Airworthiness Directives; Boeing Model 767 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 95-NM-149-AD; Amendment 39-9372; AD 95-19-10]

Airworthiness Directives; Boeing Model 767 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that

is applicable to all Boeing Model 767 series airplanes. This action

requires operators to perform visual inspections of the outer cylinder

aft trunnion on the main landing gear to determine if the fillet seal

is cracked or missing. This action also requires operators to inspect

for evidence of corrosion in this location. Finally, this action

prescribes the procedures that operators must follow if corrosion is

found. This amendment is prompted by several reports of fractures of

the outer cylinder aft trunnion due to stress corrosion cracking. The

actions specified in this AD are intended to ensure that corrosion is

not present in this location, thereby preventing future failures due to

stress corrosion cracking.

DATES: Effective September 29, 1995.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of September 29, 1995.

Comments for inclusion in the Rules Docket must be received on or

before November 13, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 95-NM-149-AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056.

The service information referenced in this AD may be obtained from

Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington

98124-2207. This information may be examined 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.

FOR FURTHER INFORMATION CONTACT: James G. Rehrl, Aerospace Engineer,

Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office,

1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2783;

fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received reports of fractures of

the outer cylinder of the aft trunnion of the main landing gear (MLG)

on three Boeing Model 767 series airplanes. One of the three airplanes

was six years old and had accumulated 28,887 total flight hours;

another was six years old and had accumulated 25,841 total flight

hours; and the third was eight years old and had accumulated 27,177

total flight hours. All of these airplanes were equipped with the

original MLG, none of which had been overhauled at the time of the

failure. Investigation revealed that in each case, moisture had entered

the area between the outer cylinder of the MLG and a mating bushing.

The effects of such moisture subsequently caused stress corrosion

cracking. This condition, if not detected and corrected in a timely

manner, could cause more fractures of the outer cylinder of the aft

trunnion, which could result in the loss of the MLG.

The FAA has reviewed and approved Boeing Service Letter 767-SL-32-

067, dated August 4, 1995, which describes the following procedures:

1. Performing repetitive visual inspections to determine if the

fillet seal of the outer cylinder aft trunnion is cracked or missing;

2. Removing the fillet seal, solvent-cleaning the adjacent area,

applying corrosion inhibiting compound (CIC),

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and visually inspecting to detect corrosion, if any fillet seal is

found cracked or missing; and

3. Re-applying CIC and greasing, if no corrosion is detected, or

repairing the aft trunnion, if any corrosion is detected.

Accomplishment of this repair eliminates the need for the repetitive

inspections.

Since an unsafe condition has been identified that is likely to

exist or develop on other Boeing Model 767 series airplanes of the same

type design, this AD is being issued to prevent stress corrosion

cracking, which could result in fractures of the outer cylinder aft

trunnion and the subsequent loss of the MLG. This AD requires visual

inspections to determine if the fillet seal of the outer cylinder aft

trunnion is cracked or missing, and the correction of any discrepancy

or follow-on actions, if necessary. Repairing the aft trunnion

constitutes terminating action for the repetitive inspection

requirements. The actions are required to be accomplished in accordance

with the service letter described previously.

Operators should note that this AD requires repetitive application

of CIC and grease every 500 flight hours, rather than at the 2A check

interval (1,000 flight hours), as recommended in the service letter. In

developing an appropriate compliance time for this action, the FAA

considered not only the degree of urgency associated with addressing

the subject unsafe condition, but the susceptibility of the subject

area to a high velocity of water spray (such as, landing on wet

runways, high pressure washing, etc.), which could lead to the

accumulation of water and subsequent stress corrosion cracking of the

outer cylinder of the aft trunnion.

The FAA considers this AD to be interim action. The manufacturer

has advised that it is developing a modification that will prevent

future occurrences of this unsafe condition. Once this modification is

developed, approved, and available, the FAA may consider additional

rulemaking.

As a result of recent communications with the Air Transport

Association (ATA) of America, the FAA has learned that, in general,

some operators may misunderstand the legal effect of AD's on airplanes

that are identified in the applicability provision of the AD, but that

have been altered or repaired in the area addressed by the AD. The FAA

points out that all airplanes identified in the applicability provision

of an AD are legally subject to the AD. If an airplane has been altered

or repaired in the affected area in such a way as to affect compliance

with the AD, the owner or operator is required to obtain FAA approval

for an alternative method of compliance with the AD, in accordance with

the paragraph of each AD that provides for such approvals. A note has

been included in this rule to clarify this long-standing requirement.

Since a situation exists that requires the immediate adoption of

this regulation, it is found that notice and opportunity for prior

public comment hereon are impracticable, and that good cause exists for

making this amendment effective in less than 30 days.

Comments Invited

Although this action is in the form of a final rule that involves

requirements affecting flight safety and, thus, was not preceded by

notice and an opportunity for public comment, comments are invited on

this rule. Interested persons are invited to comment on this rule by

submitting such written data, views, or arguments as they may desire.

Communications shall identify the Rules Docket number and be submitted

in triplicate to the address specified under the caption ADDRESSES. All

communications received on or before the closing date for comments will

be considered, and this rule may be amended in light of the comments

received. Factual information that supports the commenter's ideas and

suggestions is extremely helpful in evaluating the effectiveness of the

AD action and determining whether additional rulemaking action would be

needed.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the rule that might

suggest a need to modify the 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

AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this rule must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket Number 95-NM-149-AD.'' The postcard will be date-stamped and

returned to the commenter.

The regulations adopted herein will 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 final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency

regulation that must be issued immediately to correct an unsafe

condition in aircraft, and that it is not a ``significant regulatory

action'' under Executive Order 12866. It has been determined further

that this action involves an emergency regulation under DOT Regulatory

Policies and Procedures (44 FR 11034, February 26, 1979). If it is

determined that this emergency regulation otherwise would be

significant under DOT Regulatory Policies and Procedures, a final

regulatory evaluation will be prepared and placed in the Rules Docket.

A copy of it, if filed, 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), 40101, 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

95-19-10 Boeing: Amendment 39-9372. Docket 95-NM-149-AD.

Applicability: All Model 767 series airplanes, certificated in

any category.

Note 1: 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 use the authority

provided in paragraph (d) of this AD to request approval from the

FAA. This approval may address either no action, if the current

configuration eliminates the unsafe condition; or different actions

necessary to address the unsafe condition described in this AD. Such

a request should include an assessment of the effect of the changed

configuration on the unsafe condition

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addressed by this AD. In no case does the presence of any modification,

alteration, or repair remove any airplane from the applicability of

this AD.

Compliance: Required as indicated, unless accomplished

previously. -

To prevent stress corrosion cracking, which could result in

fractures of the outer cylinder aft trunnion and the subsequent loss

of the main landing gear (MLG), accomplish the following:

(a) Within 5-\1/2\ years since the last overhaul of the MLG or

since the date of manufacture of the MLG (for MLG's that have not

been overhauled), or within 60 days after the effective date of this

AD, whichever occurs later: Perform a visual inspection to determine

if the fillet seal of the outer cylinder aft trunnion is cracked or

missing, in accordance with Boeing Service Letter 767-SL-32-067,

dated August 4, 1995. For the purposes of this AD, fillet seals are

not considered to be ``cracked'' if cracks are found in the fillet

seal paint only (where the fillet seal itself is not cracked).

(b) If no cracked fillet seal is found during the inspection

required by paragraph (a) of this AD, repeat the inspection

thereafter at intervals not to exceed 18 months.

(c) If any fillet seal is found to be cracked or missing during

the inspection required by paragraph (a) of this AD, prior to

further flight, remove the fillet seal (if present), clean the

adjacent area with a solvent, apply corrosion inhibiting compound

(CIC), and perform a visual inspection to detect corrosion, in

accordance with Boeing Service Letter 767-SL-32-067, dated August 4,

1995.

(1) If no corrosion is detected, prior to the accumulation of

500 flight hours, reapply CIC and grease in accordance with the

service letter. Thereafter, repeat the application of CIC and grease

at intervals not to exceed 500 flight hours.

(2) If any corrosion is detected, prior to further flight,

repair the aft trunnion in accordance with the service letter.

Accomplishment of this repair constitutes terminating action for the

repetitive inspection requirements of this AD.

(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, Seattle Aircraft Certification

Office (ACO), 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, Seattle ACO.

Note 2: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Seattle ACO.

(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.

(f) The actions shall be done in accordance with Boeing Service

Letter 767-SL-32-067, dated August 4, 1995. 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 Boeing Commercial Airplane Group, P.O. Box 3707,

Seattle, Washington 98124-2207. 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.

(g) This amendment becomes effective on September 29, 1995.

Issued in Renton, Washington, on September 7, 1995.

D. L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 95-22715 Filed 9-13-95; 8:45 am]

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