Discussion
AlliedSignal recently notified the FAA that their global positioning system (GPS) Flight Management System Models GNS-XLS and GNS-XL are malfunctioning. The AlliedSignal Models GNS-XLS and GNS-XL are used to determine the flight course of an airplane for previously published non-precision approaches to an airport. The GPS flight management system is integrated into the software of the flight management system recorder (black box) in the airplane. These GNS-XLS and GNS-XL GPS can be installed on, but are not limited to the following airplanes:
Manufacturer
Models
British Aerospace, Ltd. (BAe)
146-100A and 146-200A
Cessna Aircraft Corporation
525, 550, and 560
Dassault Aviation
Mystere-Falcon 20 and 50
Avions Marcel Dassault
Falcon 10
Gulfstream Aerospace
G-1159 (G-II) and G-1159A (G-III)
Raytheon Corporate Jets
Hawker 800
Israel Aircraft Industries, Ltd.
1124
Sabreliner Corporation
NA-65
Learjet Inc.
35
Jetstream Aircraft Ltd.
4101
Problems arose with these GPS flight management systems units after an installation of a GNS-XLS unit for certification in a Cessna Model 550 airplane. During this flight certification, the AlliedSignal Model GNS-XLS GPS provided erroneous information to the Flight Management System which caused the airplane to deviate from the previously published non-precision approach. Further investigation with flight tests on other airplane models confirmed this software malfunction. The manufacturer conducted bench tests on these models, and was also successful in duplicating the deviation occurring within the GPS flight management software while it is used in a previously published non-precision approach situation. The tests also showed that this malfunction is only randomly occurring approximately 20 percent of the time.
The FAA's Determination
After examining the circumstances and reviewing all available information related to the incidents described above, including the relevant service information, the FAA has determined that AD action should be taken to prevent deviation of an intended flight path during a non-precision approach to an airport.
Explanation of the Provisions of the AD
Since an unsafe condition has been identified that is likely to exist or develop in other AlliedSignal Models GNS-XLS and GNS-XL GPS Flight Management Systems of the same type design, this AD requires inserting the following limitation into the Operations Limitations Section of the AFM or Flight Manual Supplement:
Operating Limitations
The GNS-XL (or GNS-XLS) is not approved for non-precision approaches.
NOTE
The GNS-XL (or GNS-XLS) may generate misleading information during non-precision GPS or Overlay approaches due to software limitations.
The FAA and AlliedSignal are currently working together toward an approved revision to the software problem on these GPS Flight Management System units.
Compliance Time of this AD
The compliance time of this AD is in calendar time instead of hours time-in-service (TIS). The average daily usage of the affected airplanes will have different ranges throughout the fleets. For example, one owner may operate the airplane 5 hours TIS in one day, while another operator may operate the airplane 5 hours TIS in one week. In order to ensure that all of the owners/operators of the affected airplanes have the chance to insert the limitation into the operating limitations of their Airplane Flight Manual or Flight Manual Supplement within a reasonable amount of time, the FAA is setting a compliance time of within the next 5 days after the effective date of this AD.
Determination of the Effective Date of the AD
Since a situation exists (misleading flight course information to the pilot during non-precision approaches) that requires the immediate adoption of this regulation, it is found that notice and opportunity for public prior comment hereon are impracticable, and that goodcause exists for making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves requirements affecting immediate flight safety and, thus, was not preceded by notice and opportunity to 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 should 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 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 No. 97-CE-07-AD." The postcard will be date stamped and returned to the commenter.
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.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and 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 (otherwise, an evaluation is not required). A copy of it, if filed, may be obtained from the Rules Docket.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
Adoption of the Amendment
Accordingly, pursuant tothe 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 USC 106(g), 40113, 44701.
39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows: