[Federal Register Volume 64, Number 222 (Thursday, November 18, 1999)]
[Proposed Rules]
[Pages 62995-62996]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-30151]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-136-AD]
RIN 2120-AA64


Airworthiness Directives; Cessna Model 500, 501, 550, 551, and 
560 Series 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 
Cessna Model 500, 501, 550, 551, and 560 series 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 the AFM 
revision is unneccessary. Accordingly, the proposed rule is withdrawn.

FOR FURTHER INFORMATION CONTACT: Carlos Blacklock, Aerospace Engineer, 
Flight Test Branch, ACE-117W, FAA, Small Airplane Directorate, Wichita 
Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-
Continent Airport, Wichita, Kansas 67209; telephone (316) 946-4166; fax 
(316) 946-4407.

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 Cessna Models 500, 501, 550, 551, 
and 560 series airplanes, was published in the Federal Register as a 
Notice of Proposed Rulemaking (NPRM) on July 16, 1999 (64 FR 38374). 
The proposed rule would have required revising the Airplane Flight 
Manual (AFM) to include requirements for activation of the airframe 
pneumatic deicing boots. That NPRM 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 actions 
specified by that NPRM were 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 Cessna Model 
500, 501, 550, 551, and 560 series airplanes has requested that the 
NPRM be withdrawn. The manufacturer contends that these models have 
similar handling characteristics in icing, and that, based on the 
service history and data provided to the FAA, the proposed AFM revision 
for those models is unnecessary. The manufacturer concludes that the 
testing summarized in its comment provides

[[Page 62996]]

evidence that the current procedures demonstrate a safe method to 
operate the airplane.
    The FAA concurs that the notice of proposed rulemaking for Cessna 
Model 500, 501, 550, 551, and 560 series airplanes should be withdrawn 
based on the following information. The manufacturer performed a 
complete evaluation of the stall and handling characteristics with 
simulated ice shapes on the Model 550 (Bravo) series airplanes. Stall 
speeds and warning margins were evaluated with a \1/2\-inch glaze ice 
shape and with a 23-minute system failure configuration. This \1/2\-
inch ice shape simulated the ice shape prior to deicing boot 
activation. Maneuver margin testing consisted of left and right 40-
degree bank turns. Stall characteristics were performed with a \1/2\-
inch rime ice shape configuration. Stall characteristic testing 
consisted of wings level and 30-degree bank turns. At the conclusion of 
the testing it was determined that the airplane had acceptable stall 
warning margin with ice shapes present. The manufacturer maintains that 
the Model 500/501, Model 550/551, and Model 550 (Bravo) series 
airplanes all use a common wing airfoil with some minor differences in 
span and wing loading. These aircraft also use a common tail 
configuration (airfoil, span, and leading edge sweep).
    The Model 560 (Ultra) series airplanes underwent an extensive ice 
shape stall investigation. This investigation consisted of stall 
testing of the baseline airplane and the airplane with the most adverse 
simulated inter-cycle ice shapes. The ice shapes consisted of \1/2\-
inch shapes on the surfaces protected by boots and 3-inch shapes on 
unprotected flight surfaces. The stall speeds determined by this 
testing were incorporated into the Safeflight Angle of Attack computer 
to increase the stall warning margin during flight in icing conditions. 
The Model 560 series airplanes angle of attack computer was also 
updated to incorporate a normal mode and an ice mode stall warning 
system. [The changes to the angle of attack computer on Model 560 and 
560 (Ultra) series airplanes were mandated by an airworthiness 
directive, Rules Docket No. 98-NM-312-AD.] Additionally, the FAA 
reviewed the Type Inspection Report (TIR) for Model 550 (Bravo) series 
airplane testing and found that ice shapes were placed on both the 
protected and unprotected surfaces.
    Therefore, the FAA concurs that the proposal should be withdrawn. 
The FAA notes that the extensive testing of Model 550 series airplanes 
and the similarity of Model 500 series airplanes demonstrated that 
these airplanes can safely operate if the procedures for operation of 
the deicing boot as specified in the applicable AFM are followed. The 
FAA also notes that testing of Model 560 series airplanes revealed 
problems in the stall warning margin for flight in icing conditions 
that were addressed by previously issued airworthiness directives.

FAA's Conclusions

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

The Withdrawal

    Accordingly, the notice of proposed rulemaking, Docket 99-NM-136-
AD, published in the Federal Register on July 16, 1999 (64 FR 38374), 
is withdrawn.

    Issued in Renton, Washington, on November 10, 1999.
John J. Hickey,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-30151 Filed 11-17-99; 8:45 am]
BILLING CODE 4910-13-P