Airworthiness directives: British Aerospace; withdrawn,

[Federal Register: November 18, 1999 (Volume 64, Number 222)]

[Proposed Rules]

[Page 62990-62991]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr18no99-16]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-146-AD]

RIN 2120-AA64

Airworthiness Directives; British Aerospace Jetstream Model 4101 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Proposed rule; withdrawal.

SUMMARY: This action withdraws a notice of proposed rulemaking (NPRM) that proposed a new airworthiness directive (AD), applicable to certain British Aerospace Jetstream Model 4101 airplanes. That action would have required revising the Airplane Flight Manual (AFM) to include requirements for activation of the airframe pneumatic deicing boots. Since the issuance of the NPRM, the Federal Aviation Administration (FAA) has received new data that indicates that the specified AFM revision is not necessary. Accordingly, the proposed rule is withdrawn.

FOR FURTHER INFORMATION CONTACT: Norman Martenson, Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2110; fax (425) 227-1149.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add a new airworthiness directive (AD), applicable to certain British Aerospace Jetstream Model 4101 airplanes, was published in the Federal Register as a Notice of Proposed Rulemaking (NPRM) on July 16, 1999 (64 FR 38335). The proposed rule would have required revising the Airplane Flight Manual (AFM) to include requirements for activation of the airframe pneumatic deicing boots. That action was prompted by reports of inflight incidents and an accident that occurred in icing conditions where the airframe pneumatic deicing boots were not activated. The action specified by the proposed AD was intended to ensure that flightcrews activate the pneumatic wing and tail deicing boots at the first signs of ice accumulation. Such ice accumulation, if not corrected, could result in reduced controllability of the aircraft due to adverse aerodynamic effects of ice adhering to the airplane prior to the first deicing cycle.

Actions that Occurred Since the NPRM Was Issued

Since the issuance of that NPRM, the manufacturer of British Aerospace Jetstream Model 4101 airplanes has requested that the NPRM be withdrawn. The manufacturer advises that, based on the service history and data provided to the FAA, the proposed AFM revision for those models is unnecessary.

The FAA concurs that the notice of proposed rulemaking for British Aerospace Jetstream Model 4101 airplanes should be withdrawn based on the following information. British Aerospace submitted a summary of the handling and performance flight test results that were produced during the original flight in icing certification, and referenced the data summary in response to the proposed rulemaking. The FAA requested and subsequently received copies of the full handling and performance flight test results for certification in the icing conditions specified in Appendix C of part 25 of the Federal Aviation Regulations (14 CFR 25), and the draft issue of AMJ25.1419, which was used as guidance for compliance with JAR/FAR 25.1419. The FAA reviewed these reports and guidance material and finds that the Jetstream 4101 airplane was adequately tested with a variety of natural ice accretions on both the protected and unprotected surfaces. Handling and performance flight test was accomplished for the following: Normal Operation of the Deicing Boots, \1/2\-to \3/4\-inch of ice on the protected wing leading edges and up to 3 inches of ice on unprotected leading edges; Simulated Failure of the Deicing Boots, approximately 1-to 1\1/2\-inches of ice on all leading edges; and Ice Accreted During the Take-off Phase, a thin rough layer of ice accreted during the initial take-off phase to 400 feet, prior to operation of deicing boots.

These ice accretion depths are consistent with the operational procedure of the airframe deicing system, and were established to address the following: Ice accreted during the rest time of a deicing cycle, delayed operation or failure of the system, and residual ice accumulations. The flight testing examined stall speeds, stall warning margins, stall characteristics, maneuver margins, longitudinal controllability, flap configuration changes, ability to trim, susceptibility to tailplane stall, and longitudinal, lateral, and directional stability. The angles of attack for activation of the stall warning system and stall identification system (i.e., stick shaker or stick pusher) are reset to lower values (i.e., higher speeds) for flight in icing and safe flight speeds (minimum operating speeds) established accordingly. Affected AFM performance information was derived for icing conditions based on the higher operating speeds, in accordance with JAA draft AMJ25.1419.

FAA's Conclusions

Upon further consideration, the FAA has determined that, in light of the above information, it is unnecessary to require the AFM revision as proposed. Accordingly, the proposed rule is hereby withdrawn.

Withdrawal of this notice of proposed rulemaking constitutes only such action, and does not preclude the agency from issuing another notice in the future, nor does it commit the agency to any course of action in the future.

Regulatory Impact

Since this action only withdraws a notice of proposed rulemaking, it is neither a proposed nor a final rule and therefore is not covered under Executive Order 12866, the Regulatory Flexibility Act, or DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

[[Page 62991]]

The Withdrawal

Accordingly, the notice of proposed rulemaking, Docket 99-NM-146- AD, published in the Federal Register on July 16, 1999 (64 FR 38335), is withdrawn.

Issued in Renton, Washington, on November 10, 1999. John J. Hickey, Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 99-30148Filed11-17-99; 8:45 am]

BILLING CODE 4910-13-P

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