80 FR 30134 - Special Conditions: Bombardier Aerospace, Models BD-500-1A10 and BD-500-1A11; Electronic Flight Control System: Lateral-Directional and Longitudinal Stability and Low-Energy Awareness

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration

Federal Register Volume 80, Issue 101 (May 27, 2015)

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 when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. This design feature is a fly-by-wire electronic flight control system that provides an electronic interface between the pilot's flight controls and the flight control surfaces for both normal and failure states. The system generates the actual surface commands that provide for stability augmentation and control about all three airplane axes. 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.

[Federal Register Volume 80, Number 101 (Wednesday, May 27, 2015)]
[Rules and Regulations]
[Pages 30134-30136]
From the Federal Register Online  [www.thefederalregister.org]
[FR Doc No: 2015-12699]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2015-0455; Special Conditions No. 25-584-SC]


Special Conditions: Bombardier Aerospace, Models BD-500-1A10 and 
BD-500-1A11; Electronic Flight Control System: Lateral-Directional and 
Longitudinal Stability and Low-Energy Awareness

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 when compared to 
the state of technology envisioned in the airworthiness standards for 
transport category airplanes. This design feature is a fly-by-wire 
electronic flight control system that provides an electronic interface 
between the pilot's flight controls and the flight control surfaces for 
both normal and failure states. The system generates the actual surface 
commands that provide for stability augmentation and control about all 
three airplane axes. 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 July 13, 2015.

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 425-227-1320.

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 CSeries flight control system design incorporates normal load 
factor limiting on a full time basis that will prevent the pilot from 
inadvertently or intentionally exceeding the positive or negative 
airplane limit load factor. The FAA considers this feature to be 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 14 CFR part 25 as amended by 
Amendments 25-1 through 25-129.
    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

[[Page 30135]]

include any other model that incorporates the same novel or unusual 
design feature, these 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 incorporate the following novel or 
unusual design feature: Fly-by-wire electronic flight control system 
that provides an electronic interface between the pilot's flight 
controls and the flight control surfaces for both normal and failure 
states. The system generates the actual surface commands that provide 
for stability augmentation and control about all three airplane axes.

Discussion

    In the absence of positive lateral stability, the curve of lateral 
control surface deflections against sideslip angle should be in a 
conventional sense and reasonably in harmony with rudder deflection 
during steady heading sideslip maneuvers.
    Since conventional relationships between stick forces and control 
surface displacements do not apply to the ``load factor command'' 
flight control system on the CSeries airplanes, Bombardier should 
evaluate the longitudinal stability characteristics by assessing the 
airplane handling qualities during simulator and flight test maneuvers 
appropriate to the operation of the airplane. Bombardier may accomplish 
this by using the Handling Qualities Rating Method presented in 
appendix 5 of Advisory Circular (AC) 25-7C, Flight Test Guide for 
Certification of Transport Category Airplanes, dated October 16, 2012, 
or they may propose an acceptable alternative method. Important 
considerations are as follows:
    (a) Adequate speed control without creating excessive pilot 
workload;
    (b) Acceptable high- and low-speed protection; and
    (c) Provision of adequate cues to the pilot of significant speed 
excursions beyond VMO/MMO and low-speed awareness 
flight conditions.
    The airplane should provide adequate awareness cues to the pilot of 
a low-energy (i.e., a low-speed, low-thrust, or low-height) state to 
ensure that the airplane retains sufficient energy to recover when 
flight control laws provide neutral longitudinal stability 
significantly below the normal operating speeds. This may be 
accomplished as follows:
    (a) Adequate low-speed/low-thrust cues at low altitude may be 
provided by a strong positive static stability force gradient (1 pound 
per 6 knots applied through the sidestick); or
    (b) Low-energy awareness may be provided by an appropriate warning 
with the following characteristics:
    (i) It should be unique, unambiguous, and unmistakable.
    (ii) It should be active at appropriate altitudes and in 
appropriate configurations (i.e., at low altitude, in the approach and 
landing configurations).
    (iii) It should be sufficiently timely to allow recovery to a 
stabilized flight condition inside the normal flight envelope while 
maintaining the desired flight path and without entering the flight 
control's angle-of-attack protection mode.
    (iv) It should not be triggered during normal operation, including 
operation in moderate turbulence, for recommended maneuvers at 
recommended speeds.
    (v) It should not be cancelable by the pilot other than by 
achieving a higher-energy state.
    (vi) There should be an adequate hierarchy among the warnings so 
that the pilot is not confused and led to take inappropriate recovery 
action if multiple warnings occur.
    Bombardier should use simulator and flight tests in the whole take-
off and landing altitude range for which certification is requested to 
evaluate global energy awareness and non-nuisance of low-energy cues. 
This would include all relevant combinations of weight, center-of-
gravity position, configuration, airbrakes position, and available 
thrust, including reduced and de-rated take-off thrust operations and 
engine failure cases. Bombardier should conduct a sufficient number of 
tests to assess the level of energy awareness and the effects of energy 
management errors.
    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.

Discussion of Comments

    Notice of proposed special conditions No. 25-15-04-SC for the 
Bombardier CSeries airplanes was published in the Federal Register on 
March 5, 2015 (80 FR 11958). No comments were received, and the special 
conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Bombardier BD-500-1A10 and BD-500-1A11. 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, 
these 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 Bombardier Aerospace Models BD-500-
1A10 and BD-500-1A11 series airplanes.
    1. Electronic Flight Control System: Lateral-Directional and 
Longitudinal Stability and Low-Energy Awareness. In lieu of the 
requirements of Sec. Sec.  25.171, 25.173, 25.175, and 25.177:
    (a) The airplane must be shown to have suitable static lateral, 
directional, and longitudinal stability in any condition normally 
encountered in service, including the effects of atmospheric 
disturbance. The showing of suitable static lateral, directional, and 
longitudinal stability must be based on the airplane handling 
qualities, including pilot workload and pilot compensation, for 
specific test procedures during the flight test evaluations.
    (b) The airplane must provide adequate awareness to the pilot of a 
low-energy (low-speed/low-thrust/low-height) state when fitted with 
flight control laws presenting neutral longitudinal stability 
significantly below the normal operating speeds.

[[Page 30136]]

``Adequate awareness'' means warning information must be provided to 
alert the crew of unsafe operating conditions and to enable them to 
take appropriate corrective action.
    (c) The static directional stability (as shown by the tendency to 
recover from a skid with the rudder free) must be positive for any 
landing gear and flap position and symmetrical power condition, at 
speeds from 1.13 VSR1, up to VFE, VLE, 
or VFC/MFC (as appropriate).
    (d) The static lateral stability (as shown by the tendency to raise 
the low wing in a sideslip with the aileron controls free), for any 
landing-gear and wing-flap position and symmetric-power condition, may 
not be negative at any airspeed (except that speeds higher than 
VFE need not be considered for wing-flaps-extended 
configurations nor speeds higher than VLE for landing-gear-
extended configurations) in the following airspeed ranges:
    (i) From 1.13 VSR1 to VMO/MMO.
    (ii) From VMO/MMO to VFC/
MFC, unless the divergence is--
    (1) Gradual;
    (2) Easily recognizable by the pilot; and
    (3) Easily controllable by the pilot.
    (e) In straight, steady sideslips over the range of sideslip angles 
appropriate to the operation of the airplane, but not less than those 
obtained with one half of the available rudder control movement (but 
not exceeding a rudder control force of 180 pounds), rudder control 
movements and forces must be substantially proportional to the angle of 
sideslip in a stable sense; and the factor of proportionality must lie 
between limits found necessary for safe operation. This requirement 
must be met for the configurations and speeds specified in paragraph 
(c) of this section.
    (f) For sideslip angles greater than those prescribed by paragraph 
(e) of this section, up to the angle at which full rudder control is 
used or a rudder control force of 180 pounds is obtained, the rudder 
control forces may not reverse, and increased rudder deflection must be 
needed for increased angles of sideslip. Compliance with this 
requirement must be shown using straight, steady sideslips, unless full 
lateral control input is achieved before reaching either full rudder 
control input or a rudder control force of 180 pounds; a straight, 
steady sideslip need not be maintained after achieving full lateral 
control input. This requirement must be met at all approved landing 
gear and wing-flap positions for the range of operating speeds and 
power conditions appropriate to each landing gear and wing-flap 
position with all engines operating.

    Issued in Renton, Washington, on May 15, 2015.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2015-12699 Filed 5-26-15; 8:45 am]
 BILLING CODE 4910-13-P