AD 98-14-10

Effective July 22, 1998.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of July 22, 1998.

Comments for inclusion in the Rules Docket must be received on or before September 8, 1998.

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-155-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The service information referenced in this AD may be obtained from AlliedSignal Aerospace, Technical Publications, Dept. 65-70, P.O. Box 52170, Phoenix, Arizona 85072-2170. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Jay Yi, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1013; fax (425) 227-1181.

The FAA has received a report indicating that, during a test flight of a Boeing airplane, the flightcrew detected discrepancies in the glide slope deviation provided by one of the onboard Instrument Landing System (ILS) receivers. (The glide slope is the flight path that an airplane is to follow when making an ILS landing. The display of the glide slope deviation indicates the position of the airplane relative to the glide slope and indicates to the flightcrew whether the airplane needs to be at a higher or lower altitude to be on the normal approach flight path.) The discrepancies in the glide slope deviation provided by the discrepant ILS receiver resulted in the display showing that the airplane was on the glide slope, when the airplane was approximately one dot low on the glide slope (as determined from the data provided by the ILS receivers that were operating correctly). The flightcrew received no annunciation that there were discrepancies between the glide slope deviations being provided by the ILS receivers.

An investigation conducted by AlliedSignal, the manufacturer of the RIA-35B ILS receivers installed on the airplane, has revealed that the discrepancies in the glide slope deviation were caused by failure of an internal component of the ILS receiver due to that component's sensitivity to temperature. Due to the nature of the failure, that component also could fail on other airplanes.

The same ILS receiver provides localizer deviation. (The display of the localizer deviation indicates the position of the airplane relative to the center line of the runway during an ILS landing.) Faults in the ILS receiver, if not corrected, could result in a landing outside the lateral boundary of the runway. If a faulty ILS receiver provides a localizer deviation that contains errors that are not detected by the flightcrew, use of a single ILS receiver for ILS or localizer approaches could result in the pilot being directed to land the airplane outside the lateral boundary of the runway. If the localizer deviations generated by two of the ILS receivers onboard the airplane contain errors that are not detected by the flightcrew, during category II and III operations, the autopilot system may land the airplane outside the lateral boundary of the runway.

The FAA finds that flightcrews are not currently provided with adequate information necessary to address the potential hazard of performing an ILS or localizer approach using a localizer deviation provided by a faulty ILS receiver. Therefore, the FAA has determined that flightcrews must be provided with such information and must be made aware that certain types of operations are prohibited when only one RIA-35B ILS receiver (with the affected part number) is operational.

The RIA-35B ILS receivers installed on certain Boeing Model 747-400, 757, 767, and 777 series airplanes are the same type as those on the affected Boeing airplane. Therefore, those Boeing Model 747-400, 757, 767, and 777 series airplanes may be subject to the same unsafe condition.

The FAA has reviewed and approved AlliedSignal Electronic and Avionics Systems Service Bulletin M-4426 (RIA-35B-34-6), Revision 3, dated May 1998, which describes procedures for modifying RIA-35B ILS receivers, part number (P/N) 066-50006-0101. The modification includes removing the radio frequency (RF) assembly; modifying the RF module by cutting two solder-side tracks, installing two 221-ohm resistors, and replacing components U8009 and U8206; and reinstalling the modified RF assembly. Once modified, the P/N of the ILS receiver is converted to 066-50006-1101. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, this AD is being issued to detect and correct faulty ILS receivers, and to ensure that the flightcrew is advised of the potential hazard of performing ILS approaches using a localizer deviation from a faulty ILS receiver and also advised of the procedures necessary to address that hazard. This AD requires a revision to the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to prohibit ILS or localizer approaches if only one ILS receiver is operational. This AD also requires repetitive visual inspections for faults stored in the internal fault memory of all RIA-35B ILS receivers, P/N 066-50006-0101; or, alternatively, an additional revision to the Limitations Section of the AFM and installation of a placard in the cockpit to prohibit category II and III operations. For cases where certain faults are detected in the internal fault memory, this AD also requires replacement of the faulty ILS receiver with a new, serviceable, or modified part. If accomplished, replacement of all ILS receivers, P/N 066-50006-0101, with modified ILS receivers terminates the repetitive inspections and AFM revisions described previously.

The FAA may consider separate rulemaking to address the identified unsafe condition on other transport category airplanes equipped with the affected ILS receiver. The FAA notes that its general policy is that, when an unsafe condition results from the installation of an appliance or other item that is installed in a limited number of airplane models, an AD is issued so that it is applicable to those airplanes, rather than the item. The reason for this is simple: making the AD applicable to the airplane models on which the item is installed ensures that operators of those airplanes will be notified directly of the unsafe condition and the action required to correct it. While it is assumed that an operator will know the models of airplanes that it operates, there is a potential that the operator will not know or be aware of specific items that are installed on its airplanes. Therefore, calling out the airplane model as the subject of the AD prevents ``unknowing non-compliance'' on the part of the operator.

This is considered to be interim action. The FAA is considering further rulemaking action to supersede this AD to require replacement of all existing RIA-35B ILS receivers with modified parts. However, the planned compliance time for such replacement is sufficiently long so that notice and opportunity for prior public comment will be practicable.

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 98-NM-155-AD.'' The postcard will be date stamped and returned to the commenter.

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.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a ``significant regulatory action'' under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

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:

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.