Proposed Rule2024-16979
Special Conditions: The Boeing Company Model 777-9 Airplane; Operation Without Normal Electrical Power
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Published
August 2, 2024
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
This action proposes to amend Special Conditions No. 25-791-SC for The Boeing Company (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 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.
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<title>Federal Register, Volume 89 Issue 149 (Friday, August 2, 2024)</title>
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[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 [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[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 <a href="https://www.regulations.gov">https://www.regulations.gov</a> 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
<a href="https://www.regulations.gov">https://www.regulations.gov</a> 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 <a href="/cdn-cgi/l/email-protection#3d535c4754551356555c524851447d5b5c5c135a524b"><span class="__cf_email__" data-cfemail="d5bbb4afbcbdfbbebdb4baa0b9ac95b3b4b4fbb2baa3">[email protected]</span></a>.
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 <a href="https://www.regulations.gov">https://www.regulations.gov</a> 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
[[Page 63114]]
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
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