Memorandum by Sherman S Smith Esq, Orcon
Corporation (AS 33)
I recently heard that the Parliamentary Sub-Committee
on Transport is holding an inquiry into aviation safety. Orcon
Corporation has developed a thermal/acoustic insulation system
that provides safety enhancements to the flying public.
The Federal Aviation Administration is expected
to issue a Notice of Proposed Rule Making in June that will set
new safety standards for insulation. Orcon has been supporting
the FAA, and the CAA's programme at Darchem, to develop new materials
tests that will underlie the new standards.
The initiative for looking at this issue came
first from the CAA, following a tragic accident in 1985 in Manchester,
England. Fifty-five people died in that accident when an on the
ground fuel file burned through the aluminum fuselage in about
one minute. Curlon insulation developed by Orcon Corporation increases
the "burnthrough" time to up to 10 minutes, giving passengers
time to escape.
A second safety issue is in-flight flammability.
This was highlighted by the Swissair crash off Nova Scotia on
2 September, 1998. Investigators are looking into whether thermal/acoustic
insulation may have provided fuel to fire an on-board fire. Don't
confuse this issue with electrical wiring insulation. Investigators
believe wiring with frayed insulation or an overheated electrical
device may have sparked the fire.
I am attaching a White Paper that provides more
background on the issue.
Sherman S Smith
Orcon General Manager
New Enterprise Development, Aerospace Division
8 March 1999
ORCON CORPORATION, UNION CITY, CA, USA
Aircraft Thermal/Acoustic Insulation
FAA Flammability Issue
On 14 October, 1998, the FAA issued the following
"Statement by FAA Administrator Jane
Garvey on Aircraft Insulation
The Federal Aviation Administration (FAA) will
developwithin six monthsa new test specification
for insulation that will result in increased fire safety on aircraft.
The FAA also will propose requiring the use of improved insulation
once the new test standard is developed.
Today, the FAA urged Boeing, Airbus, Fokker,
and other manufacturers as well as the Air Transport Association
and Regional Airline Association to take advantage of any reasonable
maintenance opportunity to replace existing insulation materials.
Preliminary work has identified materials that provide a substantial
increase in fire resistance over some materials now in use. The
two identified so far are fiberglass and a material known as Curlon,
each wrapped in a polyimide film. Polyimide is the chemical name
for Kapton-like compounds that have very high heat resistance
Manufacturers and operators are reviewing service
bulletins that address possible hidden fire sources to determine
the status of compliance. Service bulletins are advisories issued
by manufacturers to share information and recommend maintenance
and other actions to operators. If necessary, additional service
bulletins and new maintenance practices may be developed to reduce
possible fire sources while the new standard for insulation is
developed. Mandatory airworthiness directives also may be issued.
The FAA also has begun discussions with the international
aviation community through the Joint Aviation Authority in Europe
and with the British, French and Japanese airworthiness authorities
on the work undertaken by the FAA.
In addition to developing the new standard for
testing insulation, the FAA will require that existing materials
be replaced with insulation that can pass the new test. The new
regulation will accept or "grandfather," any aircraft
already retrofitted with fiberglass or Curlon, wrapped in polyimide
The Curlon/Kapton insulation system has been
called a "breakthrough" in Federal Aviation Administration
studies in regard to the increased protection it provides to the
aircraft and flying public. It addresses real world safety threats
and also adds a new safety component to the aircraft that can
contain fires, shielding other components and systems.
New standards for aircraft insulation will address
two very different fire safety risks:
in-flight flammability, fires inside
the aircraft involving insulation covering films; and
burnthrough, post crash fires burning
through the fuselage from outside the plane.
The Curlon/Kapton insulation system significantly
reduces the potential of in-flight fires that could result in
smoke in the cockpit or lead to tragic events. It also increases
the amount of time a passenger has to escape before flames penetrate
the aircraft interiorfrom 1 or 1½ minutes to as much
as 10 minutes.
The issue of in-flight flammability concerns
fires that occur inside the aircraft and may be fed by an insulation
covering film. Fires can be ignited by overheated wiring or electrical
devices that are in close proximity to the surface of the insulation
behind interior panels. The use of a polyimide base film product,
like Kapton, virtually eliminates this problem.
Concern, particularly about metalised Mylar
film, increased following the Swissair crash off Nova Scotia 2
September, 1998. The investigation into the cause of the crash
may take two years to complete. However, investigators have said
publicly that a fire on board may have been sparked by wiring.
Charred and incomplete pieces of metalised Mylas insulation covering
film recovered from the crash site indicate it may have provided
some fuel to the fire.
Prior to the Swissair crash, insulation film
flammability was an issue noted in several incidents that resulted
in significant damage to aircraft on the ground, but fortunately
no loss of life. Flammability incidents have also been reported
from around the world involving non-metalised Mylar and metalised
Tedlar covering films.
Currently the only FAA flammability requirement
is the 12-second vertical burn test (FAR 25.853), requiring an
8 inch maximum burn length. This test has been shown to be inadequate.
Metalised Mylar covering films, used in the McDonnell Douglas
aircraft until 1993, pass this test, but will propagate flame
under some actual aircraft situations. Boeing developed a test
for insulation blankets in the mid-1970s and added it to their
specifications. It is known as the "Q-Tip" test. A swab
soaked in alcohol is ignited and placed on insulation samples.
It is a more stringent test and metalised Mylar does not pass
Boeing has been using metallised Tedlar and
non-metallised Mylar. In 1996, McDonnell Douglas recommended airlines
begin replacing the metallised-Mylar insulation in their older
planes during regular maintenance. Kapton, a polyimide film developed
by Dupont 30 years ago, is demonstrably superior on all tests
for flammability. A Kapton film system was installed on the Lockheed
The second scenario is a fuel fire burning outside
the aircraft after a survivable crash. Fire-blocking insulation
batting, such as Curlon, combined with Kapton-like covering film,
can hold back the fire, delaying it from burning through into
the passenger compartment for as long as 10 minutes. This will
give passengers time to escape.
The British initiated study of fuselage burnthrough
resistance in 1985. That year, a Boeing 737 caught fire on the
ground in Manchester, England. Investigators concluded that a
fuel fire outside the aircraft burned through in less than 60
seconds. Fifty-five people were killed because they did not have
enough time to get out of the plane. The tragedy was particularly
frustrating because rescuers were at the scene within minutes
with fire fighting equipment. The FAA and British authorities
began investigating the thermal/acoustic blankets as a means to
provide the most practical way to increase burnthrough protection.
In 1996, the FAA tested an Orcon insulation
batting, called Curlon, as a substitute for fiberglass in a full-scale
section of a plane fuselage. The first test showed Curlon alone
increased escape time by a factor of five. Subsequent tests combining
Curlon with Kapton have shown even better results, described as
"a breakthrough" in FAA reports. Separate smaller-scale
tests have been conducted by the British CAA and by the French
CEAT. The FAA has accelerated testing and is developing new types
of tests with the aim of setting a reliable performance gauge
that correlates well with real world conditions.
Looking at the question of how long is long
enough to hold back a fire, a British study determined that after
five minutes the benefits of fuselage burnthrough protection begins
to diminish. It is assumed that passengers who have not exited
a burning plane after five minutes are trapped or seriously injured.
Kapton and Curlon combinations have held back flames up to 10
minutes in some tests. Insulation systems that provide burnthrough
protection for five minutes will give passengers a reasonable
added measure of safety.
There will be sufficient supply of Curlon and
Kapton to meet anticipated demand. The base substrate polyimide
films, such as Kapton, are readily available. Orcon has capacity
in place to convert these films into insulation covering. Orcon's
new facility in Kennesaw, Georgia, will have Curlon in full production
by June 1999.
The use of Curlon and Kapton instead of non-metallised
Mylar or Tedlar with fiberglass represents a marginal increase
in cost. Orcon estimates the cost of supplying a new Boeing 737-400
with insulation blankets is $56,000. Shifting to Curlon and Kapton
would increase that cost to $84,000.
The FAA recommended insulation system represents
an approximately 50 per cent increase in cost over current materials.
The Kapton film is a more durable covering film and will significantly
reduce maintenance cost over a 30-year period. The increase in
cost is minimal relative to the total $30-150 million selling
price of commercial jets, while reducing maintenance costs and
According to airlines, the downtime and labour
involved to retrofit planes pose the largest costs. The slight
increase in cost of materials is not the major factor. The major
factor is the compliance schedule. If new regulations allow for
airlines to retrofit the aircraft in the course of normal heavy
maintenance, this cost will be greatly reduced.
Orcon has a 30-year track record of creating
customised solutions for aviation insulation systems for both
aircraft manufacturers and airlines. Orcon works with customers
to analyse insulation needs and design high quality insulation
systems, including manufacturing the component materials, fabricating
insulation blankets and facilitating installation.
Today the company continues to develop the best
materials available to create insulation blankets. Orcon obtained
the Curlon technology because it is a proven way to provide burnthrough
safety. It allows insulation systems to provide warmth and sound
proofing while elevating the standards of fire safety.
Insulation blanket materials
Most insulation blankets contain a special fine
fiberglass batting to provide thermal and acoustic insulation.
These products are lightweight and relatively inexpensive. However,
fiberglass provides only a few seconds of protection in the presence
of a fire.
Curlon is a processed polyacrylonitrile fibre.
It is easier to work with than fiberglass and does not introduce
harmful particles into the air when disturbed. It is a non-conductive
material; it will not short out electrical equipment and will
not promote corrosion. It is a new product that will be in full
commercial production at Orcon's new 120,000 square-foot facility
in Kennesaw, Georgia, by June 1999.
Covering films are often referred to by their
substrate material, i.e., Mylar, Tedler or Kapton. However, the
covering film is an engineered product consisting of the base
film, sometimes metallised to improve moisture resistance and
with film coatings added to provide heat-seal capabilities and
flame retardants. Reinforcing yarns are adhesively attached to
increase strength and durability.
This is a lightweight film used in McDonnell
Douglas planes until 1993. As outlined above, it meets FAA flammability
requirements, but subsequent experience and tests have shown that
it can propagate flame.
Non-metallised Mylar and metalised Tedlar
There are film substrates in use by all major
aircraft OEMs. They pass the FAA requirements and the Q-Tip flammability
test. But they do not perform as well on newer tests, such as
tests for "flashover", where a film ignites spontaneously
at elevated temperatures. These products are also a source of
fuel for a fire.
Covering films made with Kapton (polyimide)
are significantly less flammable than other known films in all
tests. This product was used on the Lockheed L-1011. The Lockheed
spec Kapton film does not propagate flame and is not a fire fuel.
It has a much higher melt temperature and consequently increases
fuselage burnthrough time. It also does not ignite spontaneously
(flashover) at elevated temperatures.