[Federal Register Volume 86, Number 189 (Monday, October 4, 2021)]
[Rules and Regulations]
[Pages 54588-54590]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-21540]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2021-0894; Special Conditions No. 25-791-SC]


Special Conditions: Boeing Commercial Airplanes Model 777-9 
Airplane; Operation Without Normal Electrical Power

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 Boeing Commercial 
Airplanes (Boeing) Model 777-9 series 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 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 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 Boeing on October 4, 2021. Send 
comments on or before November 18, 2021.

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.
    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 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. Submissions containing CBI should 
be sent to Steve Slotte, Aircraft Systems, AIR-623, 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-
3160;

[[Page 54589]]

[email protected]. 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: Stephen Slotte, Aircraft Systems, AIR-
623, 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) 231-3163; [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 has determined that prior public notice and comment 
are unnecessary, and finds that, for the same reason, good cause exists 
for adopting these special conditions upon publication in the Federal 
Register.

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 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.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR), Sec.  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 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 five 
minutes after 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 five-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.
    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.

[[Page 54590]]

Applicability

    As discussed above, these special conditions are applicable to the 
Boeing Model 777-9 series airplane. Should Boeing 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 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, 
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 Boeing Commercial Airplanes Model 
777-9 series airplanes.
    In lieu of 14 CFR 25.1351(d), the following special conditions 
apply:
    (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 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 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.
    (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 operating limitations section of the AFM must incorporate non-
normal procedures that will direct the pilot to take appropriate 
actions.

    Issued in Kansas City, Missouri, on September 29, 2021.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2021-21540 Filed 10-1-21; 8:45 am]
BILLING CODE 4910-13-P