[Federal Register Volume 61, Number 181 (Tuesday, September 17, 1996)]
[Rules and Regulations]
[Pages 48822-48824]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-23710]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 96-NM-63-AD; Amendment 39-9759; AD 96-19-13]
RIN 2120-AA64
Airworthiness Directives; Gates Learjet Model 35 and 36 Series
Airplanes Modified by Raisbeck Supplemental Type Certificate (STC)
SA766NW
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: This amendment adopts a new airworthiness directive (AD),
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 requires a reduction of the maximum
operating limit speed on the affected airplanes to prevent encountering
certain potentially hazardous conditions. This amendment is prompted by
reports of incidents of aileron buffet or buzz experienced during high
speed cruise. The actions specified by this 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.
EFFECTIVE DATE: October 22, 1996.
ADDRESSES: Information concerning the subject of this rule may be
obtained from Jet Air Corporation, P.O. Box 245, Bellevue, Washington
98009. Information concerning this rulemaking action may be examined at
the Federal Aviation Administration (FAA), Transport Airplane
Directorate, Rules Docket, 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: A proposal to amend part 39 of the Federal
Aviation Regulations (14 CFR part 39) to include an 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 was published in the
Federal Register on May 13, 1996 (61 FR 21982). That action proposed to
require a reduction of the maximum operating limit speed on the
affected airplanes to prevent encountering certain potentially
hazardous conditions.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the single comment received.
Request to Require New Part Numbers of Modified Parts
One commenter requests that the proposal be revised to require
that, once the overspeed warning switch is recalibrated and the
airspeed indicators are modified [in accordance with OPTION I of the
proposed AD], new part numbers should be assigned to those items.
Additionally, the commenter requests that a parts catalog supplement be
issued with the STC, calling out the correct new part number of the
devices for future reference by maintenance personnel. The commenter
considers that merely ink-stamping
[[Page 48823]]
these parts once the required actions have been accomplished on them,
as the proposed rule specifies, is not generally acceptable practice.
The commenter states that, if either of those items is replaced in the
future, there is no mechanism in place that would prevent the
installation of a standard (unmodified) part number device in the
airplane. Therefore, the airplane would no longer be in compliance with
the AD, and would not be airworthy.
. The FAA does not concur with the commenters request for two
reasons:
1. First, assigning and changing part numbers, and developing a
parts catalog supplement, would be more labor-intensive and time
consuming than ink-stamping a recalibrated or modified part.
Additionally, the FAA is not convinced that the actions suggested by
the commenter would be any more effective than the requirements of this
AD.
2. Second, to show that actions specified in this AD have been
complied with, it is necessary for the operator to make a maintenance
log book entry indicating that the modified and ink-stamped warning
switch and airspeed indicators are installed. If these items are
replaced in the future (with parts that are not modified and not ink-
stamped), a review of the log book entry would readily inform the
mechanic or inspector that the airplane is not in compliance with the
AD. Further, this process for verifying compliance would be identical
whether the part is ink-stamped or has a new part number.
Conclusion
After careful review of the available data, including the comments
noted above, the FAA has determined that air safety and the public
interest require the adoption of the rule as proposed.
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 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. 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 must 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
would not adversely affect safety, and 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 will 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 provided by ``Option I'' of the proposed rule, it will
take approximately 5 work hours per airplane, at an average labor rate
of $60 per work hour. The FAA estimates that it will 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
(Option 1 of the AD) on U.S. operators is estimated to be $1,300 per
airplane.
To accomplish the removal of the STC modifications, as provided by
``Option II'' of the rule, it will 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 (Option II of the 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 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 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.
For the reasons discussed above, I certify that this action (1) Is
not a ``significant regulatory action'' under Executive Order 12866;
(2) is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action
and it is contained in the Rules Docket. A copy of it 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:
96-19-13 Gates Learjet: Amendment 39-9759. Docket 96-NM-63-AD.
Applicability: Model 35, 35A, 36, and 36A series airplanes;
certificated in any category; that have been modified in accordance
with Raisbeck Group Supplemental Type Certificate (STC) SA766NW, and
that do not have one of the airplane serial numbers listed in Table
1 of this AD.
Table 1.--Serial Numbers* NOT affected by this AD
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 ................
*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
[[Page 48824]]
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) (``OPTION
I'') or (a)(2) (``OPTION II'') 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 Mach .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
recalibrated 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 Mach number .80. The instrument must be recalibrated by the
instrument manufacturer or a certified repair station. Reidentify
the modified 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.
(d) This amendment becomes effective on October 22, 1996.
Issued in Renton, Washington, on September 10, 1996.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-23710 Filed 9-16-96; 8:45 am]
BILLING CODE 4910-13-U