FAA Flammability Rule and ORCON Solutions

Aircraft vulnerability to in-flight fires in inaccessible areas has always been one of the important safety concerns of the aviation industry. The fatal crash of Swissair Flight 111 (SR 111) off the cost of Nova Scotia on September 2, 1998, brought the issue of the in-flight fire safety to a new level. Investigation conducted by the Transportation Safety Board of Canada revealed that the fire onboard the SR 111 most likely started with an electrical arcing event that ignited the covering material on the thermal/acoustic insulation blankets. Insulation materials manufactured in accordance with the then-current flammability standards did not contain fire and contributed to the rapid spread of flame that eventually led to the loss of the aircraft and those onboard.

Soon after the tragic accident with the Swissair aircraft, the FAA issued Airworthiness Directives requiring replacement of metallized PET thermal/acoustic insulation on the McDonnell Douglas MD-11, DC-10, MD-80 and MD-90 aircraft with materials that meet new flame propagation test requirements. The new Radiant Panel Test involves evaluation of the flammability of the aircraft thermal / acoustic insulation system under the combined exposure to the source of flame and radiant heat. This test is considered to represent a more realistic fire propagation scenario compared to the standard tests.

In the mean time, the FAA found that not only metallized Mylar insulation covering film but also the majority of other metallized and non-metallized PET and PVF films widely used in the industry would not pass the Radiant Panel Test and could propagate the flame. According to the FAA, during the period of 1967 through 1998, three fatal in-flight fires occurred on part 121 aircraft in North America as well as six more throughout the rest of the world. Moreover, there were three to five in-flight fires causing serious damage on part 121 aircraft in the U.S. each year. All cases involved fires started in an inaccessible area and further flame propagation on the thermal/acoustic insulation covering film.

Regulations

In 2000, a Notice on Proposed Rulemaking (NPRM) was issued.  It proposed upgraded flammability standards for thermal/acoustic insulation materials by adopting new flammability test methods (Radiant Panel Test) and criteria that specifically address flame propagation under realistic fire scenarios. The NPRM also introduced burnthrough protection requirements and proposed a test method for determining aircraft thermal/acoustic insulation resistance to flame penetration.

On July 31, 2003, the Federal Aviation Administration issued the Final Rule on Improved Flammability Standards for Thermal/acoustic Insulation Materials Used in Transport Category Airplanes (FAA 2000-7909). The Rule became effective on September 2, 2003, and gives industry two years to comply to the new, more stringent, flame propagation standards, and four years to meet newly developed flame penetration requirements.

The flame propagation part of the Final Rule is applicable to:

A.  All part 91, 121, 125 and 135 transport aircraft manufactured after September 2, 2005;
B.  All part 91, 121, 125 and 135 transport aircraft manufactured before September 2, 2005, when thermal/acoustic insulation materials are installed in the fuselage as replacements after September 2, 2005.

The Burnthrough part applies to:

A.  All airplanes with passenger capacity of twenty and greater operating under part 121, manufactured after September 2, 2007.

Solution

ORCON Corporation has been supplying the aerospace industry with thermal/acoustic insulation films, tapes and systems for more than forty years. Working closely with OEMs, the FAA, and other rulemaking authorities, ORCON has always been on the edge of the continuous process of improvement of flammability characteristics of aircraft insulation.

Covering Films and Tapes

In the late 90s, in response to the McDonnell Douglas operators' demand for Radiant Panel Test compliant materials to meet the FAA AD, ORCON Corporation developed a series of Polyimide and PVF products that met the most stringent FAA flammability requirements. Currently, hundreds of retrofitted McDonnell Douglas aircraft have new ORCON thermal/acoustic insulation covering materials onboard. Also, even though there was no requirement for use of Radiant Panel Test compliant materials on any aircraft other than MD-80, MD-90 and DC-10/MD-11 affected by the FAA AD, the new materials have been widely used in the aftermarket insulation systems by the most pro-active aircraft operators.

Product development efforts continue and as a result ORCON Corporation is now offering a broad line of reinforced insulation covering films and tapes compliant to the latest flame propagation requirements. All covering films are optimized for impulse and ultrasonic heat sealing that guarantees their excellent performance in current insulation blanket manufacturing processes. Films and tapes are available in a variety of configurations, depending on the level of reinforcement, weight, and substrate material.<

STC/PMA Thermal/acoustic Insulation Kits

As one of the largest suppliers of aircraft fabricated  products in the North America, ORCON Corporation provides complete nose-to-tail thermal / acoustic insulation solutions specifically engineered to meet both flame propagation and flame penetration requirements of the FAA Rule.

Substrate Material Choice

Two major types of the film, polyimide and polyvinyl fluoride (PVF), are available to be used in thermal/acoustic insulation systems. Not all polyimide and PVF insulation covering films currently on the market pass the Radiant Panel Test. The films that do pass have different mechanisms of passing the test:

The Polyimide (i.e. Kapton®) covering film mechanism for passing the RPT is that it doesn't burn; the only damage to the covering film on the test blanket is a penetration and surrounding char from the propane torch ignition source.

Polyvinyl fluoride (i.e. Tedlar®) covering film passes the RPT by shrinking away from the heat source; it may suggest that the covering film may burn if restrained in place.

Polyimide film is considerably more expensive than Tedlar®. On the shipset basis, thought, the price difference between Tedlar® and polyimide insulation covering film options usually does not exceed 15%-20%. Polyimide has a proven record of being more durable than both Tedlar® and Mylar® (PET) which, along with the superior fire resistance performance, offsets the cost disadvantage associated with use of more expensive covering film.

Both options are available from ORCON Corporation. However, ORCON strongly believes that polyimide should be considered as a material of choice for the thermal/acoustic insulation of aircraft.