Document ID: FAA-2017-0636-0001
Agency: faa
Document Type: Proposed Rule
Title: Special Conditions: The Boeing Company Model 777-8 and 777-9 Airplanes; Folding Wingtips
Posted Date: 2017-11-01T04:00Z

[Federal Register Volume 82, Number 210 (Wednesday, November 1, 2017)]
[Proposed Rules]
[Pages 50581-50583]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-23698]

 ========================================================================
 Proposed Rules
                                                 Federal Register
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 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. 82, No. 210 / Wednesday, November 1, 2017 / 
Proposed Rules  

[[Page 50581]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2017-0636; Notice No. 25-17-02-SC]

Special Conditions: The Boeing Company Model 777-8 and 777-9 
Airplanes; Folding Wingtips

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for Boeing Model 777-8 
and 777-9 airplanes. These airplanes 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 folding wingtips. The applicable airworthiness 
regulations do not contain adequate or appropriate safety standards for 
this design feature. 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 December 18, 2017.

ADDRESSES: Send comments identified by docket number FAA-2017-0636 
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 202-493-2251.
    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).
    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 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: Ian Won, FAA, Airframe and Cabin 
Safety Section, AIR-675, Policy and Innovation Division, Transport 
Standards Branch, Aircraft Certification Service, 1601 Lind Avenue SW., 
Renton, Washington 98057-3356; telephone 425-227-2145; facsimile 425-
227-1360.

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 by the closing date for 
comments. We may change these special conditions based on the comments 
we receive.

Background

    On April 19, 2017 (for the Model 777-8 airplane), and May 12, 2015 
(for the 777-9 airplane), Boeing applied for an amendment to Type 
Certificate (TC) No. T00001SE to include the new Model 777-8 and 777-9 
airplanes. These airplanes are constructed with new carbon-fiber-
reinforced plastic (CFRP) wings with folding wingtips.
    The Model 777-9 airplane, a derivative of the Model 777-300ER 
airplane currently approved under TC No. T00001SE, is a stretched-
fuselage, large, twin-engine airplane with seating for 408 passengers 
and a maximum takeoff weight of 775,000 pounds.
    The Model 777-8 airplane, a shortened-body derivative of the Model 
777-9 airplane, is a large, twin-engine airplane with seating for 359 
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) 21.101, Boeing must show that the Model 777-8 and 777-9 airplanes 
meet the applicable provisions of the regulations listed in TC 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 (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Model 777-8 and 777-9 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, the Model 777-8 and 777-9 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

[[Page 50582]]

the type certification basis under Sec.  21.101.

Novel or Unusual Design Features

    The Model 777-8 and 777-9 airplanes will incorporate the following 
novel or unusual design features: CFRP wings with folding wingtips.
    Boeing proposes to incorporate this on-ground wingtip-fold 
capability to reduce the wingspan from 235 to 212 feet when folded. 
These folding wingtips, when extended into the flight-deployed 
position, provide improved aerodynamic performance and efficiency, and 
comply with Code E \1\ gate compatibility when folded during ground 
operations.
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    \1\ A Code E gate is designed to accommodate aircraft wingspans 
between 170.6 ft. (52m) and 213.3 ft. (65m), and outer main-gear 
wheel spans between 29.5 ft. (9m) and 45.9 ft. (14m). Boeing 777 
airplanes are in this gate-code category.
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Discussion

    Boeing proposes adding folding wingtips to their Model 777-8 and 
777-9 airplane wings to improve aerodynamic performance and efficiency 
when the wingtips are extended into the flight-deployed position, while 
maintaining Code E gate compatibility when folded during ground 
operations. This wing-folding feature will be operable on the ground 
only. Boeing has no plan to carry fuel in the folding sections of the 
wings.
    Boeing has determined that a catastrophic event could occur if the 
777-8 and 777-9 airplane wingtips are not properly positioned and 
secured for takeoff and during flight. In service, numerous takeoff 
operations with improper airplane configurations have occurred due to 
failures of the takeoff warning systems, or inadvertent crew actions. 
For these proposed special conditions, a parallel is drawn between 
taking off with gust locks engaged and taking off with the wingtips 
folded, as either condition could result in a catastrophic event. 
Consequently, the FAA has determined that the level of safety in 
protecting a misconfigured airplane from takeoff with wingtips folded 
should be the same as taking off with the gust locks engaged. 
Therefore, condition 2 of these proposed special conditions has the 
same intent as Sec.  25.679(a)(2). Per Sec.  25.1309, the applicant 
must show that such an event is extremely improbable, must not result 
from a single failure, and that appropriate alerting must be provided 
for the crew to manage unsafe system-operating conditions. In addition, 
the applicant must ensure that the wingtips are properly secured during 
ground operations to protect ground personnel against bodily injury.
    Factors to be considered when showing compliance to these proposed 
special conditions include, but are not limited to:
     With wingtips in the folded position, the conventional 
airplane-wingtip-position lights may have reduced visibility due to the 
upward position of the wingtips, possibly impacting ground-operation 
safety. Light placement may require special consideration to retain the 
current ground-operation safety, and mitigate any adverse impact this 
light position may have on pilot visibility during night-lighting 
conditions.
     Due to upward wingtip positioning on the ground, 
significant loads may be imposed by wind gusts combined with taxi speed 
during the transition from the unfolded to the folded position.
     The FAA issued Policy Statement No. PS-ANM-25-12, 
``Certification of Structural Elements in Flight Control Systems,'' to 
address structural elements in systems that act as both structure and 
as part of a system. This policy provides additional guidance on the 
appropriate application of the fatigue and damage-tolerance 
requirements of Sec.  25.571, and the system-safety requirements of 
Sec. Sec.  25.671 and 25.1309.
    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.

Applicability

    As discussed above, these special conditions are applicable to 
Boeing Model 777-8 and 777-9 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.

    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, 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 777-8 and 777-9 
airplanes.

    Note: The term ``latch'' refers to the mechanism that allows the 
wingtip to carry flight loads in the down (flight-deployed) 
position. The term ``lock'' refers to the mechanism that prevents 
disconnection of the latch when the wing tip is down.

    1. More than one means must be available to alert the flightcrew 
that the wingtips are not properly positioned and secured prior to 
takeoff. Each of these means must be unique in their wingtip-monitoring 
function. When meeting this condition, the applicant must add a 
function to the takeoff warning system, as required by Sec.  
25.703(a)(1) and (2), to warn of an unlocked or improperly positioned 
wingtip, including indication to the flightcrew when a wingtip is in 
the folded position during taxi.
    2. In addition to a takeoff warning in accordance with Sec.  
25.703, a means must be provided to prevent airplane takeoff if a 
wingtip is not properly positioned and secured for flight.
    3. The applicant must consider the effects of folding-wingtip 
freeplay when evaluating compliance to the design load requirements of 
14 CFR subpart C, and the aeroelastic stability (including flutter, 
divergence, control reversal, and any undue loss of stability and 
control as a result of structural deformation) requirements of Sec.  
25.629. Thus, the effects of normal wear, and other long-term 
durability conditions (such as corrosion) of the folding-wingtip 
operating mechanism on freeplay, and its impact on loads and 
aeroelastic stability, must be considered. Where freeplay limitations 
are required to ensure aeroelastic stability, acceptable freeplay 
limits and freeplay check procedures must be established. If 
lubrication is required to control excessive wear, lubrication 
intervals must be established. These procedures and limitations must be 
documented in accordance with Sec.  25.1529. The freeplay-check and 
mechanism-lubrication intervals, if required, must be documented as a 
certification maintenance requirement (CMR). Guidance for CMRs can be 
found in Advisory Circular 25-19A, ``Certification Maintenance 
Requirements.'' The effects of freeplay on wing-joint torsional and 
bending stiffness, as well as wing frequencies, must be evaluated when 
showing compliance to loads and aeroelastic stability requirements. 
Also, the effects of freeplay on fatigue and damage

[[Page 50583]]

tolerance must be considered when showing compliance with Sec.  25.571.
    4. The folding wingtips and their operating mechanism must be 
designed for 65 knot, horizontal, ground-gust conditions in any 
direction as specified in Sec.  25.415(a). Relevant design conditions 
must be defined using combinations of steady wind and taxi speeds 
determined by rational analysis utilizing airport wind data. The 
folding wingtip is not a control surface as specified in Sec.  
25.415(b)(c). Therefore, in lieu of the equation provided in Sec.  
25.415(b), the hinge moment may be calculated from rational wind-tunnel 
data. The 1.25 factor specified in Sec.  25.415(d) need not be applied 
to the portion of the system that is isolated in flight and is not 
critical for safe flight and landing. The folding-wingtip system must 
be designed for the conditions specified in Sec.  25.415(e), (f), and 
(g). Runway roughness, as specified in Sec.  25.491, must be evaluated 
separately up to the maximum relevant airplane ground speeds. All of 
the above conditions must be applied to the folding wingtips in the 
extended (flight-deployed), folded, and transient positions.
    5. The airplane must demonstrate acceptable handling qualities 
during rollout in a crosswind environment, as wingtips transition from 
the flight-deployed to folded position, as well as during the unlikely 
event of asymmetric wingtip folding.
    6. The wingtip-fold operating mechanism must have stops that 
positively limit the range of motion of the wingtips. Each stop must be 
designed to the requirements of Sec.  25.675.
    7. The wingtip hinge structure must be designed for inertia loads 
acting parallel to the hinge line. In the absence of more rational 
data, the inertia loads may be assumed to be equal to KW as referenced 
in Sec.  25.393. Hinge design must meet the requirements of Sec.  
25.657.
    8. In lieu of Sec.  25.1385(b): The forward position lights must be 
installed such that they consist of a red and a green light spaced 
laterally as far apart as practicable, and installed forward on the 
airplane, so that, with the airplane in the normal flying position and 
with the wingtips in the folded position for ground operations, the red 
light is on the left side and the green light is on the right side at 
approximately the level of the wingtips in the takeoff configuration. 
Each light must be approved and must meet the requirements of Sec.  
25.1385(a) and (d). The lights must not impair the vision of the 
flightcrew when the wingtips are in the folded and transient positions.
    9. The applicant must include design features that ensure the 
wingtips are properly secured during ground operations, to protect 
ground personnel from bodily injury as well as to prevent damage to the 
airframe, ground structure, and ground support equipment.
    10. The wingtips must have means to safeguard against unlocking 
from the extended, flight-deployed position in flight, as a result of 
failures, including the failure of any single structural element. All 
sources of airplane power that could initiate unlocking of the wingtips 
must be automatically isolated from the wingtip-fold operating system 
(including the latching and locking system) prior to flight, and it 
must not be possible to restore power to the system during flight. The 
wingtip latching and locking mechanisms must be designed so that, under 
all airplane flight-load conditions, no force or torque can unlatch or 
unlock the mechanisms. The latching system must include a means to 
secure the latches in the latched position, independent of the locking 
system. It must not be possible to position the lock in the locked 
position if the latches and the latching mechanisms are not in the 
latched position, and it must not be possible to unlatch the latches 
with the locks in the locked position.

    Issued in Renton, Washington, on October 25, 2017.
Victor Wicklund,
Manager, Transport Airplane Directorate, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2017-23698 Filed 10-31-17; 8:45 am]
BILLING CODE 4910-13-P