Special Conditions: Aerocon Engineering Company, Airbus Model A350-941 Airplane; Forward Lower Lobe Crew Rest Compartment Installation, 100723-100727 [2024-29432]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 89, Number 240 (Friday, December 13, 2024)]
[Rules and Regulations]
[Pages 100723-100727]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-29432]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2024-1310; Special Conditions No. 25-873-SC]


Special Conditions: Aerocon Engineering Company, Airbus Model 
A350-941 Airplane; Forward Lower Lobe Crew Rest Compartment 
Installation

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Airbus Model A350-
941 airplane. This airplane, as modified by Aerocon Engineering Company 
(Aerocon), 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 an installation of 
a lower lobe crew rest (LLCR) compartment located under the passenger 
cabin floor in the cargo compartment. 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: Effective December 13, 2024.

FOR FURTHER INFORMATION CONTACT: Daniel Jacquet, Cabin Safety, AIR-624, 
Technical Policy Branch, Policy and Standards Division, Aircraft 
Certification Service, Federal Aviation Administration, 2200 South 
216th Street, Des Moines, Washington 98198; telephone and fax (206) 
231-3208; email [email protected].

SUPPLEMENTARY INFORMATION:

Background

    On August 27, 2021, Aerocon applied for a supplemental type 
certificate for a LLCR installation in the Model A350-941 airplane. The 
Airbus Model A350-941 airplane is a twin-engine, transport-category 
airplane with a maximum takeoff weight of 623,908 pounds and maximum 
seating for 480 passengers.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Aerocon must show that the 
Airbus Model A350-941 airplane, as changed, continues to meet the 
applicable provisions of the regulations listed in Type Certificate No. 
T000631B 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 Airbus A350-941 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 applicant apply for a supplemental type 
certificate to modify any other model included on the same type 
certificate 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 Airbus A350-941 series airplane must comply with the 
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 Airbus A350-941 airplane will incorporate the following novel 
or unusual design feature:
    The installation of a LLCR under the passenger cabin floor in the 
cargo compartment.

Discussion

    Section 25.819 applies to lower deck service compartments 
(including galleys) but is not directly applicable to forward LLCR 
compartments. The applicable airworthiness regulations do not contain 
adequate or appropriate safety standards for this design feature. 
Special conditions are required for the certification of the LLCR to 
supplement part 25.
    The LLCR will be located under the passenger cabin floor in the 
forward cargo compartment of Airbus A350-941 model airplanes. It will 
be the size of three standard airfreight containers and be removeable 
from the cargo compartment. Occupancy of the LLCR will be limited to a 
maximum of eight crew members, and it will only be occupied in flight, 
i.e., not during taxi, takeoff or landing. A smoke detection system, 
fire extinguishing system, oxygen system and occupant amenities will be 
provided.
    The LLCR will be accessed from the main deck via a stair house. The 
floor within the stair house has an access hatch that leads to the 
stairs, which occupants use to descend into the LLCR. This hatch locks 
automatically in the open position when fully opened. In addition, 
there will be an emergency hatch, which opens directly into the main 
passenger cabin area.
    The LLCR also has a maintenance access/ground loading door, which 
allows access to and from the cargo compartment. The intended use of 
this door is to allow cargo loading and maintenance personnel to enter 
the LLCR from the cargo compartment when

[[Page 100724]]

the airplane is on the ground and not moving.
    The 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.

Discussion of Comments

    The FAA issued Notice of Proposed Special Conditions No. 25-24-04-
SC for Airbus Model A350-941 airplanes, which was published in the 
Federal Register on September 11, 2024 (89 FR 73604).
    The FAA received a response from Airbus Commercial Aircraft 
(Airbus) requesting the FAA consider Special Conditions No. 25-281-SC 
as the minimum set of requirements for the design of the A350-941 lower 
deck crew rest compartment. Airbus request the FAA issue special 
conditions consistent with previously approved special conditions for 
similar installations.
    The FAA agrees with the Airbus response. The limitations and 
conditions of this special condition are essentially the same as the 
limitations and conditions listed in special condition number 25-281-
SC.
    The special conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to 
Airbus Model A350-941 airplanes as modified by Aerocon. Should the 
applicant apply for a supplemental type certificate to modify any other 
model included on the same type certificate to incorporate the same 
novel or unusual design feature, these special conditions would apply 
to the other model as well.
    Under standard practice, the effective date of final special 
conditions would be 30 days after the date of publication in the 
Federal Register. However, as the certification date for the Airbus 
Model A350-941 is imminent, the FAA finds that good cause exists to 
make these special conditions effective upon publication.

Conclusion

    This action affects only certain novel or unusual design feature on 
the Airbus 350-941 airplane. It is not a rule of general applicability 
and affects only the applicant who applied to the FAA for approval of 
these features on the airplane.

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 Airbus Model A350-941 airplanes, as 
modified by Aerocon Engineering Company. The LLCR must meet the below 
requirements:
    1. Occupancy of the forward lower lobe crew rest compartment is 
limited to a maximum of eight. There must be an approved seat or berth 
able to withstand the maximum flight loads when occupied for each 
occupant permitted in the crew rest compartment.
    (a) There must be appropriate placards displayed in a conspicuous 
place at each entrance to the LLCR compartment to indicate:
    (1) The maximum number of occupants allowed;
    (2) That occupancy is restricted to crewmembers trained in the 
evacuation procedures for the crew rest compartment;
    (3) That occupancy is prohibited during taxi, take-off and landing;
    (4) That smoking is prohibited in the crew rest compartment;
    (5) That hazardous quantities of flammable fluids, explosives, or 
other dangerous cargo is prohibited from the crew rest compartment.
    (6) That the crew rest area must be limited to the stowage of crew 
personal luggage and must not be used for the stowage of cargo or 
passenger baggage.
    (b) There must be at least one ashtray located conspicuously on or 
near the entry side of any entrance, usable in-flight, to the crew rest 
compartment.
    (c) There must be a means to prevent passengers from entering the 
compartment in the event of an emergency or when no flight attendant is 
present.
    (d) There must be a means for any door installed between the crew 
rest compartment and passenger cabin to be capable of being quickly 
opened from inside the compartment, even when crowding occurs at each 
side of the door.
    (e) For all doors installed in the evacuation routes, there must be 
a means to preclude anyone from being trapped inside the compartment. 
If a locking mechanism is installed, it must be capable of being 
unlocked from the outside without special tools. The lock must not 
prevent opening from the inside of the compartment at any time.
    2. There must be at least two emergency evacuation routes, which 
could be used by each occupant of the crew rest compartment to rapidly 
evacuate to the main cabin and be able to be closed from the main 
passenger cabin after evacuation. In addition--
    (a) The routes must be located with one at each end of the 
compartment, or with two having sufficient separation within the 
compartment and between the routes to minimize the possibility of an 
event (either inside or outside of the crew rest compartment) rendering 
both routes inoperative.
    (b) The routes must be designed to minimize the possibility of 
blockage, which might result from fire, mechanical or structural 
failure, or persons standing on top of or against the escape route. If 
an evacuation route utilizes an area where normal movement of 
passengers occurs, it must be demonstrated that passengers would not 
impede egress to the main deck. If a hatch is installed in an 
evacuation route, the point at which the evacuation route terminates in 
the passenger cabin should not be located where normal movement by 
passengers or crew occurs (main aisle, cross aisle, passageway or 
galley complex). If such a location cannot be avoided, special 
consideration must be taken to ensure that the hatch or door can be 
opened when a person, the weight of a ninety-fifth percentile male, is 
standing on the hatch or door. The use of evacuation routes must not be 
dependent on any powered device. If there is low headroom at or near an 
evacuation route, provisions must be made to prevent or to protect 
occupants of the crew rest area from head injury.
    (c) Emergency evacuation procedures, including the emergency 
evacuation of an incapacitated occupant from the crew rest compartment, 
must be established. All of these procedures must be transmitted to the 
operator for incorporation into their training programs and appropriate 
operational manuals.
    (d) There must be a limitation in the airplane flight manual or 
other suitable means requiring that crewmembers be trained in the use 
of evacuation routes.
    3. There must be a means for the evacuation of an incapacitated 
person (representative of a 95th percentile male) from the crew rest 
compartment to the passenger cabin floor. The evacuation must be 
demonstrated for all evacuation routes. A flight attendant or other 
crewmember (a total of one assistant within the crew rest area) may 
provide assistance in the evacuation.

[[Page 100725]]

Additional assistance may be provided by up to three persons in the 
main passenger compartment. For evacuation routes having stairways, the 
additional assistants may descend down to one half the elevation change 
from the main deck to the lower deck compartment, or to the first 
landing, whichever is higher.
    4. The following signs and placards must be provided in the crew 
rest compartment:
    (a) At least one exit sign, located near each exit, meeting the 
requirements of Sec.  25.812(b)(1)(i) at Amendment 25-58, except that a 
sign with reduced background area of no less than 5.3 square inches 
(excluding the letters) may be utilized, provided that it is installed 
such that the material surrounding the exit sign is light in color 
(e.g., white, cream, light beige). If the material surrounding the exit 
sign is not light in color, a sign with a minimum of a one-inch wide 
background border around the letters would also be acceptable;
    (b) An appropriate placard located near each exit defining the 
location and the operating instructions for each evacuation route;
    (c) Placards must be readable from a distance of 30 inches under 
emergency lighting conditions; and
    (d) The exit handles and evacuation path operating instruction 
placards must be illuminated to at least 160 microlamberts under 
emergency lighting conditions.
    5. In the event of failure of the aircraft's main power system, or 
of the normal crew rest compartment lighting system, there must be a 
means for emergency illumination to be automatically provided for the 
crew rest compartment.
    (a) This emergency illumination must be independent of the main 
lighting system.
    (b) The sources of general cabin illumination may be common to both 
the emergency and the main lighting systems if the power supply to the 
emergency lighting system is independent of the power supply to the 
main lighting system.
    (c) The illumination level must be sufficient for the occupants of 
the crew rest compartment to locate and transfer to the main passenger 
cabin floor by means of each evacuation route.
    (d) The illumination level must be sufficient with the privacy 
curtains in the closed position for each occupant of the crew rest to 
locate a deployed oxygen mask.
    6. There must be means for two-way voice communications between 
crewmembers on the flight deck and occupants of the crew rest 
compartment. There must also be public address (PA) system microphones 
at each flight attendant seat required to be near a floor level exit in 
the passenger cabin per Sec.  25.785(h) at Amendment 25-51. The PA 
system must allow two-way voice communications between flight 
attendants and the occupants of the crew rest compartment, except that 
one microphone may serve more than one exit provided the proximity of 
the exits allows unassisted verbal communication between seated flight 
attendants.
    7. There must be a means for manual activation of an aural 
emergency alarm system, audible during normal and emergency conditions, 
to enable crewmembers on the flight deck and at each pair of required 
floor level emergency exits to alert occupants of the crew rest 
compartment of an emergency situation. Use of a public address or crew 
interphone system will be acceptable, provided an adequate means of 
differentiating between normal and emergency communications is 
incorporated. The system must be powered in flight, after the shutdown 
or failure of all engines and auxiliary power units (APU), or the 
disconnection or failure of all power sources dependent on their 
continued operation (i.e., engine & APU), for a period of at least ten 
minutes.
    8. There must be a means, readily detectable by seated or standing 
occupants of the crew rest compartment, which indicates when seat belts 
should be fastened. In the event there are no seats, at least one means 
must be provided to cover anticipated turbulence (e.g., sufficient 
handholds). Seat belt type restraints must be provided for berths and 
must be compatible for the sleeping attitude during cruise conditions. 
There must be a placard on each berth requiring that seat belts must be 
fastened when occupied. If compliance with any of the other 
requirements of these special conditions is predicated on specific head 
location, there must be a placard identifying the head position.
    9. In lieu of the requirements specified in Sec.  25.1439(a) at 
Amendment 25-38 that pertain to isolated compartments and to provide a 
level of safety equivalent to that which is provided occupants of a 
small, isolated galley, the following equipment must be provided in the 
crew rest compartment:
    (a) At least one approved hand-held fire extinguisher appropriate 
for the kinds of fires likely to occur;
    (b) Two protective breathing equipment (PBE) devices approved to 
Technical Standard Order (TSO)-C116 or equivalent, suitable for 
firefighting, or one PBE for each hand-held fire extinguisher, 
whichever is greater; and
    (c) One flashlight.

    Note:  Additional PBEs and fire extinguishers in specific 
locations (beyond the minimum numbers prescribed in Special 
Condition no. 9) may be required as a result of any egress analysis 
accomplished to satisfy Special Condition no. 2(a).

    10. A smoke or fire detection system (or combination of systems) 
must be provided that monitors each occupiable area within the crew 
rest compartment, including those areas partitioned by curtains. Flight 
tests must be conducted to show compliance with this requirement. Each 
system (or combination of systems) must provide:
    (a) A visual indication to the flight deck within one minute after 
the start of a fire;
    (b) An aural warning in the crew rest compartment; and
    (c) A warning in the main passenger cabin. This warning must be 
readily detectable by a flight attendant, and considering the 
positioning of flight attendants throughout the main passenger 
compartment during various phases of flight.
    11. The crew rest compartment must be designed such that fires 
within the compartment can be controlled without a crewmember having to 
enter the compartment, or the design of the access provisions must 
allow crewmembers equipped for firefighting to have unrestricted access 
to the compartment. The time for a crewmember on the main deck to react 
to the fire alarm, to don the firefighting equipment, and to gain 
access must not exceed the time for the compartment to become smoke-
filled, making it difficult to locate the fire source.
    12. The crew rest compartment design must incorporate a means 
provided to exclude hazardous quantities of smoke or extinguishing 
agent originating in the crew rest compartment from entering any other 
compartment occupied by crewmembers or passengers. This means must 
include the time periods during the evacuation of the crew rest 
compartment and, if applicable, when accessing the crew rest 
compartment to manually fight a fire. Smoke entering any other 
compartment occupied by crewmembers or passengers when the access to 
the crew rest compartment is opened, during an emergency evacuation, 
must dissipate within five minutes after the access to the crew rest 
compartment is closed. Hazardous quantities of smoke may not enter any 
other compartment occupied by crewmembers or passengers during 
subsequent access to manually fight a

[[Page 100726]]

fire in the crew rest compartment (the amount of smoke entrained by a 
firefighter exiting the crew rest compartment through the access is not 
considered hazardous). The firefighting procedures must include a 
provision to ensure that all door(s) and hatch(es) at the crew rest 
compartment outlets are closed after evacuation of the crew rest 
compartment and during firefighting to minimize smoke and extinguishing 
agent from entering other occupiable compartments. During the 1-minute 
smoke detection time, penetration of a small quantity of smoke from the 
crew rest compartment into an occupied area is acceptable. Flight tests 
must be conducted to show compliance with this requirement. If a built-
in fire extinguishing system is used in lieu of manual firefighting, 
then the fire extinguishing system must be designed so that no 
hazardous quantities of extinguishing agent will enter other 
compartments occupied by passengers or crew. The system must have 
adequate capacity to suppress any fire occurring in the crew rest 
compartment, considering the fire threat, volume of the compartment and 
the ventilation rate.
    13. The crew rest compartment design must include a supplemental 
oxygen system equivalent to that provided for main deck passengers for 
each seat and berth in the crew rest compartment. The system must 
provide an aural and visual warning to the occupants of the crew rest 
compartment to don oxygen masks in the event of decompression. The 
warning must activate before the cabin pressure altitude exceeds 15,000 
feet. The aural warning must sound continuously for a minimum of five 
minutes or until a reset push button in the crew rest compartment is 
depressed. Procedures for crew rest occupants in the event of 
decompression must be established. These procedures must be transmitted 
to the operator for incorporation into their training programs and 
appropriate operational manuals.
    14. The following requirements apply to crew rest compartments that 
are divided into several sections by the installation of curtains or 
partitions:
    (a) To compensate for sleeping occupants, there must be an aural 
alert that can be heard in each section of the crew rest area 
compartment that accompanies automatic presentation of supplemental 
oxygen masks. A visual indicator that occupants must don an oxygen mask 
is required in each section where seats or berths are not installed. A 
minimum of two supplemental oxygen masks is required for each seat or 
berth. There must also be a means by which the oxygen masks can be 
manually deployed from the flight deck.
    (b) A placard is required adjacent to each curtain that visually 
divides or separates, for privacy purposes, the crew rest area 
compartment into small sections. The placard must require that the 
curtain(s) remains open when the private section it creates is 
unoccupied.
    (c) For each crew rest section created by the installation of a 
curtain, the following requirements of these special conditions must be 
met with the curtain open or closed:
    (1) Emergency illumination (Special Condition no. 5);
    (2) Emergency alarm system (Special Condition no. 7);
    (3) Seat belt fasten signal or return to seat signal as applicable 
(Special Condition no. 8); and
    (4) The smoke or fire detection system (Special Condition no. 10).
    (d) Crew rest compartments visually divided to the extent that 
evacuation could be affected must have exit signs that direct occupants 
to the primary stairway exit. The exit signs must be provided in each 
separate section of the crew rest compartment and must meet the 
requirements of Sec.  25.812(b)(1)(i) at Amendment 25-58. An exit sign 
with reduced background area as described in Special Condition no. 
4.(a) may be used to meet this requirement.
    (e) For sections within a crew rest compartment that are created by 
the installation of a partition with a door separating the sections, 
the following requirements of these special conditions must be met with 
the door open or closed:
    (1) There must be a secondary evacuation route from each section to 
the main deck, or alternatively, it must be shown that any door between 
the sections is designed to preclude anyone from being trapped inside 
the compartment. Removal of an incapacitated occupant within this area 
must be considered. A secondary evacuation route from a small room 
designed for only one occupant for short time duration, such as a 
changing area or lavatory, is not required. However, removal of an 
incapacitated occupant within this area must be considered.
    (2) Any door between the sections must be shown to be openable when 
crowded against, even when crowding occurs at each side of the door.
    (3) There may be no more than one door between any seat or berth 
and the primary stairway exit.
    (4) There must be exit signs in each section meeting the 
requirements of Sec.  25.812(b)(1)(i) at Amendment 25-58 that direct 
occupants to the primary stairway exit. An exit sign with reduced 
background area as described in Special Condition no. 4.(a) may be used 
to meet this requirement.
    (5) Special Conditions no. 5 (emergency illumination), no. 7 
(emergency alarm system), no. 8 (fasten seat belt signal or return to 
seat signal as applicable) and no. 10 (smoke or fire detection system) 
must be met with the door open or closed.
    (6) Special Conditions no. 6 (two-way voice communication) and no. 
9 (emergency firefighting and protective equipment) must be met 
independently for each separate section except for lavatories or other 
small areas that are not intended to be occupied for extended periods 
of time.
    15. Where a waste disposal receptacle is fitted, it must be 
equipped with a built-in fire extinguisher designed to discharge 
automatically upon occurrence of a fire in the receptacle.
    16. Materials (including finishes or decorative surfaces applied to 
the materials) must comply with the flammability requirements of Sec.  
25.853 at Amendment 25-66. Mattresses must comply with the flammability 
requirements of Sec.  25.853(b) and (c) at Amendment 25-66.
    17. All lavatories within the crew rest are required to meet the 
same requirements as those for a lavatory installed on the main deck 
except with regard to Special Condition no. 10 for smoke detection.
    18. When a crew rest compartment is installed or enclosed as a 
removable module in part of a cargo compartment or is located directly 
adjacent to a cargo compartment without an intervening cargo 
compartment wall, the following applies:
    (a) Any wall of the module (container) forming part of the boundary 
of the reduced cargo compartment, subject to direct flame impingement 
from a fire in the cargo compartment and including any interface item 
between the module (container) and the airplane structure or systems, 
must meet the applicable requirements of Sec.  25.855 at Amendment 25-
60.
    (b) Means must be provided so that the fire protection level of the 
cargo compartment meets the applicable requirements of Sec. Sec.  
25.855 at Amendment 25-60, 25.857 at Amendment 25-60 and 25.858 at 
Amendment 25-54 when the module (container) is not installed.
    (c) Use of each emergency evacuation route must not require 
occupants of the crew rest compartment to enter the cargo compartment 
in order to return to the passenger compartment.
    (d) The aural warning in Special Condition no. 7 must sound in the 
crew

[[Page 100727]]

rest compartment in the event of a fire in the cargo compartment.
    19. Means must be provided to prevent access into the Class C cargo 
compartment during all airplane operations and to ensure that the 
maintenance door is closed during all airplane flight operations.
    20. All enclosed stowage compartments within the crew rest that are 
not limited to stowage of emergency equipment or airplane-supplied 
equipment (e.g., bedding) must meet the design criteria given in the 
table below. As indicated by the table below, this special condition 
does not address enclosed stowage compartments greater than 200 ft\3\ 
in interior volume. The in-flight accessibility of very large, enclosed 
stowage compartments and the subsequent impact on the crewmembers' 
ability to effectively reach any part of the compartment with the 
contents of a hand fire extinguisher will require additional fire 
protection considerations similar to those required for inaccessible 
compartments such as Class C cargo compartments.

----------------------------------------------------------------------------------------------------------------
                                                          Stowage compartment interior volumes
       Fire protection features       --------------------------------------------------------------------------
                                          Less than 25 ft\3\      25 ft\3\ to 57 ft\3\    57 ft\3\ to 200 ft\3\
----------------------------------------------------------------------------------------------------------------
Materials of Construction \1\........  Yes....................  Yes....................  Yes.
Detectors \2\........................  No.....................  Yes....................  Yes.
Liner \3\............................  No.....................  No.....................  Yes.
Locating Device \4\..................  No.....................  Yes....................  Yes.
----------------------------------------------------------------------------------------------------------------
\1\ Material: The material used to construct each enclosed stowage compartment must at least be fire resistant
  and must meet the flammability standards established for interior components per the requirements of Sec.
  25.853. For compartments less than 25 ft\3\ in interior volume, the design must ensure the ability to contain
  a fire likely to occur within the compartment under normal use.
\2\ Detectors: Enclosed stowage compartments equal to or exceeding 25 ft\3\ in interior volume must be provided
  with a smoke or fire detection system to ensure that a fire can be detected within a one-minute detection
  time. Flight tests must be conducted to show compliance with this requirement. Each system (or systems) must
  provide:
(a) A visual indication in the flight deck within one minute after the start of a fire;
(b) An aural warning in the crew rest compartment; and
(c) A warning in the main passenger cabin. This warning must be readily detectable by a flight attendant, taking
  into consideration the positioning of flight attendants throughout the main passenger compartment during
  various phases of flight.
\3\ Liner: If it can be shown that the material used to construct the stowage compartment meets the flammability
  requirements of a liner for a Class B cargo compartment, then no liner would be required for enclosed stowage
  compartments equal to or greater than 25 ft\3\ in interior volume but less than 57 ft\3\ in interior volume.
  For all enclosed stowage compartments equal to or greater than 57 ft\3\ in interior volume but less than or
  equal to 200 ft\3\, a liner must be provided that meets the requirements of Sec.   25.855 at Amendment 25-60
  for a class B cargo compartment.
\4\ Location Detector: Crew rest areas which contain enclosed stowage compartments exceeding 25 ft\3\ interior
  volume and which are located away from one central location such as the entry to the crew rest area or a
  common area within the crew rest area would require additional fire protection features and/or devices to
  assist the firefighter in determining the location of a fire.


    Issued in Kansas City, Missouri, on December 9, 2024.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service.
[FR Doc. 2024-29432 Filed 12-12-24; 8:45 am]
BILLING CODE 4910-13-P