[Federal Register Volume 62, Number 50 (Friday, March 14, 1997)]
[Proposed Rules]
[Pages 12121-12123]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-6436]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 97-NM-28-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
installation of a newly designed rudder-limiting device and yaw damper
system. This proposal is prompted by a report indicating that a full
rudder input, either commanded or uncommanded, could result in a rapid
roll upset; and by reports of malfunctions of the yaw damper system.
The actions specified by the proposed AD are intended to prevent
excessive rudder authority and consequent reduced controllability of
the airplane; and malfunctions of the yaw damper system, which could
result in sudden uncommanded yawing of the airplane and consequent
injury to passengers and crewmembers.
DATES: Comments must be received by April 23, 1997.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 97-NM-28-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.
FOR FURTHER INFORMATION CONTACT: T. Tin Truong, Aerospace Engineer,
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056; telephone (206) 227-2552; fax (206)
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-28-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-28-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
[[Page 12122]]
Discussion
In September 1994, an accident involving a Boeing Model 737-300
series airplane occurred near Pittsburgh, Pennsylvania. The National
Transportation Safety Board (NTSB) has not yet determined the cause of
that accident. However, the FAA has received a report indicating that
piloted computer simulations of the accident revealed that a full
rudder input, either commanded or uncommanded, could result in a rapid
roll upset similar to the aircraft responses recorded on the flight
data recorder of the accident airplane. Investigation revealed that,
during certain combinations of flap settings and airspeeds, the amount
of rudder deflection available is greater than needed for control of
the airplane. A full rudder deflection (hardover) with such excessive
rudder authority can result in a rolling moment due to sideslip that
exceeds the maximum rolling moment available by control wheel inputs.
This condition, if not corrected, could result in reduced
controllability of the airplane unless the flight crew takes prompt and
appropriate action. [In this regard, the FAA issued AD 96-26-07,
amendment 39-9871 (62 FR 15, January 2, 1997) to amend the Airplane
Flight Manual to provide the flight crew with the proper control
techniques in the event of such an occurrence.]
Additionally, the FAA has received a number of reports of
malfunctions of the yaw damper system. These malfunctions may have been
caused by failure of the 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 has 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.
FAA's Determinations
In light of this information, the FAA finds that installation of a
newly designed rudder-limiting device and yaw damper system are
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 installation of a newly designed rudder-
limiting device and yaw damper system. The actions would be required to
be accomplished in accordance with a method approved by the FAA.
Cost Impact
There are approximately 2,900 Model 737 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 1,350
airplanes of U.S. registry would be affected by this proposed AD.
The FAA estimates that it would take approximately 87 work hours
per airplane to accomplish the proposed installation of a newly
designed rudder-limiting device, and that the average labor rate is $60
per work hour. Required parts would be supplied by the manufacturer at
no cost to operators. Based on these figures, the cost impact of the
proposed AD on U.S. operators is estimated to be $7,047,000, or $5,220
per airplane.
The FAA also estimates that it would take approximately 20 work
hours per airplane to accomplish the proposed installation of a newly
designed yaw damper system, and that the average labor rate is $60 per
work hour. Required parts would be supplied by the manufacturer at no
cost to operators. Based on these figures, the cost impact of the
proposed AD on U.S. operators is estimated to be $1,620,000, or $1,200
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 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.
[[Page 12123]]
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-28-AD.
Applicability: All Model 737-100, -200, -300, -400, and -500
series airplanes, certificated in any category.
Note 2: 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
otherwise 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 (b) 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 excessive rudder authority and consequent reduced
controllability of the airplane; and malfunctions of the yaw damper
system, which could result in sudden uncommanded yawing of the
airplane and consequent injury to passengers and crewmembers;
accomplish the following:
(a) Within 3 years after the effective date of this AD,
accomplish paragraphs (a)(1) and (a)(2) of this AD in accordance
with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO), FAA, Transport Airplane Directorate.
(1) Install a newly designed rudder-limiting device that reduces
the rudder authority at altitudes above 1,500 feet above ground
level (AGL).
(2) Install a newly designed yaw damper system that improves the
reliability and fault monitoring capability.
(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 ACO. 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.
(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.
Issued in Renton, Washington, on March 7, 1997.
Ronald T. Wojnar,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 97-6436 Filed 3-13-97; 8:45 am]
BILLING CODE 4910-13-P
