Rule2023-23519
Special Conditions: The Boeing Company Model 777 Series Airplanes; Passenger Seats With Pretensioner Restraint Systems
Primary source
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Published
October 25, 2023
Effective
November 24, 2023
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
These special conditions are issued for The Boeing Company (Boeing) Model 777 series airplanes. These airplanes 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 pretensioner restraint systems installed on passenger seats. 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.
Full Text
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<title>Federal Register, Volume 88 Issue 205 (Wednesday, October 25, 2023)</title>
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[Federal Register Volume 88, Number 205 (Wednesday, October 25, 2023)]
[Rules and Regulations]
[Pages 73219-73221]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2023-23519]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2022-1740; Special Conditions No. 25-841-SC]
Special Conditions: The Boeing Company Model 777 Series
Airplanes; Passenger Seats With Pretensioner Restraint Systems
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for The Boeing Company
(Boeing) Model 777 series airplanes. These airplanes 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 pretensioner restraint systems
installed on passenger seats. 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 November 24, 2023.
FOR FURTHER INFORMATION CONTACT: Shannon Lennon, 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-
3209; email <a href="/cdn-cgi/l/email-protection#82f1eae3ececedecaceee7ececedecc2e4e3e3ace5edf4"><span class="__cf_email__" data-cfemail="b5c6ddd4dbdbdadb9bd9d0dbdbdadbf5d3d4d49bd2dac3">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Background
On September 30, 2021, Boeing applied for an amendment to Type
Certificate No. T00001SE for Boeing Model 777 series airplanes. These
airplanes, currently approved under Type Certificate No. T00001SE, are
twin-engine, transport-category airplanes with maximum seating for 495
passengers and a maximum takeoff weight of 775,000 pounds.
Type Certification Basis
Under the provisions of 14 CFR 21.101, Boeing must show that Model
777 series airplanes meet 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 Boeing Model 777 series airplanes
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, Boeing Model 777 series airplanes 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
Boeing Model 777 series airplanes will incorporate the following
novel or unusual design feature:
Forward-facing seats incorporating a shoulder harness with
pretensioner
[[Page 73220]]
device, otherwise known as a pretensioner restraint system, which is
intended to protect the occupants from head injuries.
Discussion
Boeing will install, in Model 777 series airplanes, forward-facing
seats that incorporate a shoulder harness with a pretensioner system,
for head-injury protection, at each seat place.
Shoulder harnesses have been widely used on flight-attendant seats,
flight-deck seats, in business jets, and in general-aviation airplanes
to reduce occupant head injury in the event of an emergency landing.
Special conditions, pertinent regulations, and published guidance
relate to other restraint systems. However, the use of pretensioners in
the restraint system on transport-airplane seats is a novel design.
The pretensioner restraint system utilizes a retractor that
eliminates slack in the shoulder harness and pulls the occupant back
into the seat prior to impact. This has the effect of reducing forward
translation of the occupant, reducing head arc, and reducing loads in
the shoulder harness.
Pretensioner technology involves a step-change in loading
experienced by the occupant for impacts below and above that at which
the device deploys, because activation of the shoulder harness, at the
point at which the pretensioner engages, interrupts upper-torso
excursion. Such excursion could result in the head-injury criteria
(HIC) being higher at an intermediate impact condition than that
resulting from the maximum impact condition corresponding to the test
conditions specified in Sec. 25.562. See condition 1 in these special
conditions.
The ideal triangular maximum-severity pulse is defined in Advisory
Circular (AC) 25.562-1B, ``Dynamic Evaluation of Seat Restraint Systems
and Occupant Protection on Transport Airplanes.'' For the evaluation
and testing of less-severe pulses for purposes of assessing the
effectiveness of the pretensioner setting, a similar triangular pulse
should be used with acceleration, rise time, and velocity change scaled
accordingly. The magnitude of the required pulse should not deviate
below the ideal pulse by more than 0.5g until 1.33 t1 is reached, where
t1 represents the time interval between 0 and t1 on the referenced
pulse shape, as shown in AC 25.562-1B. This is an acceptable method of
compliance to the test requirements of the special conditions.
Additionally, the pretensioner might not provide protection, after
actuation, during secondary impacts. Therefore, the case where a small
impact is followed by a large impact should be addressed. If the
minimum deceleration severity at which the pretensioner is set to
deploy is unnecessarily low, the protection offered by the pretensioner
may be lost by the time a second, larger impact occurs.
Conditions 1 through 4 ensure that the pretensioner system
activates when intended, to provide the necessary protection of
occupants. This includes protection of a range of occupants under
various accident conditions. Conditions 5 through 10 address
maintenance and reliability of the pretensioner system, including any
outside influences on the mechanism, to ensure it functions as
intended.
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. 25-23-01-
SC for Boeing Model 777 airplanes, which was published in the Federal
Register on May 11, 2023 (88 FR 30262).
The FAA received one response, from the Air Line Pilots
Association, International, in support of the special conditions. The
special conditions are adopted as proposed.
Applicability
As discussed above, these special conditions are applicable to
Boeing Model 777 series airplanes. 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
0
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 Boeing Model 777 series airplanes.
In addition to the requirements of Sec. 25.562, forward-facing
passenger seats with pretensioner restraint systems must meet the
following:
(1) Head Injury Criteria (HIC)
The HIC value must not exceed 1000 at any condition at which the
pretensioner does or does not deploy, up to the maximum severity pulse
that corresponds to the test conditions specified in Sec. 25.562.
Tests must be performed to demonstrate this, taking into account any
necessary tolerances for deployment.
When an airbag device is present in addition to the pretensioner
restraint system, and the anthropomorphic test device (ATD) has no
apparent contact with the seat/structure but has contact with an
airbag, a HIC unlimited score in excess of 1000 is acceptable, provided
the HIC15 score (calculated in accordance with 49 CFR 571.208) for that
contact is less than 700.
ATD head contact with the seat or other structure, through the
airbag, or contact subsequent to contact with the airbag, requires a
HIC value that does not exceed 1000.
(2) Protection During Secondary Impacts
The pretensioner activation setting must be demonstrated to
maximize the probability of the protection being available when needed,
considering secondary impacts.
(3) Protection of Occupants Other Than 50th Percentile
Protection of occupants for a range of stature from a 2-year-old
child to a 95th percentile male must be shown. For shoulder harnesses
that include pretensioners, protection of occupants other than a 50th
percentile male may be shown by test or analysis. In addition, the
pretensioner must not introduce a hazard to passengers due to the
following seating configurations:
(a) The seat occupant is holding an infant.
(b) The seat occupant is a child in a child-restraint device.
(c) The seat occupant is a pregnant woman.
(4) Occupants Adopting the Brace Position
Occupants in the traditional brace position when the pretensioner
activates must not experience adverse effects from the pretensioner
activation.
[[Page 73221]]
(5) Inadvertent Pretensioner Actuation
(a) The probability of inadvertent pretensioner actuation must be
shown to be extremely remote (i.e., average probability per flight hour
of less than 10<SUP>-7</SUP>.
(b) The system must be shown not to be susceptible to inadvertent
pretensioner actuation as a result of wear and tear, nor inertia loads
resulting from in-flight or ground maneuvers likely to be experienced
in service.
(c) The seated occupant must not be seriously injured as a result
of inadvertent pretensioner actuation.
(d) Inadvertent pretensioner actuation must not cause a hazard to
the airplane, nor cause serious injury to anyone who may be positioned
close to the retractor or belt (e.g., seated in an adjacent seat or
standing adjacent to the seat).
(6) Availability of the Pretensioner Function Prior to Flight
The design must provide means for a crewmember to verify the
availability of the pretensioner function prior to each flight, or the
probability of failure of the pretensioner function must be
demonstrated to be extremely remote (i.e., average probability per
flight hour of less than 10<SUP>-7</SUP>) between inspection intervals.
(7) Incorrect Seat Belt Orientation
The system design must ensure that any incorrect orientation
(twisting) of the seat belt does not compromise the pretensioner
protection function.
(8) Contamination Protection
The pretensioner mechanisms and controls must be protected from
external contamination associated with that which could occur on or
around passenger seating.
(9) Prevention of Hazards
The pretensioner system must not induce a hazard to passengers in
case of fire, nor create a fire hazard, if activated.
(10) Functionality After Loss of Power
The system must function properly after loss of normal airplane
electrical power and after a transverse separation in the fuselage at
the most critical location. A separation at the location of the system
does not have to be considered.
Issued in Kansas City, Missouri, on October 19, 2023.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division,
Aircraft Certification Service.
[FR Doc. 2023-23519 Filed 10-24-23; 8:45 am]
BILLING CODE 4910-13-P
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</html>Indexed from Federal Register on October 25, 2023.
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