[Federal Register Volume 59, Number 241 (Friday, December 16, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-30801]


[[Page Unknown]]

[Federal Register: December 16, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-210-AD; Amendment 39-9097; AD 94-26-01]

 

Airworthiness Directives; Learjet Model 24, 25, 31, 35, 36, and 
55 Series Airplanes, and Learjet Model 28 and 29 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Learjet Model 24, 25, 31, 35, 36, and 55 
series airplanes, and Learjet Model 28 and 29 airplanes. This action 
requires a revision to the Limitations Section of the FAA-approved 
Airplane Flight Manual (AFM) to prohibit flight above an altitude of 
41,000 feet. This action also provides optional terminating action for 
that AFM revision. This amendment is prompted by a report of failure of 
a safety valve in the pressurization system on a Learjet Model 31A 
airplane and reports of cracks found in the poppets of certain outflow/
safety valves due to an improper molding process. The actions specified 
in this AD are intended to prevent such cracking and subsequent failure 
of the valves, which could result in rapid decompression of the 
airplane.

DATES: Effective January 3, 1995.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of January 3, 1995.
    Comments for inclusion in the Rules Docket must be received on or 
before February 14, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-210-AD, 1601 Lind Avenue SW., Renton, 
Washington 98055-4056.

FOR FURTHER INFORMATION CONTACT: Walter Eierman, Aerospace Engineer, 
Systems and Equipment Branch, ANM-131L, FAA, Transport Airplane 
Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount 
Boulevard, Lakewood, California 90712; telephone (310) 627-5336; fax 
(310) 627-5210.

SUPPLEMENTARY INFORMATION: Recently, the FAA received a report of 
failure of a safety valve in the pressurization system on a Learjet 
Model 31A airplane. Failure of the valve resulted in depressurization 
of the cabin. Investigation revealed that the poppets of certain 
outflow/safety valves were cracked. These discrepant valves, including 
the safety valve installed on the incident airplane, had been 
manufactured since January 1, 1989. Certain valves manufactured since 
that date have been found to be susceptible to cracking due to an 
improper molding process. Cracking in the poppets of the outflow/safety 
valves in the pressurization system can result in an open valve with an 
effective flow area of 4.4 square inches; additionally, the valve may 
close and remain closed. These conditions, if not corrected, could 
result in rapid decompression of the airplane.
    The FAA has reviewed and approved Allied Signal Aerospace Alert 
Service Bulletins 130406-21-A4011, Revision 2, dated September 28, 
1994, and 102850-21-A4021, Revision 2, dated October 6, 1994. These 
alert service bulletins describe procedures for replacement of certain 
outflow/safety valves in the pressurization system with serviceable 
valves. Further, the alert service bulletins recommend that the maximum 
altitude for operation of airplanes that may be equipped with these 
outflow/safety valves be limited to 41,000 feet as an interim measure 
until the affected valves are replaced.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of the same type design, this AD is 
being issued to prevent rapid decompression of the airplane. This AD 
requires a revision to the Limitations Section of the FAA-approved 
Airplane Flight Manual (AFM) to prohibit flight above an altitude of 
41,000 feet. This AD also provides for replacement of certain outflow/
safety valves in the pressurization system as optional terminating 
action for the AFM revision.
    This is considered to be interim action. The FAA is considering 
further rulemaking action to supersede this AD to require replacement 
of certain outflow/safety valves within 18 months. However, the 
proposed compliance time for the replacement is sufficiently long so 
that notice and time for public comment would not be impracticable.
    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

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 94-NM-210-AD.'' The postcard will be date stamped and 
returned to the commenter.
    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, 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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

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

94-26-01 Learjet: Amendment 39-9097. Docket 94-NM-210-AD.

    Applicability: Model 24, 25, 31, 35, 36, and 55 series 
airplanes, and Model 28 and 29 airplanes; equipped with Allied 
Signal outflow/safety valves, number 130406-1 or 102850-5; as 
identified in Allied Signal Aerospace Alert Service Bulletin 130406-
21-A4011, Revision 2, dated September 28, 1994; or 102850-21-A4021, 
Revision 2, dated October 6, 1994; certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent rapid decompression of the airplane due to cracking 
and subsequent failure of certain outflow/safety valves, accomplish 
the following: 
    (a) Within 30 days after the effective date of this AD, revise 
the Limitations Section of the FAA-approved Airplane Flight Manual 
(AFM) to include the following. This may be accomplished by 
inserting a copy of this AD in the AFM.
    ``Operation of the airplane at any altitude above 41,000 feet is 
prohibited.''
    (b) Replacement of outflow/safety valves, part numbers 130406-1 
and 102850-5, as identified in Allied Signal Aerospace Alert Service 
Bulletin 130406-21-A4011, Revision 2, dated September 28, 1994, or 
102850-21-A4021, Revision 2, dated October 6, 1994, as applicable; 
with a serviceable part in accordance with the procedures described 
in the applicable alert service bulletin; constitutes terminating 
action for the AFM limitation required by paragraph (a) of this AD. 
Following such replacement, that AFM limitation may be removed from 
the AFM.
    (c) As of the effective date of this AD, no person shall install 
an outflow/safety valve, part number 130406-1 or 102850-5, as 
identified in Allied Signal Aerospace Alert Service Bulletin 130406-
21-A4011, Revision 2, dated September 28, 1994, or 102850-21-A4021, 
Revision 2, dated October 6, 1994, as applicable; on any airplane 
unless that valve is considered to be serviceable in accordance with 
the specifications contained in the Accomplishment Instructions of 
the applicable alert service bulletin.
    (d) 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 
Operations 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.

    (e) Special flight permits may be issued in accordance with 
Secs. 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.
    (f) The replacement shall be done in accordance with Allied 
Signal Aerospace Alert Service Bulletin 130406-21-A4011, Revision 2, 
dated September 28, 1994; or Allied Signal Aerospace Alert Service 
Bulletin 102850-21-A4021, Revision 2, dated October 6, 1994; as 
applicable. 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 Allied Signal, Inc., 
Controls & Accessories, 11100 N. Oracle Road, Tucson, Arizona 85737-
9588; telephone (602) 469-1000. Copies may be inspected 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; or at the Office of the Federal Register, 800 
North Capitol Street, NW., suite 700, Washington, DC.
    (g) This amendment becomes effective on January 3, 1995.

    Issued in Renton, Washington, on December 9, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-30801 Filed 12-15-94; 8:45 am]
BILLING CODE 4910-13-U