Craig Amad eo General Manager Engineering Standards & Chief Engineer Delta Air Lines, Inc.

1775 Aviation Blvd

Atlanta, Ga. 30320

T. +1 404 714 1312

F. +1 404 773 3675 craig.amadeo@delta.com

Septem ber 30, 2011

U.S. Department of Transportation Docket Operations, M-30, West Building Ground Floor, Room W12-140 1200 New Jersey Avenue SE Washington, DC 20590 Fax: (202) 493-2251

Subject: D ocket No. FAA-2011-0836; Directorate Identifier 2010-NE-38-AD: RB211-Trent 800 Series Turbofan Engines – Inspection of LP Fuel Tubes for wear from clamps – Proposed Rule

Reference: (A ) Notice of Proposed Rule Making (NPRM): Docket No. FAA-2011-0836 ; Directorate

Identifier 2010-NE-38-AD. (B) Rolls Royce Service Bulletin RB.211-73-D685 Revision 5, dated August 18, 2010. (C) Rolls Royce Service Bulletin RB.211-73-D685 Revision 6, dated February 21, 2011.

SUMMARY:

Reference (A) proposes a Trent 800 Series Engine Airwor thiness Directive (AD) that would require initial and repetitive visual inspections of Low Pressure (LP) fuel tubes for evidence of fretting wear from the securing clamps that hold them in place on the engine fan case. The inspections are to be accomplished per certain steps of Reference (B). If wear is severe enough, the tube wall thickness is compro mised and tube may fracture resulting in fuel loss. Tubes failing the inspection are to be removed from service.

DELTA’S COMMENTS Delta agrees with the need to mitigate the LP fuel tube wear and leakage issue. However, we have the following

comments on the NPRM language as proposed:

Service Bulletin Reference Questions: 1) The latest version of Reference B service bulletin is now Revision 6 dated February 21, 2011. Delta would request the final rule reference this latest SB version and numbering. NOTE: Paragraphs (f)(1), (f)(2), and (g) list the SB number as RB.211-73-D685 (the ‘A’ was inadvertently omitted). DAL requests that the “A’ be added so the current service bulletin number is actually RB.211-73-AD685, Revision 6 dated February 21, 2011. 2) Delta would request the final rule allow that engines previously inspected per SB RB.211-73-D685 Revision 3, 4, or 5 to have met the “initial inspection” requirements of proposed rule.

Inspection Procedure Questions: 1) In the proposed rule paragraph (f), one of the interval options is to do initial inspection before 3,000 hrs since last inspection. Delta would like the final rule to provide the references by which the last inspection could

have been done to be considered acceptable to use this option. 

### 2) Proposed rule paragraph (f)(1) requires inspecting both the LP fuel tubes and the clips that hold the tube in place using Reference B, Paragraphs 3.A.(2) and 3.A.(3) (On-wing) or Paragraphs 3.B.(2) and 3.B.(3) (In shop). When looking at these service bulletin paragraphs , there are no insp ection criteria for the clips. ThereOctober 10, 2011 Page 2 of 2

are only inspection criteria for the wear on the tube. There are, instead, requirements in Reference B for replacement of the clips with new. De lta would like the final rule to prov ide clear direction for handling the clips (either require inspection per a particular reference or require clip replacement with new/serviceable part per the note in Paragraph 3.A of the SB).



### 3) Paragraph (g) of proposed rule requires repeat inspectio ns and, if necessary, replacement of fuel tubes and clips. Delta believes there is a chance to misinterpret the instructions as written and would propose the change in language given below to help clarify. The concern is the existing language might be perceived as requiring both the inspection and tube replacement to be accomp lished per Ref B paragraphs 3.A(2) and 3.A(3) and 3.B(2) and 3.B(3). Since these paragraphs are only ap plicable for the inspections and do not pertain to replacement of the tubes, Delta believe s the language could be clarified to something similar to the following: “Following accomplishment of the initial inspection in compliance with the requirements of paragraph (f)(1) or (f)(2) of this AD, repeat the inspection at intervals not exceeding 3,000 hours. Accomplish the inspections per SB RB.211-73-AD685 Revision 6, paragraphs 3.A(2) and 3.A(3) for on wing and 3.B(2) and 3.B(3) for in shop. If the inspection results indicate that either the fu el tubes (P/N FK22617, FK19213, and FK23986) or the clips that hold them in place do not meet requirements, they must be replaced before further flight.”



### 4) The proposed rule paragraphs (f)(1) and (f)(2) do not contain any statements about replacing tubes/clips when necessary as a result of the inspections. This is contra sted against paragraph (g) which currently does discuss replacement of these parts when necessary. For consis tency, Delta believes these paragraphs should have similar information related to tube/clip repl acement when the final rule is issued.

5) The proposed rule currently does not require inspection of the Fuel Oil Heat Exchanger (FOHE) mounts during initial or repetitive inspections even though the Reference B service bulletin does emphasize this action and has this requirement. By contrast, the EASA AD 2 010-0188 does require this FO HE mount inspection because it requires accomplishment of the entire service bulletin when doing the inspection. For clarity, Delta would request the final rule include a comment that the inspection requirements of the proposed AD do not mandate the FOHE mount inspections of Reference B, Paragrap hs 3.A.(4) and 3.B.(4). This would eliminate any ambiguity in the inspection requirements.

If you have any further questions or re quire additional information, please contact Steven Botts – Principal Engineer, Propulsion Engineering, at (612) 266-3876 or email at steven.botts@delta.com.

Thank you,

Peter Lauria Acting Chief Engineer; ODA administrator for Craig Amadeo General Manager – Engineering Standards & Chief Engineer Dept. 567

Cc: Amber Krchnavy Maggie Broder Alan Strom, F AA Engine Certification Office