Objective: Reduce The Risk Of In-Flight Fire

To reduce the risk of fire spreading aboard aircraft, the FAA Friday proposed requiring operators of more than 800 US-registered Boeing aircraft to replace or modify certain insulation blankets over the next six years.

The primary purpose of aircraft insulation blankets is to protect the passengers and crew from engine noise and frigid temperatures at high altitudes. Like silver-lined household insulation, they often are backed with a transparent film that helps hold them together. The proposed airworthiness directive (AD) was prompted by the discovery that some insulation blankets, which are coated with a film called AN-26, no longer meet the standards for preventing the spread of fire.

There are about 1,600 Boeing 727, 737, 747, 757 and 767 aircraft worldwide with this insulation, of which 831 are US-registered.

As an alternative to replacing the insulation, Boeing is developing a spray-on barrier that, if successful, would correct the problem and meet the requirements of the proposed directive.  Boeing expects to have the product ready by April 2006.

In June 2000, the FAA ordered insulation covered with metalized Mylar removed from more than 700 McDonnell Douglas models by June 30, 2005.  This followed the 1998 in-flight fire and crash off Nova Scotia of an MD-11 operating as Swissair flight 111. AN-26, manufactured by Orcon Corporation of Union City, CA, between 1981 and 1988, is different from the metalized Mylar used on insulation blankets installed previously on the McDonnell Douglas aircraft.

Although AN-26 appears to impede the spread of flames better than metalized Mylar, tests conducted by the FAA’s William J. Hughes Technical Center on 1980s-vintage AN-26 blankets indicated they no longer meet safety standards in a consistent manner.

The estimated cost of replacing the blankets on the US fleet is approximately $330 million. If Boeing’s alternate spray-on method is used, the cost may be less than $200 million. Replacing the blankets on a Boeing 737 requires about 4,200 labor hours, and 16,000 labor hours on a Boeing 747.

FMI: www.access.gpo.gov/su_docs/aces