
[Federal Register Volume 79, Number 109 (Friday, June 6, 2014)]
[Rules and Regulations]
[Pages 32636-32637]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-13241]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-1039; Notice No. 25-547-SC]


Special Conditions: Bombardier Aerospace, Models BD-500-1A10 and 
BD-500-1A11 Series Airplanes; Flight Envelope Protection: Normal Load 
Factor (g) Limiting

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final Special Conditions.

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SUMMARY: These special conditions are issued for the Bombardier 
Aerospace Models BD-500-1A10 and BD-500-1A11 series airplanes. These 
airplanes will have a novel or unusual design feature associated with 
an electronic flight control system that prevents the pilot from 
inadvertently or intentionally exceeding the positive or negative 
airplane limit load factor. The applicable airworthiness regulations do 
not contain adequate or appropriate safety standards for this design 
feature. These 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.

DATES: Effective Date: July 7, 2014.

FOR FURTHER INFORMATION CONTACT: Joe Jacobsen, FAA, Airplane and Flight 
Crew Interface Branch, ANM-111, Transport Airplane Directorate, 
Aircraft Certification Service, 1601 Lind Avenue SW., Renton, 
Washington 98057-3356; telephone 425-227-2011; facsimile 425-227-1149.

SUPPLEMENTARY INFORMATION: 

Background

    On December 10, 2009, Bombardier Aerospace applied for a type 
certificate for their new Models BD-500-1A10 and BD-500-1A11 series 
airplanes (hereafter collectively referred to as ``CSeries''). The 
CSeries airplanes are swept-wing monoplanes with an aluminum alloy 
fuselage sized for 5-abreast seating. Passenger capacity is designated 
as 110 for the Model BD-500-1A10 and 125 for the Model BD-500-1A11. 
Maximum takeoff weight is 131,000 pounds for the Model BD-500-1A10 and 
144,000 pounds for the Model BD-500-1A11.
    The design of the electronic flight control system for the CSeries 
airplanes incorporates normal load factor limiting on a full time basis 
that prevents the flightcrew from inadvertently or intentionally 
exceeding the positive or negative airplane limit load factor. This 
feature is considered novel and unusual in that the current regulations 
do not provide standards for maneuverability and controllability 
evaluations for such systems.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14 
CFR) 21.17, Bombardier Aerospace must show that the CSeries airplanes 
meet the applicable provisions of part 25 as amended by Amendments 25-1 
through 25-129 thereto.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the CSeries airplanes because of a 
novel or unusual design feature, special conditions are prescribed 
under the provisions of Sec.  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 Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the CSeries airplanes must comply with the fuel vent and 
exhaust emission requirements of 14 CFR part 34 and the noise 
certification requirements of 14 CFR part 36, and the FAA must issue a 
finding of regulatory adequacy under Sec.  611 of Public Law 92-574, 
the ``Noise Control Act of 1972.''
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type-
certification basis under Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The CSeries airplanes will use a fly-by-wire electronic flight 
control system (EFCS). This system provides an electronic interface 
between the pilot's flight controls and the flight control surfaces for 
both normal and failure states; and it generates the actual surface 
commands that provide for stability augmentation and control about all 
three airplane axes.
    The design of the EFCS incorporates the following novel or unusual 
design feature: Normal load factor limiting on a full-time basis that 
will prevent the flight crew from inadvertently or intentionally 
exceeding the positive or negative airplane limit load factor. This 
feature is considered novel or unusual because the current regulations 
do not provide standards for maneuverability and controllability 
evaluations for such systems. Therefore, special conditions are needed 
to ensure adequate maneuverability and controllability when using this 
design feature.

Discussion

    Title 14, Code of Federal Regulations, part 25 does not specify 
requirements or policy for demonstrating maneuver control that impose 
any handling qualities requirements beyond the design limit structural 
loads. Nevertheless, some pilots have become accustomed to the 
availability of this excess maneuver capacity in case of extreme 
emergency such as upset recoveries or collision avoidance.
    As with previous fly-by-wire airplanes, the FAA has no regulatory 
or safety reason to prohibit a design for an electronic flight control 
system with load factor limiting. It is possible that pilots accustomed 
to this feature feel more freedom in commanding full-stick displacement 
maneuvers because of the following:
     Knowledge that the limit system will protect the 
structure,
     Low stick force/displacement gradients,
     Smooth transition from pilot elevator control to limit 
control.
    These special conditions will ensure adequate maneuverability and 
controllability when using this design feature.

[[Page 32637]]

    The normal load factor limit on the CSeries airplanes is unique in 
that traditional airplanes with conventional flight control systems 
(mechanical linkages) are limited in the pitch axis only by the 
elevator surface area and deflection limit. The elevator control power 
is normally derived for adequate controllability and maneuverability at 
the most critical longitudinal pitching moment. The result is that 
traditional airplanes have a significant portion of the flight envelope 
wherein maneuverability in excess of limit structural design values is 
possible.
    These special conditions for the CSeries airplanes supplement the 
applicable regulations, including Sec.  25.143, to accommodate the 
unique features of the flight envelope limiting systems, and establish 
an equivalent level of safety to the existing regulations.

Discussion of Comments

    Notice of proposed special conditions No. 25-13-38-SC for the 
Bombardier CSeries airplanes was published in the Federal Register on 
December 11, 2013 (78 FR 75285). No comments were received, and the 
special conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Models BD-500-1A10 and BD-500-1A11 series airplanes. Should Bombardier 
Aerospace apply at a later date for a change to the type certificate to 
include another model incorporating the same novel or unusual design 
feature, the special conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on two model series of airplanes. It is not a rule of general 
applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for the Bombardier Aerospace Models BD-
500-1A10 and BD-500-1A11 series airplanes.

Flight Envelope Protection: Normal Load Factor (g) Limiting

0
1. To meet the intent of adequate maneuverability and controllability 
required by Sec.  25.143(a), and in addition to the requirements of 
Sec.  25.143(a) and in the absence of other limiting factors, the 
following special conditions based on Sec.  25.333(b) apply:
    a. The positive limiting load factor must not be less than:
    (1) 2.5g for the normal state of the electronic flight control 
system with the high lift devices retracted.
    (2) 2.0g for the normal state of the electronic flight control 
system with the high lift devices extended.
    b. The negative limiting load factor must be equal to or more 
negative than:
    (1) Minus 1.0g for the normal state of the electronic flight 
control system with the high lift devices retracted.
    (2) 0.0g for the normal state of the electronic flight control 
system with high lift devices extended.
    c. Maximum reachable positive load factor wings level may be 
limited by the characteristics of the electronic flight control system 
or flight envelope protections (other than load factor protection) 
provided that:
    (1) The required values are readily achievable in turns, and
    (2) That wings level pitch up is satisfactory.
    d. Maximum achievable negative load factor may be limited by the 
characteristics of the electronic flight control system or flight 
envelope protections (other than load factor protection) provided that:
    (1) Pitch down responsiveness is satisfactory, and
    (2) From level flight, 0g is readily achievable or alternatively, a 
satisfactory trajectory change is readily achievable at operational 
speeds. For the FAA to consider a trajectory change as satisfactory, 
the applicant should propose and justify a pitch rate that provides 
sufficient maneuvering capability in the most critical scenarios.
    e. Compliance demonstration with the above requirements may be 
performed without ice accretion on the airframe.
    These special conditions do not impose an upper bound for the 
normal load factor limit, nor do they require that the limit exist. If 
the limit is set at a value beyond the structural design limit 
maneuvering load factor ``n'' of Sec. Sec.  25.333(b) and 25.337(b) and 
(c), there should be a very obvious positive tactile feel built into 
the controller so that it serves as a deterrent to inadvertently 
exceeding the structural limit.

    Issued in Renton, Washington, on April 22, 2014.
Jeffrey E. Duven,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2014-13241 Filed 6-5-14; 8:45 am]
BILLING CODE 4910-13-P


