AD 2000-18-05

This amendment adopts a new airworthiness directive (AD), applicable to all Aerospatiale Model ATR42 and ATR72 series airplanes, that requires modification of the alerting capability of the anti-icing advisory system to improve crew awareness of icing conditions, replacement of the median wing de-icing boots with extended de-icing boots, and installation of de-icing boots on the metallic wing leading edge. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to reduce the degradation of lift and drag characteristics in prolonged severe icing exposure, which could result in loss of lift and consequent reduced controllability of the airplane.

Final rule.

2000-18-05 AEROSPATIALE: Amendment 39-11890. Docket 99-NM-183-AD.

Applicability: The following airplanes, certificated in any category:
- Model ATR42 series airplanes, excluding those modified in accordance with Aerospatiale Matra ATR Modifications 4993, 4998, and 5008
- Model ATR72 series airplanes, excluding those modified in accordance with Aerospatiale Matra ATR Modifications 4994, 4997, and 5008

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repairon the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To reduce the degradation of lift and drag characteristics in prolonged severe icing exposure, which could result in loss of lift and consequent reduced controllability of the airplane, accomplish the following:

Boot Replacement/Installation
(a) Within 30 months after the effective date of this AD, replace the median wing de-icing boots with extended de-icing boots in accordance with Avions de Transport Regional Service Bulletin ATR42-30-0063, Revision 2, dated October 1, 1999 (for Model ATR42 series airplanes), or ATR72-30-1032, Revision 2, dated October 1, 1999 (for Model ATR72 series airplanes); as applicable.

(b) Within 30 months after the effective date of this AD, install de-icing boots on the metallic wing leading edge inaccordance with Avions de Transport Regional Service Bulletin ATR42-30-0064, Revision 2, dated October 1, 1999 (for Model ATR42 series airplanes), or ATR72-30-1033, Revision 2, dated October 1, 1999 (for Model ATR72 series airplanes); as applicable.

Modification
(c) Within 30 months after the effective date of this AD, modify the ICING light flashing logic of the Anti-icing Advisory System (AAS), in accordance with Avions de Transport Regional Service Bulletin ATR42-30-0065, Revision 2, dated October 25, 1999 (for Model ATR42 series airplanes), or Avions de Transport Regional Service Bulletin ATR72-30-1034, Revision 2, dated October 19, 1999 (for Model ATR72 series airplanes); as applicable.

NOTE 2: Accomplishment of the boot replacement, boot installation, and modification is also considered acceptable for compliance with the applicable requirements of paragraphs (a), (b), and (c) of this AD, if accomplished in accordance with Revision 1 of the following Avions de Transport Regional service bulletins: (For Model ATR42 Series Airplanes) ATR42-30-0063, dated May 7, 1999, ATR42-30-0064, dated May 7, 1999, or ATR42-30-0065, dated May 17, 1999; and (For Model ATR72 Series Airplanes) ATR72-30-1032, dated May 7, 1999, ATR72-30-1033, dated May 7, 1999, or ATR72-30-1034, dated May 17, 1999.

Alternative Methods of Compliance
(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, International Branch, ANM-116.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

Special Flight Permits
(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Incorporation by Reference
(f) The actions shall be done in accordance with the following Avions de Transport Regional Service Bulletins, as applicable:

Service Bulletin And Date
Page Numbers
Revision Level Shown on the Page
Date Shown on Page
ATR72-30-1032, Revision 2, October 1, 1999
1 10, 14 16, 33, 34, 43
2
October 1, 1999

11 13, 17 32, 35 42, 44, 45
1
May 7, 1999
ATR72-30-1033, Revision 2, October 1, 1999
1, 2, 6, 7, 8, 15
2
October 1, 1999

3 5, 9 14, 16 43
1
May 7, 1999
ATR72-30-1034, Revision 2, October 19, 1999
1, 2, 4, 8 31
2
October 19, 1999

3
1
May 17, 1999

5, 6, 7
Original
February 2, 1999
ATR42-30-0063, Revision 2, October 1, 1999
1 5, 9, 10, 13, 14, 16, 18, 19, 37, 38, 43, 47
2
October 1, 1999

6 8,11, 12, 15, 17, 20 36, 39 42, 44 46, 48, 49
1
May 7, 1999
ATR42-30-0064, Revision 2, October 1, 1999
1 5, 8 10, 12 14, 20, 21, 35 54, 59, 60
2
October 1, 1999

6, 7, 11, 15 19, 22 34, 55 58, 61
1
May 7, 1999
ATR42-30-0065, Revision 2, October 25, 1999
1 5, 7 52
2
October 25, 1999

6
1
May 17, 1999

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Aerospatiale, 316 Route de Bayonne, 31060 Toulouse, Cedex 03, France. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

NOTE 4: The subject of this AD is addressed in French airworthiness directives 1999-165-077(B) and 1999-166-041(B), both dated April 21, 1999.

(g) This amendment becomes effective on October 13, 2000.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Aerospatiale Model ATR42 and ATR72 series airplanes was published in the Federal Register on October 27, 1999 (64 FR 57787). That action proposed to require modification of the alerting capability of the anti-icing advisory system to improve flight crew awareness of icing conditions, replacement of the median wing de-icing boots with extended de-icing boots, and installation of de- icing boots on the metallic wing leading edge. Explanation of Relevant Service Information

Aerospatiale has issued Revision 2 of the following Avions de Transport Regional Service Bulletins:

Service Bulletin
Date
Model
ATR42-30-0064
October 1, 1999
ATR42
ATR42-30-0063
October 1, 1999
ATR42
ATR42-30-0065
October 25, 1999
ATR42
ATR72-30-1032
October 1, 1999
ATR72
ATR72-30-1033
October 1, 1999
ATR72
ATR72-30-1034
October 19, 1999
ATR72

The service bulletins that were cited in the proposed AD as the appropriate sources of service information were all at Revision 1. The procedures described in Revisions 1 and 2 are essentially the same; Revision 2 was issued to correct certain technical errors. Accomplishment of the actions specified in Revision 2 of the service bulletins is intended to adequately address the identified unsafe condition.

Comments
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Support for the Modification Requirement
One commenter agrees that the modifications specified in the proposed AD "represent a step forward in providing a higher level of protection for an aircraft operating in icing conditions or with airframe ice accretions."

Request to Revise Intent of AD
Two commenters request that certain language of the proposed AD be revised to more accurately explain the scope and purpose of the proposed actions.

1. One commenter requests that the proposed AD be revised to indicate that the proposed modifications represent only improvements over the present system, not a solution to the degradation of lift and drag in prolonged exposures to severe icing.

2. This same commenter requests a revision of certain portions of the proposed AD that state that the proposed modifications are intended to "prevent degradation of lift and drag characteristics in prolonged severe icing exposure, which could result in loss of lift and consequent reduced controllability of the airplane." The commenter notes that, "if degradations in lift and drag are being prevented, the aircraft is not in severe icing."

3. Another commenter requests that the proposed AD be revised to reflect that the actions are intended to "prevent degradation of lift and drag characteristics in prolonged severe icing exposure, which could resultin wing stall."

4. This same commenter disagrees with certain statements in the Discussion section of the proposed AD, and proposes the following revision:

"The DGAC advises that the existing median wing de-icing boots may not be adequate to protect the airplane during prolonged exposure to severe icing conditions, outside of those for which the airplane has been certificated. Such prolonged exposure could produce degradation of lift and drag characteristics which could result in wing stall.

In addition, DGAC reports that in several instances, crews have failed to activate the de-icing boots, despite the fact that ice accretion had been detected by the Anti-icing Advisory System (AAS). This failure could indicate that the current design of the AAS may not provide adequate alerting signal to the flight crew in case of lack of awareness or vigilance."

The commenter requests this revision of the Discussion section for the following reasons:

- The commenter states that, "[p]riority should be given to the median de-icing boot extension to further enhance the airplane's robustness in case of prolonged severe icing encounters." [The FAA infers that the commenter objects to the order in which the issues were presented in the proposed AD (the icing light logic problem was discussed before the boot modification), although the issues were presented in no particular order.]

- The modification of the ICING light flashing logic should be considered only a reinforcement of crew awareness and vigilance, considering the importance of human factors during flight in severe icing conditions.

- The proposed AD states that failure to activate the boots may indicate that the AAS may not provide adequate alerting "in all instances of ice accretion." The commenter suggests that this could be interpreted to mean that the AAS system could malfunction under some ice accretion conditions. The commenter points out that the AAS modification addresses only its warning logic, not its detection capability.

- In line with its policy to avoid relying only on procedures to address safety issues, the DGAC mandated the modifications proposed in the NPRM.

FAA's Response: Clarification of Intent
In response to these comments, the FAA agrees that clarification of the intent of the AD may be necessary. The actions proposed by this AD are intended to enhance the alerting capability and performance of the airplane ice protection system. Accomplishment of these actions will result in a more robust icing protection system that will provide an increased level of safety during flight in icing conditions.

It was not the FAA's intent to suggest that the new de-icing boots proposed by this AD would provide a permanent solution for prolonged flight in severe icing conditions. The new de-icing boots are not FAA-approved for operation in severe icing, although they represent product improvements that may provide some benefit during an inadvertent encounter with a severe icing environment. The FAA Aeronautical Information Manual defines "severe icing" as follows:

"The rate of [ice] accumulation is such that the de-icing/anti-icing equipment fails to reduce or control the hazard. Immediate flight diversion is necessary."

It is therefore clear that no airplane is approved for operations in severe icing conditions, and, if such conditions are inadvertently encountered, an immediate diversion is the only practical means to deal with the hazard at this time. The FAA and the aviation industry are working to define a "severe icing envelope," i.e., icing conditions that may be outside the present certification envelope (as required by Appendix C of part 25 of the Federal Aviation Regulations). Until the FAA and the aviation industry agree on the definition of this new severe icing envelope and a means to operate safely within it, the FAA is not prepared to consider approval of operations in such conditions. Therefore, the finalrule has been revised (in several places) to state that the required actions are intended to reduce (rather than "prevent") the degradation of lift and drag characteristics in prolonged severe icing exposure, which could result in loss of lift and consequent reduced controllability of the airplane.

The DGAC has advised the FAA of a few instances in which flightcrews failed to activate the de-icing boots, despite the fact that ice accretion had been detected by the AAS. As a result, the manufacturer has developed an enhancement of the alerting capability of the AAS system that reinforces flightcrew awareness of icing conditions. This modification results in the ICING light on the instrument panel continuing to flash as long as both level 2 and level 3 ice protection systems are not selected, once ice accretion has been detected by the electronic ice detection system. [Note: Level 1 (windshield heat and pitot-probe heat) is always on for every flight. Level 2 is the "anti-icing"mode (propeller and elevator/rudder horn heat, side window heat, and engine ice protection). Level 3 is the "de-icing" mode (airframe de-icing boots activated), and is on when level 2 is still in effect.]

In an effort to further enhance safety, the DGAC has also mandated a modification that extends the chord-wise coverage of the median wing boots. That mandate [French airworthiness directives 1999-165-077(B) (for Model ATR42 series airplanes) and 1999-166-041(B) (for Model ATR72 series airplanes); both dated April 21, 1999] prompted the issuance of the proposed AD. The new boots extend farther back on both the upper and lower surfaces of the wing. These extended boots have not been shown to provide any measurable improvement in the airplane's ability to operate safely in severe icing conditions, and are not offered by Aerospatiale in order to gain any operational advantage in these severe conditions. However, if the flightcrew inadvertently encounters severe icing, these extended boots may increase the level of safety while the flightcrew takes the required steps to immediately exit the severe icing conditions.

The FAA agrees that rewording the Discussion section of the proposed AD might clarify the purpose and anticipated benefit of the modifications; however, the Discussion section is not restated in a final rule.

Request to Revise Applicability
One commenter requests that the applicability of the proposed AD be revised to exclude airplanes on which the proposed modifications have been accomplished.

The FAA concurs. To better define the airplanes affected by this AD, the FAA has revised the applicability to exclude airplanes on which certain modifications have been accomplished.

Request to Require Revised Service Bulletins
One commenter has identified certain minor technical errors in Revision 1 of the service bulletins that would "prevent proper operation of the entire modification" if accomplished strictly in accordance with the accomplishment instructions. (Revision 1 was cited in the proposed AD as the appropriate source of service information.) The commenter reports that it was advised by the manufacturer that those technical issues will be corrected in the next service bulletin revisions.

The FAA partially concurs. Revision 2 of the service bulletins incorporates the corrected information. However, the manufacturer advises that clarification and correct instructions were provided so that the modification can be accomplished with the Revision 1 instructions. The manufacturer further advises that no additional work should be necessary for an airplane modified in accordance with Revision 1. Therefore, the final rule has been revised to require accomplishment of the modification in accordance with Revision 2, and to include a note that credits operators for prior accomplishment in accordance with Revision 1.

Conclusion
After careful review of the available data, including the comments noted above,the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact
The FAA estimates that 140 airplanes of U.S. registry will be affected by this AD.

The replacement of existing de-icing boots and the new installation of de-icing boots will take approximately 75 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $5,500 per airplane. Based on these figures, the cost impact of the replacement/installation required by this AD on U.S. operators is estimated to be $1,400,000, or $10,000 per airplane.

The modification of the alerting capability of the Anti-icing Advisory System (AAS) will take approximately 30 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $2,000 per airplane. Based on these figures, the cost impact of the modification required by this AD on U.S. operators is estimated to be $532,000, or $3,800 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact
The regulations adopted herein will not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: PART 39 - AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive: