[Federal Register Volume 64, Number 222 (Thursday, November 18, 1999)]
[Proposed Rules]
[Pages 62990-62991]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-30148]


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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.

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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 Accordingly, the proposed rule is withdrawn.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. 99-30148 Filed 11-17-99; 8:45 am]
BILLING CODE 4910-13-P