[Federal Register Volume 63, Number 231 (Wednesday, December 2, 1998)]
[Rules and Regulations]
[Pages 66422-66423]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-32100]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-334-AD; Amendment 39-10929; AD 98-24-51]
RIN 2120-AA64
Airworthiness Directives; McDonnell Douglas Model MD-11 Series
Airplanes Equipped with Certain Collins LRA-900 Radio Altimeters
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule; request for comments.
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SUMMARY: This document publishes in the Federal Register an amendment
adopting airworthiness directive (AD) T98-24-51 that was sent
previously to all known U.S. owners and operators of certain McDonnell
Douglas Model MD-11 series airplanes by individual telegrams. This AD
requires a revision to the Airplane Flight Manual to prohibit autopilot
coupled autoland operations in certain conditions; or, for certain
airplanes, replacement of certain Collins LRA-900 radio altimeters with
Collins LRA-700 radio altimeters. This action is prompted by a report
that a fault in certain Collins LRA-900 radio altimeters could result
in an incorrect and unbounded output of radio altitude to other
airplane systems. The actions specified by this AD are intended to
prevent an undetected anomalous radio altitude signal that is passed
along to the flare control law of the flight control computer, which
could cause the airplane to flare too high or too low during landing,
and consequently result in a hard landing.
DATES: Effective December 7, 1998, to all persons except those persons
to whom it was made immediately effective by telegraphic AD T98-24-51,
issued November 19, 1998, which contained the requirements of this
amendment.
Comments for inclusion in the Rules Docket must be received on or
before February 1, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 98-NM-334-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056.
Information pertaining to this amendment may be examined at the
FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,
Washington; or at the FAA, Transport Airplane Directorate, Los Angeles
Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood,
California.
FOR FURTHER INFORMATION CONTACT: Brett Portwood, Aerospace Engineer,
ANM-130L, FAA, Transport Airplane Directorate, Los Angeles Aircraft
Certification Office, 3960 Paramount Boulevard, Lakewood, California
90712; telephone (562) 627-5347; fax (562) 627-5210.
SUPPLEMENTARY INFORMATION: On November 19, 1998, the FAA issued
telegraphic AD T98-24-51, which is applicable to certain McDonnell
Douglas Model MD-11 series airplanes equipped with certain Collins LRA-
900 radio altimeters. That action was prompted by a report from
Rockwell Collins that a fault in certain Collins LRA-900 radio
altimeters has been identified, which could result in an incorrect and
unbounded output of radio altitude to other airplane systems.
The fail-operational autoland installation on McDonnell Douglas
Model MD-11 series airplanes utilizes a dual-dual architecture that
relies on the self-monitoring capability of the Collins LRA-900 radio
altimeters. Any undetected anomalous radio altitude signal that is
passed along to the flare control law of the flight control computer
(FCC) could cause the initiation of the flare mode at an altitude that
is either too high or too low for safe landing during autoland
operations.
This fault does not affect airplanes equipped with either an
autoland system architecture that utilizes triplex radio altimeter
sensors or a dual fail-passive autoland architecture. The triplex radio
altimeter sensors are able to ``vote out'' the undetected radio
altimeter anomaly. The dual fail-passive autoland architecture compares
both radio altimeters and passively disconnects when the signals do not
match (i.e., radio altimeter miscompare).
In light of these findings, the FAA has determined that the
reported anomaly is limited to airplanes with fail-operational autoland
systems with a dual-dual fail-operational radio altimeter architecture.
An undetected anomalous radio altitude signal that is passed along
to the flare control law of the FCC, if not corrected, could cause the
airplane to flare too high or too low during landing, and consequently
result in a hard landing.
Explanation of Requirements of the Rule
Since the unsafe condition described is likely to exist or develop
on other airplanes of the same type design, the FAA issued telegraphic
AD T98-24-51 to require a revision to the Limitations Section of the
FAA-approved Airplane Flight Manual (AFM) to prohibit autopilot coupled
autoland operations in certain conditions; or, for certain airplanes,
replacement of certain Collins LRA-900 radio altimeters with Collins
LRA-700 radio altimeters.
This is considered to be interim action until final action is
identified, at which time the FAA may consider further rulemaking.
Since it was found that immediate corrective action was required,
notice and opportunity for prior public comment thereon were
impracticable and contrary to the public interest, and good cause
existed to make the AD effective immediately by individual telegrams
issued on November 19, 1998, to all known U.S. owners and operators
[[Page 66423]]
of certain McDonnell Douglas Model MD-11 series airplanes equipped with
certain Collins LRA-900 radio altimeters. These conditions still exist,
and the AD is hereby published in the Federal Register as an amendment
to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to
make it effective to all persons.
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 98-NM-334-AD.'' The postcard will be date stamped and
returned to the commenter.
Regulatory Impact
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, 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:
98-24-51 McDonnell Douglas: Amendment 39-10929. Docket 98-NM-334-
AD.
Applicability: Model MD-11 series airplanes, equipped with
certain Collins LRA-900 radio altimeters, having part number 822-
0334-002, 822-0334-020, or 822-0334-220; certificated in any
category.
Compliance: Required as indicated, unless accomplished
previously. To detect and correct an undetected anomalous radio
altitude signal that is passed along to the flare control law of the
flight control computer, which could cause the airplane to flare too
high or too low during landing, and consequently result in a hard
landing, accomplish the following:
(a) Within 24 hours after the effective date of this AD,
accomplish either paragraph (a)(1) or (a)(2) of this AD:
(1) Revise the Limitations Section of the FAA-approved Airplane
Flight Manual to include the following statement:
``Autopilot coupled autoland operations below 100 feet above
ground level (AGL) are prohibited.''
(2) For airplanes on which the LRA-700 radio altimeter
installation has been approved in accordance with Type Certificate
or Supplemental Type Certificate procedures: Replace both Collins
LRA-900 radio altimeters having part number 822-0334-002, 822-0334-
020, or 822-0334-220, with Collins LRA-700 radio altimeters having
part number 622-4542-221.
(b) As of the effective date of this AD, no person shall install
on any airplane a Collins LRA-900 radio altimeter, having part
number 822-0334-002, 822-0334-020, or 822-0334-220.
(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, Los Angeles 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, Los Angeles ACO.
Note: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Los Angeles 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.
(e) This amendment becomes effective on December 7, 1998, to all
persons except those persons to whom it was made immediately
effective by telegraphic AD T98-24-51, issued on November 19, 1998,
which contained the requirements of this amendment.
Issued in Renton, Washington, on November 25, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-32100 Filed 12-1-98; 8:45 am]
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