Airworthiness Directives; Cessna Model 500, 501, 550, 551, and 560 Series Airplanes

[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]

-----------------------------------------------------------------------

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.

-----------------------------------------------------------------------

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 Accordingly, the proposed rule is withdrawn.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