or their international equivalent,
or ASTM K2 fuel -- number 2 grade kerosene --
to yield the desired fuel flow rate
within the specified pressure range.
Diesel fuel may also be used,
however the test condition may be more severe.
A high-voltage oil burner ignition transformer
with an output of 10 kilovolts
is used to create an arc across an automotive-type
spark plug mounted in the burner extension cone.
This spark plug uses a standard 14-millimeter-diameter
thread size with a thread pitch of 1.25 millimeters.
The threaded segment of the spark plug
is 0.36 inches in length.
The exposed portion of the central insulator
measures 0.70 inches in length.
The spark plug gap must be open to 0.100 inches in order
to consistently ignite the fuel/ air charge in the burner cone.
A suitable spark plug is manufactured
by Champion Products,
manufacturer part number RJ19LM,
and can be purchased through Grainger at www.grainger.com,
part number 12U891.
A heat exchange system is used to regulate
the temperature of the burner inlet air and fuel,
as the flow rate of each
is dependent upon the density of the air and fuel.
An ice bath can be constructed from an insulated cooler
or a chest freezer with temperature control capability.
The fuel travels through coiled copper tubing in the ice bath
and out to the burner.
The air is cooled in a heat exchanger such as McMaster-Carr
part number 43865K78,
which has ice water or coolant
traveling through the outer shell,
removing heat from the air.
The ice water or coolant is circulated
in a closed loop from the cooler
to the heat exchanger by means of a submersible pump.
The exact dimensions of the copper coils
and the flow rate of the water pump is dependent
upon the particular conditions in the laboratory.
Alternate methods such as active heating
and cooling systems can be used,
allowing greater precision, but may be more costly.
A 12-plus-or-minus-0.125-inch burner extension cone
is fitted to the end of the draft tube.
The cone is constructed from 16 gauge
American Iron and Steel Institute type 310
stainless steel with a thickness of 0.0625
plus or minus 0.015 inches.
The cone exit plane must be 6 plus or minus 0.250 inches high
and 11 plus or minus 0.250 inches wide.
The hot and cold cycling that occurs during typical testing
can cause the cone exit plane dimensions to shift
due to warpage.
It is critical to periodically check the exit plane
dimensions to ensure they remain within the specified tolerances.
It is recommended this be performed at the beginning
and end of each day the burner is operated.
A threaded boss must be welded to the top surface of the burner
extension cone for acceptance of the spark plug
used to ignite the fuel charge.
The threaded boss must be fabricated from
American Iron and Steel Institute
type 310 stainless steel.
The cylindrical boss must measure 1.125 inches in diameter
with a thickness of 0.250 inches.
The boss must be threaded using an SAE standard 14 millimeter
by 1.25 millimeter spark plug tap.
Accurate measurements of the burner inlet parameters
are critical to proper operation.
The measurement locations of the burner air and fuel supply
are typically located just prior to entering the burner housing,
or as near the burner housing as possible.
The sonic nozzle inlet pressure
is measured with a suitable pressure gauge
or transducer mounted into the airstream
just upstream from the sonic nozzle.
The gauge or transducer should measure accurately in the range
of 0 to 60 pounds per square inch
with an accuracy of plus or minus 2 percent maximum.
Bourden-type gauges and pressure transducers have proven
to be suitable for this measurement.
The burner air temperature is measures
with a 0.125-inch-diameter, ceramic packed,
310 stainless steel sheathed, type-K (Chromel-Alumel)
grounded junction thermocouple with a nominal 24 AWG conductor.
The thermal couple should be inserted into the air stream
just upstream of the sonic nozzle.
In some testing situations, flame radiation
may be incident upon the inlet air lines,
causing heating of the air
and possible bursting of flexible hoses.
It is important to shield all air lines with thermal
wrapping to prevent an unsafe condition
and maintain a steady air temperature.
The burner fuel pressure is measured with
a suitable pressure gauge
or transducer mounted in a T-connection
in the fuel inlet line near the back of the burner.
It is important that the measurement location
be as close to the back of the burner as possible
to accurately measure the fuel pressure at the point
it enters the burner.
The burner fuel temperature is measured
with a 0.125-inch-diameter, ceramic packed,
310 stainless steel sheathed, type-K (Chromel-Alumel)
grounded junction thermocouple with a nominal 24 AWG conductor.
The thermocouple should be mounted in a T-fitting,
such that the probe tip is located
just upstream of the fuel tube.
In some testing situations, flame radiation may be incident
upon the inlet fuel lines,
causing heating of the fuel
and possible bursting of flexible hoses.
It is important to shield all fuel lines
with thermal wrapping to prevent an unsafe condition
and maintain a steady fuel temperature.
A seat test sample consists of one vertical assembly
and one horizontal assembly.
The vertical assembly is the back cushion
located in the vertical orientation.
The vertical assembly may be representative
of the production seat back, seat bottom,
or both if the production articles
have the same construction.
The constructed, finished vertical cushion assembly
must be 18 plus 0, minus 0.125 inches
by 25 plus 0, minus 0.125 inches
by 2 plus 0, minus 0.125 inches,
not including fabric closures,
hook and loop, et cetera, as well as seam overlap.
The horizontal assembly is the bottom cushion
in the horizontal orientation.
The horizontal assembly may be representative
of the production seat back, seat bottom
or both if the production articles
have the same construction.
The constructed, finished horizontal cushion assembly
must be 18 plus 0, minus 0.125 inches
by 20 plus 0, minus 0.125 inches
by 4 plus 0, minus 0.125 inches,
not including fabric closures,
hook and loop, et cetera, as well as seam overlap.
A sample set includes a minimum of three seat test samples
prepared for testing.
All samples in this set are of the same construction
and configuration.
Each seat test sample tested must be fabricated
using the principal components,
in other words, foam core, flotation material,
fire-blocking material, if used, and dress covering,
and assembly processes,
representative seams and closures
intended for use in the production articles.
If a different material combination is used
for the production back cushion
than for the production bottom cushion,
both material combinations must be tested
as a complete seat test sample.
Each seat test sample consists of a vertical assembly
and a horizontal assembly.
For lightweight seat test samples,
test samples weighing less than 3 pounds,
refer to policy memo ANM-115-07-002.
If a cushion is constructed with a fire-blocking material,
the fire-blocking material must completely enclose
the cushion foam core material.
The method of fabricating blocking layer seams
and closures must be the same as the production method.
In fabricating a seat test sample,
the fire-blocking layer must be configured
so that any possible weak point is exposed to the burner flame.
This may require configuring a seat test sample
so that the seam is exposed to the test burner,
even though a seam may not be positioned
as such on a production cushion.
If more than one fire-blocking layer material is used
on a given production cushion,
each blocking layer material must be subjected
to this test procedure
as separate seat test samples with the fire-blocking material
completely encapsulating
both vertical and horizontal cushion assemblies
so that all fire-blocking layers are subjected
to the same level of test severity.
Fire-blocking layers cannot be used in combination
for this test.
The example production cushion shown would require
three different seat test sample constructions.
One construction to substantiate the horizontal production
cushion encapsulated in blocking layer B.
One construction to substantiate the horizontal production
cushion encapsulated in blocking layer B1.
And one construction to substantiate
the vertical production cushion.
Seats that utilize more than one variety of foam, composition,
density, et cetera, will have seat test samples
constructed that reflect the foam combination used.
If several seat models use similar foam combinations,
it is not necessary to test each combination
if it is possible to bracket the various combinations.
For example, if foam A makes up 80 percent and foam B
makes up 20 percent of the foam volume in one seat model,
and in another similar seat model,
foam A makes up 20 percent and foam B
makes up 80 percent of the foam volume,
it is generally acceptable to approve all combinations of
A and B foams between these limits if the 20/80
and 80/20 extremes are tested and pass.
In addition, for foams of a given chemical composition,
low density foam can be used in lieu of foams of higher density.
In this case, as in the case of foam combinations,
all other elements that make up the cushion must be the same.
If a production seat construction
utilizes more than one dress covering,
the seat test sample configuration
may be represented as shown.
The samples must be conditioned at 70 degrees
Fahrenheit plus or minus 5 degrees Fahrenheit,
and 55 percent plus or minus
10 percent relative humidity for a minimum of
24 hours prior to testing.
Move the test sample mounting frame into position
in front of the burner
and check for proper alignment.
In other words, distance from exit of burner cone
to face of test sample, proper sample position
with respect to cone center line, et cetera.
The movable assembly should incorporate mechanical stops,
or detents,
to ensure that the samples can be moved into position
quickly without measurement during testing.
Check to insure the horizontal center line
passing through the welded seams on each side of the cone
is level with respect to the ground.
Turn on the ventilation hood for the test chamber.
Do not turn on the burner air, fuel, or ignition.
Measure the airflow in the test chamber
using a hot wire anemometer or equivalent measuring device.
The vertical air velocity can be measured
0.5 inches from the rear face of the vertical assembly
and 2 inches below the midpoint
of the vertical assembly top surface.
The vertical air velocity must be no greater
than 100 feet per minute.
The horizontal air velocity can be measured 0.5 inches
above the midpoint of the horizontal assembly top surface.
The horizontal air velocity must be no greater
than 50 feet per minute.
Personnel present within the test cell
may affect air velocity readings.
This may be avoided by mounting the anemometer instrumentation
to the sample mounting frame
during test cell air velocity measurements.
The temperature of the air in the test chamber
should be between 50 degrees Fahrenheit and 100 degrees
Fahrenheit before the start of each test.
The chamber air temperature should be measured 0.5 inches
above the midpoint of the horizontal assembly top surface.
The tip of the fuel nozzle or fuel exit plane
must be located 0.1875 plus or minus
0.020 inches from the exit plane of the turbulator.
The stator is positioned
by adjusting the translational position
as well as its axial position on the fuel tube.
The front face of the stator must be located 2.6875 plus
or minus 0.020 inches from the exit plane of the turbulator.
The stator translational position is also 2.5 inches
from the tip of the fuel nozzle.
The line running through the setscrew
and geometric center of the stator
is used as a reference for properly
orienting the rotational position of the stator.
The stator must be positioned so the reference line angle
is 0 degrees from the 0 position
when looking into the burner draft tube.
The spark plug should be mounted in the threaded boss
on the top surface of the burner.
The spark plug is located at a distance of 6 plus or minus
0.125 inches from the end of the intake plane of the burner cone.
The spark plug gap distance between the two electrodes
must be 0.100 inches.
The length and arrangement of the spark plug wires
must be monitored to prevent contact with the burner cone
or other hot surfaces, resulting in heat damage
during flame consistency validation and testing.
Once the air fuel mixture is ignited,
the outside surface temperature of the burner cone
will increase rapidly,
becoming capable of damaging the wire
if it comes in contact with the cone.
The spark plug wire should be carefully routed
to prevent contact with the cone or other hot surfaces,
and should also be shielded in a heat-resistant covering
to further protect it
from convective heat damage from the burner flames.
The volumetric airflow is controlled
via a regulated sonic nozzle.
Adjust the upstream supply air pressure
to 45 pounds per square inch
plus or minus 1 pound per square inch.
The intake air temperature must be maintained within the range
of 40 degrees Fahrenheit to 60 degrees Fahrenheit.
If a calibrated fuel flow meter is not available,
measure the fuel flow directly using a length of Tygon tubing
and appropriately sized graduated cylinder.
Slip the Tygon tubing over the end of the fuel nozzle,
making certain to establish a good seal.
Direct the exit of the Tygon tubing into a small bucket
or other collection basin.
Turn on the fuel solenoid,
making sure the ignition system is off.
After establishing a steady stream of fuel flow
from the tubing exit,
simultaneously direct the tubing exit
into the graduated cylinder
while beginning the stopwatch or timing device.
Collect the fuel for a 2-minute period,
making certain to immediately direct the tubing exit
away from the graduated cylinder at precisely 2 minutes.
Calculate the flow rate and ensure that it is 2 plus
or minus 0.1 gallon per hour.
If the flow rate is not within the tolerance,
adjust the fuel pressure accordingly.
The temperature of the fuel must be maintained
within the range of 32 degrees Fahrenheit
to 52 degrees Fahrenheit for the duration of the test.
The fuel pressure at the burner inlet should be monitored
while the burner is operating.
The fuel pressure must not fluctuate more than plus
or minus 2 pounds per square inch
from the fuel pressure obtained
during the fuel flow calibration procedure.
A flame temperature validation or sample test will be void
should the fuel pressure fluctuate outside this range
during either procedure.
Seven thermocouples must be used to check
the flame temperature of the burner.
The thermocouples must be 0.125 inches in diameter,
ceramic packed,
310 stainless steel sheathed, type-K (Chromel-Alumel)
grounded-junction with a nominal 24 AWG size conductor.
The seven thermocouples must be attached to a steel
mounting plate to form a thermocouple rake
for placement in the test stand
during the burner flame consistency validation.
The thermocouple mounting plate should be a minimum of 4 inches
away from the tips of the thermocouples.
A calibrated recording device
or a computerized data acquisition system
with an appropriate range must be used to measure
and record the outputs of the thermocouples.
A stopwatch or other device accurate to within plus or minus
1 second per 8 hours must be used to measure
the time of application of the burner flame,
duration of any test sample ignition,
and sample extinguishment time.
A suitable weight scale must be used to determine the initial
and final weights of the seat test sample.
This scale must have a resolution of 0.02 pounds,
and an accuracy of plus or minus 0.02 pounds.
A handheld hot wire or similar type air velocity sensing unit
must be used to monitor the flow of air inside the test chamber
when the ventilation hood is operating.
Airflow measurements should be taken
at the beginning of the day
prior to operating the test burner.
A suitable hot-wire anemometer
which may be mounted to the sample test frame
is manufactured by Dwyer Instruments,
model number 641-6-LED.
A suitable handheld hot-wire anemometer
is manufactured by TSI,
model number 9515.
A suitable test chamber must be used to reduce
or eliminate the possibility of test fluctuation
due to air movement.
It is recommended the test chamber
have a minimum floor area of 15 feet by 15 feet.
Smaller test cells may experience
elevated air temperatures within the cell.
This may influence the burning of the test sample
and increase the time period for the test cell to cool
to the 100-degree-Fahrenheit upper temperature limit
before the start of each test.
The test chamber must have an exhaust system
capable of removing the products of combustion
expelled during the tests.
The sonic burner used in the test must be checked
to ensure the proper flame temperature is being produced
for consistent and accurate test results.
Examine and clean the burner cone
of any evidence of buildup of combustion products,
soot, et cetera.
Soot buildup inside the cone
may affect the flame characteristics
and cause difficulties
during flame consistency validation.
Since the burner cone may distort with time,
the cone should be inspected at the beginning of each day
the burner is operated to ensure all dimensions
are within specified tolerances.
Mount the thermocouple rake on a movable stand
that is capable of being quickly translated into position
in front of the burner.
Move the rake into the flame validation test position
and check the distance of each of the seven thermocouples
to ensure that they are located 4 plus or minus
0.125 inches from the exit plane of the burner cone.
Ensure that the seven thermocouple ends, or tips,
are offset 1 plus or minus
0.0625 inches above the horizontal center line
passing through the welded seams on each side of the burner cone.
Align the center thermocouple, thermocouple number four tip,
in front of the vertical center line of the burner cone exit.
Note that the thermocouple rake movable stand
must incorporate detents
that ensure proper centering of the thermocouple rake
with respect to the burner cone
so that rapid positioning of the rake
can be achieved during the validation procedure.
Once the proper position is established,
move the thermocouple rake away
and move it back into the flame validation position
and recheck distances.
When all distances and positions are confirmed,
move the thermocouple rake away from the burner.
While the thermocouple rake is away from the burner,
turn on the spark plug, pressurized air and fuel flow,
and light the burner.
Allow the burner to warm up for a period of 2 minutes.
After the warm-up period,
move the thermocouple rake into position
in front of the burner cone
and allow 1 minute for thermocouple stabilization.
Then record the temperatures of each of the seven
thermocouples once every second for a period of 30 seconds.
No baffles, fire-resistant boards,
or partitions of any kind
that may influence temperature readings
of the thermocouple rake
are to be used during flame consistency validation.
Remove the thermocouple rake from the flame temperature
validation position and turn off the burner.
Calculate the average temperature of each thermocouple
over this period and record.
Although not a requirement for testing,
the recommended average temperature of each of the seven
thermocouples should be 1700 degrees Fahrenheit
plus or minus 100 degrees Fahrenheit.
This criteria applies to the sonic burner only.
The burner should be rechecked to ensure that it is configured
properly if temperatures are measured
outside of this recommended range.
A fine adjustment of the internal stator orientation
and or distance from the end of the draft tube
may be necessary to achieve the required temperatures,
provided the adjustments are within allowable tolerances.
It is crucial that the fuel nozzle be aligned
to the geometric center of the turbulator.
A slight adjustment of the fuel tube
between the stator and fuel nozzle
may be required to obtain
an even temperature profile
across the thermocouple rake.
The center point of the nozzle where the fuel exits,
should not deviate more than 0.0625 inches
from the geometric center of the turbulator exit plane
when looking into the burner draft tube.
If no problems are found with the burner,
any temperature reading outside of this range
may require thermocouple replacement.
It is recommended that the burner flame temperature
be validated at the beginning and end of each day
testing is to be performed to ensure test result consistency.
Examine and clean the cone of soot deposits and debris.
Move the sample test frame into the test position
and clean the frame of any debris.
Place the restraint rod, or three restraint rods
if testing leather dress samples,
on the test sample frame and zero out the weight scale.
This ensures the weight of the rods
do not alter the measured sample weight.
Mount the seat test sample with rod restraints
and record the weight of the sample
to the nearest 0.02 pound.
Ensure that the vertical exit plane of the burner cone
is at a distance of 4 plus or minus
0.125 inches from the seat test sample horizontal assembly,
and that the horizontal center line
running through the welded seams
on each side of the burner cone
is aligned with the horizontal center line
of the horizontal assembly as shown.
The geometric center of the vertical burner cone exit plane
should be aligned with the center point
of the horizontal cushion assembly.
Dress cover features, such as hook and loop closures,
may protrude beyond the dress covering material.
The additional thickness of such features is not to be included
in the 4 plus or minus 0.125-inch distance
from the test sample horizontal assembly
to the vertical center line of the burner cone exit plane.
When ready to begin the test, move the test sample
apparatus away from the test position
to the warm-up position,
a minimum of 36 inches,
so that the flame will not impinge on the seat test sample.
Turn on and light the burner
and allow it to stabilize for 2 minutes.
To begin the test, move the test sample
apparatus into the test position
and simultaneously start the timing device
when the test apparatus is fully in the test position.
Expose the seat test sample to the burner flame for 2 minutes,
and then turn off the burner.
Immediately move the test sample
apparatus out of the test position
so that the hot burner cone does not influence
the burning of the sample.
Observe the seat test sample and terminate the test
when the seat test sample self-extinguishes.
Immediately after test termination,
record the posttest weight
of the remains of the seat test sample
to the nearest 0.02 pound, excluding droppings.
If a sample does not self-extinguish after 5 minutes
from the time the burner had been turned off,
record the posttest weight of the sample,
then terminate the test
by extinguishing the seat test sample.
Extinguishing the flame prior
to recording the posttest sample weight
may alter the final test weight measurement.
Measure the four principle burn lengths of the sample.
The burn lengths are measured along the top side
of the horizontal assembly,
bottom side of the horizontal assembly,
front side of the vertical assembly,
and the back side of the vertical assembly.
The four burn lengths are defined as the distance
measured, in inches,
from the inside edge of the test sample
mounting frame closest to the burner cone
to the farthest point where the damage to the seat test sample
has occurred due to the area's combustion,
including partial or complete consumption,
charring or embrittlement.
However, this does not include areas which are merely sooted,
stained, warped, or discolored.
An industry practice acceptable to the FAA
for determining cushion assembly burn length damage
has been to use an object with a dull point, such as a pencil,
and scrape the dress covering.
If the object used penetrates the dress covering,
damage has occurred due to that area's combustion.
Identify and describe the seat test sample being tested.
Report the type of foam
(flame retardant, molded or cut);
foam density, if known;
and manufacturer and type of flame retardant treatment
if known.
Report the number of seat test samples tested.
Report the pretest and posttest weight of each seat test sample,
the calculated percentage weight loss of each seat test sample,
the calculated average percentage weight
for the total number of seat test samples tested,
and the time to test sample self-extinguishment.
Report each of the four burn lengths
for each seat test sample tested.
Provide a record of burner flame temperature validation.
Report the type of burner used and manufacturer.
It may be helpful to note the date, time,
ambient air temperature,
humidity level, and any other data
that may be used to study
the burn characteristics of the samples.
For each of the burn lengths measured,
the burn length may not exceed 17 inches on
at least two-thirds of the total number of sampled tested.
Should the burn length on the underside
of the horizontal cushion assembly
extend to the frame angle support farthest
from the burner cone,
it is considered to have exceeded
the 17-inch burn length criteria.
In other words, it has reached the side of the cushion
opposite to the burner and is a failure.
The combined average percentage weight loss
of all samples tested may not exceed 10 percent.
The individual percentage weight loss of
at least two-thirds of the total number of samples
tested may not exceed 10 percent.
Example one -- two of the three samples
tested have burn lengths exceeding 17 inches.
This sample set fails based on the two-thirds
burn length criteria.
Example two -- the average percent weight loss
for the three samples tested has exceeded 10 percent.
This sample set fails based on the average percent
weight loss criteria.
Example three -- two of the three samples
tested have a weight loss exceeding 10 percent.
This sample set fails based on the two-thirds
weight loss criteria.
Example four -- one sample has a burn length exceeding 17 inches,
while another has weight loss exceeding 10 percent.
Although two of the three samples have failed,
the failure modes are different.
Failure criteria for weight loss and burn length
are independent of each other.
This sample set is a pass.