Airworthiness Directives; Boeing Model 747 Series Airplanes

[Federal Register Volume 66, Number 227 (Monday, November 26, 2001)]
[Rules and Regulations]
[Pages 58918-58922]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-29185]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-350-AD; Amendment 39-12512; AD 2001-23-13]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 747 series airplanes, that requires 
an inspection of the flap drive transmission of the trailing edge flaps 
at positions 2 and 7 to determine if a discrepant torque brake is 
installed; and corrective action, if necessary. The action specified by 
this AD are intended to prevent damage to the flap system, adjacent 
systems, or structural components; or excessive skew of the trailing 
edge flap, which could result in flap asymmetry and consequent reduced 
controllability of the airplane. This action is intended to address the 
identified unsafe condition.

DATES: Effective December 31, 2001.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of December 31, 2001.

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: Barbara Mudrovich, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 227-2983; fax (425) 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 747 series 
airplanes was published in the Federal Register on May 14, 2001 (66 FR 
24304). That action proposed to require an inspection of the flap drive 
transmission of the trailing edge flaps at positions 2 and 7 to 
determine if a wound-spring torque brake is installed; and corrective 
action, if necessary.

Comments

    Interested persons have been afforded an opportunity to participate 
in the

[[Page 58919]]

making of this amendment. Due consideration has been given to the 
comments received. The Air Transport Association of America, on behalf 
of its members, states that two commenters agree with the intent of the 
proposal, but recommend certain changes. These recommendations and 
additional requests are described in the following paragraphs.

Request To Extend the Compliance Time in Paragraph (a)

    A number of commenters request an extension to the proposed 
compliance time of 6,000 flight hours in paragraph (a) of the proposed 
AD. These comments and the rationale for requesting such an extension 
are described in the following paragraphs.
    <bullet> One commenter states that 6,000 flight hours would fall 
short of its average C-check, which is usually at 7,500 flight hours. A 
compliance time of 10,000 flight hours would be more appropriate.
    <bullet> One commenter states that 6,000 flight hours would require 
accomplishment of the work at another repair facility, which would put 
the airplane out of service for at least 1 month. In addition, 
modification of its fleet of 12 affected airplanes is estimated at 2 to 
3 years. In light of this, the commenter recommends a compliance time 
of 3 years.
    <bullet> Two commenters recommend that the requirements of the 
proposed AD be accomplished at a D-check interval. Both commenters are 
concerned about the availability of spare parts within the proposed 
compliance time.
    The first commenter recommends a compliance time of between 5 and 8 
years (25,000 to 38,000 flight hours) for several reasons. Over a 30-
year period, none of its Model 747 series airplanes have experienced 
the unsafe condition cited in the proposed AD (i.e., damage to the flap 
system, adjacent systems, or structural components; or excessive skew 
of the trailing edge flap). It is not aware of any incidents related to 
such a condition anywhere in the world. In light of this, it considers 
that such a compliance time is unwarranted and unrealistic. In 
addition, the manufacturer recommended that the proposed actions be 
accomplished at the earliest convenient maintenance opportunity, which 
is more realistic.
    The second commenter states that a large number of components and 
special maintenance schedules would be required to accomplish the 
proposed actions within 6,000 flight hours. The commenter recommends 
that the FAA consider how the costs of accomplishing the required 
actions would affect operators worldwide, and suggests a compliance 
time of 5 years.
    <bullet> One commenter contends that the turnaround time required 
to accomplish the proposed inspection and corrective actions would 
exceed 6,000 flight hours. In addition, the affected airplanes would 
need to be transported to a specific repair station because of the test 
equipment available at that facility. The commenter recommends 
extending the compliance time to 10,000 flight hours so that the 
proposed actions could be accomplished during regular maintenance 
schedules.
    <bullet> One commenter suggests an 18-month compliance time instead 
of 6,000 flight hours. The commenter notes that the proposed work could 
be best accomplished during a C-check maintenance schedule, which 
coincides with an 18-month compliance time. In addition, all of its 
Model 747 series airplanes are on an 18-month flight cycle. During that 
period, a Model 747-200 series airplane accumulates about 6,000 flight 
hours; however, a Model 747-400 series airplane can accumulate up to 
7,000 flight hours. Because flaps typically are used only during climb 
and descent, flap transmissions are more dependent on flight cycles 
than flight hours. Therefore, 18 months would provide an equivalent 
level of safety because actual use of the flap transmission, by cycles, 
is less on Model 747-400 series airplanes than on Model 747-200 series 
airplanes. For these reasons, the commenter suggests that the 
compliance time be revised to ``Within 6,000 flight hours or 18 months 
after the effective date of this AD, whichever is later.''
    <bullet> One commenter, the manufacturer, states that 6,000 flight 
hours would be unduly restrictive, with an unjustified impact on 
airline operations. It suggests scheduling the rework during a D-check, 
and recommends extending the compliance time to 3 years or 15,000 
flight hours, whichever occurs later. The commenter also requests an 
extension of the proposed compliance time so that it could buy ``seed'' 
transmissions that will be required by the operators for their 
replacement program. This extension would avoid creating an undue 
burden.
    The FAA partially concurs with the commenters' requests, and has 
determined that the compliance time can be extended somewhat. We point 
out that the ``Differences'' paragraph in the proposed AD is not 
included in the final rule, so no change to that paragraph is 
necessary. However, we have extended the compliance time somewhat in 
paragraph (a) of the final rule.
    Our intent in developing an appropriate compliance time for the 
inspections and corrective actions was that the proposed actions be 
conducted during a regularly scheduled maintenance visit for the 
majority of the affected fleet. We also intended that the proposed 
actions be accomplished when the airplanes are located at a facility 
where special equipment and trained personnel are readily available. 
Based on the information provided by the commenters, we now recognize 
that a compliance time of within 18 months or 7,500 flight hours after 
the effective date of this AD, whichever occurs later, corresponds more 
closely to the interval that represents most of the affected operators' 
normal maintenance schedules. This extension will allow operators to 
schedule the required actions during a convenient maintenance 
opportunity, and will not adversely affect safety. Paragraph (a) of the 
final rule is revised accordingly.

Request To Revise Compliance Time in Paragraph (a)(2)(ii)

    One commenter requests revising the compliance time in paragraph 
(a)(ii), which is cited as (a)(2)(ii) in the proposed AD. The commenter 
considers that, given the level of the hazard posed to the fleet by the 
torque brake discrepancy, requiring replacement of the torque brake 
``before further flight'' is not warranted. Instead, the proposed AD 
should allow operators to accomplish the corrective action at a 
convenient maintenance opportunity. The FAA infers that the commenter 
is requesting that we revise paragraph (a)(2)(ii) of this AD to require 
the corrective action within 18 months or 7,500 flight hours after the 
effective date of this AD, instead of ``before further flight.''
    The FAA concurs with the commenter's request. The extended 
compliance time in paragraph (a) of this AD should allow sufficient 
time for operators to accomplish the rework or replacement action 
specified in paragraph (a)(2)(ii) at a convenient maintenance 
opportunity. However, in the final rule we have revised paragraph 
(a)(2)(ii) to require such action ``within the compliance time required 
by paragraph (a) of this AD,'' instead of ``before further flight.''

Request To Clarify the Rework or Replacement Action

    One commenter requests a revision to the ``Explanation of Relevant 
Service Information'' paragraph in the proposed AD. The AD should 
clarify that operators have the option of either replacing the 
transmission with a new,

[[Page 58920]]

improved transmission or reworking the existing transmission by 
replacing the torque brake with a new or reworked torque brake.
    The FAA partially concurs with the commenter's request. Although 
the ``Explanation of Relevant Service Information'' paragraph is not 
included in the final rule, we agree that the replacement and rework 
action should be revised. In response, we have revised paragraph 
(a)(2)(ii) in the final rule to require operators to either replace the 
transmission with a new, improved transmission or rework the existing 
transmission by replacing the torque brake with a new or reworked 
torque brake per the service bulletin.

Request To Revise the Applicability

    One commenter states that ``an Information Notice (IN) made 
available for 747-27-2374 (IN 01)'' was issued June 1, 2000, to clarify 
that Model 747SP series airplanes are excluded from the effectivity. 
The notice lists 10 Model 747SP series airplanes by line number and 
variable number. In addition, those same airplanes are excluded from 
the effectivity of Boeing Service Bulletin 747-27-2374. The FAA infers 
that the commenter is suggesting that we revise the applicability of 
the proposed AD to reflect the exclusion of these airplanes.
    The FAA concurs that the applicability of this AD should be 
changed. We agree that Model 747SP series airplanes should be excluded 
from the applicability of this AD, and have determined that further 
clarification of the applicability is necessary. We point out that the 
applicability of the proposed AD references Boeing Service Bulletin 
747-27-2374, dated November 18, 1999, as the appropriate source of 
service information for determining the affected Model 747 series 
airplanes. We have revised the applicability of the final rule to 
include line numbers 0001 through 1207, and to exclude the airplane 
having line number 1174 and Model 747SP series airplanes.

Request To Correct the Torque Brake References in the Proposed AD

    One commenter requests that all references to ``wound-spring'' 
torque brakes be removed from the proposed AD. That type of brake is 
not used in the rework or replacement actions required by the proposed 
AD.
    The FAA concurs. We have removed all references to ``wound-spring'' 
torque brakes in the final rule, and have clarified that the 
``Belleville'' spring design is the discrepant torque brake.

Request To Resolve Parts Discrepancies

    One commenter states that the Boeing and Moog service bulletins 
list different part numbers for the flap drive transmission and torque 
brake installed on Model 747 series airplanes. Any such discrepancies 
should be resolved before the final rule is issued.
    The FAA concurs that any parts discrepancies should be resolved 
before issuance of the final rule. However, we point out that the parts 
references included in the Boeing and Moog service bulletins are 
correct, and that the incorrect parts references were included in the 
proposed AD. After contacting Boeing, we were informed that it had 
contacted United to explain that the discrepant torque brake is a 
``Belleville'' spring design, not a ``wound-spring'' design as cited in 
the proposed AD. This clarification resolved the commenter's confusion. 
We have removed all references to the wound-spring torque brake from 
the final rule, and clarified that the Belleville spring design is the 
discrepant torque brake.

Request To Revise the Cost Estimate

    One commenter states that only 1 hour for the inspection was 
estimated in the cost impact information in the proposed NPRM to 
determine whether the affected transmissions are installed on an 
airplane. The cost of removal, overhaul, and reinstallation of the 
transmission is not included, and the service bulletin estimates 50 
hours per airplane for the associated costs. The FAA infers that the 
commenter considers that the cost estimate in the proposed AD is too 
low.
    The FAA partially concurs with the commenter. However, we do not 
agree with the cost estimate of 50 hours specified by the service 
bulletin for the removal, overhaul, and reinstallation of 
transmissions. We point out that the estimate in the service bulletin 
included the action required to replace or rework the torque brake in 
positions 2, 4, 5, and 7. However, the proposed AD only requires rework 
or replacement action for positions 2 and 7. As indicated in the 
preamble of this AD, the economic analysis is limited only to the cost 
of actions actually required by the rule and does not include the costs 
of on-condition actions, such as the rework or replacement action 
specified in paragraph (a)(2)(ii) of the NPRM. However, in this case we 
have included the on-condition action. These costs include a total of 
32 hours per airplane for accomplishing the replacement or rework 
action for transmission positions 2 and 7 (10 hours for the replacement 
and 6 hours for the rework). We also have included an estimate of 
$12,942 for parts. The final rule is revised accordingly.

Request To Reduce the Compliance Time

    The Civil Aviation Authority (CAA), which is the airworthiness 
authority of the United Kingdom, requests reducing the compliance time 
for the inspection and corrective action if a discrepant part is found 
installed on the airplane. The CAA considers that the proposed 6,000 
flight hours for the inspection is excessively long. It recommends full 
accomplishment of the inspection and corrective action within 3,000 
flight hours, which is approximately 1 year for most operators. In 
addition, operators should have the discretion of accomplishing 
corrective action within the recommended total timeframe of 3,000 
flight hours.
    The FAA does not concur with the need for a shorter compliance 
time, although operators are always permitted to accomplish the 
requirements of an AD at a time earlier than that specified as the 
compliance time. As described earlier, we have determined that it is 
necessary to somewhat extend the compliance time in paragraphs (a) and 
(a)(2)(ii) of the final rule to require accomplishment of the actions 
within 18 months or 7,500 flight hours. We consider such an extension 
appropriate in consideration of the safety implications, practical 
aspects of accomplishing the work during regular maintenance periods, 
and availability of required parts. Therefore, a reduction to the 
compliance time in paragraph (a) of the final rule would not be 
warranted.

Request To Correct Paragraph References

    One commenter states that, in paragraph (a) of the proposed AD, 
paragraphs (a)(3) and (a)(4) do not exist. The FAA concurs and has 
deleted those two paragraph references in paragraph (a) of the final 
rule.

Conclusion

    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.

Cost Impact

    There are approximately 1,181 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA

[[Page 58921]]

estimates that 263 airplanes of U.S. registry will be affected by this 
AD.
    It will take approximately 1 work hour per airplane to accomplish 
the inspection, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the required inspection on U.S. 
operators is estimated to be $15,780, or $60 per airplane.
    The 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. The cost impact figures discussed 
in AD rulemaking actions represent only the time necessary to perform 
the specific actions actually required by the AD. These figures 
typically do not include incidental costs, such as the time required to 
gain access and close up, planning time, or time necessitated by other 
administrative actions.
    If an operator is required to accomplish the replacement or rework 
action, it will take approximately 32 work hours per airplane to 
accomplish such action, at an average labor rate of $60 per work hour. 
Required parts will cost approximately $12,942 per airplane. Based on 
these figures, the cost impact of the required replacement or rework is 
estimated to be $14,862 per airplane.

Regulatory Impact

    The regulations adopted herein will not have a substantial direct 
effect 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, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

2001-23-13  Boeing: Amendment 39-12512. Docket 2000-NM-350-AD.

    Applicability: Model 747 series airplanes, line numbers 0001 
through 1207, certificated in any category; excluding those 
airplanes having line number 1174 and Model 747SP series airplanes.

    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 request approval for an 
alternative method of compliance in accordance with paragraph (c) 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 indicated, unless accomplished 
previously.
    To prevent damage to the flap system, adjacent systems, or 
structural components; or excessive skew of the trailing edge flap; 
which could result in flap asymmetry and consequent reduced 
controllability of the airplane, accomplish the following:

Part Verification/Replacement/Modification

    (a) Within 18 months or 7,500 flight hours after the effective 
date of this AD, whichever occurs later: Inspect the flap drive 
transmission of the trailing edge flaps at positions 2 and 7 to 
determine if a discrepant (``Belleville'' spring design) torque 
brake is installed in the transmission, by verifying the 
transmission part number, per Boeing Service Bulletin 747-27-2374, 
dated November 18, 1999. Then do the actions specified in paragraphs 
(a)(1) and (a)(2) of this AD, as applicable.
    (1) If the part number of the flap drive transmission shows that 
no discrepant torque brake is installed, no further action is 
required by this AD.
    (2) If the part number of the flap drive transmission shows that 
a discrepant torque brake may be installed, within the compliance 
time required by paragraph (a) of this AD: Inspect the part number 
of the torque brake to verify whether it is a discrepant torque 
brake, per the Accomplishment Instructions of the service bulletin.
    (i) If the part number of the torque brake shows that it is not 
a discrepant torque brake, no further action is required by this AD.
    (ii) If the part number of the torque brake shows that it is a 
discrepant torque brake: Within the compliance time required by 
paragraph (a) of this AD either replace the transmission with a new, 
improved transmission or rework the existing transmission by 
replacing the torque brake with a new or reworked torque brake 
having the part number specified in the service bulletin; per the 
Accomplishment Instructions of the service bulletin.

Spares

    (b) As of the effective date of this AD, no person shall install 
on any airplane any transmission or torque brake assembly identified 
in the ``Existing Part Number'' column of Paragraph 2.E. of Boeing 
Service Bulletin 747-27-2374, dated November 18, 1999.

Alternative Methods of Compliance

    (c) 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. 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.

Special Flight Permit

    (d) 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.

Incorporation by Reference

    (e) The actions shall be done in accordance with Boeing Service 
Bulletin 747-27-2374, dated November 18, 1999. 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.

Effective Date

    (f) This amendment becomes effective on December 31, 2001.


[[Page 58922]]


    Issued in Renton, Washington, on November 15, 2001.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-29185 Filed 11-23-01; 8:45 am]
BILLING CODE 4910-13-U

The complete text was extracted from the official GovInfo HTML edition for this publication. Acquired 2026-10-09T04:24:52.855104+00:00. Text extraction preserves the recorded source wording; it does not determine current requirements.

Open the captured official edition

Source SHA-256

bf58ec6240d3f9edb9ff8d4f2ed6fecd33e5b928cf2eb161afb77a1d08ca3b44

Text SHA-256

1d11dd0fb9b0f23040fbe153c4326900d07161ccf578ef06c4b29762c3445e61