03-13049. Proposed Revisions to Advisory Circular 25.1419-1, Certification of Transport Category Airplanes for Flight in Icing Conditions

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed advisory circular revision and request for comments.

SUMMARY:

The Federal Aviation Administration invites comments concerning a proposed revision to Advisory Circular 25.1419-1, “Certification of Transport Category Airplanes for Flight in Icing Conditions.” The proposed revision provides revised guidance for certification of airframe ice detection and protection systems on transport category airplanes. This action provides interested persons an opportunity to comment on the proposed revision to the AC.

DATES:

Send your comments on or before July 22, 2003.

ADDRESSES:

You should send your comments on the proposed AC revision to the Federal Aviation Administration, Attention: Robert Jones, Propulsion/Mechanical Systems Branch, ANM-112, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Ave SW., Renton, WA 98055-4056. You may examine comments at this address between 7:30 a.m. and 4 p.m. weekdays, except Federal holidays.

FOR FURTHER INFORMATION CONTACT:

Robert Jones at the above address, telephone [phone], facsimile [phone], or e-mail at: [e-mail].

SUPPLEMENTARY INFORMATION:

How Do I Submit Comments on the Advisory Circular Revision?

You are invited to comment on the proposed revision to AC 25.1419-1 by submitting written comments, data, or views. You should identify the title of the AC and submit comments in duplicate to the address specified above. The Transport Airplane Directorate will consider all comments received on or before the closing date for comments before issuing a revision to the AC. You may view the complete text of AC 25.1419-1 at the following Internet address: http://www.airweb.faa.gov/​rgl. At the home page, click on “Advisory Circulars,” then at the next page, enter “AC 25.1419-1” in the “Search” box and press “GO.”

Discussion

AC 25.1419-1, “Certification of Transport Category Airplanes for Flight in Icing Conditions,” dated August 18, 1999, provides guidance for certification of airframe ice detection and protection systems on transport category airplanes. Paragraph 3, Analyses, describes information that should be included in a certification plan submitted by the applicant. Note 2 of that paragraph states:

An applicant may determine that protection is not required for one or more of these areas or components. If so, the applicant should include supporting data and rationale in the analyses for allowing those areas or components to go unprotected. The applicant should show that the lack of protection does not adversely affect the handling characteristics or performance of the airplane. If there is uncertainty about the effects of the lack of protection, the effects should be determined by flight test demonstration.

Several questions regarding the meaning of this note have been raised. Several applicants have erroneously thought this note allowed adequate analysis and testing to preclude the requirement for flight test demonstrations. However, 14 CFR 25.1419(b) at amendment level 25-72 requires flight testing in natural icing conditions as a means to verify the analyses required by paragraph (a) to check for icing anomalies, and to demonstrate that the ice protection system and its components are effective. Guidance material may not supersede the rule and, therefore, Note 2 does not preclude the need for flight testing in natural icing conditions.

As part of a new type certification program, flight in natural icing conditions is required to show compliance with § 25.1419(b). In addition to flight in natural icing conditions, additional wind tunnel, laboratory, and other flight tests may be required to verify the analyses required by § 25.1419(a). However, under some circumstances, flight test data acquired on a previous certification program may be found to be applicable to a new or modified airplane (such a derivative model). To use the previous flight test data, the applicant is required to provide supporting data and rationale that show:

a. The original flight test data is applicable (similarity)

b. The applicant possesses the flight test data

c. The new or modified configuration is safe for flight in icing conditions.

Because of the erroneous interpretations, the following clarification is provided.

Proposed Revision to AC 25.1419-1

Replace the existing Note 2, paragraph 3a, with the following:

Note 2:

An applicant may determine that protection is not required for one or more of these areas or components. If so, the applicant should include supporting data and rationale in the analyses for allowing those areas or components to go unprotected. The applicant should show that the lack of protection does not adversely affect the handling characteristics or performance of the airplane. Section 25.1419(b) of part 25 at amendment level 25-72 requires certain flight testing. However, flight test data from previous certification programs may be used to show partial compliance with § 25.1419(b) if it can be shown that the data is applicable to the airplane in question. This would generally require a similarity analysis. If a similarity analysis is used, the guidelines of paragraph 3(f) of this AC are applicable. If there is uncertainty about the effects of the lack of protection, or the similarity analysis, the manufacturer should conduct flight test demonstrations.

Issued in Renton, Washington, on May 12, 2003.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.