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Federal Aviation Administration Fire-Safety Mission
Thomas E. McSweeny*
Aircraft fire safety has always been an issue of high priority with the flying public. As
the agency with prime responsibility for aviation safety, the Federal Aviation Administration
(FAA) continuously endeavors to maintain and enhance fire safety. These attempts include
ensuring the safety of new aircraft designs through the certification process, of new aircraft in
production through manufacturing inspection, and of aircraft in use through strict maintenance
and inspection requirements. All attempts involve enforcement of standing safety requirements
as laid down in the Federal Aviation Regulations and elaborated upon in a variety of documents,
such as Aerospace Recommended Practices, Advisory Circulars, and technical reports. These
requirements are kept technologically current by dozens of ad hoc committees operating under
the aegis of organizations like the Society of Automotive Engineers.
in addition to the standing regulatory requirements, new standards for aircraft fire safety
are periodically imposed. In the case of an immediate and known threat to safety, FAA
certification authorities issue Airworthiness Directives. These require modification of specific
aircraft models that have a feature identified as a safety threat. Occasionally, aircraft accidents
or tests allow the FAA to pinpoint an area where a new fire safety requirement could offer
demonstrable safety improvements for all aircraft of a given size or class. Such new
requirements are established through a formal public rule-making process. FAA fire-safety
research and development, as well as test and evaluation, have traditionally been directed to
support the rule-making process for near-term attainable improvements. Such work has also
served to screen out unproductive or counterproductive regulatory endeavors whose deficiencies
are identified in full-scale testing.
At the present time, major near-term f~re-safety research and development efforts are
aimed at Malone replacement, fuselage burnthrough resistance, onboard cabin water-spray
systems, cargo compartment protection, and flight data recorder fire resistance. These near-term
activities have resulted in the technical basis for many fire-safety design considerations.
The FAA's role in air transport safety has been fundamentally mollified through the
provisions of the Aviation Safety and Research Act of 1988. This legislation has charged the
FAA with the new mandate of carrying out long-term, basic research in many areas. These
include not only improvement of fire safety but also how to deal with the safety of operating
aging aircraft; how to understand human factors issues involving flight crews, aircraft
mechanics, and air traffic controllers; and how to develop an air traffic control system to handle
future fleet growth safely. Such long-range research offers the FAA a new dimension to our
responsibilities of promoting a safe aviation system. It presents the FAA with organizational
challenges such as obtaining resources, identifying the most productive research directions, and
integrating this work into the FAA safety processes.
In the specific area of fire safely, which is the subject of this conference, the FAA has
developed a plan or framework for initiatives with a longer-term safety payoff. A successful
*Director, Aircraft Certification Service, Federal Aviation Administration, Washington, D.C.
3
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4
Improved Fire- arm Smoke-Resistant Materials
long-term fire research program will provide the FAA with the third leg of a platform to provide
a stable basis for future f~re-safe aircraft. Rulemaking and Airworthiness Directives have proven
their worth in the fire-safety record of today's aircraft. The flying public demands that
tomorrow's record be even better, and the FAA hopes that the results of this f~re-safety research
effort will provide quantum improvements over today's technology.
This research framework includes six major research thrust areas. They are
I. fire modeling;
2. vulnerability analysis;
3. fire-resistant materials;
4. improved systems;
5. advanced suppression; and
6. fuel safety.
These areas were identified through consultations with technical experts throughout the
country and together represent the FAA's view of the best comprehensive approach that could
be followed with unconstrained resources. Of these fire-safety research areas, fire-resistant
materials is the topic on which the Congress has placed its greatest emphasis, and coincidentally
it is the one area of the six that was rated highest in priority by FAA certification personnel.
Consequently, this is the first area for which the FAA has sought full funding.
The quest for cabin interior materials that are more fire resistant poses considerable
challenges. In only a very superficial sense can an aircraft cabin interior be compared with other
~ .~ ~ it, ~
. . . . . . .
inhabited structures. While the major function of a building structure is for self-support, aircraft
fuselage structural toads are dominated by the pressure differential between the interior and the
low pressures found at high altitudes. Whereas building insulation is rated for its characteristics
of thermal protection, aircraft insulation has a primary sound-absorbing function. This list of
unique selection criteria can go on, but the importance of low weight for all elements making
up the aircraft cabin interior can never be underestimated. it is for this reason that new fabrics
had to be developed to provide means to fire-block aircraft passenger seats to satisfy new fire-
safely standards.
In a modern jet transport, the sidewall panels, partitions, ceiling, and stowage bins are
typically honeycomb composite assemblies with Nomex~ core, phenolic-impregnated fabric
facesheets, and decorative layers of inks and thermoplastics. Seat covers are typically wool/nylon
blends, while the fire-blocking layer may be polybenzimidazole, or a blend of loomed and
Kevla~9. Seat back trays are typically molded polycarbonate. Overhead passenger service units
can be of metal or Declare construction. Windows are stretched acrylic, while carpets are woo!
or nylon. Floor panels might be of honeycomb construction with a Nomex~ core and epoxy-
impregnated graphite facings. The insulation behind the interior panels is fiberglass bagged in
MylaI49 liners. Cargo liners might be polyester or epoxy-impregnated fiberglass. Graphite fabrics
are gradually moving in as lighter-weight replacements for fiberglass within the cabin. Polymers
play a major role in the construction of aircraft interiors due to their many remarkable
properties, which allow for a variety of desired end properties, ranging from weight and
durability to comfort and aesthetics.
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Thomas E. McSweeny
5
A number of fire-safety considerations are involved with airplane design, certification,
and operation. Engines, as well as auxiliary power units, include fire-detection and extinguishing
systems. Wing fuel vents have flashback arrestors to minimize lightning hazards. Designated
engine firewalls acne flammable fluid-hose assembly designs must pass specified fire-endurance
tests. Ducts carrying heated air from engine compressors have associated hot-air leak detectors
for hot-air lakes. The routing of flammable fluid lines avoids areas having potential ignition
sources. Main landing gear wheels are braked to a stop after lift-off to prevent damage to
hydraulic systems from thrown tire belts. Landing gear tires are pressurized with nitrogen to
prevent auto-ignition of tire pyrolyzate resulting from overheated brake mechanisms. Wiring
within the airplane pressure vessel employs low-flammabiliyv insulation like Kanton@. Circuit
breakers further protect the wiAng from overheat.
-her
The basic philosophy for fire safety in materials design and selection involves one or
more of four goals depending on the fire threat and required functional performance of the
material. These goals are
1.
2.
3.
4.
low ignitability;
low heat release;
fire containment; and
fire endurance.
Low ignitability, as demonstrated by a modified Bunsen burner test, is a requirement for
most aircraft interior materials. Seats, as well as cabin interior panels, must demonstrate low
heat release in addition to the ignitability requirement. Seat cushions configured in a mock-up
assembly are allowed a specified weight loss when exposed to direct flames from a 2-gallon-per-
hour of! burner. Panels are limited in both peak and total allowable heat release as tester! in the
Ohio State University Rate of Heat Release Apparatus.
A fire containment requirement is imposed on cargo liner materials. The liners are
expected to prevent cargo compartment fires from spreading beyond the confines of the
compartment. For small compartments, fire control is achieved through oxygen starvation. In
larger compartments, a detection and suppression system is deployed. In the former case, cargo
liner integrity is needed to keep fresh air out of the compartment. In the latter case, the liner
integrity is needed to keep in both the fire and the extinguishing agent. The test requirement for
cargo liners also involves the use of a 2-gallon-per-hour burner. Fire containment clearly
includes fire endurance as a necessary requirement.
Fire endurance is the goal of fire-safety requirements for emergency escape slides. The
fire test involves exposing slide fabric, stretched by pressurization, to a radiant source. The
endurance of slide material to the radiant heat from a fuel fire is enhanced when the slide fabric
has an aluminized coating.
Additional aircraft cabin fire-safety features include lavatory smoke detectors and trash-
bin extinguisher bottles, mandatory hand-held extinguishers for onboard use, floor proximity
escape path lighting, and protective breathing equipment for the cabin and flight deck crew.
Aircraft fire safely is a complex issue. Quantum safety improvements will require a joint
effort between the FAA, the air transportation industry, and other interested and affected parties.
To be successful in this effort, we in the FAA need your help to meet these new challenges.
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6
Improved Fire- arm Smoke-Resistant Materials
This conference hosted by the National Materials Advisory Board is a beginning to get your
input, and ~ am confident that the conference will be productive.
Representative terms from entire chapter:
cabin interior
