[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]
BILLING CODE 4910-13-U