Airworthiness Directives; Boeing Model 757 and 767 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-03-AD; Amendment 39-9014; AD 94-18-01]

Airworthiness Directives; Boeing Model 757 and 767 Series

Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

applicable to certain Boeing Model 757 and 767 series airplanes, that

requires modification of the latch hook installation for the number two

cockpit window frame. This amendment is prompted by reports of the

flight crew executing rejected takeoffs (RTO) and air turnbacks (ATB)

due to false ``closed'' indications for the number two cockpit window.

The actions specified by this AD are intended to prevent unlatched (not

completely closed) number two cockpit windows and the resultant

execution of RTO's and ATB's by the flight crew.

DATES: Effective October 11, 1994.

The incorporation by reference of certain publications listed in

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

of October 11, 1994.

ADDRESSES: 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 Federal

Aviation Administration (FAA), Transport Airplane Directorate, Rules

Docket, 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: Roy Boffo, Aerospace Engineer,

Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle

Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056; telephone (206) 227-2780; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to include an airworthiness

directive (AD) that is applicable to certain Boeing Model 757 and 767

series airplanes was published in the Federal Register on March 8, 1994

(59 FR 10759). That action proposed to require modification of the

latch hook installation for the number two cockpit window frame.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter supports the proposal.

Several commenters question the need for the rule and consider that

the proposal should be withdrawn for various reasons:

One of these commenters contends that the nature of the addressed

problem does not constitute an unsafe condition. This commenter states

that, if the window is not completely closed, it is not possible for

the latch cams to engage with the latch posts; thus, improperly closed

windows are readily identified by physically trying to open the window.

The FAA does not concur. If the window latch cams do not engage with

the latch posts, it is still possible to rotate the latch handle.

Whenever the latch handle is rotated, a ``closed'' indicator appears

above the window. This makes it possible for the window actually to be

open, but to appear to be closed and to have a ``closed'' indicator as

well. The modification required by this AD addresses that situation,

since it will prevent the possibility of rotating the latch handle into

the forward, latched position unless the window is fully closed.

Because of the consequences associated with an open window, the FAA

considers this modification to be warranted and appropriate.

Some of these commenters consider that current flight crew

procedures are adequate to address the problem that is the subject of

the proposed AD. These commenters point out that current procedures

provide for a check of these windows to ensure that they are closed and

locked; some operators' procedures require that the flight crew check

the windows twice. The FAA does not concur. As described above, the

current configuration of the window latching mechanism and associated

indicator make it possible for the window to appear to be closed and to

have a ``closed'' indicator, even though the window is not actually

closed and latched. Service experience has shown that the flight crew

will not always verify that the window is closed if they have a

``closed'' indication. For these reasons, the FAA finds that flight

crew procedures alone are not effective in addressing the identified

unsafe condition.

Another of these commenters states that there has been only a

limited number of operators that have experienced difficulty with the

subject windows; this commenter does not consider that it is reasonable

for the FAA to burden all operators with the requirements of the rule

because of the service experience of only a few operators. The FAA

acknowledges that only a few operators have experienced in service the

problems addressed by this AD action. However, since the configuration

of the windows, the window latching mechanism, and the associated

indicating system is similar on all of the affected Model 757 and 767

series airplanes, the FAA has determined that the potential exists for

this problem to occur on any of these airplanes.

Another of these commenters states that the referenced service

bulletin describes the modification as desirable only to ``reduce noise

in the cockpit'' should the subject windows not be latched. This

commenter states that at no time have there been reports of an

uncommanded window opening; instead, there have been reports only of

false window latching, which resulted in air leakage and noise.

Therefore, the commenter considers the proposed modification to be

merely a ``product improvement'' and not necessarily meant to correct

an unsafe condition. The FAA does not concur. The modifications

described in the referenced service bulletins eliminate the possibility

of the ``closed'' indicator being visible when the window is not

actually fully closed. The air leakage and noise that have resulted

from open windows have led to rejected takeoffs (RTO's) and air

turnbacks (ATB's); some of the RTO's have resulted in considerable

damage to the airplane. To address this unsafe condition, the FAA has

determined that the need for the proposed modification is warranted. -

Finally, one of these commenter states that there have been reports

of RTO's and ATB's involving airplanes that have incorporated the

modification; therefore, the modification will not eliminate these

occurrences. The FAA acknowledges that RTO's and ATB's have taken place

after modification, and points out that the subject modification is not

intended to prevent all future occurrences of these incidents.

Conversely, it is not intended that the modification terminate any

requirements for crew preparation of the flight deck for flight. The

modification does address a design problem that can lead the crew to

believe that the window is closed when, in fact, it is not. -

One commenter requests that the proposed rule be revised to provide

``credit'' to operators with Model 767 series airplanes that have been

previously modified only in accordance with Boeing Service Bulletin

767-56-0002, dated August 30, 1985, and not in accordance with that

service bulletin as amended by Notice of Status Change (NSC) 1, dated

July 3, 1986, as specified in the notice. This commenter points out

that NSC 1 simply added data concerning existing part accountability;

additionally, NSC 1 contains a statement indicating that ``no more work

is necessary on airplanes changed by the initial release of this

service bulletin.'' The FAA concurs, and has revised the final rule

accordingly. -

This same commenter requests that the comment period be extended by

an additional 60 days in order to obtain information as to whether or

not all affected Model 767 series airplanes have already been modified

in accordance with the proposed requirements of the rule. The commenter

considers that, by obtaining such affirmative data, the Model 767 could

be eliminated from the applicability of the rule. The FAA does not

concur, and considers that such a delay in this rulemaking action is

inappropriate. Regardless, as specified in the ``Compliance'' statement

of the final rule, airplanes that have been modified previously in

accordance with the requirements of the rule are considered in

compliance and require no additional work relative to this rule. -

One commenter requests that the proposed compliance time of 18

months be extended to 30 months in order to accommodate parts delivery

time and orderly modification of the fleet. This commenter states that

the lead time necessary for obtaining the modification parts is

extensive (44 weeks), and an 18-month compliance time is unreasonably

short to expect operators of large fleets to modify all of the affected

airplanes. The FAA concurs. In developing an appropriate compliance

time for this AD action, the FAA intended that it fall during a time of

regularly scheduled maintenance in order to allow the modification to

be performed at a base where special equipment and trained maintenance

personnel will be available if necessary. The FAA considers that

extending the compliance time to 30 months will not adversely affect

safety and will allow timely and orderly modification of the affected

fleet. -

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the changes previously

described. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD. -

There are approximately 640 Model 757 and 767 series airplanes of

the affected design in the worldwide fleet. The FAA estimates that 409

airplanes of U.S. registry will be affected by this AD, that it will

take approximately 8 work hours per airplane to accomplish the required

actions, and that the average labor rate is $55 per work hour. Required

parts will cost approximately $2,000 per airplane. Based on these

figures, the total cost impact of the AD on U.S. operators is estimated

to be $997,960, or $2,440 per airplane. -

The total cost impact figure discussed above is based on

assumptions that no operator has yet accomplished any of the

requirements of this AD action, and that no operator would accomplish

those actions in the future if this AD were not adopted. However, the

FAA has been advised that at least 44 of the affected airplanes have

already been modified in accordance with the requirements of this AD,

and that numerous others are either currently undergoing or will have

undergone modification by the date that this AD is effective.

Therefore, the future economic cost impact of this rule on U.S.

operators is now only $890,600 (and, most likely, considerably less

than that amount as of the effective date of this AD). -

The FAA recognizes that the obligation to maintain aircraft in an

airworthy condition is vital, but sometimes expensive. Because AD's

require specific actions to address specific unsafe conditions, they

appear to impose costs that would not otherwise be borne by operators.

However, because of the general obligation of operators to maintain

aircraft in an airworthy condition, this appearance is deceptive.

Attributing those costs solely to the issuance of this AD is

unrealistic because, in the interest of maintaining safe aircraft, most

prudent operators would accomplish the required actions even if they

were not required to do so by the AD. -

A full cost-benefit analysis has not been accomplished for this AD.

As a matter of law, in order to be airworthy, an aircraft must conform

to its type design and be in a condition for safe operation. The type

design is approved only after the FAA makes a determination that it

complies with all applicable airworthiness requirements. In adopting

and maintaining those requirements, the FAA has already made the

determination that they establish a level of safety that is cost-

beneficial. When the FAA, as in this AD, makes a finding of an unsafe

condition, this means that the original cost-beneficial level of safety

is no longer being achieved and that the required actions are necessary

to restore that level of safety. Because this level of safety has

already been determined to be cost-beneficial, a full cost-benefit

analysis for this AD would be redundant and unnecessary. -

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. -

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) 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 final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it 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. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-18-01 Boeing: Amendment 39-9014. Docket 94-NM-03-AD.

Applicability: Model 757 series airplanes having line positions

1 through 534 inclusive, and Model 767 series airplanes having line

positions 1 through 114 inclusive; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent unlatched (not completely closed) number two cockpit

windows and the resultant execution of rejected takeoffs and air

turnbacks by the flight crew, accomplish the following:

(a) Within 30 months after the effective date of this AD, modify

the latch hook installation for the number two cockpit window frame

in accordance with the applicable service bulletin indicated in

either paragraph (a)(1) or (a)(2) of this AD.

(1) For Model 757 series airplanes: Boeing Service Bulletin 757-

56-0007, dated May 6, 1993.

(2) For Model 767 series airplanes: either Boeing Service

Bulletin 767-56-0002, dated August 30, 1985; or Boeing Service

Bulletin 767-56-0002 as amended by Notice of Status Change Number

767-56-0002 NSC 1, dated July 3, 1986.

(b) 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: Information concerning the existence of approved

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

obtained from the Seattle ACO.

(c) 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.

(d) The modification shall be done in accordance with Boeing

Service Bulletin 757-56-0007, dated May 6, 1993; or Boeing Service

Bulletin 767-56-0002, dated August 30, 1985; or Boeing Service

Bulletin 767-56-0002, as amended by Notice of Status Change Number

767-56-0002 NSC 1, dated July 3, 1986; as applicable. 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.

(e) This amendment becomes effective on October 11, 1994.

Issued in Renton, Washington, on August 18, 1994.

James V. Devany,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-20754 Filed 9-8-94; 8:45 am]

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