[Federal Register Volume 88, Number 60 (Wednesday, March 29, 2023)]
[Rules and Regulations]
[Pages 18389-18391]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-06395]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2023-0137; Special Conditions No. 25-836-SC]


Special Conditions: The Boeing Company Model 777-9 Airplane; 
Installation of Large Non-Structural Glass in the Passenger Compartment

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 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 the installation of large, non-
structural glass in the passenger cabin. 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 March 29, 2023. Send 
comments on or before May 15, 2023.

ADDRESSES: Send comments identified by Docket No. FAA-2023-0137 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), Sec.  
11.35, the FAA will post all comments

[[Page 18390]]

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 
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: Shannon Lennon, Human Machine 
Interface Section, AIR-626, Transport Standards Branch, Policy and 
Innovation Division, Aircraft Certification Service, Federal Aviation 
Administration, 2200 South 216th Street, Des Moines, Washington 98198; 
telephone and fax 206-231-3209; 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 14 CFR 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, 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.

Background

    On August 19, 2022, Boeing applied for an amendment to Type 
Certificate No. T00001SE to include the new Model 777-9 series 
airplane. The Boeing Model 777-9 series airplane, which is a derivative 
of the Model 777-300ER currently approved under Type Certificate No. 
T00001SE, is a twin-engine, transport category airplane, with capacity 
for 495 passengers, and a maximum takeoff weight of 775,000 pounds.

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 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:
    This design feature is the installation of large, non-structural 
glass in the passenger cabin. Possible installations of large non-
structural glass items include, but are not limited to, the following 
items:

 Glass partitions
 Glass floor installations
 Glass attached to the ceiling
 Glass parts integrated in the stairway
 Wall or Door mounted mirrors and glass panels
 Mirrors as part of a door blow out panel
 Glass plate installed in a doorframe
 Washstand with glass-panel

    The installation of these glass items in the passenger compartment, 
which can be occupied during taxi, take-off and landing (TT&L), is a 
novel or unusual design feature with respect to the installed material. 
The applicable airworthiness regulations do not contain adequate or 
appropriate safety standards for these design features.

Discussion

    The use of glass results in trade-offs between the one unique 
characteristic of glass--its capability for undistorted or controlled 
light transmittance, or transparency--and the negative aspects of the 
material. Glass, in its basic form as annealed, untreated sheet, plate, 
or float glass, when compared to metals, is extremely notch-sensitive, 
has a low fracture resistance, has a low modulus of elasticity, and can 
be highly variable in its properties. While reasonably strong, it is 
nonetheless not a desirable material for traditional airplane 
applications because it is heavy (about the same density as aluminum), 
and when it fails, it breaks into extremely sharp fragments that have 
the potential for injury, and which have been known to be lethal. Thus, 
the use of glass traditionally was limited to windshields, and 
instrument or display transparencies. The regulations in 14 CFR 25.775 
only address, and likewise only recognize, the unique use of glass in 
windshield or window applications where no other material will serve. 
This

[[Page 18391]]

regulation does address the adverse properties of glass, but pilots 
occasionally are injured from shattered glass windshields.
    The FAA divides other uses of glass in the passenger cabin into 
four groups. These groups were created to address the practical and 
functional uses of glass. The four groups are as follows:
    The first group is glass items installed in rooms or areas in the 
cabin that are not occupied during taxi, takeoff, and landing (TT&L), 
and a person does not have to enter or pass through the room or area to 
get to any emergency exit.
    The second group is glass integrated into a functional device the 
operation of which is dependent upon the characteristics of glass, such 
as instrument or indicator protective transparencies, or monitor 
screens such as liquid crystal displays or plasma displays. This group 
may be installed in any area in the cabin regardless of occupancy 
during TT&L. Acceptable means of compliance for these items may depend 
on the size and specific location of the device containing the glass.
    The third group is small glass items installed in occupied rooms or 
areas during TT&L, or rooms or areas that a person does not have to 
enter or pass through to get to any emergency exit. The FAA defines a 
small glass item as less than 8.8 lbs (4 kg) in mass.
    The fourth group is large glass items, the subject of these special 
conditions, installed in occupied rooms or areas during TT&L, or rooms 
or areas that a person must enter or pass through to get to any 
emergency exit. A large glass item is defined as 8.8 lbs (4 kg) or 
greater in mass. Groups of glass items that collectively weigh 4 kg or 
more would also be included. The mass is based on the amount of glass 
that becomes hazardous in high inertial loads.
    The glass items in groups one, two, and three are restricted to 
applications where the potential for injury is either highly localized, 
such as flight-instrument faces, or the location is such that injury 
due to failure of the glass is unlikely, for example mirrors in 
lavatories, because these installations necessitate the use of glass. 
These glass items typically are addressed in a method-of-compliance 
issue paper for each project based on existing part 25 regulations, or 
in established policy. These issue papers identify specific tests that 
could include abuse loading and ball-impact testing. In addition, these 
items are subject to the inertia loads contained in Sec.  25.561, and 
maximum positive-differential pressure for items like video monitors to 
meet Sec.  25.789.
    The items in group four are much larger and heavier than previously 
approved, and raise additional safety concerns. These large, heavy 
glass panels, primarily installed as architectural features, were not 
envisioned in the regulations. The unique aspects of glass, with the 
potential to become highly injurious or lethal objects during emergency 
landing, minor crash conditions, or in flight, warrant a unique 
approach to certification that addresses the characteristics of glass 
that prevented its use in the past. These special conditions were 
developed to ensure that airplanes with large glass features in 
passenger cabins provide the same level of safety as airplanes using 
traditional, lightweight materials. The FAA reiterates this intention 
in the text of the special conditions by qualifying their use for group 
four glass items.
    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 
Boeing Model 777-9 airplane. 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, 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 Company Model 777-9 series 
airplanes.
    For large glass items (a single item, or a collective group of 
glass items, that weigh 4 kg or more in mass) installed in passenger-
occupied rooms or areas during taxi, takeoff, and landing, or installed 
in rooms or areas that occupants must enter or pass through to access 
any emergency exit, the glass installations on the Boeing Model 777-9 
series airplanes must meet the following conditions:
    1. Material Fragmentation--The glass used must be tempered or 
otherwise treated to ensure that when fractured, it breaks into small 
pieces with relatively dull edges. The glass component installation 
must retain all glass fragments to minimize the danger from flying 
glass shards or pieces. The applicant must demonstrate this by impact 
and puncture testing and testing to failure.
    2. Strength--The glass component must be strong enough to meet the 
load requirements for all flight and landing loads, including any of 
the applicable emergency landing conditions in subparts C & D of 14 CFR 
part 25. In addition, glass components that are located such that they 
are not protected from contact with cabin occupants must not fail due 
to abusive loading, such as impact from occupants stumbling into, 
leaning against, sitting on, or performing other intentional or 
unintentional forceful contact. The effect of design details such as 
geometric discontinuities or surface finish e.g., embossing, etching, 
etc., must be assessed.
    3. Retention--The glass component, as installed in the airplane, 
must not come free of its restraint or mounting system in the event of 
an emergency landing. Both the directional loading and rebound 
conditions must be assessed. The effect of design details such as 
geometric discontinuities or surface finish e.g., embossing, etching, 
etc., must be assessed.
    4. Instructions for Continued Airworthiness--The instructions for 
continued airworthiness must reflect the fastening method used and must 
ensure the reliability of the methods used (e.g., life limit of 
adhesives, or clamp connection). Inspection methods and intervals must 
be defined based upon adhesion data from the manufacturer of the 
adhesive or actual adhesion test data, if necessary.

    Issued in Washington, DC, on date March 23, 2023.
Gregg Nesemeier, III,
Acting Manager, Technical Innovation Policy Branch, Policy and 
Innovation Division, Aircraft Certification Service.
[FR Doc. 2023-06395 Filed 3-28-23; 8:45 am]
BILLING CODE 4910-13-P