# AD 98-25-02: Top-mounted Antenna

- Type: Airworthiness directive
- Status: Current
- Products: Bell Helicopter Textron Canada 407, 172, 172A, 172B, 172C, 172D, 172E, 172F (USAF T-41A), 172G, 172H (USAF T-41A), 172I, 172K and 234 more
- Effective: December 22, 1998
- Published: December 3, 1998, 63 FR 66746–66751
- Issued: November 24, 1998
- Issued as: Final rule; request for comments
- Superseded by: Nothing supersedes this AD
- Product type: Appliance
- Amendment: 39-10924
- Docket: 98-CE-107-AD
- Registered aircraft: 62,196 may be affected, by airframe or engine model (OpenAirDocs)
- Official PDF: https://openairdocs.org/files/sha256/0c/2d/0c2d9d0175f4194d6d68c6b4f89b2c53abd495031e282be00bbb59c177694fed (from https://www.govinfo.gov/content/pkg/FR-1998-12-03/pdf/98-32101.pdf)
- Federal Register: https://www.federalregister.gov/documents/1998/12/03/98-32101/airworthiness-directives-bfgoodrich-avionics-systems-inc-skywatch-sky497-installations-with-a
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/1EBF0AA24910728C86256A40006C38D9.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/98-25-02

## Summary

This amendment adopts a new airworthiness directive (AD) that applies to all BF Goodrich Avionics Systems, Inc. (BF Goodrich) SKYWATCH SKY497 installations with a top-mounted antenna that are installed on aircraft. This AD requires incorporating information into the airplane flight manual (AFM) that specifies verifying the correct antenna configuration each time an aircraft equipped with a SKY497 installation with a top-mounted antenna is powered-up. The AD also requires removing from service any of these SKY497 installations with an incorrect antenna configuration. This AD results from numerous reports of internal component failure of the above-referenced installations, which changed the antenna configuration (from TOP to BOTTOM mount). The actions specified by this AD are intended to prevent the display of target indicators on the wrong side of the aircraft caused by an internal component failure in the SKY497 installations with a top-mounted antenna, which could resultin the pilot making an incorrect initial maneuver based on the displayed information while trying to visually acquire the aircraft.

## The airworthiness directive

98-25-02 BFGOODRICH AVIONICS SYSTEMS, INC.: Amendment 39-10924, Docket No. 98-CE-107-AD.

Applicability: SKYWATCH SKY497 installations with a top-mounted antenna that are installed on, but not limited to, the following aircraft, all serial numbers, certificated in any category:

Manufacturer Aircraft Models and/or Series Raytheon Beech 90, 100, 200, and 300 Series Cessna 172, 182, 206, 208, 210, 300, 400, and 500 Series Piper PA-23, PA-31-360, PA-31T, PA-32, PA-34, PA-42, and PA-46 Hawker HS-700 and HS-800 Mitsubishi MU-2 Series Dassault F10 Mooney M20 Series Bombardier DHC-6 Series Westwind 1124 Bell 407 Eurocopter AS365 Socata TBM700

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been 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 (e) 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 in the body of this AD, unless already accomplished.

To prevent the display of target indicators on the wrong side of the aircraft caused by an internal component failure in the SKY497 installations with a top-mounted antenna, which could result in the pilot making an incorrect initial maneuver based on the displayed information while trying to visually acquire the aircraft, accomplish the following:

  (a) Within the next 25 hours time-in-service (TIS) after the effective date of this AD, place the information in the Appendix to this AD into the Limitations Section of the airplane flight manual (AFM).

  (1) This information specifies verifying the correct antenna configuration each time an aircraft equipped with a SKY497 installation with a top-mounted antenna is powered-up.

  (2) This information is a duplication of the information presented in BF Goodrich Alert Service Bulletin #78A, dated October 21, 1998.

  (b) If an incorrect antenna configuration is found during any of the power-up procedures specified in the AFM information required by this AD, prior to further flight, remove the SKY497 installation from service.

  (c) Inserting the information into the Limitations Section of the AFM as required by paragraph (a) of this AD may be performed by the owner/operator holding at least a private pilot certificate as authorized by section 43.7 of the Federal Aviation Regulations (14 CFR 43.7), and must be entered into the aircraft records showing compliance with this AD in accordance with section 43.9 of the Federal Aviation Regulations (14 CFR 43.9).

  (d) 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.

  (e) An alternative method of compliance or adjustment of the compliance times that provides an equivalent level of safety may be approved by the Manager, Chicago Aircraft Certification Office (ACO), 2300 East Devon Avenue, Des Plaines, Illinois 60018. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Chicago ACO.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Chicago ACO.

  (f) The service information referenced in this AD may be obtained from BF Goodrich Avionics Systems, Inc. 5353 52nd Street,Southeast, P.O. Box 873, Grand Rapids, Michigan 49588-0873. This document or other information related to this AD may be inspected at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri.

  (g) This amendment becomes effective on December 22, 1998.

APPENDIX TO AD 98-25-02; AMENDMENT 39-10924; DOCKET NO. 98-CE-107-AD.

POWER-UP PROCEDURES FOR SKYWATCH SKY497 INSTALLATIONS WITH A TOP-MOUNTED ANTENNA ___________________________________________________________________________________________________

The following power-up procedure must be accomplished each time the system is powered-up:

1. If a WX-1000 is installed with the SKYWATCH, ensure that the STORMSCOPE/CWS switch is in the CWS position.

2. At the SKYWATCH display, access the service menu by holding the left two buttons depressed and switch the system on. Hold the buttons until the Service Menu is displayed. The Service Menu is shown in figure 1.3. Highlight SYSTEM DATA (press NEXT button two times) and then press SELECT. The SYSTEM DATA screen, as shown in figure 2 will be displayed.

4. Highlight CONFIGURATION by pressing the NEXT button and then press SELECT. The configuration display consists of 4 pages. Advance to Page 3 of 4 (see figure 3) by pressing the NEXT button two times.

5. Verify that the antenna position is configured for TOP mount (i.e., as shown in figure 3).

APPENDIX TO AD 98-25-02; AMENDMENT 39-10924; DOCKET NO. 98-CE-107-AD.

POWER-UP PROCEDURES FOR SKYWATCH SKY497 INSTALLATIONS WITH A TOP-MOUNTED ANTENNA (Continued) ___________________________________________________________________________________________________

6. If the antenna configuration is correct, press EXIT until the start-up screen (see figure 4) is displayed.

7. If a WX-1000 is installed, position the STORMSCOPE/CWS switch to the STORMSCOPE position and exit the STORMSCOPE servicemenu by pressing the EXIT button.

8. If the antenna configuration is not correct (i.e., configured for Bottom mount), turn SKYWATCH off and return the unit for service.

## Rule preamble

### Supplementary information

Discussion BF Goodrich has communicated to the FAA 11 reports of internal component failure of BF Goodrich SKYWATCH SKY497 installations with a top-mounted antenna. When this failure occurs, the antenna configuration changes from the TOP to BOTTOM mount; e.g., the actual target at the 9 o'clock position relative to the aircraft shows on the SKY497 installation in the 3 o'clock position.

This condition, if not corrected in a timely manner, could result in the display of target indicators on the wrong side of the aircraft. The SkyWatch system is an advisory system and the pilot should not maneuver based on the displayed information alone. However, the pilot may make an incorrect initial maneuver based on the displayed information while trying to visually acquire the aircraft.

Relevant Service Information BF Goodrich has issued Alert Service Bulletin SB #78A, dated October 21, 1998, which specifies procedures for verifying that the SKY497 antenna configuration is in the top mount position every time an affected aircraft is powered-up.

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 the display of target indicators on the wrong side of the aircraft caused by the current design of the SKY497 installations with a top-mounted antenna. This could result in the pilot making incorrect aircraft maneuvers based on the displayed information.

Explanation of the Provisions of the AD Since an unsafe condition has been identified that is likely to exist or develop in other aircraft equipped with SKY497 installations with a top-mounted antenna, the FAA is taking AD action. This AD requires incorporating information into the airplane flight manual (AFM) that specifies verifying the correct antenna configuration each time an aircraft equipped with a SKY497 installation with a top-mounted antenna is powered-up. The AD also requires removing from service any of these SKY 497 installations with an incorrect antenna configuration.

Determination of the Effective Date of the AD Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for public prior comment hereon are impracticable, and that good cause 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. 98-CE-107-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 thatthis 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 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.

§ 39.13 (Amended) 2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows:

## Affected data sheets (39) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 3A13](https://openairdocs.org/tcds/3A13): Textron Aviation Inc.; names 19 of 23 models: 182D, 182A, 182J, 182P, 182B, 182L, 182G, 182Q…
- [TCDS 3A10](https://openairdocs.org/tcds/3A10): Textron Aviation Inc.; names 18 of 23 models: 310I, 310L, 310P, 310A, 310R, 310Q, 310B, 310D…
- [TCDS 3A12](https://openairdocs.org/tcds/3A12): Textron Aviation Inc.; names 18 of 18 models: 172F (USAF T-41A), 172M, 172Q, 172R, 172K, 172G, 172A, 172L…
- [TCDS A24CE](https://openairdocs.org/tcds/A24CE): Textron Aviation Inc.; names 17 of 37 models: B200CT, A100-1 (U-21J), 200, A200C (UC-12B), A200 (C-12A), 300, 200CT, 200T…
- [TCDS 3A21](https://openairdocs.org/tcds/3A21): Textron Aviation Inc.; names 16 of 28 models: 210J, 210D, 210R, 210M, 210-5A (205A), 210H, 210B, 210E…
- [TCDS A7CE](https://openairdocs.org/tcds/A7CE): Textron Aviation Inc.; names 16 of 16 models: 421C, 425, 402C, 402B, 411A, 414, 402, 421B…
- [TCDS 2A3](https://openairdocs.org/tcds/2A3): Mooney International Corporation; names 15 of 17 models: M20F, M20E, M20K, M20D, M20A, M20B, M20S, M20C…
- [TCDS A3SO](https://openairdocs.org/tcds/A3SO): Piper Aircraft Inc.; names 12 of 13 models: PA-32-300, PA-32-301, PA-32-301FT, PA-32R-300, PA-32-260, PA-32-301T, PA-32RT-300, PA-32S-300…
- [TCDS 3A20](https://openairdocs.org/tcds/3A20): Textron Aviation Inc.; names 11 of 22 models: B90, 65-A90-2, 65-A90-1, 65-A90-3, E90, 65-A90, C90A, H90…
- [TCDS 3A25](https://openairdocs.org/tcds/3A25): Textron Aviation Inc.; names 11 of 11 models: 320, 320D, 320-1, 320B, 320E, 335, 340A, 320C…
- [TCDS A6CE](https://openairdocs.org/tcds/A6CE): Textron Aviation Inc.; names 9 of 19 models: 337, 337D, 337G, 337H, 337F, 337C, 337A, 337E…
- [TCDS A14CE](https://openairdocs.org/tcds/A14CE): Textron Aviation Inc.; names 5 of 12 models: A100C, A100A, B100, A100, 100
- [TCDS A22CE](https://openairdocs.org/tcds/A22CE): Textron Aviation Inc.; names 5 of 6 models: 550, 552, 500, 560XL, 560
- [TCDS A2PC](https://openairdocs.org/tcds/A2PC): Mitsubishi Heavy Industries Ltd. 203; names 5 of 7 models: MU-2B, MU-2B-30, MU-2B-20, MU-2B-35, MU-2B-36
- [TCDS A10SW](https://openairdocs.org/tcds/A10SW): Mitsubishi Heavy Industries Ltd.; names 4 of 6 models: MU-2B-26A, MU-2B-36A, MU-2B-60, MU-2B-40
- [TCDS A1WI](https://openairdocs.org/tcds/A1WI): Textron Aviation Inc.; names 4 of 4 models: 525, 525C, 525B, 525A
- [TCDS A25SO](https://openairdocs.org/tcds/A25SO): Piper Aircraft Inc.; names 4 of 6 models: PA-46-310P, PA-46-500TP, PA-46-350P, PA-46R-350T
- [TCDS A9EA](https://openairdocs.org/tcds/A9EA): De Havilland Aircraft of Canada Limited; names 4 of 5 models: DHC-6-1, DHC-6-100, DHC-6-200, DHC-6-300
- [TCDS A23SO](https://openairdocs.org/tcds/A23SO): Piper Aircraft Inc.; names 3 of 3 models: PA-42-1000, PA-42, PA-42-720
- [TCDS A7SO](https://openairdocs.org/tcds/A7SO): Piper Aircraft Inc.; names 3 of 5 models: PA-34-200 (Seneca), PA-34-200T (Seneca II), PA-34-220T (Seneca V)
- [TCDS A25CE](https://openairdocs.org/tcds/A25CE): Textron Aviation Inc.; names 2 of 2 models: 406, 404
- [TCDS A27CE](https://openairdocs.org/tcds/A27CE): Textron Aviation Inc.; names 2 of 2 models: 551, 501
- [TCDS A37CE](https://openairdocs.org/tcds/A37CE): Textron Aviation Inc.; names 2 of 2 models: 208B, 208
- [TCDS A3EU](https://openairdocs.org/tcds/A3EU): Textron Aviation Inc.; names 2 of 50 models: HS.125 Series 700A, HS.125 Series 700B
- [TCDS H10EU](https://openairdocs.org/tcds/H10EU): Airbus Helicopters; names 2 of 10 models: AS 365 N2, AS 365 N3
- [TCDS 1A10](https://openairdocs.org/tcds/1A10): Piper Aircraft Inc.; names 1 of 6 models: PA-23
- [TCDS 3A11](https://openairdocs.org/tcds/3A11): Textron Aviation Inc.; names 1 of 1 models: 321
- [TCDS 3A17](https://openairdocs.org/tcds/3A17): Textron Aviation Inc.; names 1 of 12 models: 172RG
- [TCDS A28CE](https://openairdocs.org/tcds/A28CE): Textron Aviation Inc.; names 1 of 1 models: 441
- [TCDS A2CE](https://openairdocs.org/tcds/A2CE): Textron Aviation Inc.; names 1 of 1 models: 336
- [TCDS A2SW](https://openairdocs.org/tcds/A2SW): Israel Aircraft Industries Ltd.; names 1 of 6 models: 1124
- [TCDS A31CE](https://openairdocs.org/tcds/A31CE): Textron Aviation Inc.; names 1 of 1 models: F90
- [TCDS A32SO](https://openairdocs.org/tcds/A32SO): Piper Aircraft Inc.; names 1 of 1 models: PA-42-720R
- [TCDS A33EU](https://openairdocs.org/tcds/A33EU): Dassault Aviation; names 1 of 1 models: Falcon 10
- [TCDS A4CE](https://openairdocs.org/tcds/A4CE): Textron Aviation Inc.; names 1 of 29 models: 206H
- [TCDS A60EU](https://openairdocs.org/tcds/A60EU): Daher Aircraft SAS; names 1 of 1 models: TBM 700
- [TCDS A6SW](https://openairdocs.org/tcds/A6SW): Mooney Aircraft Corporation; names 1 of 1 models: M22
- [TCDS A8EA](https://openairdocs.org/tcds/A8EA): Piper Aircraft Inc.; names 1 of 6 models: PA-31T
- [TCDS H2SW](https://openairdocs.org/tcds/H2SW): Bell Textron Canada Limited; names 1 of 12 models: 407

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 62,196 (62,196 by airframe model, 0 by engine model)
- Makers: Cessna 41,286, Piper 6,513, Mooney 6,213, Textron 3,023, Beech 1,652, Socata 643, Raytheon 611, Bell Helicopter Textron Canada 418, Bell 387, Compagnie Daher 314

Models with the most aircraft:

- [Cessna 172M](https://openairdocs.org/model/cessna-172m): 3,573 aircraft (airframe model)
- [Cessna 172N](https://openairdocs.org/model/cessna-172n): 3,138 aircraft (airframe model)
- [Cessna 182P](https://openairdocs.org/model/cessna-182p): 2,099 aircraft (airframe model)
- [Cessna 172S](https://openairdocs.org/model/cessna-172s): 1,914 aircraft (airframe model)
- [Cessna 172](https://openairdocs.org/model/cessna-172): 1,805 aircraft (airframe model)
- [Cessna 182Q](https://openairdocs.org/model/cessna-182q): 1,565 aircraft (airframe model)
- [Mooney M20J](https://openairdocs.org/model/mooney-m20j): 1,408 aircraft (airframe model)
- [Mooney M20C](https://openairdocs.org/model/mooney-m20c): 1,258 aircraft (airframe model)
- [Textron 172S](https://openairdocs.org/model/textron-172s): 1,239 aircraft (airframe model)
- [Cessna 172P](https://openairdocs.org/model/cessna-172p): 1,111 aircraft (airframe model)
- [Cessna 172K](https://openairdocs.org/model/cessna-172k): 1,026 aircraft (airframe model)
- [Piper PA-32-300](https://openairdocs.org/model/piper-pa-32-300): 992 aircraft (airframe model)
- [Cessna 182T](https://openairdocs.org/model/cessna-182t): 968 aircraft (airframe model)
- [Cessna 172L](https://openairdocs.org/model/cessna-172l): 857 aircraft (airframe model)
- [Mooney M20E](https://openairdocs.org/model/mooney-m20e): 829 aircraft (airframe model)
- [Cessna 182A](https://openairdocs.org/model/cessna-182a): 784 aircraft (airframe model)
- [Cessna 172H](https://openairdocs.org/model/cessna-172h): 780 aircraft (airframe model)
- [Mooney M20K](https://openairdocs.org/model/mooney-m20k): 771 aircraft (airframe model)
- [Cessna 172G](https://openairdocs.org/model/cessna-172g): 722 aircraft (airframe model)
- [Mooney M20F](https://openairdocs.org/model/mooney-m20f): 721 aircraft (airframe model)

All 304 models: https://openairdocs.org/ad/98-25-02/models.md
Every aircraft: https://openairdocs.org/ad/98-25-02/aircraft.md

No proposed rule in this release led to it. Its text cites no advisory circulars or STCs.

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