Document ID: FAA-2020-1039-0001
Agency: faa
Document Type: Rule
Title: Special Conditions: Dassault Aviation Model Falcon 6X Airplane; Electronic Flight-Control System: Lateral-Directional and Longitudinal Stability and Low-Energy Awareness
Posted Date: 2022-02-14T05:00Z

[Federal Register Volume 87, Number 30 (Monday, February 14, 2022)]
[Rules and Regulations]
[Pages 8145-8147]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-03026]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2020-1039; Special Conditions No. 25-807-SC]

Special Conditions: Dassault Aviation Model Falcon 6X Airplane; 
Electronic Flight-Control System: Lateral-Directional and Longitudinal 
Stability and Low-Energy Awareness

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (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 an electronic flight-control system 
(EFCS) associated with lateral-directional and longitudinal stability, 
and low-energy awareness. 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 February 14, 2022. Send 
comments on or before March 31, 2022.

ADDRESSES: Send comments identified by Docket No. FAA-2020-1039 using 
any of the following methods:
     Federal eRegulations Portal: Go to https://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 title 14, Code of Federal Regulations (14 CFR) 11.35, the 
FAA will post all comments received without change to https://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 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 
this rulemaking.
    Docket: Background documents or comments received may be read at 
https://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: Troy Brown, Performance and 
Environment Section, AIR-625, Technical Innovation Policy Branch, 
Policy and Innovation Division, Aircraft Certification Service,

[[Page 8146]]

Federal Aviation Administration, 1801 S Airport Rd., Wichita, KS 67209-
2190; telephone and fax 405-666-1050; 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 July 1, 2012, Dassault applied for a type certificate for its 
new Model Falcon 5X airplane. However, Dassault has decided not to 
release an airplane under the model designation Falcon 5X, instead 
choosing to change that model designation to Falcon 6X.
    In February of 2018, due to engine supplier issues, Dassault 
extended the type certificate application date for its Model Falcon 5X 
airplane under new Model Falcon 6X. This airplane is a twin-engine 
business jet with seating for 19 passengers, and has a maximum takeoff 
weight of 77,460 pounds.

Type Certification Basis

    Under the provisions of 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 features:
    Lateral-directional and longitudinal stability, and low-energy 
awareness, functions of the EFCS.

Discussion

    Lateral-directional Static Stability: The Dassault Model 6X 
airplane includes a flight-control design feature within the normal 
operational envelope in which side-stick deflection in the roll axis 
commands roll rate; and stick force in the roll axis will be zero 
(neutral stability) during the straight, steady sideslip flight 
maneuver required by Sec.  25.177(c), which will not be ``substantially 
proportional to the angle of sideslip'' as required by the rule.
    Longitudinal Static Stability: The longitudinal flight control laws 
for the Model Falcon 6X airplane provide neutral static stability 
within the normal operational envelope; therefore, the airplane design 
does not comply with the static longitudinal stability requirements of 
Sec. Sec.  25.171, 25.173, and 25.175.
    Low Energy Awareness: Static longitudinal stability provides 
awareness to the flight crew when they have deviated from a trimmed 
state. This could also be an important factor in their awareness of a 
low energy state (low speed and thrust at low altitude) if they are 
flying at low speeds. Entry into a low energy state may be less 
noticeable due to this lack of static stability and recovery may become 
more hazardous when associated with a low altitude and performance 
limiting conditions. These low energy situations must therefore be 
avoided, and pilots must be given adequate cues when approaching such 
situations.
    The EFCS affects the following stability and energy-awareness 
features of the airplane:

1. Lateral-Directional Static Stability

    The EFCS on the Dassault Model Falcon 6X contains fly-by-wire 
control laws that can result in neutral lateral-directional static 
stability. Therefore, the airplane does not meet the conventional 
requirements in the regulations.
    Positive static directional stability is defined as the tendency to 
recover from a skid with the rudder free. Positive static lateral 
stability is defined as the tendency to raise the low wing in a 
sideslip with the aileron controls free. These control criteria are 
intended to accomplish the following:
    a. Provide additional cues of inadvertent sideslips and skids 
through control-force changes.
    b. Ensure that short periods of unattended operation do not result 
in any significant changes in yaw or bank angle.
    c. Provide predictable roll and yaw response.
    d. Provide an acceptable level of pilot attention (workload) to 
attain and maintain a coordinated turn.

2. Static Longitudinal Stability

    Static longitudinal stability on airplanes with mechanical links to 
the pitch-control surface means that a pull force on the controller 
results in a reduction in speed relative to the trim speed, and a push 
force results in higher than trim speed. Longitudinal stability is 
required by the regulations for the following reasons:
    a. Speed-change cues are provided to the pilot through increased 
and decreased forces on the controller.
    b. Short periods of unattended control of the airplane do not 
result in significant changes in attitude, airspeed, or load factor.
    c. A predictable pitch response is provided to the pilot.
    d. An acceptable level of pilot attention (workload) to attain and 
maintain trim speed and altitude is provided to the pilot.
    e. Longitudinal stability provides gust stability.
    The pitch-control movement of the side stick on the Model Falcon 6X 
airplane is designed to be a normal load factor, or ``g'' command, that 
results in an initial movement of the elevator surface to attain the 
commanded load factor that is then followed by integrated movement of 
the stabilizer and elevator to automatically trim the airplane to a 
neutral, 1g, stick-free stability. The flight path commanded by the 
initial side-stick input will remain, stick-free, until the pilot 
provides another command. This control function is

[[Page 8147]]

applied during ``normal'' control law within the speed range, from 
initiation of the angle-of-attack protection limit, Vprot, 
to VMO/MMO. Once outside this speed range, the 
control laws introduce the conventional longitudinal static stability 
as described above.
    As a result of neutral static stability, the Model Falcon 6X 
airplane does not meet the regulatory requirements for static 
longitudinal stability.

3. Low Energy Awareness

    Past experience on airplanes fitted with a flight-control system 
providing neutral longitudinal stability reveals insufficient feedback 
cues to the pilot of excursion below normal operational speeds. The 
maximum angle-of-attack protection system limits the airplane angle of 
attack and prevents stall during normal operating speeds, but this 
system is not sufficient to prevent stall at low-speed excursions below 
normal operational speeds. Until intervention, there are no stability 
cues because the aircraft remains trimmed. Additionally, feedback from 
the pitching moment due to thrust variation is reduced by the flight-
control laws. Low-speed excursions may become more hazardous without 
the typical longitudinal stability, and recovery is more difficult when 
the low-speed situation is associated with a low altitude, and with the 
engines at low thrust or with performance-limiting conditions.
    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.

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 Aviation Model Falcon 6X 
airplane.
    In lieu of the requirements of Sec. Sec.  25.171, 25.173, 25.175, 
and 25.177(c), the following special conditions apply:
    1. 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.
    2. 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. ``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.
    3. The following requirement must be met for the configurations and 
speed specified in paragraph (a) of Sec.  25.177. In straight, steady 
sideslips over the range of sideslip angles appropriate to the 
operation of the airplane, the rudder-control movements and forces must 
be substantially proportional to the angle of sideslip in a stable 
sense. This factor of proportionality must lie between limits found 
necessary for safe operation. The range of sideslip angles evaluated 
must include those sideslip angles resulting from the lesser of:
    a. One-half of the available rudder control input; and
    b. A rudder control force of 180 pounds.

    Issued in Kansas City, Missouri, on February 8, 2022.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2022-03026 Filed 2-11-22; 8:45 am]
BILLING CODE 4910-13-P