The Departmento de Aviacao Civil (DAC), which is the airworthiness authority for Brazil, notified the FAA that an unsafe condition may exist on all Empresa Brasileira de Aeronautica S.A. (EMBRAER) ERJ 170 series airplanes. The DAC advises that, during some flight tests performed by the manufacturer on Model ERJ 170 prototype airplanes, a temporary loss of all display units (DU) occurred. Post-incident investigation showed that this failure could be traced to a failure on the master timer network interface card (NIC)/ network interface integrated module (NIM) synchronizer, which provides timing signals for the avionics standard communication bus (ASCB). In that scenario, for approximately 4 seconds, the pilots were left with only the integrated electronic standby system (IESS) for basic flying, with only a very high frequency (VHF) radio for voice communication. In all reported cases, the system recovered without any specific pilot action. However, further investigation showed the theoretical possibility of a sustained loss of all modular avionics units (MAU), which triggers a cascade of failures in systems dependent on MAU functionalities. These functionalities include DUs, flight control system normal mode, autopilot, and autothrottle.
Temporary or possible sustained loss of all MAUs, if not corrected, could trigger a cascade of failures in systems dependent on MAU functionalities. Such failures could reduce the flightcrew's situational awareness and increase workload and consequently reduce the ability of the flightcrew to maintain the safe flight and landing of the airplane.
Other Relevant Rulemaking
We have determined that Gulfstream Model GV-SP series airplanes may be subject to an unsafe condition similar to that addressed in this AD. Therefore, we are considering additional rulemaking to address that unsafe condition on that airplane model.
Relevant Service Information
EMBRAER has issued Operational Bulletin 170-011/04, Revision 1, dated December 23, 2004. The operational bulletin informs operators of the possibility of loss of all MAUs, and provides procedures for operation in the event that this type of failure occurs. The operational bulletin also prohibits operators from dispatch with the IESS inoperative, even though it is allowed by the current version of the Master Minimum Equipment List.
EMBRAER has issued Service Bulletin 170-31-0003, dated December 23, 2004. This service bulletin describes procedures for performing a test to assess the general conditions of the NIC communications, and making repairs if necessary.
EMBRAER has issued Service Bulletin 170-31-0002, dated December 23, 2004. This service bulletin describes procedures for installing the software version of the PRIMUS EPIC system identified as "load 15.3" or higher, after which the AFM revision described previously may be removed.
Accomplishing the actions specified in the service information is intended toadequately address the unsafe condition. The DAC mandated the service information and issued Brazilian emergency airworthiness directive 2004-12-04, effective December 27, 2004, to ensure the continued airworthiness of these airplanes in Brazil.
FAA's Determination and Requirements of This AD
This airplane model is manufactured in Brazil and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the DAC has kept the FAA informed of the situation described above. We have examined the DAC's findings, evaluated all pertinent information, and determined that we need to issue an AD for products of this type design that are certificated for operation in the United States.
Therefore, we are issuing this AD to prevent temporary or possible sustained loss of all MAUs, which triggers a cascade of failures in systems dependent on MAUs functionalities. Such failures could reduce the flightcrew's situational awareness and increase workload and consequently reduce the ability of the flightcrew to maintain the safe flight and landing of the airplane. This AD requires accomplishing the actions specified in the service information described previously, except as discussed under "Differences Between This AD and the Service Information."
Differences Between This AD and the Service Information
EMBRAER Service Bulletin 170-31-0003 specifies that you may contact the manufacturer for instructions on how to repair certain conditions, but this AD requires you to repair those conditions using a method that we or the DAC (or its delegated agent) approve. In light of the type of repair that is required to address the unsafe condition, and consistent with existing bilateral airworthiness agreements, we have determined that, for this AD, a repair we or the DAC approve is acceptable for compliance with this AD.
Although the Accomplishment Instructions of EMBRAER Service Bulletin 170-31-0003 specify submitting test results to the airplane manufacturer, this AD does not require that action.
Differences Between This AD and the Brazilian AD
Although the Brazilian AD requires operators to revise the Emergency and Abnormal Procedures Sections of the AFM, this AD requires that the Limitations Section of the AFM be revised. The Limitations Section of the AFM is the only mandatory AFM section.
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-2004-19972; Directorate Identifier 2004-NM-273-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 19477-78), or you can visit http://dms.dot.gov.
Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, "General requirements." Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.
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.
39.13 [Amended]
2. The FAA amends 39.13 by adding the following new airworthiness directive (AD):