[Federal Register Volume 87, Number 57 (Thursday, March 24, 2022)]
[Rules and Regulations]
[Pages 16626-16630]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-06178]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-FAA-2021-0630; Special Conditions No. 25-801-SC]


Special Conditions: Dassault Aviation Model Falcon 6X Airplane; 
Interaction of Systems and Structures

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for the Dassault Aviation 
(Dassault) Model Falcon 6X airplane. This airplane 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 installed systems that, directly or 
as a result of failure or malfunction, affect airplane structural 
performance. 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: This action is effective on Dassault on March 24, 2022. Send 
comments on or before May 9, 2022.

ADDRESSES: Send comments identified by Docket No. FAA-2021-0630 using 
any of the following methods:
     Federal eRegulations Portal: Go to http://www.regulations.gov/ and follow the online instructions for sending 
your comments electronically.
     Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE, Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
     Hand Delivery or Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: Except for Confidential Business Information (CBI) as 
described in the following paragraph, and other information as 
described in 14 CFR 11.35, the FAA will post all comments received 
without change to http://www.regulations.gov/, including any personal 
information you provide. The FAA will also post a report summarizing 
each substantive verbal contact received about these special 
conditions.
    Confidential Business Information: Confidential Business 
Information (CBI) is commercial or financial information that is both 
customarily and actually treated as private by its owner. Under the 
Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from 
public disclosure. If your comments responsive to these special 
conditions contain commercial or financial information that is 
customarily treated as private, that you actually treat as private, and 
that is relevant or responsive to these special conditions, it is 
important that you clearly designate the submitted comments as CBI. 
Please mark each page of your submission containing CBI as ``PROPIN.'' 
The FAA

[[Page 16627]]

will treat such marked submissions as confidential under the FOIA, and 
the indicated comments will not be placed in the public docket of these 
special conditions. Send submissions containing CBI to the Information 
Contact below. Comments the FAA receives, which are not specifically 
designated as CBI, will be placed in the public docket for these 
special conditions.
    Docket: Background documents or comments received may be read at 
http://www.regulations.gov/ at any time. Follow the online instructions 
for accessing the docket or go to Docket Operations in Room W12-140 of 
the West Building Ground Floor at 1200 New Jersey Avenue SE, 
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Todd Martin, Materials and Structural 
Properties Section, AIR-621, Technical Innovation Policy Branch, Policy 
and Innovation Division, Aircraft Certification Service, Federal 
Aviation Administration, 2200 South 216th Street, Des Moines, 
Washington 98198; telephone and fax 206-231-3210; email 
[email protected].

SUPPLEMENTARY INFORMATION: The substance of these special conditions 
has been published in the Federal Register for public comment in 
several prior instances with no substantive comments received. 
Therefore, the FAA finds, pursuant to Sec.  11.38(b), that new comments 
are unlikely, and notice and comment prior to this publication are 
unnecessary.

Comments Invited

    The FAA invites interested people to take part in this rulemaking 
by sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data.
    The FAA will consider all comments received by the closing date for 
comments. The FAA may change these special conditions based on the 
comments received.

Background

    On February 1, 2018, Dassault applied for a type certificate for 
their new Model Falcon 6X airplane. This airplane is a twin-engine 
business jet with seating for 19 passengers and a maximum takeoff 
weight of 77,460 pounds.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.17, Dassault must show that the Model Falcon 6X airplane meets 
the applicable provisions of part 25, as amended by amendments 25-1 
through 25-146.
    If the Administrator finds that the applicable airworthiness 
regulations (e.g., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Dassault Model Falcon 6X airplane 
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 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 Dassault Model Falcon 6X airplane 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.
    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 Dassault Model Falcon 6X airplane will incorporate the 
following novel or unusual design feature:
    Installed systems that, directly or as a result of failure or 
malfunction, affect airplane structural performance.

Discussion

    The Dassault Model Falcon 6X airplane is equipped with systems that 
directly, or as a result of failure or malfunction, affect its 
structural performance. These systems include the digital flight-
control system, which includes maneuver-load and gust-load alleviation, 
and the fuel-management system. Current FAA regulations do not take 
into account the effects of systems on structural performance, 
including normal operation and failure conditions. Special conditions 
are needed to account for these features. These special conditions 
define criteria to be used in the assessment of the effects of these 
systems on structures. The general approach of accounting for the 
effect of system failures on structural performance is extended to 
include any system in which partial or complete failure, alone or in 
combination with other system partial or complete failures, would 
affect structural performance.
    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.
    These special conditions are similar to those previously applied to 
other airplane models.

Applicability

    As discussed above, these special conditions are applicable to the 
Dassault Model Falcon 6X airplane. Should Dassault 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 a certain novel or unusual design feature 
on one model of airplane. It is not a rule of general applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(f), 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 Dassault Model Falcon 6X airplane.
    For airplanes equipped with systems that affect structural 
performance, either directly or as a result of a failure or 
malfunction, the influence of these systems and their failure 
conditions must be taken into account when showing compliance with the 
requirements of 14 CFR part 25 subparts C and D.
    The following criteria must be used for showing compliance with 
these special conditions for airplanes equipped with flight-control 
systems, autopilots, stability-augmentation systems, load-alleviation 
systems, flutter-control systems, fuel-management systems, and other 
systems that either directly, or as a result of failure or malfunction, 
affect structural performance. If these special conditions are used for 
other systems, it may be necessary to adapt the criteria to the 
specific system.
    1. The criteria defined herein only address the direct structural

[[Page 16628]]

consequences of the system responses and performance. They cannot be 
considered in isolation, but should be included in the overall safety 
evaluation of the airplane. These criteria may, in some instances, 
duplicate standards already established for this evaluation. These 
criteria are only applicable to structure the failure of which could 
prevent continued safe flight and landing. Specific criteria that 
define acceptable limits on handling characteristics or stability 
requirements, when operating in the system degraded or inoperative 
mode, are not provided in these special conditions.
    2. Depending upon the specific characteristics of the airplane, 
additional studies that go beyond the criteria provided in these 
special conditions may be required to demonstrate the airplane's 
capability to meet other realistic conditions, such as alternative gust 
or maneuver descriptions for an airplane equipped with a load-
alleviation system.
    3. The following definitions are applicable to these special 
conditions.
    a. Structural performance: Capability of the airplane to meet the 
structural requirements of 14 CFR part 25.
    b. Flight limitations: Limitations that can be applied to the 
airplane flight conditions following an in-flight occurrence, and that 
are included in the airplane flight manual (e.g., speed limitations, 
avoidance of severe weather conditions, etc.).
    c. Operational limitations: Limitations, including flight 
limitations, that can be applied to the airplane operating conditions 
before dispatch (e.g., fuel, payload and master minimum-equipment list 
limitations).
    d. Probabilistic terms: Terms such as probable, improbable, and 
extremely improbable, as used in these special conditions, are the same 
as those used in Sec.  25.1309.
    e. Failure condition: This term is the same as that used in Sec.  
25.1309. However, these special conditions apply only to system-failure 
conditions that affect the structural performance of the airplane 
(e.g., system-failure conditions that induce loads, change the response 
of the airplane to inputs such as gusts or pilot actions, or lower 
flutter margins).

Effects of Systems on Structures

    The following criteria will be used in determining the influence of 
a system and its failure conditions on the airplane structure.
    1. System fully operative. With the system fully operative, the 
following apply:
    a. Limit loads must be derived in all normal operating 
configurations of the system from all the limit conditions specified in 
14 CFR part 25, subpart C (or defined by special conditions or 
equivalent level of safety in lieu of those specified in subpart C), 
taking into account any special behavior of such a system or associated 
functions, or any effect on the structural performance of the airplane 
that may occur up to the limit loads. In particular, any significant 
nonlinearity (rate of displacement of control surface, thresholds, or 
any other system nonlinearities) must be accounted for in a realistic 
or conservative way when deriving limit loads from limit conditions.
    b. The airplane must meet the strength requirements of 14 CFR part 
25 (static strength, residual strength), using the specified factors to 
derive ultimate loads from the limit loads defined above. The effect of 
nonlinearities must be investigated beyond limit conditions to ensure 
that the behavior of the system presents no anomaly compared to the 
behavior below limit conditions. However, conditions beyond limit 
conditions need not be considered when it can be shown that the 
airplane has design features that will not allow it to exceed those 
limit conditions.
    c. The airplane must meet the aeroelastic stability requirements of 
Sec.  25.629.
    2. System in the failure condition. For any system-failure 
condition not shown to be extremely improbable, the following apply:
    a. At the time of occurrence. Starting from 1g level flight 
conditions, a realistic scenario, including pilot corrective actions, 
must be established to determine the loads occurring at the time of 
failure and immediately after the failure.
    i. For static-strength substantiation, these loads, multiplied by 
an appropriate factor of safety that is related to the probability of 
occurrence of the failure, are ultimate loads to be considered for 
design. The factor of safety is defined in Figure 1, below.
[GRAPHIC] [TIFF OMITTED] TR24MR22.060

    ii. For residual-strength substantiation, the airplane must be able 
to withstand two-thirds of the ultimate loads defined in special 
condition 2.a.i above. For pressurized cabins, these loads must be 
combined with the normal operating differential pressure.
    iii. Freedom from aeroelastic instability must be shown up to the 
speeds defined in Sec.  25.629(b)(2). For failure conditions that 
result in speeds beyond VC/MC, freedom from 
aeroelastic instability must be shown to increased speeds, so that the 
margins intended by Sec.  25.629(b)(2) are maintained.
    iv. Failures of the system that result in forced structural 
vibrations (oscillatory failures) must not produce loads that could 
result in detrimental deformation of primary structure.
    b. For the continuation of the flight. For the airplane in the 
system-failed state, and considering any appropriate reconfiguration 
and flight limitations, the following apply:

[[Page 16629]]

    i. The loads derived from the following conditions (or used in lieu 
of the following conditions) at speeds up to VC/
MC (or the speed limitation prescribed for the remainder of 
the flight) must be determined:
    1. The limit symmetrical maneuvering conditions specified in 
Sec. Sec.  25.331 and 25.345.
    2. The limit gust and turbulence conditions specified in Sec. Sec.  
25.341 and 25.345.
    3. The limit rolling conditions specified in Sec.  25.349, and the 
limit unsymmetrical conditions specified in Sec. Sec.  25.367, and 
25.427(b) and (c).
    4. The limit yaw-maneuvering conditions specified in Sec.  25.351.
    5. The limit ground-loading conditions specified in Sec. Sec.  
25.473 and 25.491.
    ii. For static-strength substantiation, each part of the structure 
must be able to withstand the loads in special condition 2.b.i., 
multiplied by a factor of safety depending on the probability of being 
in this failure state. The factor of safety is defined in Figure 2, 
below.
[GRAPHIC] [TIFF OMITTED] TR24MR22.061

Q j = (Tj)(Pj)

Where:

Q j = Probability of being in failure mode j
Tj = Average time spent in failure mode j (in hours)
Pj = Probability of occurrence of failure mode j (per 
hour)

    Note:  If Pj is greater than 
10-3 per flight hour, then a 1.5 factor of 
safety must be applied to all limit load conditions specified in 14 
CFR part 25, subpart C.

    iii. For residual-strength substantiation, the airplane must be 
able to withstand two-thirds of the ultimate loads defined in special 
condition 2.b.ii. For pressurized cabins, these loads must be combined 
with the normal operating differential pressure.
    iv. If the loads induced by the failure condition have a 
significant effect on fatigue or damage tolerance, then their effects 
must be taken into account.
    v. Freedom from aeroelastic instability must be shown up to a speed 
determined from Figure 3, below. Flutter clearance speeds V' and V'' 
may be based on the speed limitation specified for the remainder of the 
flight using the margins defined by Sec.  25.629(b).
[GRAPHIC] [TIFF OMITTED] TR24MR22.062

V' = Clearance speed as defined by Sec.  25.629(b)(2).
V'' = Clearance speed as defined by Sec.  25.629(b)(1).
Q j = (Tj)(Pj)
where:

Q j = Probability of being in failure mode j
Tj = Average time spent in failure mode j (in hours)
Pj = Probability of occurrence of failure mode j (per 
hour)

    Note:  If Pj is greater than 
10-3 per flight hour, then the flutter 
clearance speed must not be less than V''.

    vi. Freedom from aeroelastic instability must also be shown up to 
V' in Figure 3, above, for any probable system-failure condition, 
combined with any damage required or selected for investigation by 
Sec.  25.571(b).
    c. Consideration of certain failure conditions may be required by 
other sections of 14 CFR part 25 regardless of calculated system 
reliability. Where analysis shows the probability of these failure 
conditions to be less than 10-9 per flight hour, 
criteria other than those specified in this paragraph may be used for 
structural substantiation to show continued safe flight and landing.
    3. Failure indications. For system-failure detection and 
indication, the following apply:
    a. The system must be checked for failure conditions, not extremely

[[Page 16630]]

improbable, that degrade the structural capability below the level 
required by part 25, or that significantly reduce the reliability of 
the remaining system. As far as reasonably practicable, the flightcrew 
must be made aware of these failures before flight. Certain elements of 
the control system, such as mechanical and hydraulic components, may 
use special periodic inspections, and electronic components may use 
daily checks, in lieu of detection and indication systems, to achieve 
the objective of this requirement. These certification-maintenance 
requirements must be limited to components that are not readily 
detectable by normal detection-and-indication systems, and where 
service history shows that inspections will provide an adequate level 
of safety.
    b. The existence of any failure condition, not extremely 
improbable, during flight, that could significantly affect the 
structural capability of the airplane, and for which the associated 
reduction in airworthiness can be minimized by suitable flight 
limitations, must be signaled to the flightcrew. For example, failure 
conditions that result in a factor of safety between the airplane 
strength and the loads of part 25, subpart C, below 1.25, or flutter 
margins below V'', must be signaled to the crew during flight.
    4. Dispatch with known failure conditions. If the airplane is to be 
dispatched in a known system-failure condition that affects structural 
performance, or that affects the reliability of the remaining system to 
maintain structural performance, then the provisions of these special 
conditions must be met, including the provisions of special condition 
1, ``System Fully Operative'' for the dispatched condition, and special 
condition 2, ``System in the Failure Condition'' for subsequent 
failures. Expected operational limitations may be taken into account in 
establishing Pj as the probability of failure occurrence for 
determining the safety margin in Figure 1. Flight limitations and 
expected operational limitations may be taken into account in 
establishing Qj as the combined probability of being in the 
dispatched failure condition and the subsequent failure condition for 
the safety margins in Figures 2 and 3. These limitations must be such 
that the probability of being in this combined failure state, and then 
subsequently encountering limit load conditions, is extremely 
improbable. No reduction in these safety margins is allowed if the 
subsequent system-failure rate is greater than 
10-3 per flight hour.

    Issued in Kansas City, Missouri, on March 18, 2022.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2022-06178 Filed 3-23-22; 8:45 am]
BILLING CODE 4910-13-P


