[Federal Register Volume 62, Number 122 (Wednesday, June 25, 1997)]
[Proposed Rules]
[Pages 34185-34187]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-16569]
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Proposed Rules
Federal Register
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This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.
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Federal Register / Vol. 62, No. 122 / Wednesday, June 25, 1997 /
Proposed Rules
[[Page 34185]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-NM-45-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-100, -200, -300, -400,
and -500 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to all Boeing Model 737-100, -200, -
300, -400, and -500 series airplanes. This proposal would require
removing the yaw damper coupler; replacing its internal rate gyroscope
with a new or overhauled unit; and performing a test to verify the
integrity of the yaw damper coupler, and repair, if necessary. This
proposal is prompted by an FAA determination that requiring replacement
of the internal rate gyroscope will significantly increase the
reliability of the yaw damper coupler system. The actions specified by
the proposed AD are intended to prevent sudden uncommanded yawing of
the airplane due to potential failures within the yaw damper system,
and consequent injury to passengers and crewmembers.
DATES: Comments must be received by July 21, 1997.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 97-NM-45-AD, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056. Comments may be inspected at this location
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal
holidays.
The service information referenced in the proposed rule 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.
FOR FURTHER INFORMATION CONTACT: Hania Younis, Aerospace Engineer,
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft
Certification Office, 1601 Lind Avenue, SW., Renton, Washington;
telephone (425) 227-2764; fax (425) 227-1181.
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 shall 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 summarizing 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 Number 97-NM-45-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, Transport Airplane Directorate, ANM-103, Attention: Rules
Docket No. 97-NM-45-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On August 21, 1996, the FAA issued a notice of proposed rulemaking
(NPRM), Docket Number 96-NM-151-AD (61 FR 44243, August 28, 1996),
applicable to all Boeing Model 737-100, -200, -300, -400, and -500
series airplanes, which proposed to require repetitive tests to verify
the integrity of the yaw damper coupler, and various follow-on actions.
That NPRM also proposed to require a one-time inspection to determine
the part number of the engage solenoid valve of the yaw damper, and
replacement of the valve with a valve having a different part number,
if necessary. That NPRM was prompted by a review of the design of the
flight control systems on Model 737 series airplanes. The actions
specified by that proposed AD were intended to prevent sudden
uncommanded yawing of the airplane due to potential failures within the
yaw damper system, and consequent injury to passengers and crewmembers.
Actions Since Issuance of the NPRM
Since the issuance of the NPRM described previously, the FAA has
determined that the requirements contained in paragraph (b) of the NPRM
must be expanded to require hard-time replacement of the internal rate
gyroscope of the yaw damper coupler. That paragraph originally proposed
to require, in part, replacement of the internal rate gyroscope only if
necessary following testing. The FAA made this determination based on
data submitted by Boeing, which indicates that requiring replacement of
the internal rate gyroscope within a specified time will significantly
increase the reliability of the yaw damper coupler system. The FAA
finds that such hard-time replacement is necessary in order to address
the unsafe condition identified in the original NPRM (i.e., sudden
uncommanded yawing of the airplane due to potential failures within the
yaw damper system, and consequent injury to passengers and
crewmembers).
In addition, a commenter to the original NPRM suggests that it be
separated into two independent AD's--one action to address the internal
rate gyroscope, and the other action to address the engage solenoid
valve. The commenter states that the actions required for each of these
parts are
[[Page 34186]]
sufficiently different that recordkeeping requirements warrant separate
rules.
In response to that commenter, the FAA determined that issuance of
two separate AD's is appropriate. Therefore, on April 24, 1997, the FAA
issued AD 97-09-15, amendment 39-10011 (62 FR 24325, May 5, 1997), to
require accomplishment of the actions contained in the original NPRM
that address the engage solenoid valve. [Those actions appeared in
paragraph (b) of the original NPRM.] This proposed rule addresses
actions contained in the original NPRM that are associated with the
internal rate gyroscope of the yaw damper coupler. [Those actions
appeared in paragraph (a) of the original NPRM.]
Additionally, on March 7, 1997, the FAA issued an NPRM to require
installation of a newly designed rudder-limiting device and yaw damper
system [reference Docket 97-NM-28-AD (62 FR 12121, March 14, 1997)].
That proposal was issued in response to a number of reports of
malfunctions of the yaw damper system, which may have been caused by
failure of the internal rate gyroscope of the yaw damper coupler as a
result of wear of the rotor bearing, and contamination and shorting of
the electrical connectors or surface position sensors in the area of
the yaw damper servo-actuator. Such malfunctions of the yaw damper
system, if not corrected, could result in sudden uncommanded yawing of
the airplane and consequent injury to passengers and crewmembers.
Boeing advised the FAA that it has designed a rudder-limiting
device and a new yaw damper for installation on the latest versions of
Model 737 series airplanes currently undergoing certification. Both of
these systems are capable of being installed on the existing fleet of
Model 737 series airplanes. (Boeing has not yet released a service
bulletin reflecting these changes.)
In light of that information, the FAA made a determination that
installation of a newly designed rudder-limiting device and yaw damper
system is required to ensure the safety of the affected fleet.
Installation of a rudder-limiting device is necessary to reduce the
rudder authority at altitudes above 1,500 feet above ground level (AGL)
so that, if any inadvertent hardover occurs, the resultant roll upset
can be controlled with control wheel inputs. Installation of a new yaw
damper system is necessary to improve the reliability of the system and
its fault monitoring capability, which will prevent uncommanded yawing
of the airplane.
Explanation of Requirements of Proposed Rule
Since an unsafe condition has been identified that is likely to
exist or develop on other products of this same type design, the
proposed AD would require removing the yaw damper coupler; replacing
its internal rate gyroscope with a new or overhauled unit; and
performing a test to verify the integrity of the yaw damper coupler,
and repair, if necessary. The actions would be required to be
accomplished in accordance with a method approved by the FAA.
Explanation of Proposed Compliance Times
This proposal would require that the actions be accomplished within
6,000 hours time-in-service (for yaw damper couplers on which the last
maintenance activity occurred within less than 12,000 hours time-in-
service as of the effective date of the AD), or 3,000 hours time-in-
service (for yaw damper couplers on which the last maintenance activity
occurred within 12,000 hours time-in-service or more as of the
effective date of the AD). Thereafter, repetitive tests would be
accomplished every 9,000 hours time-in-service.
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 availability of
required parts and the practical aspect of accomplishing the required
actions within an interval of time that parallels normal scheduled
maintenance for the majority of affected operators. The repetitive test
interval was established based on analyses submitted by Boeing;
accomplishment of tests at this interval will ensure that the overall
reliability of the yaw damper coupler system is maximized.
Cost Impact
There are approximately 2,675 Model 737 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 1,091
airplanes of U.S. registry would be affected by this proposed AD, that
it would take between 8 and 13 work hours per airplane to accomplish
the proposed actions, and that the average labor rate is $60 per work
hour. Required parts would cost approximately $2,500 per airplane.
Based on these figures, the cost impact of the proposed AD on U.S.
operators is estimated to be between $3,251,180 and $3,578,480, or
between $2,980 and $3,280 per airplane.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the proposed requirements
of this AD action, and that no operator would accomplish those actions
in the future if this AD were not adopted.
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,
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
proposed 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 proposed 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 proposed 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 proposed AD would be
redundant and unnecessary.
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 proposed
regulation (1) is not a ``significant regulatory action'' under
Executive Order 12866; (2) is not a ``significant rule'' under the DOT
Regulatory Policies and Procedures (44
[[Page 34187]]
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 is contained 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.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Boeing: Docket 97-NM-45-AD.
Applicability: All Model 737-100, -200, -300, -400, and -500
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 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 sudden uncommanded yawing of the airplane due to
potential failures within the yaw damper system, and consequent
injury to passengers and crewmembers, accomplish the following:
(a) Remove the yaw damper coupler, replace the internal rate
gyroscope with a new or overhauled unit, and perform a test to
verify the integrity of the yaw damper coupler, all in accordance
with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO), FAA, Transport Airplane Directorate, at
the applicable time specified in paragraph (a)(1) or (a)(2) of this
AD.
(1) For airplanes on which the yaw damper coupler has
accumulated less than 12,000 hours time-in-service since its last
maintenance activity as of the effective date of this AD: Perform
the actions within 6,000 hours time-in-service after the effective
date of this AD; and thereafter at intervals not to exceed 9,000
hours time-in-service.
(2) For airplanes on which the yaw damper coupler has
accumulated 12,000 or more hours time-in-service since its last
maintenance activity as of the effective date of this AD: Perform
the actions within 3,000 hours time-in-service after the effective
date of this AD; and thereafter at intervals not to exceed 9,000
hours time-in-service.
(b) If the yaw damper coupler fails the test required by
paragraph (a) of this AD, prior to further flight, repair the
coupler in accordance with a method approved by the Manager, Seattle
ACO.
(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, 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.
(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.
Issued in Renton, Washington, on June 18, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 97-16569 Filed 6-24-97; 8:45 am]
BILLING CODE 4910-13-U
