### Page 1 of 6 **Disposition Comments Docket No:**  

### 2010

- 0720 SNPRM **Directorate ID:** 

### 2010

- SW

- 050

- AD Originating Office Tracking No.: 

### SP1415B)

- R NO COMMENTS RECEIVED

– If this box is checked, no signatures are required. No 

### Has the reference d service information been revised since the NPRM was issued? I f ye s, list latest revision and attach a cop y. Note that changes beyond the scope of the previously published NPRM will require a new notice. Contact the Directorate focal point for guidance.

Instructions: Summarize all comments **by issue** (not by commenter) and provide your recommended resolution of each issue. **All comments relating to the sam e issue should be**  **discussed together.** Do not list all of the issues from one commenter together. If changes to the AD are required based on the comments received, explain why and describe in detail what change(s) you recommend. Reference FAA

- IR
- M
- 8040.1C Chapter 9. **ISS UE 1:**  Select one o

f the following : service info If other, explain : Commenter(s): 

### Sikorsky What change to the AD action is requested? 

### Summary Section; The second sentence of this section states “This proposal would require revising the airworthiness limitations section of the Instructi ons for Continued Airworthiness (ICA) to reduce the life limit of the main gearbox housing and replacing any main gearbox housing that exceeds the life limit.” Sikorsky presents the Airworthiness Limitations in Chapter 4 of I CA SA S92A

- AWL

- 000. These lim itations are expressed in terms of Replacement Intervals. Sikorsky proposes that the term “life limit” be replaced with “replacement interval” (2 instances). Why is the change requested or how is it justified? Do we agree? If **YES,** we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because

Make the following changes to the AD: If **NO** , we don’t agree because 

### when the main gearbox housing has reached its life limit it has reached the end of its useful life. The phase “replacement interval” is not as specific.
**ISSUE 2**  **:** Select one of the following : service info

If other, explain : Commenter(s): 

### Sikorsky What change to the AD action is requested? 

### Summary Section; Also within the sec ond sentence of this section the phrase “replacing an y main gearbox” exceeds the scope of this NPRM. While the applicability

section denotes the specific main gearbox housing part numbers, the invocation of the term “an y” in the Summary section may invite confusion and should be clarified.

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Sikorsky proposes that the phrase “... replacing any applicable main gearbox housing...” be used instead. Why is the change requested or how is it justified? Do we agree? If **YES,** we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don’t agree because 

### i n the context of the sentence, the word “applicable” does not add to the clarification.

**ISSUE 3**  **:** Select one of the following : Service Info If other, explain : Commenter(s): Sikorsky What change to the AD action is requested? Summary Section; The third sentence of this section states “This pro posal is prompted by a fatigue analysis conducted after a helicopter was found with a severed main gearbox mounting foot pad (foot pad) that failed due to fatigue”. Crack mode was determined to be surface corrosion cracking with fatigue as possible second ary contributor. Sikorsky proposes that this sentence should read that the foot pad failed due to corrosion/fatigue. Why is the change requested or how is it justified? Do we agree? If **YES** , we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don't agree because t he surface corrosion cracking reduced the fatigue life of the main gearbox mounting foot pad. The fatigue analysis was performed to determine the life of the foot pad should surface corrosion cracking exist.
**ISSUE 4**  **:** Select one of the following : Service Info If other, explain : Commenter(s): Sikorsky What c hange to the AD action is requested? Summary Section; Also within the third sentence of this section, the investigation is comprised of many elements and the resultant decrease in replacement interval is not attributed exclusively to a fatigu e analysis. Accordingly, Sikorsky proposes that the phrase “a fatigue analysis” be replaced with “an evaluation”. Why is the change requested or how is it justified?

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Do we agree? If **YES** , we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don't agree because a lthough many elements are part of the investigation, the fatigue analysis is the primary source for determining th e residual life of the part.
**ISSUE 5**  **:** Select one of the following : Service Info If other, explain : Commenter(s): Sikorsky What change to the AD action is requested? Discussion Sec tion; The second sentence of this section cites two instances of “life limit”. For the reason described in issue 1 above, Sikorsky proposes that these two entries should be replaced with “replacement interval”. Why is the change requested or how is it justified? Do we agree? If **YES** , we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don't agree because when the main gearbox housing has reached its life limit it has reached the end of its useful life. The phase “repl acement interval” is not as specific.
**ISSUE 6**  **:** Select one of the following : Service Info If other, explain : Commenter(s): Sikorsky What change to the AD action is requested? Dis cussion Section; Also within the second sentence of this section, Sikorsky proposes that the phrase “... replace any main gearbox housing... ” should read “... replace any applicable main gearbox housing...”, for the reason specified in issue 2 above. Why is th e change requested or how is it justified? Do we agree? If **YES** , we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don't agree because i n the context of the sentence, the word “applicable” does not add to the clarification.
**ISSUE 7**  **:** Select one of the following : Service Info

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If other, explain : Commenter(s): Sikorsky What change to the AD action is requested? Discussion Section; The third sentence of this section iterates that this “proposal is prompted by a review of a fatigue analysis conducted after a helicopter was found with a severed foot pad due to the effect of fatigue of the main gearbox housing.” For the reason cited in issue 3 above, Sikorsky proposes that this sente nce should read that the foot pad failed due to corrosion/fatigue. Why is the change requested or how is it justified? Do we agree? If **YES** , we agree because Make the following changes to the A D: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don't agree b ecause t he surface corrosion cracking reduced the fatigue life of the main gearbox mounting foot pad. The fatigue analysis was performed to determine the life of the foot pad should surface corrosion cracking exist.
**ISSUE 8**  **:** Select one of the following : Service Info If other, explain : Commenter(s): Sikorsky What change to the AD action is requested? Discussion Section; Also within the third sentence of this section, an d for the reason cited in issue 4 above, Sikorsky proposes that the phrase “a fatigue analysis” be replaced with “an evaluation”. Why is the change requested or how is it justified? Do we agree? If **YES** , we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don't agree because a lthough many elements are part of the investigation, the fatigue analysis is the primary source for determining the residual life of the part.
**ISSUE 9**  **:** Select one of the following : Service Info If other, explain : Commenter(s): Sikorsky What change to the AD action is requested? Discussion Section; The second sentence of the second paragraph of thi s section proposes, within 60 days, revising the airworthiness limitations section of the ICA “to reduce the life limit of the main gearbox of the main gearbox housing from 2700 hours TIS to

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1000 hours TIS and replacing, before further flight, any main gearbox housing that has exceeded the 1000

- hour TIS life limit”. For the reason described in issue 1 above, Sikorsky proposes that these two entries should be replaced with “replacement interval”. Why is the change requested or how is it justified? Do we agree? If **YES** , we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don't agree because when the main gearbox housing has reached its life limit it has reached the end of its useful life. The phas e “replacement interval” is not as specific.
**ISSUE 10**  **:** Select one of the following : Service Info If other, explain : Commenter(s): Sikorsky What change to the AD action is requested? Compliance Section; Compliance item (a) specifies reducing the life limit of the affected main gearbox housing. For the reason described in issue 1 above, Sikorsky proposes that the term “life limit” be replaced with “replacement interval”. Why is the change requested or how is it justified? Do we agree? If **YES** , we agree because Make the following changes to the AD: If **PARTIALLY AGREE** , we agree with because We disagree with because Make the following changes to the AD: If **NO** , we don't agree because when the main gearbox housing has reached its life limit it has reached the end of its useful life. The phase “replacement interval” is not as specific. **For additional issues, double -**  **click here** 

### Page 6 of 6 **S ignature Section**  Signature indicates concurrence with this action. Originating Office Tracking No.: ANE

- 150

**ASE Date** 

**Branch Manager Date**