| ASW 2000-06-05
Burning Blankets: A Chronology of Fire
Hardening
June 5, 2000
May 1996: The Aircraft
Airworthiness Center of the Civil Aviation Administration of China (CAAC)
advises the Federal Aviation Administration (FAA) via letter of a 1995 fire
on a Chinese registered MD-11, in which the metalized Mylar insulation
blanketing burned. The CAAC report cited the "potential danger" posed by the blanket
material.
September 1997: FAA
Technical Center Report finds that metalized Mylar blanketing "was totally
consumed" when subjected to the flame from a Q-tip soaked in alcohol,
concluding darkly that the metalized Mylar film "could propagate a fire in a
realistic situation" (Report No. DOT/FAA/AR-97/58).
October 1997: Douglas
Aircraft issues service bulletins encouraging operators to replace metalized
Mylar blanketing on DC-8, DC-9, DC-10, MD-11 and MD-80/90 aircraft.
September 1998: Swissair
Flight 111 crashes. The accident airplane is an MD-11 with metalized Mylar
thermal acoustic blanketing installed throughout.
October 1998: FAA
Administrator Jane Garvey announces that fire test standards for thermal
acoustic blanketing will be upgraded in a "fast track" development effort
over the next six months at the FAA Technical Center. This effort was
announced as part of an FAA
program to remove metalized Mylar thermal acoustic insulation blanketing
from an estimated 1,200 aircraft (700 in U.S. registry). The
Administrator assured that blankets with polyimide (Kapton)
covering film and Curlon filler would be "grandfathered."
January 1999: FAA and
industry begin a series of discussions on potential flammability tests;
these discussions continue through June.
April 1999: FAA misses
6-month deadline for new burn test of insulation blankets. On April 6 the
FAA issues an emergency airworthiness directive in the wake of a below-deck
arcing event on an MD-11 that burnt the metalized Mylar insulation
blanketing. Operators of 62 MD-11's are ordered to inspect and repair the
applicable wire bundles. The case provides a vivid illustration of the type
of arcing that can burn insulation.
June 1999: The UK's Air
Accidents Investigation Branch issues a report of wiring damaged by
replacement of thermal acoustic insulation blanketing in the bilge area of a
B747. The arced wiring burned through the outer film of the thermal acoustic
insulation blanket. The case illustrates the potential of creating a new
danger while attempting to mitigate the hazard posed by flammable insulation
blanketing (see AAIB Bulletin No. 6/99 at the AAIB website:
http://www.open.gov.uk/aaib/jun99htm/vhojd.htm).
August 1999: FAA issues
NPRM/AD calling for removal of metalized Mylar insulation blankets on
Douglas-built narrowbodies (DC-9, MD-80 series) and widebodies (DC-10,
MD-11), and replacement with more fire-resistant materials within four
years. Comments to be received by 27 Sept.
The 11 August AD's
appear literally hours after the Transportation Safety Board of Canada
(TSB), the agency investigating the Swissair Flight 111 disaster, issues an
urgent safety recommendation calling for Metalized Mylar to be replaced. The
TSB recovered burned metalized Mylar insulation from the accident aircraft.
The TSB declares flatly the "unnecessary risk" posed by the material in all
aircraft.
In addition to
announcing its program to remove metalized Mylar, the FAA outlines its new
Radiant Panel Test, which is considerably more demanding than either the
12-inch flame test or the "Q-tip" test of insulation blanket material.
Development of the Radiant Panel Test took about 4 months longer than the 6
months envisioned originally.
November 1999: FAA
extends comment period from 27 Sept. to 13 December.
That same month a team
from Douglas and Swissair replace the insulation in the forward section of
an MD-11. The trial project goes smoothly, with Boeing [BA] contributing
$32,000 to the cost of materials. Swissair decides to selectively replace
the metalized Mylar in all of its MD-11's (about 15% of the total amount of
insulation blanking in the airplane, in areas identified as critical for
added fire hardening). Swissair replaces the metalized Mylar with Tedlar, a
material that passes the FAA's new radiant heat test.
Also that month, a team
from Douglas and American Airlines [AMR] undertake to replace the metalized
Mylar insulation on a prototype American Airlines MD-80.The objective of the
project is to determine how difficult the retrofit would be and how it would
impact other systems, such as wiring.
December 1999: A program
is initiated by Delta Air Lines [DAL] to replace some insulation on its
MD-11's as a trial to prepare for the FAA's final ruling. Delta elects to
use blanketing with Kapton film, based on the good service experience with
Kapton film on its L-1011 fleet.
February 2000: Work on
the American Airlines MD-80 prototype project is completed at a cost of
nearly $2 million cost. $1.1 million is for out of service revenue losses.
May 2000: FAA issues
final ruling, requiring metalized Mylar changeout in all areas of the
airplane, but extending the original 4 year deadline to 5 years. With an
effective date of June 30, 2000, the 5-year period established a deadline of
June 2005. By this means, operators will have an opportunity to do the work
during overhauls that occur on about a 4-5 year cycle, minimizing
out-of-service time.
June 2000: Service
Bulletins from Boeing's Douglas Products Division containing detailed
replacement instructions are scheduled for release at the end of the month.
June 2005: All metalized
Mylar thermal acoustic blankets to be removed from the fleet. Time elapsed
from the 1995 fire on the Chinese MD-11, about 11 years.
Sources: Compiled from
multiple sources, including FAA,
TSB, and past ASW coverage of this issue
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