Lake Wing Spar NPRM PDF Print E-mail

[4910-13-U]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39 [64 FR 54234 No. 193 10/06/99]

[Docket No. 99-CE-27-AD]

RIN 2120-AA64

Airworthiness Directives; REVO, Incorporated Models Lake LA-4, Lake LA-4A, Lake LA-4P, Lake LA-4-200, and

Lake Model 250 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

 

SUMMARY: This document proposes to adopt a new airworthiness directive (AD) that would apply to certain REVO, Incorporated (REVO) Models Lake LA-4, Lake LA-4A, Lake LA-4P, Lake LA-4-200, and Lake Model 250 airplanes. The proposed AD would require inspecting the left and right wing upper and lower spar caps and doublers for cracks, replacing any cracked parts and/or incorporating a modification kit depending on the extent of the damage, and reporting the results of the inspection to the Federal Aviation Administration (FAA). The proposed AD is the result of a report of a fatigue crack found at the second most inboard wing attachment bolt hole on one of the affected airplanes. Similar fatigue cracking has since been reported on seven more of the affected airplanes. The actions specified by the proposed AD are intended to detect and correct cracks in the wing spar caps and doublers, which could result in loss of the wing with consequent loss of control of the airplane.

 

DATES: Comments must be received on or before December 14, 1999.

 

ADDRESSES: Submit comments in triplicate to the FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 99-CE-27-AD, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106. Comments may be inspected at this location between 8 a.m. and 4 p.m., Monday through Friday, holidays excepted.

 

Service information (PDF, 85KB) that applies to the proposed AD may be obtained from REVO, Incorporated, P.O. Box 312, One High Street, Sanford, Maine 04073. This information also may be examined at the Rules Docket at the address above.

 

FOR FURTHER INFORMATION CONTACT: Mr. Richard B. Noll, Aerospace Engineer, FAA, Boston Aircraft Certification Office, 12 New England Executive Park, Burlington, Massachusetts 01803; telephone: (781) 238-7160; facsimile: (781) 238-7199.

 

SUPPLEMENTARY INFORMATION:

 

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received.

 

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

 

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 99-CE-27-AD." The postcard will be date stamped and returned to the commenter.

 

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 99-CE-27-AD, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106.

 

Discussion

The FAA has received a report of fatigue cracks that were found at the second-most inboard wing attachment bolt hole on a REVO Lake Model 250 airplane. The cracks were detected during wing repair where the wing spar and wing skin were disassembled. Further analysis indicated that the cracks initiated at a machined notch at the flange termination point of the spar cap.

The REVO Models Lake LA-4, Lake LA-4A, Lake LA-4P, and Lake LA-4-200 airplanes are of the same type design as the Lake Model 250 airplanes. Similar fatigue cracking to that of the above-referenced report has been found on seven more of these airplanes.

This condition, if not detected and corrected in a timely manner, could result in loss of the wing with consequent loss of control of the airplane.

 

Relevant Service Information

REVO has issued Service Bulletin B-79 (PDF, 85KB), dated June 12, 1999,

which specifies procedures for accomplishing the following on the REVO Models Lake LA-4, Lake LA-4A, Lake LA-4P, Lake LA-4-200, and Lake Model 250 airplanes:

- inspecting the upper and lower wing spar doublers for fatigue cracks and corrosion;

- inspecting the upper and lower wing spar cap angles for fatigue cracks and corrosion;

- repairing or replacing any cracked or corroded parts or areas, as applicable; and

- incorporating Aerofab B-79 kit on the wing spars.

 

The FAA's Determination

After examining the circumstances and reviewing all available information related to the incidents described above, the FAA has determined that AD action should be taken to detect and correct cracks in the wing spar caps and doublers, which could result in loss of the wing with consequent loss of control of the airplane.

 

Explanation of the Provisions of the Proposed AD

Since an unsafe condition has been identified that is likely to exist or develop in other REVO Models Lake LA-4, Lake LA-4A, Lake LA-4P, Lake LA-4-200, and Lake Model 250 airplanes of the same type design, the FAA is proposing AD action. The proposed AD would require inspecting the left and right wing upper and lower spar caps and doublers for cracks, replacing any cracked parts and/or incorporating a modification kit depending on the extent of the damage, and reporting the results of the inspection to the FAA.

Accomplishment of the proposed actions would be required in accordance with REVO Service Bulletin B-79 (PDF, 85KB), dated June 12, 1999.

 

Cost Impact

The FAA estimates that 641 airplanes in the U.S. registry would be affected by the actions specified in the proposed AD.

Wing removal and reinstallation to perform the proposed inspection would take approximately 32 workhours and the proposed inspection itself would take approximately 8 workhours per airplane. The average labor rate is approximately $60 an hour. Based on these figures, the total cost impact of the proposed inspection, including wing removal and reinstallation, on U.S. operators is estimated to be $1,538,400, or $2,400 per airplane.

The incorporation of the modification kit proposed in this action would take approximately 12 workhours (6 hours per wing) to accomplish at an average labor rate of $60 per hour. The modification kit costs $2,000 for Model Lake 250 airplanes and $1,600 for Models Lake LA-4 and Lake LA-4-200 airplanes (average of $1,800 for cost impact considerations). Based on these figures, the total cost impact of the proposed modification on U.S. operators is estimated to be $1,615,320, or $2,520 per airplane.

These figures do not take into account the costs of any part replacements that would be necessary if the FAA adopted the proposed rule. The FAA has no way of determining whether part replacements would be necessary for any affected airplane.

 

Compliance Time of the Proposed AD

The compliance time of the proposed AD is presented in both hours time-in-service (TIS) and calendar time with the prevalent one being that which occurs first. The reason for this is that the fatigue cracks on the affected airplanes may have already initiated and could be further developing on the low-usage airplanes as well as high-usage airplanes. Utilizing the dual compliance times would assure that cracks in the wing spars would be detected on all affected airplanes in a timely manner without inadvertently grounding any of the affected airplanes.

 

Differences Between the Proposed AD and the Relevant Service Information

REVO Service Bulletin B-79 (PDF, 85KB), dated June 12, 1999, specifies an inspection of the spar caps and angles for corrosion, as well as for fatigue cracks. After analyzing all service history and information related to this subject, the FAA has determined that the fatigue cracks that are developing in the spar cap angle are not associated with corrosion. Therefore, the proposed inspection in this AD only incorporates the fatigue crack specifications and does not include the corrosion specifications.

 

Regulatory Impact

The regulations proposed herein would not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

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) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action has been placed in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption "ADDRESSES".

 

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

 

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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 a new airworthiness directive (AD) to read as follows:

REVO, INCORPORATED: Docket No. 99-CE-27-AD.

Applicability: The model and serial numbers airplanes, certificated in any category, that are listed in the following chart and incorporate any of the wing spar part numbers (or FAA-approved equivalent part numbers) that are in the chart below the airplane models and serial numbers:

 

Affected Airplanes

Model

Serial Numbers

Lake LA-4

246 through 421, 423 through 429, 445, and 446

Lake LA-4A

244 and 245

Lake LA-4P

121

Lake LA-4-200

422, 430 through 444, and all serial numbers after 446

Lake Model 250

1 through 232

 

Wing Span Part Number Incorporated

Wing Spar Parts

Part Numbers

Upper Spar Cap Angles

2-1610-015 and 2-1610-016

Lower Spar Cap Angles

2-1610-075 and 2-1610-076

Upper Spar Doublers

2-1610-061 and 2-1610-081 and 2-1610-065

Lower Spar Doublers

2-1610-063 and 2-1610-083

NOTE 1: Improved design spar cap angles and the doubler kit referenced in this AD were incorporated at manufacture on the Lake Model 250 airplanes beginning with serial number 233. This AD does not apply to those airplanes.

NOTE 2: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been 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 (h) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on 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 follows, unless already accomplished:

Inspections Required by Paragraph (a) of this AD

At whichever of the following that occurs FIRST:

- Upon the accumulation of 500 hours time-in-service (TIS) on the wing spars or within the next 50 hours TIS after the effective date of this AD, whichever occurs later; or

- Upon the accumulation of 500 hours TIS on the wing spars or within the next 12 calendar months after the effective date of this AD, whichever occurs later.

Repair, Replacement, and Kit Incorporation

Required by Paragraphs (b), (c), and (d) of This AD

- Prior to further flight after the inspection required by paragraph (a) of this AD.

To detect and correct cracks in the wing spar caps and doublers, which could result in loss of the wing with consequent loss of control of the airplane, accomplish the following:

 

NOTE 3: The paragraph structure of this AD is as follows:

Level 1:

(a), (b), (c), etc.

Level 2:

(1), (2), (3), etc.

Level 3:

(i), (ii), (iii), etc.

Level 2 and Level 3 structures are designations of the Level 1 paragraph they immediately follow.

(a) At the time specified in the Inspections Required by Paragraph (a) of this AD portion of the Compliance section of this AD, accomplish the following in accordance with the Inspection section of Service Bulletin B-79 (PDF, 85KB), dated

June 12, 1999:

(1) Remove the wings in accordance with the applicable maintenance manual. This procedure is part of the Service Bulletin B-79 (PDF, 85KB), but is repeated in the AD to assure that the inspections are not accomplished before removing the wings.

(2) Inspect the upper and lower wing spar doublers for fatigue cracks from the root end to outboard of the wing attachment fitting bolt holes, using solvent-removable fluorescent dye with a high sensitivity (Type I, Method C, Sensitivity Level 3), in accordance with ASTM E 165-95 and E 1417-95a or SAE 2647; and

(3) Inspect the upper and lower wing spar cap angles for fatigue cracks from the root end to outboard of the wing attachment fitting bolt holes, using solvent-removable fluorescent dye with a high sensitivity (Type I, Method C, Sensitivity Level 3), in accordance with ASTM E 165-95 and E 1417-95a or SAE 2647. Cracks have been found in the cutout radius of the vertical flange near the second outboard hole.

(b) If any crack(s) is(are) found in any spar doubler during any inspection required by this AD, prior to further flight, replace the spar doubler with a new part of the same part number, in accordance with the applicable maintenance manual.

(c) If more than one crack is found in any spar cap angle, prior to further flight, accomplish both (1) and (2) below:

(1) Replace any applicable spar cap angle with one of the following spar cap angles in accordance with the applicable maintenance manual:

(i) Upper Spar Cap Angles: P/N 2-1610-087 and P/N 2-1610-088;

and

(ii) Lower Spar Cap Angles: P/N 2-1610-089 and 2-1610-091.

(2) Incorporate Aerofab B-79 kit in accordance with the Kit section of Service Bulletin B-79 (PDF, 85KB), dated June 12, 1999. This kit incorporates the following parts:

(i) Upper Spar Doubler: P/N 2-1610-093

(ii) Upper Spar Filler: P/N 2-1610-095

(iii) Lower Spar Doubler: P/N 2-1610-101

(iv) Lower Spar Fillers: P/N 2-1610-097 and P/N 2-1610-099

(d) If no cracks are found in the spar cap angles or if only one crack is found in any spar cap angle (cracks have predominantly been found in the cutout radius near the second outboard hole) of any spar cap angle, prior to further flight, incorporate Aerofab B-79 kit in accordance with the Kit section of Service Bulletin B-79 (PDF, 85KB), dated June 12, 1999.

(e) After the effective date of this AD, no person may install a wing on any of the affected airplanes, unless one of the following exists:

(1) The wing is new from the factory; or

(2) The inspection, repair and replacement, and kit incorporation requirements of this AD have been accomplished at the time of installation.

(f) At the applicable compliance time presented in paragraphs (f)(1) and (f)(2) of this AD, report all inspection results to the Manager, FAA, Boston Aircraft Certification Office, Boston Aircraft Certification Office (ACO), 12 New England Executive Park, Burlington, Massachusetts 01803. Use the form that is referenced as the "Appendix to Docket No. 99-CE-27-AD" to present the findings. Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056.

(1) Within 10 calendar days after accomplishing the inspection required by paragraph (a) of this AD; or

(2) Within 10 calendar days after the effective date of this AD if the requirements of this AD have already been accomplished.

NOTE 4: The following information is helpful in accomplishing this AD:

- Cracks, if present in the affected areas, typically run fore and aft across the vertical flange thickness at or near the intersection with the horizontal flange; and

- Although this AD does not have to be accompished at a REVO-authorized repair facility, the equipment and jigs needed to accomplish parts replacement are available at REVO-authorized repair facilities.

(g) 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.

(h) An alternative method of compliance or adjustment of the compliance times that provides an equivalent level of safety may be approved by the Manager, FAA, Boston Aircraft Certification Office (ACO), 12 New England Executive Park, Burlington, Massachusetts 01803. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Boston ACO.

NOTE 5: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Boston ACO.

(i) All persons affected by this directive may obtain copies of the document referred to herein upon request to REVO, Incorporated, P.O. Box 312, One High Street, Sanford, Maine 04073; or may examine this document at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106.

 

APPENDIX TO DOCKET NO. 99-CE-27-AD INSPECTION RESULTS REPORT

Report the following information to:

Manager, Boston Aircraft Certification Office

Engine And Propeller Directorate

Aircraft Certification Service

Federal Aviation Administration

12 New England Executive Park

Burlington, MA 01803-5299

Fax: (781) 238-7199

Operator/Repair Station _______________________________

Aircraft Model _______________________________

Aircraft S/N _______________________________

Date of Inspection _______________________________

Identify Operational Use (Estimate):

Take-off/Landings:

Water, % of Total _________________

Land, % of Total _________________

Parking

Water, % of Time _________________

Land, % of Time _________________

APPENDIX TO DOCKET NO. 99-CE-27-AD (continued)

 

INSPECTION RESULTS REPORT

NOTE: Add additional pages for the following for each part inspected.

Part No. _______________________________

Inspection

Dye Penetrant: Pass _____ Fail _____ N/A _____

If a crack is found, indicate the approximate location on the part and the length of the crack in inches: _______________________________________________________________

Part Time-In Service (TIS) (Hours):

Estimated ________________

Actual ________________

Unknown ________________

At Retirement ________________

Log Book entry for Part No. ___________________ , is (date) ___________________, at retirement hours ___________________.

Issued in Kansas City, Missouri, on September 29, 1999.

 

Michael K. Dahl,

Acting Manager, Small Airplane Directorate,

Aircraft Certification Service