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
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.