[Federal Register Volume 64, Number 94 (Monday, May 17, 1999)]
[Proposed Rules]
[Pages 26703-26705]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-12298]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-372-AD]
RIN 2120-AA64
Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31,
55, and 60 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 certain Learjet Model 23, 24, 25,
28, 29, 31, 55, and 60 series airplanes. This proposal would require a
one-time detailed visual inspection of the electrical wire leads of the
horizontal stabilizer anti-ice system to verify that the numbers on the
wire leads correctly correspond to the numbers on the connected
airframe wiring; installation of a wire ID strap on the left- and
right-hand sides of each terminal block; and installation of a warning
placard. This proposal is prompted by a report of severe flight control
buffeting of a Learjet Model 55 series airplane due to a malfunction of
the horizontal stabilizer anti-ice system. The actions specified by the
proposed AD are intended to prevent undetected accretion of ice on the
leading edge of the horizontal stabilizer, which could result in the
loss of pitch control and consequent reduced controllability of the
airplane.
DATES: Comments must be received by July 1, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 98-NM-372-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 Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-
2942. This information may be examined at the FAA, Transport Airplane
Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA,
Small Airplane Directorate, Wichita Aircraft Certification Office, 1801
Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas.
FOR FURTHER INFORMATION CONTACT: Jose Flores, Senior Aerospace
Engineer, Systems and Propulsion Branch, ACE-116W, FAA, Small Airplane
Directorate, Wichita Aircraft Certification Office, 1801 Airport Road,
Room 100, Mid-Continent Airport, Wichita, Kansas 67209; telephone (316)
946-4133; fax (316) 946-4407.
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 98-NM-372-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-114, Attention: Rules
Docket No. 98-NM-372-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
[[Page 26704]]
Discussion
The FAA has received a report indicating that a Learjet Model 55
series airplane declared an emergency during flight due to severe
flight control buffeting; the airplane landed safely. Following a
detailed visual inspection of the horizontal stabilizer anti-ice
system, it was determined that the wiring on two terminal strips was
incorrectly connected, which caused electrical heating elements of the
anti-ice system to operate out of sequence and allowed ice to build up
on the horizontal stabilizer. When operating correctly, the center
electrical heating element is provided with continuous electrical
power. Incorrect wiring can cause the center element to cycle on and
off and, subsequently, the anti-ice system will not function properly,
which can cause the ice to build up on the leading edge of the
horizontal stabilizer. Further investigation revealed that during
routine maintenance of the airplane's anti-ice system, the wire numbers
connecting the airplane wiring through two terminal strips were
incorrectly matched to the electrical heating elements in the leading
edge, which led to miswiring of the connection. This condition, if not
corrected, could result in undetected accretion of ice on the leading
edge of the horizontal stabilizer, and consequent loss of pitch control
and reduced controllability of the airplane.
Explanation of Relevant Service Information
The FAA has reviewed and approved Learjet Service Bulletins SB 23/
24/25-30-3, (for Model 23, 24, and 25 series airplanes), SB 28/29-30-3
(for Model 28 and 29 series airplanes), SB 31-30-05 (for Model 31
series airplanes), SB 55-30-3 (for Model 55 series airplanes), and SB
60-30-4 (for Model 60 series airplanes); all dated October 27, 1998;
which describe procedures for a one-time detailed visual inspection of
the electrical wire leads of the horizontal stabilizer anti-ice system
to verify that the numbers on the wire leads correctly correspond to
the numbers on the connected airframe wiring; installation of a wire ID
strap on the left- and right-hand sides of each terminal block; and
installation of a warning placard. The new placard will provide clear
and visible warning that reads: ``WARNING--PROPER CONNECTION OF BOOT
WIRING IS CRITICAL, REFER TO WIRING/SERVICE MANUAL.'' Accomplishment of
the actions specified in the service bulletins is intended to
adequately address the identified unsafe condition.
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 accomplishment of the actions specified in
the service bulletins described previously, except as discussed below.
Differences Between Proposed Rule and Service Bulletins
Operators should note that, although the service bulletins
recommend accomplishing the detailed visual inspection and
installations within 300 flight hours (after the release of the service
bulletin), the FAA has determined that a compliance time of 300 flight
hours would not address the identified unsafe condition in a timely
manner. In developing an appropriate compliance time for this proposed
AD, the FAA considered not only the manufacturer's recommendation, but
the degree of urgency associated with addressing the subject unsafe
condition, the average utilization of the affected fleet, and the time
necessary to perform the inspection and installations (one work hour).
In light of all of these factors, the FAA finds a 100-flight-hour
compliance time for initiating the required actions to be warranted, in
that it represents an appropriate interval of time allowable for
affected airplanes to continue to operate without compromising safety.
Cost Impact
There are approximately 1,010 airplanes of the affected design in
the worldwide fleet. The FAA estimates that 806 airplanes of U.S.
registry would be affected by this proposed AD, that it would take
approximately 1 work hour per airplane to accomplish the proposed
inspection and installations, and that the average labor rate is $60
per work hour. Required parts would be provided by the manufacturer at
no cost to the operators. Based on these figures, the cost impact of
the proposed AD on U.S. operators is estimated to be $48,360, or $60
per airplane.
The cost impact figure discussed above is 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.
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.
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:
Learjet: Docket 98-NM-372-AD.
Applicability: Model 23, 24, 25, 28, 29, 31, 55, and 60 series
airplanes; as listed in Learjet Service Bulletins SB 23/24/25-30-3,
SB 28/29-30-3, SB 31-30-05, SB 55-30-3, and SB 60-30-4, all dated
October 27, 1998; 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 (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
[[Page 26705]]
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 undetected accretion of ice on the leading edge of
the horizontal stabilizer, which could result in the loss of pitch
control and consequent reduced controllability of the airplane,
accomplish the following:
One-Time Inspection
(a) Within 100 flight hours after the effective date of this AD:
Perform a one-time detailed visual inspection of the electrical wire
leads of the horizontal stabilizer anti-ice system to verify that
the numbers on the wire leads correctly correspond to the numbers on
the connected airframe wiring, in accordance with Learjet Service
Bulletins SB 23/24/25-30-3, (for Model 23, 24, and 25 series
airplanes), SB 28/29-30-3 (for Model 28 and 29 series airplanes), SB
31-30-05 (for Model 31 series airplanes), SB 55-30-3 (for Model 55
series airplanes), or SB 60-30-4 (for Model 60 series airplanes);
all dated October 27, 1998; as applicable.
Note 2: For the purposes of this AD, a detailed inspection is
defined as: ``An intensive visual examination of a specific
structural area, system, installation or assembly to detect damage,
failure or irregularity. Available lighting is normally supplemented
with a direct source of good lighting at intensity deemed
appropriate by the inspector. Inspection aids such as mirror,
magnifying lenses, etc. may be used. Surface cleaning and elaborate
access procedures may be required.''
Corrective Action
(1) If no discrepancy is detected during the inspection required
by paragraph (a) of this AD: Concurrent with the inspection, install
a wire ID strap on the left- and right-hand sides of each terminal
block, and install a warning placard on each terminal block, in
accordance with the applicable service bulletin.
(2) If any discrepancy is detected during the inspection
required by paragraph (a) of this AD: Prior to further flight,
repair the discrepancy in accordance with the procedures specified
in Chapter 30 of the Learjet Airplane Wiring Manual. Concurrent with
the repair, install a wire ID strap on the left- and right-hand
sides of each terminal block, and install a warning placard on each
terminal block; in accordance with the applicable service bulletin.
Alternative Methods of Compliance
(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, Wichita Aircraft Certification
Office (ACO), FAA, Small 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, Wichita ACO.
Note 3: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Wichita ACO.
Special Flight Permits
(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 May 10, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-12298 Filed 5-14-99; 8:45 am]
BILLING CODE 4910-13-P
