[Federal Register Volume 89, Number 149 (Friday, August 2, 2024)]
[Proposed Rules]
[Pages 63111-63114]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-16979]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2021-0894; Notice No. 25-23-04-SC]


Special Conditions: The Boeing Company Model 777-9 Airplane; 
Operation Without Normal Electrical Power

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Notice of proposed special conditions; amendment.

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SUMMARY: This action proposes to amend Special Conditions No. 25-791-SC 
for The Boeing Company (Boeing) Model 777-9 series airplane. This

[[Page 63112]]

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 electrical and 
electronic systems that perform critical functions, the loss of which 
could be catastrophic to the airplane. The applicable airworthiness 
regulations do not contain adequate or appropriate safety standards for 
this design feature. These proposed special conditions, as amended, 
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: Send comments on or before September 16, 2024.

ADDRESSES: Send comments identified by Docket No. FAA-2021-0894 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.
    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: Nazih Khaouly, Electrical Systems, 
AIR-626A, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service, Federal Aviation Administration, 2200 
South 216th Street, Des Moines, Washington 98198; telephone 206-231-
3160; email [email protected].

SUPPLEMENTARY INFORMATION: 

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 proposed amended 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 and will consider comments filed late if it is possible to do 
so without incurring delay. The FAA may change these special conditions 
based on the comments received.

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), Sec.  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 individual listed in the FOR FURTHER 
INFORMATION CONTACT section. Comments the FAA receives, which are not 
specifically designated as CBI, will be placed in the public docket for 
these special conditions.

Background

    On September 30, 2018, Boeing applied for an amendment to Type 
Certificate No. T00001SE to include the new Model 777-9 series 
airplane. The Boeing Model 777-9 airplane, which is a derivative of the 
Boeing Model 777 airplane currently approved under Type Certificate No. 
T00001SE, is a twin-engine, transport category airplane with seating 
for 495 passengers, and a maximum takeoff weight of 775,000 lbs.
    On September 29, 2021, special conditions (No. 25-791-SC) were 
issued for this design feature and became effective on October 4, 2021 
(86 FR 54588, Oct. 4, 2021). The FAA is proposing minor changes to 
those special conditions.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Boeing must show that the 
Model 777-9 series airplane meets the applicable provisions of the 
regulations listed in Type Certificate No. T00001SE, or the applicable 
regulations in effect on the date of application for the change, except 
for earlier amendments as agreed upon by the FAA.
    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 Boeing Model 777-9 series 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, or should any other model already included on 
the same type certificate be modified to incorporate 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 Boeing Model 777-9 series 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.  21.101.

Novel or Unusual Design Features

    The Boeing Model 777-9 series airplane will incorporate the 
following novel or unusual design feature:
    Electrical and electronic systems that perform critical functions, 
the loss of which may result in loss of flight controls and other 
critical systems and may be catastrophic to the airplane.

Discussion

    The Boeing Model 777-9 series airplane has a fly-by-wire flight 
control

[[Page 63113]]

system that requires a continuous source of electrical power in order 
to maintain an operable flight control system. Section 25.1351(d), 
``Operation without normal electrical power,'' requires safe operation 
in visual flight rule (VFR) conditions for at least 5 minutes after the 
loss of normal electrical power excluding the battery. This rule is 
structured around a traditional design using mechanical control cables 
and linkages for flight control. These manual controls allow the crew 
to maintain aerodynamic control of the airplane for an indefinite 
period of time after loss of all electrical power. Under these 
conditions, a mechanical flight control system provides the crew with 
the ability to fly the airplane while attempting to identify the cause 
of the electrical failure, restart engine(s) if necessary, and attempt 
to re-establish some of the electrical power generation capability.
    A critical assumption in Sec.  25.1351(d) is that the airplane is 
in VFR conditions at the time of the failure. This is not a valid 
assumption in today's airline operating environment where airplanes fly 
much of the time in instrument meteorological conditions (IMC) on air 
traffic control defined flight paths. Another assumption in the 
existing rule is that the loss of all normal electrical power is the 
result of the loss of all engines. The 5-minute period in the rule is 
to allow at least one engine to be restarted following an all-engine 
power loss in order to continue the flight to a safe landing. However, 
service experience on airplane models with similar electrical power 
system architecture as the Boeing Model 777-9 airplane has shown that 
at least the temporary loss of all electrical power for causes other 
than all-engine failure is not extremely improbable.
    To maintain the same level of safety envisioned by the existing 
rule with traditional mechanical flight controls, the Boeing Model 777-
9 series airplane design must not be time-limited in its operation 
under all reasonably foreseeable conditions, including loss of all 
normal sources of engine or auxiliary power unit (APU)-generated 
electrical power. Unless Boeing can show that the non-restorable loss 
of the engine and APU power sources is extremely improbable, Boeing 
must demonstrate that the airplanes can maintain safe flight and 
landing (including steering and braking on the ground for airplanes 
using steer/brake-by-wire and/or fly-by-wire speed brake panels) with 
the use of its emergency/alternate electrical power systems. These 
electrical power systems, or the minimum restorable electrical power 
sources, must be able to power loads that are essential for continued 
safe flight and landing, including those required for the maximum 
length of approved flight diversion.
    The FAA proposes to change two paragraphs from the original special 
conditions. Those paragraphs are (d)(2) and (e)(4). Paragraph (d)(2) of 
the original special conditions states that the operating limitations 
section of the airplane flight manual (AFM) must incorporate non-normal 
procedures that direct the pilot to take appropriate actions to 
activate the APU after loss of normal engine-driven generated 
electrical power. The FAA proposes to require that these non-normal 
procedures be incorporated in the AFM instead of requiring them to be 
in the operating limitations section of the AFM.
    Paragraph (e)(4) of the original special conditions states that the 
airplane must provide adequate indication of loss of normal electrical 
power to direct the pilot to the non-normal procedures, and the 
operating limitations section of the AFM must incorporate non-normal 
procedures that will direct the pilot to take appropriate actions. As 
in paragraph (d)(2), the FAA proposes to require that these non-normal 
procedures be incorporated in the AFM instead of specifying the 
particular section of the AFM that these procedures need to reside.
    The proposed changes are to remedy an oversight that occurred 
during the issuance of the original special conditions where the FAA 
inadvertently required the non-normal procedures to be in the 
limitations section of the AFM. The FAA found that this requirement is 
inconsistent with similarly issued special conditions for other 
transport category airplanes. The Boeing 777-9 electrical power system 
does not require pilot activation of the APU after loss of normal 
engine-driven generated electrical power. Paragraph (d) does not apply 
to designs that do not rely on the APU for an alternate source of 
power. The intent of paragraphs (d)(2) and (e)(4) is to ensure that 
non-normal procedures that provide instructions to the pilot to take 
appropriate action are incorporated into the AFM. These procedures are 
more appropriate for the operating procedures section of the AFM and 
were not intended to be an operating limitation.
    The proposed 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 proposed special conditions, as amended, 
are 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, or should 
any other model already included on the same type certificate be 
modified to incorporate the same novel or unusual design feature, these 
special conditions would apply to the other model as well.

Conclusion

    This action affects only a certain novel or unusual design feature 
on one 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.

Authority Citation

    The authority citation for these special conditions is as follows:

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

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions, as amended, as part of the type 
certification basis for The Boeing Company Model 777-9 series 
airplanes.
    (a) The applicant must show by test or a combination of test and 
analysis that the airplane is capable of continued safe flight and 
landing with all normal electrical power sources inoperative, as 
prescribed by paragraphs (a)(1) and (a)(2), below. For purposes of 
these special conditions, normal sources of electrical power generation 
do not include any alternate power sources such as the battery, ram air 
turbine, or independent power systems such as the flight control 
permanent magnet generating system. In showing capability for continued 
safe flight and landing, the applicant must account for systems 
capability, effects on crew workload and operating conditions, and the 
physiological needs of the flightcrew and passengers for the longest 
diversion time for which the applicant is seeking approval.
    (1) In showing compliance with this requirement, the applicant must 
account for common-cause failures, cascading failures, and zonal 
physical threats.
    (2) The applicant may consider the ability to restore operation of 
portions of the electrical power generation and distribution system if 
it can be shown

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that unrecoverable loss of those portions of the system is extremely 
improbable. The design must provide an alternative source of electrical 
power for the time required to restore the minimum electrical power 
generation capability required for safe flight and landing. The 
applicant may exclude unrecoverable loss of all engines when showing 
compliance with this requirement.
    (b) Regardless of any electrical generation and distribution system 
recovery capability shown under paragraph (a) of these special 
conditions, sufficient electrical system capability must be provided 
to:
    (1) Allow time to descend, with all engines inoperative, at the 
speed that provides the best glide distance, from the maximum operating 
altitude to the top of the engine restart envelope; and
    (2) Subsequently allow multiple start attempts of the engines and 
auxiliary power unit (APU). The design must provide this capability in 
addition to the electrical capability required by existing part 25 
requirements related to operation with all engines inoperative.
    (c) The airplane emergency electrical power system must be designed 
to supply:
    (1) Electrical power required for immediate safety, which must 
continue to operate without the need for crew action following the loss 
of the normal electrical power, for a duration sufficient to allow 
reconfiguration to provide a non-time-limited source of electrical 
power.
    (2) Electrical power required for continued safe flight and landing 
for the maximum diversion time.
    (d) If the applicant uses APU-generated electrical power to satisfy 
the requirements of these special conditions, and if reaching a 
suitable runway for landing is beyond the capacity of the battery 
systems, then the APU must be able to be started under any foreseeable 
flight condition prior to the depletion of the battery or the 
restoration of normal electrical power, whichever occurs first. Flight 
test must demonstrate this capability at the most critical condition.
    (1) The applicant must show that the APU will provide adequate 
electrical power for continued safe flight and landing.
    (2) The AFM must incorporate non-normal procedures that direct the 
pilot to take appropriate actions to activate the APU after loss of 
normal engine-driven generated electrical power.
    (e) As part of showing compliance with these special conditions, 
the tests to demonstrate loss of all normal electrical power must also 
take into account the following:
    (1) The assumption that the failure condition occurs during night 
instrument meteorological conditions (IMC) at the most critical phase 
of the flight, relative to the worst possible electrical power 
distribution and equipment-loads-demand condition.
    (2) After the un-restorable loss of normal engine generator power, 
the airplane engine restart capability is provided, and operations 
continued in IMC.
    (3) The airplane is demonstrated to be capable of continued safe 
flight and landing. The length of time must be computed based on the 
maximum diversion time capability for which the airplane is being 
certified. The applicant must account for airspeed reductions resulting 
from the associated failure or failures.
    (4) The airplane must provide adequate indication of loss of normal 
electrical power to direct the pilot to the non-normal procedures, and 
the AFM must incorporate non-normal procedures that will direct the 
pilot to take appropriate actions.

    Issued in Kansas City, Missouri, on July 29, 2024.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service.
[FR Doc. 2024-16979 Filed 8-1-24; 8:45 am]
BILLING CODE 4910-13-P