[Federal Register Volume 61, Number 93 (Monday, May 13, 1996)]
[Proposed Rules]
[Pages 21982-21984]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-11881]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 96-NM-63-AD]
RIN 2120-AA64
Airworthiness Directives; Gates Learjet Model 35 and 36 Series
Airplanes Modified by Raisbeck STC SA766NW
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 Gates Learjet Model 35 and
36 series airplanes that have been modified in accordance with Raisbeck
Supplemental Type Certificate (STC) SA766NW. This proposal would
require a reduction of the maximum operating limit speed on the
affected airplanes to prevent encountering certain potentially
hazardous conditions. This proposal is prompted by reports of incidents
of aileron buffet or buzz experienced during high speed cruise. The
actions specified by the proposed AD are intended to prevent aileron
buffet or buzz conditions, which can result in the deterioration of the
aircraft lateral control system characteristics to an unacceptable
level.
DATES: Comments must be received by June 24, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 96-NM-63-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.
Information concerning the subject of this rulemaking action may be
obtained from Jet Air Corporation, P.O. Box 245, Bellevue, Washington
98009. Information concerning this rulemaking action may be examined at
the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,
Washington.
FOR FURTHER INFORMATION CONTACT: Stan Wood, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office,
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2772;
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 96-NM-63-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. 96-NM-63-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On July 23, 1985, the FAA issued AD 85-16-04, amendment 39-5110 (50
FR 30803, July 30, 1985), which is applicable to certain Gates Learjet
Model 35 and 36 series airplanes that have been modified in accordance
with Raisbeck Supplemental Type Certificate (STC) SA766NW. That AD
requires the accomplishment of one of two optional actions, both of
which are intended to prevent the airplane from encountering the
potentially hazardous condition of aileron buffet or buzz:
1. One optional action requires operators to reduce permanently the
maximum operating Mach limit (MMO) of these airplanes from .83 to
.80. This action includes resetting the Mach
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overspeed warning switch; recalibrating the airspeed indicator; and
changing the FAA-approved Airplane Flight Manual (AFM) Supplement to
reflect the new Mach limit.
2. The other optional action requires operators to remove the
Raisbeck STC modifications and to return the airplane either to its
original configuration or to the Gates Learjet ``Softflight''
configuration.
AD 85-16-04 was prompted by several reports of incidents in which
Learjet Model 35 and 36 series airplanes modified with the Raisbeck STC
experienced aileron buffet or buzz during cruise. These incidents of
aileron instability occurred on airplanes operating at high gross
weights when they were flying above 42,000 feet at Mach .80 to .83.
Aileron buffet or buzz, if it is of a certain severity, can result in
an unacceptable deterioration in the lateral control characteristics of
the airplane.
Actions Subsequent to the Issuance of AD 85-16-04
When AD 85-16-04 was issued, its applicability included only
certain modified airplanes, which were identified by specific serial
numbers. However, since the issuance of that AD, the FAA has received a
report that at least one additional airplane, that was not included in
the applicability of the AD, has been modified in accordance with the
subject Raisbeck STC. (The STC installed on this particular airplane
was performed at a non-U.S. repair station.) In light of this, that
airplane may be subject to the same unsafe condition addressed by AD
85-16-04.
Further, since the Raisbeck STC could be installed on Model 35 or
36 series airplanes anywhere in the world, the FAA may not be
immediately aware of it. Therefore, the FAA has determined that any of
these airplanes on which the Raisbeck STC is installed could be subject
to that same unsafe condition.
Description of the Proposed AD
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 the accomplishment of one of two optional
actions, both of which are intended to prevent the airplane from
encountering the potentially hazardous condition of aileron buffet or
buzz:
1. Permanently reducing the maximum operating MMO from .83 to
.80; resetting the Mach overspeed warning switch; recalibrating the
airspeed indicator; and changing the FAA-approved Airplane Flight
Manual (AFM) Supplement to reflect the new Mach limit; or
2. Removing the Raisbeck STC modifications and returning the
airplane either to its original configuration or to the Gates Learjet
``Softflight'' configuration.
These proposed requirements are the same actions currently required
by AD 85-16-06.
The applicability of the proposed AD would include all Learjet
Model 35 and 36 series airplanes modified in accordance with Raisbeck
STC SA766NW that are not currently subject to AD 85-16-04.
[Note: The FAA's normal policy is that when an AD requires a
substantive change, such as a change (expansion) in its
applicability, the ``old'' AD is superseded by removing it from the
system and a new AD is added. In the case of this proposed AD
action, the FAA normally would have proposed superseding AD 85-16-04
to expand its applicability to include the additional affected
airplanes. However, in reconsideration of the entire fleet size that
would be affected by a supersedure action, and the consequent
workload associated with revising maintenance record entries, the
FAA has determined that a less burdensome approach is to issue a
separate AD applicable only to these additional airplanes. This
proposed AD would not supersede AD 85-16-04; airplanes listed in the
applicability of AD 85-16-04 are required to continue to comply with
the requirements of that AD. This proposed AD is a separate AD
action, and is applicable only to airplanes that are not subject to
AD 85-16-04.]
Petitioning for an Exemption of the Requirements of the Final Rule
Affected operators should note that the aileron instability that is
the subject of this proposed AD is a condition affected by the contour
of the wing leading edge, which is a function of manufacturing
tolerances. In light of this, the FAA recognizes that not all airplanes
modified in accordance with Raisbeck STC SA766NW may exhibit the
problem of aileron buffet or buzz below .83 Mach. Should this proposal
become a final rule, operators of those airplanes may wish to petition
the FAA for an exemption from the requirements of the rule, under the
provisions of part 11 of the Federal Aviation Regulations (14 CFR 11),
``General Rulemaking Procedures.''
Petitioners for such an exemption should provide data that would
justify a grant of exemption, including, but not limited to,
information concerning the number of flights the airplane has flown in
conditions involving high weight, high altitude, and high speed, and if
any incident of buffet or buzz was observed during flight in those
conditions. Based on the data submitted with the petition, the FAA will
determine on a case-by-case basis if a flight evaluation or other
additional data are necessary to determine if granting the petition (1)
would not adversely affect safety, and (2) would be in the public
interest.
Cost Impact
There are approximately 29 Gates Learjet Model 35 and 36 series
airplanes of the affected design in the worldwide fleet. The FAA
estimates that at least 1 airplane of U.S. registry would be affected
by this proposed AD.
To accomplish the removal and recalibration of the airspeed
indicators and Mach overspeed warning switch, and to revise the AFM
Supplement, as would be required by ``Option I'' of the proposed rule,
it would take approximately 5 work hours per airplane, at an average
labor rate of $60 per work hour. The FAA estimates that it would cost
approximately $1,000 per airplane to reset the airspeed indicators and
Mach overspeed warning switch. Based on these figures, the cost impact
of this action of the proposed AD on U.S. operators is estimated to be
$1,300 per airplane.
To accomplish the removal of the STC modifications, as would be
required by ``Option II'' of the proposed rule, it would take
approximately 100 work hours per airplane, at an average labor rate of
$60 per work hour. Based on these figures, the cost impact of this
action of the proposed AD on U.S. operators is estimated to be $6,000
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.
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
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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:
Gates Learjet: Docket 96-NM-63-AD.
Applicability: Model 35, 35A, 36 and 36A series airplanes,
modified in accordance with Raisbeck Group Supplemental type
Certificate (STC) SA766NW, that do not have one of the serial
numbers listed in Table 1 of this AD; certificated in any category.
Table 1
[Serial Numbers * NOT affected by this AD]
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35-023........... 35A-092 35A-192- 36-004
35-034-.......... 35A-093- 35A-203- 36-017
35-042-.......... 35A-095- 35A-206- 36-028
35-044-.......... 35A-118- 35A-207- 36A-029
35-047-.......... 35A-127- 35A-209- 36A-031
35A-068-......... 35A-132- 35A-228- 36A-038
35A-073-......... 35A-135- 35A-231- 36A-043
35A-075-......... 35A-145- 35A-244- 36A-044
35A-076-......... 35A-172- 35A-245-
35A-086 -........ 35A-185- 36-003
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*Airplanes having the serial numbers listed in Table 1 are subject to
similar requirements mandated by AD 85-16-04, amendment 39-5110.
Note 1: This AD applies to each airplane as indicated 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 deterioration of the airplane's lateral control
characteristics as a result of aileron buffet or buzz, accomplish
the following:
(a) Within 200 hours time-in-service after the effective date of
this AD, or within 6 months after the effective date of this AD,
whichever occurs first, accomplish either paragraph (a)(1) or (a)(2)
of this AD:
(1) Option I. Permanently reduce the airplane's maximum
operating Mach limit (MMO) by accomplishing the actions
specified in paragraphs (a)(1)(i), (a)(1)(ii), and (a)(1)(iii) of
this AD:
(i) Submit the FAA-approved STC SA766NW Airplane flight Manual
Supplement to the Manager, Flight Test Branch, ANM-160S, Seattle
Aircraft Certification Office, FAA, Transport Airplane Directorate,
1601 Lind Avenue SW., Renton, Washington 98055-4056; to change the
limit Mach number from .83 to .80. And
(ii) Remove the ``Mach Overspeed Warning Switch'' and have it
reset from Mach .83 to .80. Contact the manufacturer, PRECISION
SENSOR, P.O. Box 509, Milford, Connecticut 06460; telephone number
(203) 877-2795; to have the instrument recalibrated. Reidentify the
Mach overspeed warning switch by ink-stamping the words ``Mach limit
.80'' adjacent to the part number. Reinstall the ``Mach Overspeed
Warning Switch'' after it has been so recalibrated. And
(iii) Remove the pilot's and copilot's airspeed indicators and
have them modified by changing the ``barber pole'' from Mach number
.83 to .80. The instrument must be recalibrated by the instrument
manufacturer or a certified repair station. Reidentify the airspeed
indicators by ink stamping ``Mach limit .80'' adjacent to the part
number. Reinstall the pilot's and copilot's airspeed indicators
after they have been so modified.
(2) Option II. Remove the modifications installed in accordance
with Raisbeck Group STC SA766NW, and return the aircraft either to
the original type design configuration, or to the Gates Learjet
``Softflight'' configuration.
(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 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, 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 May 7, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-11881 Filed 5-10-96; 8:45 am]
BILLING CODE 4910-13-P
