2023-10971. Special Conditions: Dassault Aviation Model Falcon 6X Airplane; Flight Envelope Protection, Icing and Non-Icing Conditions; High-Incidence Protection

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final special conditions; request for comments.

SUMMARY:

These special conditions are issued for the Dassault Aviation (Dassault) Model Falcon 6X airplane. This airplane will have novel or unusual design features associated with flight-envelope protections, in icing and non-icing conditions, that use high-incidence protection to automatically advance throttles when the airplane angle of attack (AoA) reaches a predetermined value. 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 May 23, 2023. Send comments on or before July 7, 2023.

ADDRESSES:

Send comments identified by Docket No. FAA–2021–0629 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 these special conditions.

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 Unit, AIR–621A, Technical Policy Branch, Policy and Standards Division, Aircraft Certification Service, Federal Aviation Administration, 1801 S Airport Rd., Wichita, KS 67209–2190; telephone and fax [phone]; email [e-mail].

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 § 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 Aviation 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 § 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 § 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 § 11.38, and they become part of the type certification basis under § 21.17(a)(2).

Novel or Unusual Design Features

The Dassault Model Falcon 6X airplane will incorporate the following novel or unusual design features:

A high-incidence protection system that replaces the stall warning system during normal operating conditions, prohibits the airplane from stalling, limits the angle of attack at which the airplane can be flown during normal low speed operation, and cannot be overridden by the flight crew. The application of this angle-of-attack limit impacts the stall speed determination, the stall characteristics and stall-warning demonstration, and the longitudinal handling characteristics. The current airworthiness standards do not contain adequate safety standards for the unique features of the high-incidence protection system.

Discussion

The high-incidence protection system prevents the airplane from stalling at low speeds and, therefore, a stall-warning system is not needed during normal flight conditions. However, during failure conditions, which are not shown to be extremely improbable, the requirements of §§ 25.203 and 25.207 apply, although slightly modified. If there are failures not shown to be extremely improbable, the flight characteristics at the AoA for C_Lmax must be suitable in the traditional sense, and stall warning must be provided in a conventional manner.

These special conditions address this novel or unusual design feature on the Dassault Model Falcon 6X and 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 certain novel or unusual design features 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 Dassault Aviation Model Falcon 6X airplanes.

Special Conditions Part I: Stall Protection and Scheduled Operating Speeds

Foreword

In the following paragraphs, “in icing conditions” means with the ice accretions (relative to the relevant flight phase) as defined in 14 CFR part 25, Amendment 121, appendix C.

(a) Definitions

These special conditions address novel or unusual design features of the Dassault Model Falcon 6X airplane and use terminology that does not appear in 14 CFR part 25. For the purpose of these special conditions, the following terms describe certain aspects of these novel or unusual design feature:

(1) High-Incidence Protection System

A system that operates directly and automatically on the airplane's flight controls to limit the maximum angle of attack (AoA) that can be attained to a value below that at which an aerodynamic stall would occur.

(2) Alpha-Limit

The maximum AoA at which the airplane stabilizes with the high-incidence protection system operating and the longitudinal control held on its aft stop.

(3) V_min

The minimum steady flight speed in the airplane configuration under consideration with the high-incidence protection system operating. See section (c) of these special conditions.

(4) V_min1g

V_min corrected to 1-g conditions. See section (c)(3). of these special conditions. It is the minimum calibrated airspeed at which the airplane can develop a lift force normal to the flight path equal to its weight, while at an AoA not greater than that determined for V_min.

(b) Capability and Reliability of the High-Incidence Protection System

The applicant must establish the capability and reliability of the high incidence protection system. The applicant may establish this capability and reliability by flight test, simulation, or analysis as appropriate. The capability and reliability required are:

(1) It must not be possible during pilot-induced maneuvers to encounter a stall and handling characteristics must be acceptable, as required by section (e) of these Special Conditions.

(2) The airplane must be protected against stalling due to the effects of wind-shears and gusts at low speeds as required by section (f) of these Special Conditions.

(3) The ability of the high-incidence protection system to accommodate any reduction in stalling incidence must be verified in icing conditions.

(4) The high-incidence protection system must be provided in each abnormal configuration of the high lift devices that is likely to be used in flight following system failures.

(5) The reliability of the system and the effects of failures must be acceptable in accordance with § 25.1309.

(c) Minimum Steady Flight Speed and Reference Stall Speed

In lieu of § 25.103, the following requirements apply:

(1) The minimum steady flight speed, V_min, is the final, stabilized, calibrated airspeed obtained when the airplane is decelerated until the longitudinal control is on its stop in such a way that the entry rate does not exceed 1 knot per second.

(2) The minimum steady flight speed, V_min, must be determined in icing and non-icing conditions with:

(i) The high-incidence protection system operating normally.

(ii) Idle thrust and automatic thrust system (if applicable) inhibited;

(iii) All combinations of flaps setting and landing gear position for which V_min is required to be determined;

(iv) The weight used when reference stall speed, V_SR, is being used as a factor to determine compliance with a required performance standard;

(v) The most unfavorable center of gravity allowable; and

(vi) The airplane trimmed for straight flight at a speed achievable by the automatic trim system.

(3) The 1-g minimum steady-flight speed, V_min 1g, is the minimum calibrated airspeed at which the airplane can develop a lift force (normal to the flight path) equal to its weight, while at an angle of attack not greater than that at which the minimum steady flight speed of section (c)(1) was determined. It must be determined in icing and non-icing conditions.

(4) The reference stall speed, V_SR, is a calibrated airspeed defined by the applicant. V_SR may not be less than a 1g stall speed. V_SR must be determined in non-icing conditions and expressed as:

Where:

Calibrated airspeed obtained when the load factor-corrected lift coefficient

  is first a maximum during the maneuver prescribed in section (c)(5)(viii) of this paragraph,

n_zw = Load factor normal to the flight path at V_CLmax,

W = Airplane gross weight,

S = Aerodynamic reference wing area; and

q = Dynamic pressure.

(5) V_CLmax is determined in non-icing conditions with:

(i) Engines idling, or, if that resultant thrust causes an appreciable decrease in stall speed, not more than zero thrust at the stall speed;

(ii) The airplane in other respects (such as flaps and landing gear) in the condition existing in the test or performance standard in which V_SR is being used;

(iii) The weight used when V_SR is being used as a factor to determine compliance with a required performance standard;

(iv) The center of gravity position that results in the highest value of reference stall speed;

(v) The airplane trimmed for straight flight at a speed achievable by the automatic trim system, but not less than 1.13 V_SR and not greater than 1.3 V_SR;

(vi) Reserved.

(vii) The high-incidence protection system adjusted, at the option of the applicant, to allow higher incidence than is possible with the normal production system; and

(viii) Starting from the stabilized trim condition, apply the longitudinal control to decelerate the airplane so that the speed reduction does not exceed 1 knot per second.

(d) Stall Warning

In lieu of § 25.207, the following requirements apply:

(1) Normal Operation

If the design meets all conditions of Part 1, section (b) of these special conditions, then the airplane need not provide stall warning during normal operation. The conditions of section (b) provide an equivalent level of safety to § 25.207, Stall Warning, so the provision of an additional, unique warning device is not required.

(2) High-Incidence Protection System Failure

For any failure of the high-incidence protection system that the applicant cannot show to be extremely improbable, and that results in the capability of the system no longer satisfying conditions (b)(1), (b)(2), and (b)(3), the design must provide stall warning that protects against encountering unacceptable characteristics and against encountering stall.

(i) This stall warning, with the flaps and landing gear in any normal position, must be clear and distinctive to the pilot and meet the requirements specified in conditions (d)(2)(iv) and (d)(2)(v) below.

(ii) The design must also provide this stall warning in each abnormal configuration of the high lift devices that is likely to be used in flight following system failures.

(iii) The design may furnish this stall warning either through the inherent aerodynamic qualities of the airplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual stall warning device that requires the attention of the crew within the flight deck is not acceptable by itself. If a warning device is used, it must provide a warning in each of the airplane configurations prescribed in condition (d)(2)(i) above and for the conditions prescribed below in conditions (d)(2)(iv) and (d)(2)(v) below.

(iv) In non-icing conditions, stall warning must provide sufficient margin to prevent encountering unacceptable characteristics and encountering stall in the following conditions:

(A) In power-off straight deceleration not exceeding 1 knot per second to a speed 5 knots or 5 percent calibrated airspeed (CAS), whichever is greater, below the warning onset.

(B) In turning flight, stall deceleration at entry rates up to 3 knots per second when recovery is initiated not less than 1 second after the warning onset.

(v) In icing conditions, stall warning must provide sufficient margin to prevent encountering unacceptable characteristics and encountering stall, in power off straight and turning flight decelerations not exceeding 1 knot per second, when the pilot starts a recovery maneuver not less than three seconds after the onset of stall warning.

(vi) An airplane is considered stalled when the behavior of the airplane gives the pilot a clear and distinctive indication of an acceptable nature that the airplane is stalled. Acceptable indications of a stall, occurring either individually or in combination are:

(A) A nose-down pitch that cannot be readily arrested;

(B) Buffeting, of a magnitude and severity that is strong and effective deterrent to further speed reduction; or

(C) The pitch control reaches the aft stop and no further increase in pitch attitude occurs when the control is held full aft for a short time before recovery is initiated.

(vii) An aircraft exhibits unacceptable characteristics during straight or turning flight decelerations if it is not always possible to produce and to correct roll and yaw by unreversed use of aileron and rudder controls, or abnormal nose-up pitching occurs.

(e) Handling Characteristics at High Incidence

In lieu of both § 25.201 and § 25.203, the following apply:

(1) High-Incidence Handling Demonstrations

In lieu of § 25.201: the following apply:

(i) Maneuvers to the limit of the longitudinal control, in nose-up pitch, must be demonstrated in straight flight and in 30-degree banked turns with:

(A) The high-incidence protection system operating normally;

(B) Initial power conditions of:

(1) Power off; and

(2) The power necessary to maintain level flight at 1.5 V_SR1, where V_SR1 is the reference stall speed with flaps in approach position, the landing gear retracted, and maximum landing weight;

(C) None;

(D) Flaps, landing gear, and deceleration devices in any likely combination of positions;

(E) Representative weights within the range for which certification is requested; and

(F) The airplane trimmed for straight flight at a speed achievable by the automatic trim system.

(ii) The following procedures must be used to show compliance in non-icing and icing conditions:

(A) Starting at a speed sufficiently above the minimum steady flight speed to ensure that a steady rate of speed reduction can be established, apply the longitudinal control so that the speed reduction does not exceed 1 knot per second until the control reaches the stop.

(B) The longitudinal control must be maintained at the stop until the airplane has reached a stabilized flight condition and must then be recovered by normal recovery techniques.

(C) Maneuvers with increased deceleration rates:

(1) In non-icing conditions, the requirements must also be met with increased rates of entry to the incidence limit, up to the maximum rate achievable.

(2) In icing conditions, with the anti-ice system working normally, the requirements must also be met with increased rates of entry to the incidence limit, up to 3 knots per second.

(D) Maneuvers with ice accretion prior to operation of the normal anti-ice system: With the ice accretion prior to operation of the normal anti-ice system, the requirement must also be met in deceleration at 1 knot per second up to full back stick.

(2) Characteristics in High-Incidence Maneuvers

In lieu of § 25.203, the following apply in icing and non-icing conditions:

(i) Throughout maneuvers with a rate of deceleration of not more than 1 knot per second, both in straight flight and in 30-degree banked turns, the airplane's characteristics must be as follows:

(A) There must not be any abnormal nose-up pitching.

(B) There must not be any uncommanded nose-down pitching, which would be indicative of stall. However reasonable attitude changes associated with stabilizing the incidence at Alpha limit as the longitudinal control reaches the stop would be acceptable.

(C) There must not be any uncommanded lateral or directional motion and the pilot must retain good lateral and directional control, by conventional use of the controls, throughout the maneuver.

(D) The airplane must not exhibit buffeting of a magnitude and severity that would act as a deterrent from completing the maneuver specified in (e)(1)(i).

(ii) In maneuvers with increased rates of deceleration, some degradation of characteristics is acceptable, associated with a transient excursion beyond the stabilized Alpha-limit. However, the airplane must not exhibit dangerous characteristics or characteristics that would deter the pilot from holding the longitudinal control on the stop for a period of time appropriate to the maneuver.

(iii) It must always be possible to reduce incidence by conventional use of the controls.

(iv) The rate at which the airplane can be maneuvered from trim speeds associated with scheduled operating speeds, such as V₂ and V_REF up to Alpha-limit, must not be unduly damped or be significantly slower than can be achieved on conventionally controlled transport airplanes.

(3) Characteristics Up to Maximum Lift Angle of Attack

(i) In non-icing conditions:

Maneuvers with a rate of deceleration of not more than 1 knot per second up to the AoA at which V_CLmax was obtained, as defined in section (c) of these special conditions, must be demonstrated in straight flight and in 30-degree banked turns in the following configurations:

(A) The high-incidence protection deactivated or adjusted, at the option of the applicant, to allow higher incidence than is possible with the normal production system;

(B) Automatic thrust increase system inhibited (if applicable);

(C) Engines idling;

(D) Flaps and landing gear in any likely combination of positions; and

(E) The airplane trimmed for straight flight at a speed achievable by the automatic trim system.

(ii) In icing conditions:

Maneuvers with a rate of deceleration of not more than 1 knot per second up to the maximum AoA reached during maneuvers from section (e)(1)(ii)(C)(2) must be demonstrated in straight flight with:

(A) The high-incidence protection deactivated or adjusted, at the option of the applicant, to allow higher incidence than is possible with the normal production system;

(B) Automatic thrust increase system inhibited (if applicable);

(C) Engines idling;

(D) Flaps and landing gear in any likely combination of positions; and

(E) The airplane trimmed for straight flight at a speed achievable by the automatic trim system.

(iii) During the maneuvers used to show compliance with sections (e)(3)(i) and (e)(3)(ii) above, the airplane must not exhibit dangerous characteristics and it must always be possible to reduce AoA by conventional use of the controls. The pilot must retain good lateral and directional control, by conventional use of the controls, throughout the maneuver.

(f) Atmospheric Disturbances

Operation of the high-incidence protection system must not adversely affect aircraft control during expected levels of atmospheric disturbances, nor impede the application of recovery procedures in case of wind-shear. This must be demonstrated in non-icing and icing conditions.

(g) Proof of Compliance

In lieu of § 25.21(b), the design must meet the following requirement:

(b) The flying qualities must be evaluated at the most unfavorable center-of-gravity (CG) position.

(h) Sections 25.145(a), 25.145(b)(6), and 25.1323(d)

The design must meet the following modified requirements:

• Section 25.145(a) “V_min ” in lieu of “stall identification”

• Section 25.145(b)(6) “V_min ” in lieu of V_SW

• Section 25.1323(d) “From 1.23 V_SR to V_min . . .,” in lieu of “1.23 V_SR to stall warning speed. . .,” and “speeds below V_min. . .” in lieu of “speeds below stall warning. . .”.

Special Conditions Part II: Credit for Robust Envelope Protection in Icing Conditions

(a) In lieu of § 25.21(g)(1), the following requirement applies: § 25.21, Proof of compliance:

(g) The requirements of this subpart associated with icing conditions apply only if certification for flight in icing conditions is desired. If certification for flight in icing conditions is desired, the following requirements also apply (see AC 25–25):

(1) Each requirement of this subpart, except §§ 25.121(a), 25.123(c), 25.143(b)(1) and (b)(2), 25.149, 25.201(c)(2), 25.207(c) and (d), and 25.251(b) through (e), must be met in icing conditions. Compliance must be shown using the ice accretions defined in appendix C, assuming normal operation of the airplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Airplane Flight Manual.

(b) In lieu of § 25.103, define the stall speed as provided in Special Conditions Part I, section (c).

(c) In lieu of § 25.105(a)(2)(i), the following applies:

Section 25.105, Take-off:

(2) In icing conditions, if in the configuration of § 25.121(b) with the “Take-off Ice” accretion defined in appendix C:

(i) the V₂ speed scheduled in non-icing conditions does not provide the maneuvering capability specified in § 25.143(h) for the takeoff configuration, or

(d) In lieu of § 25.107(c) and (g), the following apply, with additional sections (c′) and (g′):

Section 25.107, Take-Off Speeds:

(c) In non-icing conditions V₂, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by § 25.121(b) but may not be less than—

(1) V_2min;

(2) V_R plus the speed increment attained (in accordance with § 25.111(c)(2)) before reaching a height of 35 feet above the takeoff surface; and

(3) A speed that provides the maneuvering capability specified in § 25.143(h).

(c′) in icing conditions with the “take-off ice” accretion defined in part 25, appendix C, V₂ may not be less than—

(1) the V₂ speed determined in non-icing conditions; and

(2) A speed that provides the maneuvering capability specified in § 25.143(h).

(g) In non-icing conditions, V_FTO, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by § 25.121(c), but may not be less than—

(1) 1.18 V_SR; and

(2) A speed that provides the maneuvering capability specified in § 25.143(h).

(g′) in icing conditions with the “Final take-off ice” accretion defined in part 25, appendix C, V_FTO may not be less than—

(1) the V_FTO speed determined in non-icing conditions.

(2) A speed that provides the maneuvering capability specified in § 25.143(h).

(e) In lieu of §§ 25.121(b)(2)(ii)(A), 25.121(c)(2)(ii)(A), and 25.121(d)(2)(ii), the following apply:

Section 25.121, Climb: One-Engine Inoperative:

In lieu of § 25.121(b)(2)(ii)(A):

(A) The V₂ speed scheduled in non-icing conditions does not provide the maneuvering capability specified in § 25.143(h) for the take-off configuration; or

In lieu of § 25.121(c)(2)(ii)(A):

(A) The V_FTO speed scheduled in non-icing conditions does not provide the maneuvering capability specified in § 25.143(h) for the en-route configuration; or

In lieu of § 25.121(d)(2)(ii):

(d)(2) The requirements of sub-paragraph (d)(1) of this paragraph must be met:

(ii) In icing conditions with the approach ice accretion defined in part 25, appendix C, in a configuration corresponding to the normal all-engines-operating procedure in which V_min 1g for this configuration does not exceed 110% of the V_min 1g for the related all-engines-operating landing configuration in icing, with a climb speed established with normal landing procedures, but not more than 1.V_SR (V_SR determined in non-icing conditions).

(f) In lieu of § 25.123(b)(2)(i), the following requirements apply:

Section 25.123, En-route flight paths.

(i) The minimum en-route speed scheduled in non-icing conditions does not provide the maneuvering capability specified in § 25.143(h) for the en-route configuration; or

(g) In lieu of § 25.125(b)(2)(ii)(B), replace with the following requirements and remove § 25.125(b)(2)(ii)(C):

Section 25.125, Landing.

(B) A speed that provides the maneuvering capability specified in § 25.143(h) with the landing ice accretion defined in part 25, appendix C.

(C) [removed].

(h) In lieu of § 25.143(j)(1), the following applies:

Section 25.143, General.

(1) The airplane is controllable in a pull-up maneuver up to 1.5g load factor or lower if limited by AoA protection.

(i) In lieu of § 25.207, Stall warning, change to read as the requirements defined in Part I Special Conditions, section (d).

Issued in Des Moines, Washington, on May 18, 2023.

Suzanne A. Masterson,

Acting Manager, Technical Policy Branch, Policy and Standards Division, Aircraft Certification Service.