[Federal Register Volume 79, Number 127 (Wednesday, July 2, 2014)]
[Proposed Rules]
[Pages 37670-37674]
[FR Doc No: 2014-15526]

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Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.

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Federal Register / Vol. 79, No. 127 / Wednesday, July 2, 2014 /
Proposed Rules

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2014-0421; Notice No. 25-14-07-SC]

Special Conditions: Boeing Commercial Airplanes, Model 767-2C
Airplane; Interaction of Fuel Systems and Structures

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the Boeing Model
767-2C airplane. This airplane will have novel or unusual design
features when compared to the state of technology envisioned in the
airworthiness standards for transport category airplanes. These design
features include the addition of four body fuel tanks and a modified
fuel management system that, directly or as a result of failure or
malfunction, could affect the airplane's structural performance. The
applicable airworthiness regulations do not contain adequate or
appropriate safety standards for these design features. These 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.

DATES: Send your comments on or before August 18, 2014.

ADDRESSES: Send comments identified by docket number FAA-2014-0421
using any of the following methods:
    Federal eRegulations Portal: Go to http://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<PHONE_NUMBER>.
    Privacy: The FAA will post all comments it receives, without
change, to http://www.regulations.gov/, including any personal
information the commenter provides. Using the search function of the
docket Web site, anyone can find and read the electronic form of all
comments received into any FAA docket, including the name of the
individual sending the comment (or signing the comment for an
association, business, labor union, etc.). DOT's complete Privacy Act
Statement can be found in the Federal Register published on April 11,
2000 (65 FR 19477-19478), as well as at http://DocketsInfo.dot.gov/.
    Docket: Background documents or comments received may be read at
http://www.regulations.gov/ at any time. Follow the online instructions
for accessing the docket or go to the 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: Mark Freisthler, FAA, Airframe and
Cabin Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft
Certification Service, 1601 Lind Avenue SW., Renton, Washington, 98057-
3356; telephone<PHONE_NUMBER>; facsimile<PHONE_NUMBER>.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite 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.
    We will consider all comments we receive on or before the closing
date for comments. We may change these special conditions based on the
comments we receive.

Background

    On January 18, 2010, Boeing Commercial Airplanes applied for an
amendment to Type Certificate No. A1NM to include the new Model 767-2C.
The Boeing Model 767-2C, which is a derivative of the Model 767-200
currently approved under Type Certificate No. A1NM, is a transport
category airplane, intended for use as a freighter, powered by two
PW4062 engines with a maximum takeoff weight of 415,000 pounds.
    The Boeing Model 767-2C will have more fuel capacity than a
traditional freighter through the addition of four body fuel tanks. The
Model 767-2C contains fuel systems that could, directly or as a result
of failure or malfunction, affect the aircraft's structural
performance. Current regulations do not take into account loads for the
aircraft due to the effects of fuel system failures on structural
performance; therefore, special conditions are needed.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14
CFR) 21.101, Boeing must show that the Model 767-2C meets the
applicable provisions of 14 CFR part 25, as amended by Amendments 25-0
through 25-130, except for earlier amendments as agreed upon by the
FAA. These regulations will be incorporated into Type Certificate No.
A1NM after type certification approval of the Model 767-2C.
    In addition, the certification basis includes other regulations,
special conditions, and exemptions that are not relevant to these
proposed special conditions. Type Certificate No. A1NM will be updated
to include a complete description of the certification basis for these
model airplanes.
    If the Administrator finds that the applicable airworthiness
regulations (i.e., 14 CFR part 25) do not contain adequate or
appropriate safety standards for the Model 767-2C 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 or similar
novel

or unusual design feature, or should any other model already included
on the same type certificate be modified to incorporate the same or
similar novel or unusual design feature, the special conditions would
also apply to the other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special
conditions, the Model 767-2C 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 767-2C will incorporate the following novel or
unusual design features: Fuel system changes including the addition of
forward and aft body fuel tanks, a main-to-center-tank gravity transfer
system, hydraulically-powered-pumps for jettison, a nitrogen generation
system for inerting of all fuel tanks, and a pressure-regulating closed
fuel tank vent system. Digital electronic controls (i.e., fuel
management systems) are added for control and monitoring of these
systems.

Discussion

    The fuel management system is designed to keep the fuel distributed
in accordance with fuel usage requirements. System failures of these
new and modified systems may result in adverse fuel distributions or
center-of-gravity excursions that increase the airplane loads. For
example, a failure of the main tank gravity drain valve may result in
less wing main tank fuel than normal management; or failure of the body
auxiliary tank transfer systems may result in excessive body fuel at
landing. Additionally, failures of the nitrogen generation system, fuel
transfer system, or vent/pressure regulating system may result in
excessive fuel tank pressures. These types of failures are addressed by
these proposed special conditions.
    Special conditions have been applied on past airplane programs in
order to require consideration of the effects of systems on structures.
These proposed special conditions are similar to those previously
applied except that the scope is limited to new fuel system features
unique to the Model 767-2C.

Applicability

    As discussed above, these special conditions are applicable to the
Boeing Model 767-2C airplane. Should Boeing Commercial Airplanes apply
at a later date for a change to the type certificate to include another
model incorporating the same novel or unusual design feature, the
special conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features
on one model 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.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the
following special conditions as part of the type certification basis
for Boeing Model 767-2C airplanes.
    1. Interactions of fuel systems and structures. General.
    a. For airplanes equipped with fuel systems that affect structural
performance, either directly or as a result of a failure or
malfunction, the influence of these systems and their failure
conditions must be taken into account when showing compliance with the
requirements of 14 CFR part 25 subparts C and D.
    b. The criteria in Section 2 below must be used for showing
compliance with these special conditions for airplanes equipped with
fuel systems that either directly or as a result of failure or
malfunction affect structural performance.
    c. The criteria only address the direct structural consequences of
the system responses and performances and cannot be considered in
isolation but should be included in the overall safety evaluation of
the airplane. These criteria may in some instances duplicate standards
already established for this evaluation. These criteria are only
applicable to structural elements whose failure could prevent continued
safe flight and landing. Specific criteria that define acceptable
limits on handling characteristics or stability requirements when
operating in the system degraded or inoperative mode are not provided
in these special conditions.
    d. Depending on the specific characteristics of the airplane,
additional studies may be required that demonstrate the capability of
the airplane to meet other realistic conditions such as alternative
gust or maneuver descriptions for an airplane equipped with a load
alleviation system.
    e. The following definitions are applicable to these special
conditions:
    (1) Structural performance: Capability of the airplane to meet the
structural requirements of part 25.
    (2) Flight limitations: Limitations that can be applied to the
airplane flight conditions following an in-flight occurrence and that
are included in the airplane flight manual (e.g., speed limitations,
avoidance of severe weather conditions, etc.).
    (3) Operational limitations: Limitations, including flight
limitations, that can be applied to the airplane operating conditions
before dispatch (e.g., fuel, payload and Master Minimum Equipment List
limitations).
    (4) Probabilistic terms: The probabilistic terms (probable,
improbable, extremely improbable) used in these special conditions are
the same as those used in Sec.  25.1309.
    (5) Failure condition: The term failure condition is the same as
that used in Sec.  25.1309. However, these special conditions apply
only to system failure conditions that affect the structural
performance of the airplane (e.g., system failure conditions that
induce loads, change the response of the airplane to inputs such as
gusts or pilot actions, or lower flutter margins). The system failure
conditions include consequential or cascading effects resulting from
the first failure.
    2. Effects of Fuel System Failure on Structures. The following
criteria will be used in determining the influence of the fuel system
and its failure conditions on the airplane structural elements.
    a. Fuel system fully operative. With the fuel system fully
operative, the following apply:
    (1) Limit loads must be derived in all normal operating
configurations of the fuel system from all the limit conditions
specified in subpart C (or used in lieu of those specified in subpart
C), taking into account any special behavior of such a system or
associated functions or any effect on the structural performance of the
airplane that may occur up to the limit loads. In particular, any
significant nonlinearity (rate of fuel transfer, thresholds or any
other system nonlinearities) must be accounted for in a realistic or
conservative way when deriving limit loads from limit conditions.
    (2) The airplane must meet the strength requirements of part 25
(i.e., static strength, residual strength), using the specified factors
to derive ultimate loads from the limit loads defined above. The effect
of nonlinearities must

be investigated beyond limit conditions to ensure the behavior of the
system presents no anomaly compared to the behavior below limit
conditions. However, conditions beyond limit conditions need not be
considered when it can be shown that the airplane has design features
that will not allow it to exceed those limit conditions.
    (3) The airplane must meet the aeroelastic stability requirements
of Sec.  25.629.
    b. Fuel system in the failure condition. For any fuel system
failure condition not shown to be extremely improbable, the following
apply:
    (1) At the time of occurrence, starting from 1-g level flight
conditions, a realistic scenario, including pilot corrective actions,
must be established to determine the loads occurring at the time of
failure and immediately after failure.
    (i) For static strength substantiation, these loads, multiplied by
an appropriate factor of safety that is related to the probability of
occurrence of the failure, are ultimate loads to be considered for
design. The factor of safety is defined in Figure 1.
[GRAPHIC] [TIFF OMITTED] TP02JY14.003

    (ii) For residual strength substantiation, the airplane must be
able to withstand two thirds of the ultimate loads defined in
subparagraph 2b(1)(i). For pressurized cabins, these loads must be
combined with the normal operating differential pressure.
    (iii) Freedom from aeroelastic instability must be shown up to the
speeds defined in Sec.  25.629(b)(2). For failure conditions that
result in speeds beyond VC/MC, freedom from
aeroelastic instability must be shown to increased speeds, so that the
margins intended by Sec.  25.629(b)(2) are maintained.
    (iv) Failures of the fuel system that result in forced structural
vibrations (oscillatory failures) must not produce loads that could
result in detrimental deformation of the affected structural elements.
    (2) For continuation of flight, for an airplane in the system
failed state and considering any appropriate reconfiguration and flight
limitations, the following apply:
    (i) The loads derived from the following conditions (or used in
lieu of the following conditions) at speeds up to VC/
MC, or the speed limitation prescribed for the remainder of
the flight, must be determined:
    (A) The limit symmetrical maneuvering conditions specified in
Sec. Sec.  25.331 and 25.345.
    (B) The limit gust and turbulence conditions specified in
Sec. Sec.  25.341 and 25.345.
    (C) The limit rolling conditions specified in Sec.  25.349 and the
limit unsymmetrical conditions specified in Sec. Sec.  25.367 and
25.427(b) and (c).
    (D) The limit yaw maneuvering conditions specified in Sec.  25.351.
    (E) The limit ground loading conditions specified in Sec. Sec.
25.473, 25.491, and 25.493.
    (ii) For static strength substantiation, each part of the structure
must be able to withstand the loads in paragraph 2b(2)(i) of these
special conditions multiplied by a factor of safety depending on the
probability of being in this failure state. The factor of safety is
defined in Figure 2.

[GRAPHIC] [TIFF OMITTED] TP02JY14.004

    (iii) For residual strength substantiation, the airplane must be
able to withstand two thirds of the ultimate loads defined in paragraph
2b(2)(ii) of these special conditions. For pressurized cabins, these
loads must be combined with the normal operating differential pressure.
    (iv) If the loads induced by the failure condition have a
significant effect on fatigue or damage tolerance, then their effects
must be taken into account.
    (v) Freedom from aeroelastic instability must be shown up to a
speed determined from Figure 3. Flutter clearance speeds V' and V'' may
be based on the speed limitation specified for the remainder of the
flight using the margins defined by Sec.  25.629(b).
[GRAPHIC] [TIFF OMITTED] TP02JY14.005

    (vi) Freedom from aeroelastic instability must also be shown up to
V' in Figure 3 above, for any probable system failure condition
combined with any damage required or selected for investigation by
Sec.  25.571(b).
    (3) Consideration of certain failure conditions may be required by
other sections of part 25 regardless of calculated system reliability.
Where analysis shows the probability of these failure conditions to be
less than 10-9, criteria other than those specified in this
paragraph may be used for structural substantiation to show continued
safe flight and landing.
    c. Failure indications. For fuel system failure detection and
indication, the following apply:
    (1) The fuel system must be checked for failure conditions, not
extremely improbable, that degrade the structural capability below the
level required by part 25 or significantly reduce the

reliability of the remaining system. As far as reasonably practicable,
the flight crew must be made aware of these failures before flight.
Certain elements of the fuel system, such as mechanical and hydraulic
components, may use special periodic inspections, and electronic
components may use daily checks, in lieu of detection and indication
systems to achieve the objective of this requirement. These identified
inspections must be limited to components that are not readily
detectable by normal detection and indication systems and where service
history shows that inspections will provide an adequate level of
safety.
    (2) The existence of any failure condition, not extremely
improbable, during flight that could significantly affect the
structural capability of the airplane and for which the associated
reduction in airworthiness can be minimized by suitable flight
limitations, requires a caution level alert for immediate flightcrew
awareness and a warning level alert for immediate flightcrew awareness
and corrective action. For example, a flightcrew alert during flight is
required for failure conditions that result in a factor of safety
between the airplane strength and the loads of subpart C below 1.25, or
flutter margins below V'', because it could significantly affect the
structural capability of the airplane.
    d. Dispatch with known failure conditions. If the airplane is to be
dispatched in a known fuel system failure condition that affects
structural performance, or affects the reliability of the remaining
system to maintain structural performance, then the provisions of these
special conditions must be met, including the provisions of paragraph
2a for the dispatched condition, and paragraph 2b for subsequent
failures. Expected operational limitations may be taken into account in
establishing Pj as the probability of failure occurrence for
determining the safety margin in Figure 1. Flight limitations and
expected operational limitations may be taken into account in
establishing Qj as the combined probability of being in the
dispatched failure condition and the subsequent failure condition for
the safety margins in Figures 2 and 3. These limitations must be such
that the probability of being in this combined failure state and then
subsequently encountering limit load conditions is extremely
improbable. No reduction in these safety margins is allowed if the
subsequent system failure rate is greater than 10-3 per
hour.

    Issued in Renton, Washington, on June 17, 2014.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2014-15526 Filed 7-1-14; 8:45 am]
BILLING CODE 4910-13-P