We have received a report from the airplane manufacturer, Gulfstream, that the damper shafts in two actuators broke under normal torquing requirements during assembly of the actuators for a Gulfstream Model GV-SP airplane. Approximately one week after the original occurrence, a third actuator was found with a cracked damper shaft. In each case, the cracks originated at the threaded base of the damper shaft. In addition, the third actuator was found to be from a manufacturing lot previous to that of the other two actuators. Parker Aerospace, the actuator manufacturer, notified Gulfstream that the production process used after 1998 to manufacture aileron and elevator actuator damper shafts (internal to the actuator) may induce cracks in the threaded portion of the shaft. This cracking could cause the retaining nut and the separated portion of the failed damper shaft to become dislodged from the damper body and block the movement of the assembly. This condition,if not corrected, could result in locking of an aileron or elevator actuator (hard-over condition), subsequent loss of aileron or elevator control, and consequent reduced controllability of the airplane.
The affected aileron and elevator actuators installed on Gulfstream Model G-1159, G-1159A, G-1159B, G-IV, and GV series airplanes, are identical to those installed on Model GV-SP airplanes. Therefore, all of these models may be subject to the identified unsafe condition.
Other Rulemaking for Additional Airplane Models
Operators should note that, as we explained previously, Gulfstream Model GV and GV-SP series airplanes are subject to the same unsafe condition addressed in this AD. We are currently considering additional rulemaking to address the unsafe condition for those airplanes. However, because the unsafe condition is less severe for those models, the planned compliance time for that action would allow enough time to provide notice and opportunity for prior public comment on the merits of the corrective actions.
Relevant Service Information
We have reviewed the following Gulfstream alert customer bulletins:
Table--Relevant Service Information
For model-
Alert customer bulletin-
Revision-
Dated-
G-1159 and G-1159B series airplanes
Gulfstream GII/GIIB Alert Customer Bulletin 29A.
A
August 23, 2004.
G-1159A series airplanes
Gulfstream GIII Alert Customer Bulletin 15A
A
August 23, 2004.
G-IV series airplanes
Gulfstream G300 Alert Customer Bulletin 32A
A
August 23, 2004.
G-IV series airplanes
Gulfstream G400 Alert Customer Bulletin 32A
A
August 23, 2004.
G-IV series airplanes
Gulfstream GIV Alert Customer Bulletin 32A
A
August 23, 2004.
The alert customer bulletins describe procedures for a one-time inspection of the left and right aileron and elevator actuators to determine the part number (P/N) and serial number (S/N) of each actuator. The alert customer bulletins also describe procedures for an inspection of the actuators with certain P/Ns and S/Ns to detect broken damper shafts, and replacement of any actuator having a broken damper shaft with a new or serviceable actuator.
FAA's Determination and Requirements of This AD
The unsafe condition described previously is likely to exist or develop on other airplanes of the same type design. Therefore, we are issuing this AD to detect and correct broken damper shafts, which could result in locking of an aileron or elevator actuator (hard-over condition), subsequent loss of aileron or elevator control, and consequent reduced controllability of the airplane. This AD requires accomplishing the actions specified in the service information described previously, except as discussed under "Differences Between the AD and Alert Customer Bulletins." This AD also requires that operators report any broken damper shafts found during the initial and repetitive inspections required by paragraph (h) of this AD to theFAA.
Differences Between the AD and Alert Customer Bulletins
The alert customer bulletins do not specify the type of inspection to use to determine the P/N and S/N of the actuators. We have determined that the location of the actuators will require access and possibly additional inspection aides, and therefore, this AD requires a general visual inspection to determine the P/N and S/N of the actuators. We have included the definition of a general visual inspection in this AD.
The alert customer bulletins do not specify what to do if an installed actuator either has a P/N and/or S/N that is missing or is unreadable. This AD requires that those actuators be inspected to detect broken damper shafts--as if they have a P/N and S/N listed in the alert customer bulletin.
The alert customer bulletins recommend a one-time inspection of the aileron and elevator actuators for broken damper shafts. However, a suspect damper shaft found undamaged during the initial inspection still has the potential to break at some time in the future. Because a one-time inspection alone would not provide the degree of safety necessary, we have determined that repetitive inspections of the suspect actuators are necessary to ensure an adequate level of safety for the affected transport airplane fleet. We have also determined that an interval of 500 flight hours or 12 months, whichever is first, is an appropriate compliance time for the repetitive inspections. Although the alert customer bulletins do not include repetitive inspections, they do note that a recurring inspection will be added to the applicable airplane maintenance manual.
The alert customer bulletins also do not specify the type of inspection to use to detect broken damper shafts. We have determined that a detailed inspection for this action is appropriate; we have included the definition of this inspection in this AD. Therefore, this AD requires a detailed inspection to detect broken damper shafts. We have included the definition of a detailed inspection in this AD.
The alert customer bulletins specify replacing an actuator having a broken damper shaft, but they do not specify with what type of replacement actuator. This AD requires replacement with either:
A new or serviceable actuator having a subject P/N and S/N listed in the alert customer bulletin, provided it has been inspected for broken damper shafts in accordance with the requirements of this AD; or
A new or serviceable actuator having a P/N and/or S/N different than those listed in the alert customer bulletin. Replacing an actuator with an actuator having a different P/N and/or S/N terminates the requirements of this AD for that actuator only.
We are not requiring the terminating action (i.e., replacement of all suspect actuators) at this time, because we have determined, and the actuator manufacturer has confirmed, that the necessary replacement actuators (with a P/N and/or S/N not listed in the applicable alert customer bulletin) are not yet available and will not be available for another 24 to 36 months. Therefore, we are providing the terminating action as an option for operators once those parts become available.
The alert customer bulletins do not recommend that findings of broken damper shafts be reported. This AD requires findings of all broken damper shafts be reported to the FAA. When the unsafe condition addressed by an AD is likely due to a manufacturer's quality control (QC) problem, a reporting requirement is instrumental in ensuring that we can gather as much information as possible regarding the extent and nature of the QC problem or breakdown, especially in cases where the data may not be available through other established means. This information is necessary to ensure that proper corrective action will be taken. Based on the results of these reports, we may determine that further corrective action is warranted.
The Accomplishment Instructions of the referenced alert customer bulletins specify to submit the Service Reply Card or compliance information to the manufacturer. This AD does not include those actions; we do not need this information from operators.
Clarification of Applicability
The effectivities of the alert customer bulletins include all Model G-1159, G-1159A, G-1159B, and G-IV series airplanes, equipped with aileron or elevator actuators having certain P/Ns and S/Ns. Because there is no way to determine if an actuator with a suspect P/N and S/N is installed without inspecting the airplane, this AD applies to all Model G-1159, G-1159A, G-1159B, and G-IV series airplanes. We would, however, point out that the first action in the alert customer bulletins is an inspection to determine if an actuator having a certain P/N and S/N is installed.
Interim Action
This AD is considered to be interim action. The inspection reports that are required by this AD will enable us to obtain better insight into the nature and extent of the broken damper shafts, and eventually to develop final action to address the unsafe condition. Once final action has been developed and replacement parts are available, we may consider further rulemaking.
Changes to 14 CFR Part 39/Effect on the AD Relating to Special Flight Permits
On July 10, 2002, the FAA issued a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs the FAA's airworthiness directives system. The regulation now includes material that relates to altered products, special flight permits, and alternative methods of compliance (AMOC). This material is included in part 39, except that the office authorized to approve AMOCs is identified in each individual AD.
However, as amended, part 39 provides for the FAA to add special requirements for operating an airplane to a repair facility to do the work required by an airworthiness directive. For purposes of this AD, we have determined that such a special flight permit is prohibited.
FAA's Determination of the Effective Date
An unsafe condition exists that requires the immediate adoption of this AD; therefore, providing notice and opportunity for public comment before the AD is issued is impracticable, and good cause exists to make this AD effective in less than 30 days.
Comments Invited
This AD is a final rule that involves requirements that affect flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any relevant written data, views, or arguments regarding this AD. Send your comments to an address listed under ADDRESSES. Include "Docket No. FAA-2004-19337; Directorate Identifier 2004-NM-155-AD" at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD. We will consider all comments received by the closing date and may amend the AD in light of those comments.
We will post all comments we receive,without change, to http://dms.dot.gov , including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this AD. Using the search function of our docket web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You can review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-19478), or you can visit http://dms.dot.gov.
We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications with you. You can get more information about plain language at http://www/faa.gov/language and http://www.plainlanguage.gov.
Regulatory Findings
We have determined that this AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect 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.
For the reasons discussed above, I certify that the 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. 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.
We prepared a regulatory evaluation of the estimated costs to comply with this AD. See the ADDRESSES section for a location to examine the regulatory evaluation.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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. The FAA amends Sec. 39.13 by adding the following new airworthiness directive (AD):