SUBJECT: Thermal/Acoustic Insulation Installed on Transport Category Airplanes

REFERENCE: Federal Register: December 30, 2005 (Volume 70, Number 250) 

SUMMARY: This FAA action modifies the requirements for improved flammability characteristics of thermal/acoustic insulation used as replacements on airplanes manufactured before September 2, 2005.

Major Highlights

Amendments to parts 91, 121, 125, and 135 require that insulation materials, when installed as replacements, meet the new flame propagation test requirements of Sec. 25.856.

Following publication of the final rule, and the associated Advisory Circular (AC) 25.856-1, and shortly before the September 2, 2005, compliance date, industry representatives (including AEA) told the FAA that some assumptions in the regulation were not correct.

For a number of reasons presented by the General Aviation community, the FAA has significantly changed the regulations affecting in-service aircraft. The rule now is limited to insulation blankets and removable insulation on ducting.

The materials in insulation blankets were one of the primary materials intended to be covered by the "replacement" provision in the regulation and continue to be covered by the rule.

In addition, insulation around ducts is significant for its potential fire safety ramifications. Ducts are intended to convey a fluid medium from one point to others and, therefore, provide a potential fire propagation path by their nature. Because air ducts are the most significant and common, the FAA is limiting the replacement provision in this amendment to insulation air ducts only.

Other types of piping, or fluid lines are no longer covered by the replacement provision. These items, which might otherwise be considered ducts, are not included in this amendment because they have very specialized insulation needs, and replacement parts are not readily available. In addition, they tend to be much smaller than air ducts and do not use the large quantity of insulation that was the target of the original proposal.

While some ducts and insulation are integral, meaning that replacement of the insulation includes the replacement of the duct, many ducts are insulated with separate materials. The July 2003 rule will continue to apply to those ducts insulated with separate material. However, insulation that is integral to the duct and cannot be replaced without replacing the duct will no longer be covered by the regulations for replacement. This includes insulation that is bonded or laminated to the surface of the duct.

The regulation now reads:

Sec. 91.613 Materials for compartment interiors.

(b) Thermal/acoustic insulation materials. For transport category airplanes type certificated after January 1, 1958:

(1) For airplanes manufactured before September 2, 2005, when thermal/acoustic insulation is installed in the fuselage as replacements after September 2, 2005, the insulation must meet the flame propagation requirements of Sec. 25.856 of this chapter, effective September 2, 2003, if it is:

(i) Of a blanket construction or

(ii) Installed around air ducting.

(NOTE: Sections. 91.613(b)(1), 121.312(e)(1), 125.113(c)(1), and 135.170(c)(1) have all been amended with similar language.)

This final rule is effective on January 30, 2006. Send your comments by February 28, 2006.

AEA Commentary

AEA is very pleased with the FAA's efforts to amend these regulations. The amendment is very appropriate and reasonable.

However, the Association continues to be disappointed with the Agency for not addressing the hundreds of Parts catalogs which contain hundreds of part numbers which are no longer acceptable for use on U.S. registered aircraft.

The author of these regulations makes the in-appropriate assumption that a maintenance technician will review the aircraft operating rules prior to ordering replacement parts for an aircraft.

To help prevent the technicians from ordering and installing non-compliant parts, AEA is encouraging its members to share the information contained in this Regulatory Update with the entire maintenance organization.

FMI: www.aea.net, Ric Peri: ricp@aea.net, Federal Register (Volume 70, Number 250)