Airworthiness Directives; REVO, Incorporated Models Lake LA-4, Lake LA-4A, Lake LA-4P, Lake LA-4-200, and Lake Model 250 Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[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).

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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 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

[[Page 54235]]

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, 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, 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, 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:

[[Page 54236]]

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.

Sec. 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

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Model Serial Nos.

------------------------------------------------------------------------

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.

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Wing Spar Part Numbers Incorporated

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Wing spar parts Part Nos.

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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.

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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, dated June 12, 1999:

(1) Remove the wings in accordance with the applicable

maintenance manual. This procedure is part of the service bulletin,

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, 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,

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

[[Page 54237]]

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 ____

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:

----------------------------------------------------------------------

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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.

[FR Doc. 99-25920 Filed 10-5-99; 8:45 am]

BILLING CODE 4910-13-U