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khammond on DSKJM1Z7X2PROD with PROPOSALS

Federal Register / Vol. 86, No. 18 / Friday, January 29, 2021 / Proposed Rules actuators, is a first for commercial rotorcraft use. Therefore, the regulations do not contain adequate or appropriate safety standards for this new design feature.
The rotorcraft industry is producing new generations of helicopters, and gradually increasing size, speed, load capacity, and technical sophistication.
In recent years, an accelerated trend has occurred using rotorcraft for a wide range of commercial and industrial applications. This has resulted in increased complexity of modern control systems and increased use of automation in flight control systems, including the implementation of advanced flight control systems such as FBW FCS.
Title 14, Code of Federal Regulations CFR, 29.671c, which provides requirements for transport category rotorcraft control systems, does not contain adequate or appropriate safety standards for this new design feature. 14
CFR 29.671c requires, in part, a means to allow the pilot to determine that full control authority is available prior to flight. This command control authority is typically achieved by verifying movement of the control quadrant through an unassisted mechanical pilotinitiated manipulation of the primary flight controls prior to flight. Although this approach does not guarantee that 100% maximum control movement of the flight controls has been achieved prior to flight, it has been deemed appropriate for mechanical flight control systems.
Unlike traditional mechanical flight control systems, the FBW FCS reduces the opportunity for jamming of the flight controls due to mechanical bind, improper servo adjustment resulting from faulty maintenance, or presence of a foreign object in the control mechanism that will impair safety. This reduced exposure for jams is due to the replacement of the mechanical linkages between the primary cockpit flight controls or inceptors and the main and tail rotor actuators with digital signal processing wiring. However, the FBW
FCS does increase the potential for latent failures or faults that could impair full control authority, unless a means exists to ensure the FBW FCS is fully functional and free of control authority impairment prior to flight. A FBW
system may have the ability to verify full control authority without having to move the primary flight controls.
Although part 29 does not contain adequate or appropriate safety standards for this novel or unusual design feature, 14 CFR 25.671, amendment 2523, provides these requirements for transport category airplanes.

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Accordingly, these proposed special conditions are based on 25.671 to provide requirements for a FBW FCS on the Bell Model 525 helicopter. 14 CFR
25.671c provides the same level of safety as that intended by 29.671c when employing a FBW FCS by including requirements for jamming and failure analysis. The proposed special conditions would require a comprehensive safety analysis of the aircrafts FBW FCS to include failures due to command logic software, mechanical and electronic interfaces to other systems, jamming and maintenance. Therefore, in conjunction with 29.671a and b, the proposed special conditions incorporate provisions from 25.671c to establish a level of safety equivalent to that established in the regulations.
Type Certification Basis Under the provisions of 14 CFR 21.17, Bell must show that the Model 525
helicopter meets the applicable provisions of part 29, as amended by Amendments 29 through 55 thereto. The Bell Model 525 certification basis date is December 31, 2016.
If the Administrator finds that the applicable airworthiness regulations i.e., 14 CFR part 29 do not contain adequate or appropriate safety standards for the Bell Model 525 because of a novel or unusual design feature, special conditions are prescribed under the provisions of 21.16.
Special conditions are initially applicable to the model for which they are issued. Should the type certificate for that model be amended later to include any other model that incorporates the same or similar novel or unusual design feature, the special conditions would also apply to the other model under 21.101.
In addition to the applicable airworthiness regulations and special conditions, the Bell Model 525
helicopter must comply with the the noise certification requirements of 14
CFR part 36, and the FAA must issue a finding of regulatory adequacy under 611 of Public Law 92574, the Noise Control Act of 1972..
The FAA issues special conditions, as defined in 14 CFR 11.19, in accordance with 11.38, and they become part of the type-certification basis under 21.17a2.
Novel or Unusual Design Features The Bell Model 525 helicopter will incorporate the following novel or unusual design features: A FBW FCS.
This new design feature has no direct hydro-mechanical linkage between the primary cockpit flight controls or
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inceptors and the main and tail rotor actuators, thereby eliminating the more complex elements of either a manual movement of the controls by the pilot, or another manual means.
Discussion The proposed special conditions would require that a means be available to show full control authority for all powered control systems.
The proposed special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.
Applicability As discussed above, these special conditions are applicable to the Bell Model 525 helicopter. Should Bell apply at a later date for a change to the type certificate to include aother model incorporating the same novel or unusual design feature, these special conditions would apply to that model as well.
Conclusion This action affects only a certain novel or unusual design feature on the Bell Model 525 helicopter. It is not a rule of general applicability.
List of Subjects in 14 CFR Part 29
Aircraft, Aviation safety, Reporting and recordkeeping requirements.
Authority Citation The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106f, 106g, 40113, 4470144702, 44704.

The Proposed Special Conditions Accordingly, the Federal Aviation Administration FAA proposes the following special conditions in lieu of 29.671c as part of the type certification basis for the Bell Textron Inc. Model 525 helicopter:
The rotorcraft must be shown by analysis, tests, or both, to be capable of continued safe flight and landing after any of the following failures or jamming in the flight control system within the normal flight envelope, without requiring exceptional piloting skill or strength. Probable failures must have only minor effects.
1 Any single failure not shown to be extremely improbable, excluding jamming.
2 Any combination of failures not shown to be extremely improbable, excluding jamming.
3 Any jam in a control position normally encountered during hover, takeoff, climb, cruise, normal turns,
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