While bad things happen to good people, often times some good can come as a result of the steps taken to fix problems that would prevent a future tragedy from recurring.   This happened in September 1998 in the case of SwissAir Flight 111 whose fate ended tragically when it crashed and had no survivors.  Our hearts and sympathies go out to all those families who suffered those losses.

Canada’s Transportation Safety Board investigated this accident for four years.  It was revealed that about one hour after the flight took off, the flight crew smelled smoke but nothing appeared to require immediate attention. Only thirty minutes later, the plane crashed.

A fire started because an electrical short ignited the polyethylene terephthalate foil used as a cover of thermal and acoustical insulation blankets.  The fire then damaged the air conditioning system.  Smoke and fire spread causing irreparable damage.

Introducing New Safety Measures: FAR 25.856(a)

The investigation of the accident resulted in the introduction of FAR 25.856(a) to improve flammability standards for thermal/acoustic insulation materials installed in transport category aircraft.

The most significant and stringent element of FAR 25.856(a) is the Radiant Panel Test (RPT), which requires that thermal/acoustic material is subjected to extremely high radiant temperatures, a flame source, while in a vertical position.

Upon responding to these new standards, a major aircraft manufacturer recognized that there was no chance for currently available elastomers to pass this test. A new material would need to be formulated that could pass an extreme test like RPT.

Introducing BISCO® A2

In response to this need, the Rogers BISCO A2 was developed.  This solid silicone material was specially designed with:

  • Polymers certified for continuous usage at temperatures as high as 300 °C
  • High performing additives that are not compromised at elevated temperatures
  • Material properties to transport heat away from areas where flame is applied
  • Additives to achieve optimized aerial densities for highly effective sound blocking performance
  • A formulation that allows for the material to be processed into a thin profile

The BISCO A2 formulation is the only RPT-tested material that meets FAR 25.856(a) safety requirements for use in airplanes currently on the market.  It provides:

  • Exceptional sound blocking performance in the low frequency range
  • Optimized “limpness”, which allows for ease of installation and ideal forming to curved surfaces

What’s the Difference Between Foam and the BISCO A2?

While there are foams on the market that meet FAR 25.856 (different from FAR 25.856(a)), a foam is not typically a good sound blocker.  Foam may be a good thermal insulation.  Also, it is easy to confuse FAR 25.853 with FAR 25.856.   FAR 25.853, also a difficult spec to meet, is applicable to “foams” that are used as gap sealing, gaskets, maybe vibration isolation.

FAR 25.856(a) is one of the two most difficult flame tests in the world to meet.  The other being the British Spec BS 6853 Category 1a for the rail industry.

BISCO A2 is now used by major airline manufacturers because some of the newer composite materials used in the fuselage design actually transmits much more acoustic noise than aluminum fuselages.  Thus the interiors of these aircrafts had a much higher dB level.  One manufacturer needed to block and absorb noise from entering the cabin.  This changed the spec of the material they needed to be classified as “acoustic insulation” and it needed to be installed in a vertical position (against the fuselage walls).  This meant the material had to meet FAR 25.856(a) and the RPT test.  Roger’s BISCO A2 was the only product commercially available that met these specifications.

For more information on BISCO A2:


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