Darchem Aircraft Insulation Systems

Aircraft thermal acoustic insulation

Developing New Protection & Products

New fire protection and thermal insulation products need when developed to reduce the costs of manufacturing. From prototype through to production, this can involve setting up new manufacturing processes, creating new inhouse tooling and training staff. Developments of this nature will add significant financial value to the company.

Darchem Engineering Ltd is wholly owned by the Esterline Corporation. The Insulations Systems Business Unit produces specialist lightweight, thermal insulation and fire protection for the high performance automotive, aerospace and industrial sectors. Darchem currently employs around 600 people with 450 at the Stillington site.

New systems have to continue to prove themselves on test, reducing engine bay and surface temperatures and removing the risk of fire. The use of composite materials and new production methods has also allowed a functional system to be developed that aesthetically blends in with the surrounding components.

Aerospace insulation systems

The origins of the aerospace insulation systems business are now 20 years old...

FAA Flammability Issue

On 14 October, 1998, the FAA issued the following statement:

"Statement by FAA Administrator Jane Garvey on Aircraft Insulation

The Federal Aviation Administration (FAA) will develop, within six months, a 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 characteristics.

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 aircraft 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 film."

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:

1.in-flight flammability, fires inside the aircraft involving insulation covering films; and

2.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 interior, from 1 or 1½ minutes to as much as 10 minutes.

IN-FLIGHT FLAMMABILITY

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 requirements are 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 it.

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 L-1011.

BURNTHROUGH

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 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.

COST AND SUPPLY

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 systems represent 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 enhancing safety.

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

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 aircraft 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

INSULATION

Fiberglass

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

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

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.

Metalised Mylar

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.

Kapton

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.

Address :

Stillington

Stockton-on-Tees

TS21 1LB

UK

Sales Contact : Mike Poole

mikepoole@darchem.co.uk

Phone : 01740 630461

Fax : 01740 632911

E-mail : dissales@darchem.co.uk