[Federal Register Volume 77, Number 7 (Wednesday, January 11, 2012)]
[Rules and Regulations]
[Pages 1614-1618]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-360]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2010-1193; Amdt. No. 25-136]
RIN 2120-AJ80
Harmonization of Airworthiness Standards for Transport Category
Airplanes--Landing Gear Retracting Mechanisms and Pilot Compartment
View
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
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SUMMARY: The Federal Aviation Administration amends the airworthiness
standards for transport category airplanes on landing gear retracting
mechanisms and the pilot compartment view. For the landing gear
retracting mechanism, this rulemaking adopts the 1-g stall speed as a
reference stall speed instead of the minimum speed obtained in a
stalling maneuver and adds an additional requirement to keep the
landing gear and doors in the correct retracted position in flight. For
the pilot compartment view, this rulemaking revises the requirements
for pilot compartment view in precipitation conditions. This action
eliminates regulatory differences between the airworthiness standards
of the U.S. and the European Aviation Safety Agency (EASA), without
affecting current industry design practices.
DATES: Effective March 12, 2012.
ADDRESSES: For information on where to obtain copies of rulemaking
documents and other information related to this final rule, see ``How
To Obtain Additional Information'' in the SUPPLEMENTARY INFORMATION
section of this document.
FOR FURTHER INFORMATION CONTACT: For technical questions concerning
this action, contact Mahinder Wahi, Federal Aviation Administration,
Propulsion and Mechanical Systems Branch, ANM-112, Transport Airplane
Directorate, Aircraft Certification Service, 1601 Lind Avenue SW.,
Renton, WA 98057; telephone (425) 227-1262; facsimile (425) 227-1320,
email mahinder.wahi@faa.gov.
For legal questions about this proposed rule, contact Doug
Anderson, FAA, Office of the Regional Counsel (ANM-7), 1601 Lind Avenue
SW., Renton, Washington 98057; telephone (425) 227-2166; facsimile
(425) 227-1007; email Douglas.Anderson@faa.gov.
SUPPLEMENTARY INFORMATION:
Authority for This Rulemaking
The FAA's authority to issue rules on aviation safety is found in
Title 49 of the United States Code. Subtitle I, Section 106 describes
the authority of the FAA Administrator. Subtitle VII, Aviation
Programs, describes in more detail the scope of the agency's authority.
This rulemaking is promulgated under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701, ``General
requirements.'' Under that section, the FAA is charged with promoting
safe flight of civil aircraft in air commerce by prescribing
regulations and minimum standards for the design and performance of
aircraft that the Administrator finds necessary for safety in air
commerce. This regulation is within the scope of that authority. It
prescribes new safety standards for the design and operation of
transport category airplanes.
List of Abbreviations Frequently Used in This Document
Term Definition
VS the stalling speed or the minimum steady flight speed
at which the airplane is controllable.
VS1 the stalling speed or the minimum steady flight speed
obtained in a specific configuration.
VSR reference stall speed and may not be less than a 1-g
stall speed.
VSR1 reference stall speed in a specific configuration.
1-g stall speed minimum speed at which the airplane can develop the
usable maximum lift force capable of supporting the weight of the
airplane.
List of Acronyms Frequently Used in This Document
ALPA Airline Pilots Association
ANAC Ag[ecirc]ncia Nacional de Avia[ccedil][atilde]o Civil
ARAC Aviation Rulemaking Advisory Committee
EASA European Aviation Safety Agency
FAA Federal Aviation Administration
ICAO International Civil Aviation Organization
JAA European Joint Aviation Authorities
NPRM Notice of Proposed Rulemaking
RFA Regulatory Flexibility Act
SBREFA Small Business Regulatory Enforcement Fairness Act
I. Overview of Final Rule
This action harmonizes airworthiness certification standards for
landing gear mechanisms and pilot compartment view for transport
category airplanes with those of EASA. Harmonizing these airworthiness
standards reduces costs to airplane manufacturers and operators while
retaining the level of safety.
II. Background
A. Statement of the Problem
This rulemaking results from an agreement between the European
Joint Aviation Authorities (JAA), the predecessor to EASA, and the FAA
to harmonize certain airworthiness standards between the two
authorities. Differences between the regulations of the FAA and foreign
certification authorities increase the cost and complexity of
certification without contributing significantly to safety. These rules
result from the recommendations of the Aviation Rulemaking Advisory
Committee, through its Mechanical Systems Harmonization Working Group
(MSHWG).
B. Summary of the NPRM
The FAA published a notice of proposed rulemaking (NPRM), Docket
No. FAA-2010-1193; Notice No. 10-19 in the Federal Register on January
5, 2011 (76 FR 472). The NPRM proposed to amend the standards for
landing gear retraction mechanism and pilot compartment view to
harmonize with the corresponding EASA standards. The proposed standards
for landing gear addressed reference stall speed, positive means to
keep the landing gear and doors in the correct retracted position, gear
position indication, and protection of equipment on the landing gear
and in the wheel well. The proposed standards for pilot compartment
view addressed single failures of rain removal systems, alternatives to
the openable side window requirement and certain environmental
conditions.
The comment period for the NPRM ended on April 5, 2011.
C. General Overview of Comments
The FAA received comments from Airbus, Boeing Company, Bombardier,
Cessna Aircraft Company, Embraer,
[[Page 1615]]
Hawker Beechcraft, Transport Canada, and Air Line Pilots Association,
International (ALPA). ALPA, Airbus, Bombardier, and Cessna provided
general comments in support of the proposed changes.
Embraer correctly noted that a proposed text change to Sec.
25.729(a)(3) was unnecessary since EASA had already adopted the current
FAA standard. The proposed change to Sec. 25.729(a)(3) is therefore
withdrawn. Boeing, Transport Canada, and Hawker Beechcraft proposed
changes to the regulatory text. Embraer requested that the FAA wait for
the final rule issuance of NPRM 10-10, Airplane and Engine
Certification Requirements in Supercooled Large Drop, Mixed Phase, and
Ice Crystal Icing Conditions (75 FR 37311, June 29, 2010) (Docket No.
FAA-2010-0636) before issuing this final rule. Boeing, Transport Canada
and Bombardier noted editorial errors which have been corrected.
D. Associated Advisory Circular Guidance Material
Advisory Circular AC 25.729-1 has been revised to incorporate
acceptable means of compliance to the amended requirements of this
rulemaking action. A draft of this AC was made available for public
comment during the comment period of the NPRM. The FAA received
comments on the AC from the Brazilian Civil Aviation Authority
(Ag[ecirc]ncia Nacional de Avia[ccedil][atilde]o Civil--ANAC),
Transport Canada, Boeing Company, and Embraer. The disposition of the
AC public comments is posted along with the final version of the AC on
the FAA Regulatory and Guidance Library Web site (http://rgl.faa.gov/).
III. Discussion of Public Comments and Final Rule
A. Effect of Flightcrew Alerting Rule
Boeing recommended the proposed rule for landing gear position
indication be revised to be consistent with the new flightcrew alerting
rule, Sec. 25.1322. Boeing's rationale is that the proposed wording of
Sec. 25.729(e) in the NPRM is inconsistent with retractable landing
gear and associated door indication systems on existing FAA type
certificated and recent EASA validated airplanes. Boeing also stated
the proposed wording and the associated AC guidance material are
inconsistent with the quiet and dark flight deck philosophy used on
modern airplanes.
The proposed wording would have required ``a clear indication or
warning must be provided whenever the landing gear position is not
consistent with the landing gear selector lever position.'' In some
situations, an advisory or caution message would be appropriate, not a
warning message. Boeing requested a change to make warning, caution,
and advisory messages compliant with Sec. 25.1322 and provide
information to the flight crew if the gear or doors are not in the
commanded position or are in a hazardous configuration. Boeing also
recommended deleting Sec. 25.729(e)(7) and rewording paragraph (e) to
reference Sec. 25.1322 for alerting.
We agree the specification to provide a ``warning'' as in the
proposed Sec. 25.729(e)(7) is not consistent with the Sec. 25.1322 at
the current amendment level. ARAC recommended and EASA adopted the
proposed wording prior to the development of the current Sec. 25.1322
requirements. The intent of the wording recommended by ARAC was
consistent with the definition of the term ``flightcrew alert'' in the
current Sec. 25.1322. We replaced the wording ``clear indication or
warning'' with ``flightcrew alert'' to be consistent with Sec.
25.1322. This also addresses the Boeing comment associated with the
quiet and dark flightdeck concept. It is not necessary to specifically
refer to Sec. 25.1322 in the rule text, as the current version of
Sec. 25.1322 will be in the certification basis for new type designs
and new significant changes to type design (as determined per 14 CFR
Sec. 21.101).
Boeing also noted the regulation does not address other landing
gear actuation functions, such as a landing gear lever lock or truck
tilt message to prevent retraction or the hazards associated with
retracting an out of configuration gear, or the necessary indication
for hazards associated with semi-lever gears or tail skid actuation.
The FAA considers that Sec. Sec. 25.1301, 25.1309 and 25.1322
adequately address identification and alerting of these hazards and
provide the applicant the greatest flexibility in the use of such
functions. No change to the rule will be made in this regard.
B. Wheel Brake Temperature
Hawker Beechcraft stated the proposed wording for Sec.
25.729(f)(3), ``possible wheel brake temperatures,'' is not specific
enough. Hawker Beechcraft recommends changing the text to ``excessive
wheel brake temperatures,'' or ``wheel brakes overheating.'' We note
that because Sec. 25.729(f) refers to the ``damaging effects of'' the
temperatures, we believe it is clear the regulation refers to high
``possible'' temperatures. No changes were made to the rule in response
to this comment.
C. Landing Gear Lock
Transport Canada concurs with the new requirement for a positive
means to keep the landing gear and doors in the correct retracted
position in flight, and would like a similar requirement for a
downlock. As proposed, Sec. 25.729(b) is a performance-based rule that
requires positive means to keep the landing gear extended in flight and
on the ground. Adding specificity to require a downlock, limits design
options that would otherwise meet the intent of the rule without
increasing the level of safety. No change to the rule was made in this
regard.
D. Supercooled Large Drop Rulemaking
Embraer suggested the FAA publish the final rule associated with
NPRM Notice No. 10-10, previously referenced on page 5, before
proceeding with proposed changes to Sec. 25.773(b) in this rulemaking
since the NPRM proposed to change Sec. 25.773(b)(1). This rulemaking
includes changes to Sec. 25.773(b)(2) and additionally to Sec.
25.773(b)(3) and (4), but proposed no changes to Sec. 25.773(b)(1).
Since these rulemaking changes are independent of those proposed in the
Supercooled Large Drop NPRM, the FAA does not plan to wait on
publishing this rule.
E. Lightning as a Discrete Damage Source for Pilot Compartment View
Transport Canada requested we add lightning to the list of discrete
damage sources presented in Sec. 25.773(b)(4)(ii). The FAA is not
aware of any data that indicates lightning has resulted in the
reduction of pilot compartment view, therefore changing the regulatory
text is unnecessary.
F. Differences Between the NPRM and the Final Rule
Except for the editorial correction in the rule title for Sec.
25.729, the withdrawal of proposed text change to Sec. 25.729(a)(3),
and the change in amendatory language found in Sec. 25.729(e)(7) from
``A clear indication or warning'' to ``A flightcrew alert,'' the
changes to Sec. Sec. 25.729 and 25.773 are adopted as proposed.
IV. Regulatory Notices and Analyses
A. Regulatory Evaluation
Changes to Federal regulations must undergo several economic
analyses. First, Executive Order 12866 and Executive Order 13563 direct
that each Federal agency shall propose or adopt a regulation only upon
a reasoned determination that the benefits of the intended regulation
justify its costs. Second, the Regulatory Flexibility Act
[[Page 1616]]
of 1980 (Pub. L. 96-354) requires agencies to analyze the economic
impact of regulatory changes on small entities. Third, the Trade
Agreements Act (Pub. L. 96-39) prohibits agencies from setting
standards that create unnecessary obstacles to the foreign commerce of
the United States. In developing U.S. standards, this Trade Act
requires agencies to consider international standards and, where
appropriate, that they be the basis of U.S. standards. Fourth, the
Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4) requires agencies
to prepare a written assessment of the costs, benefits, and other
effects of proposed or final rules that include a Federal mandate
likely to result in the expenditure by State, local, or tribal
governments, in the aggregate, or by the private sector, of $100
million or more annually (adjusted for inflation with base year of
1995). This portion of the preamble summarizes the FAA's analysis of
the economic impact of the final rule.
Department of Transportation Order DOT 2100.5 prescribes policies
and procedures for simplification, analysis, and review of regulations.
If the expected cost impact is so minimal that a proposed or final rule
does not warrant a full evaluation, this order permits that a statement
to that effect and the basis for it be included in the preamble if a
full regulatory evaluation of the costs and benefits is not prepared.
Such a determination has been made for this final rule.
The reasoning for this determination follows: The final rule will
amend the airworthiness standards for transport category airplanes for
landing gear retracting mechanisms and pilot compartment view to
harmonize with existing, more stringent European Aviation Safety Agency
(EASA) requirements. For landing gear retracting mechanisms, the more
stringent EASA requirements ensure (1) The landing gear is in the
appropriate configuration; (2) the landing gear and its supporting
structure, doors, and mechanisms operate properly; (3) the flight crew
is aware of the landing gear position status; and (4) critical
equipment is protected from tire failure or excessive brake
temperatures.
For the pilot compartment view, reliable and safe operation during
precipitation is ensured by adoption of the EASA design requirements
for flight deck rain removal systems because there will be no single
failure of the rain removal system that could lead to a loss of pilot
view through both windshields. The effect of this requirement is that,
for newly certificated airplanes, manufacturers must provide a
separate, mechanically and electrically independent method for clearing
the windshield during precipitation. This method may include separate
flight deck control switches for left and right windshield wipers. The
FAA has determined that installation of the second wiper switch will
require minimal additional costs when the system is initially designed
to comply with the EASA requirement and received no comments regarding
this estimate.
A review of current practices of U.S. manufacturers of transport
category airplanes has revealed that only a minority of manufacturers
are not already in compliance with the EASA requirements. For these
manufacturers, the FAA has determined that additional costs to comply
with the EASA requirements will be minimal and that there will be
additional safety benefits from adoption of the more stringent EASA
requirements. For the majority of manufacturers already in compliance
with the EASA requirements as a means of obtaining joint certification,
there will be no additional compliance costs or additional safety
benefits. We received no comments regarding this cost estimate.
However, the final rule will provide benefits from reduced joint
certification costs--in the requirements for data collection and
analysis, paperwork, and time spent applying for and obtaining approval
from the regulatory authorities. The FAA therefore has determined that
this final rule will have minimal costs and positive net benefits and
does not warrant a full regulatory evaluation.
The FAA has also determined that this final rule is not a
``significant regulatory action'' as defined in section 3(f) of
Executive Order 12866, and is not ``significant'' as defined in DOT's
Regulatory Policies and Procedures.
B. Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980 (Pub. L. 96-354) (RFA)
establishes ``as a principle of regulatory issuance that agencies shall
endeavor, consistent with the objectives of the rule and of applicable
statutes, to fit regulatory and informational requirements to the scale
of the businesses, organizations, and governmental jurisdictions
subject to regulation. To achieve this principle, agencies are required
to solicit and consider flexible regulatory proposals and to explain
the rationale for their actions to assure that such proposals are given
serious consideration.'' The RFA covers a wide-range of small entities,
including small businesses, not-for-profit organizations, and small
governmental jurisdictions.
Agencies must perform a review to determine whether a rule will
have a significant economic impact on a substantial number of small
entities. If the agency determines that it would, the agency must
prepare a regulatory flexibility analysis as described in the RFA.
However, if an agency determines that a rule is not expected to have a
significant economic impact on a substantial number of small entities,
section 605(b) of the RFA provides that the head of the agency may so
certify and a regulatory flexibility analysis is not required. The
certification must include a statement providing the factual basis for
this determination, and the reasoning should be clear.
As noted above, this final rule will impose no or little additional
costs on part 25 manufacturers. Moreover, all U.S. manufacturers of
transport category airplanes exceed the Small Business Administration
small-entity criteria of 1,500 employees. Therefore, the FAA certifies
that this final rule will not have a significant economic impact on a
substantial number of small entities.
C. International Trade Impact Assessment
The Trade Agreements Act of 1979 (Pub. L. 96-39), as amended by the
Uruguay Round Agreements Act (Pub. L. 103-465), prohibits Federal
agencies from establishing standards or engaging in related activities
that create unnecessary obstacles to the foreign commerce of the United
States. Pursuant to these Acts, the establishment of standards is not
considered an unnecessary obstacle to the foreign commerce of the
United States, so long as the standard has a legitimate domestic
objective, such the protection of safety, and does not operate in a
manner that excludes imports that meet this objective. The statute also
requires consideration of international standards and, where
appropriate, that they be the basis for U.S. standards. The FAA has
assessed the potential effect of this final rule and determined that it
will promote international trade by harmonizing U.S. standards with
corresponding EASA regulations thus reducing the cost of joint
certification.
D. Unfunded Mandates Assessment
Title II of the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-
4) requires each Federal agency to prepare a written statement
assessing the effects of any Federal mandate in a proposed or final
agency rule that may result in an expenditure of $100 million or more
(adjusted annually for inflation with the base year 1995) in any one
year by State,
[[Page 1617]]
local, and tribal governments, in the aggregate, or by the private
sector; such a mandate is deemed to be a ``significant regulatory
action.'' The FAA currently uses an inflation-adjusted value of $141.3
million.
This final rule does not contain such a mandate. The requirements
of Title II do not apply.
E. Paperwork Reduction Act
The Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)) requires
that the FAA consider the impact of paperwork and other information
collection burdens imposed on the public. The FAA has determined that
there is no new requirement for information collection associated with
this final rule.
F. International Compatibility
In keeping with U.S. obligations under the Convention on
International Civil Aviation, it is FAA policy to conform to
International Civil Aviation Organization (ICAO) Standards and
Recommended Practices to the maximum extent practicable. The FAA has
determined that there are no ICAO Standards and Recommended Practices
that correspond to these regulations.
G. Environmental Analysis
FAA Order 1050.1E identifies FAA actions that are categorically
excluded from preparation of an environmental assessment or
environmental impact statement under the National Environmental Policy
Act in the absence of extraordinary circumstances. The FAA has
determined this rulemaking action qualifies for the categorical
exclusion identified in paragraph 312d and involves no extraordinary
circumstances.
H. Regulations Affecting Intrastate Aviation in Alaska
Section 1205 of the FAA Reauthorization Act of 1996 (110 Stat.
3213) requires the FAA, when modifying its regulations in a manner
affecting intrastate aviation in Alaska, to consider the extent to
which Alaska is not served by transportation modes other than aviation,
and to establish appropriate regulatory distinctions. In the NPRM, the
FAA requested comments on whether the proposed rule should apply
differently to intrastate operations in Alaska. The agency did not
receive any comments, and has determined, based on the administrative
record of this rulemaking, that there is no need to make any regulatory
distinctions applicable to intrastate aviation in Alaska.
V. Executive Order Determinations
A. Executive Order 13132, Federalism
The FAA has analyzed this final rule under the principles and
criteria of Executive Order 13132, Federalism. The agency determined
that this action will not have a substantial direct effect on the
States, or the relationship between the Federal Government and the
States, or on the distribution of power and responsibilities among the
various levels of government, and, therefore, does not have Federalism
implications.
B. Executive Order 13211, Regulations That Significantly Affect Energy
Supply, Distribution, or Use
The FAA analyzed this final rule under Executive Order 13211,
Actions Concerning Regulations that Significantly Affect Energy Supply,
Distribution, or Use (May 18, 2001). The agency has determined that it
is not a ``significant energy action'' under the executive order and it
is not likely to have a significant adverse effect on the supply,
distribution, or use of energy.
VI. How To Obtain Additional Information
A. Rulemaking Documents
An electronic copy of a rulemaking document may be obtained by
using the Internet:
1. Search the Federal eRulemaking Portal (http://www.regulations.gov);
2. Visit the FAA's Regulations and Policies Web page at http://www.faa.gov/regulations_policies/ or
3. Access the Government Printing Office's Web page at http://www.fdsys.gov.
Copies may also be obtained by sending a request (identified by
notice, amendment, or docket number of this rulemaking) to the Federal
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence
Avenue SW., Washington, DC 20591, or by calling (202) 267-9680.
B. Comments Submitted to the Docket
Comments received may be viewed by going to http://www.regulations.gov and following the online instructions to search the
docket number for this action. Anyone is able to search the electronic
form of all comments received into any of the FAA's dockets by the name
of the individual submitting the comment (or signing the comment, if
submitted on behalf of an association, business, labor union, etc.).
C. Small Business Regulatory Enforcement Fairness Act
The Small Business Regulatory Enforcement Fairness Act (SBREFA) of
1996 requires FAA to comply with small entity requests for information
or advice about compliance with statutes and regulations within its
jurisdiction. A small entity with questions regarding this document,
may contact its local FAA official, or the person listed under the FOR
FURTHER INFORMATION CONTACT heading at the beginning of the preamble.
To find out more about SBREFA on the Internet, visit http://www.faa.gov/regulations_policies/rulemaking/sbre_act/.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety.
The Amendment
In consideration of the foregoing, the Federal Aviation
Administration amends part 25 of title 14, Code of Federal Regulations,
as follows:
PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
0
1. The authority citation for part 25 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701-44702, and 44704.
0
2. Amend Sec. 25.729 by revising paragraphs (a)(1)(ii) and (iii), (b),
(e) introductory text, and (e)(5), adding paragraph (e)(7), revising
paragraphs (f) introductory text and (f)(1), and adding paragraph
(f)(3) to read as follows:
Sec. 25.729 Retracting mechanism.
(a) * * *
(1) * * *
(ii) The combination of friction loads, inertia loads, brake torque
loads, air loads, and gyroscopic loads resulting from the wheels
rotating at a peripheral speed equal to 1.23VSR (with the
wing-flaps in take-off position at design take-off weight), occurring
during retraction and extension at any airspeed up to 1.5
VSR1 (with the wing-flaps in the approach position at design
landing weight), and
(iii) Any load factor up to those specified in Sec. 25.345(a) for
the wing-flaps extended condition.
* * * * *
(b) Landing gear lock. There must be positive means to keep the
landing gear extended in flight and on the ground. There must be
positive means to keep the landing gear and doors in the correct
retracted position in flight, unless it can be shown that lowering of
the landing gear or doors, or flight with the landing gear or doors
extended, at any speed, is not hazardous.
* * * * *
(e) Position indicator and warning device. If a retractable landing
gear is
[[Page 1618]]
used, there must be a landing gear position indicator easily visible to
the pilot or to the appropriate crew members (as well as necessary
devices to actuate the indicator) to indicate without ambiguity that
the retractable units and their associated doors are secured in the
extended (or retracted) position. The means must be designed as
follows:
* * * * *
(5) The system used to generate the aural warning must be designed
to minimize false or inappropriate alerts.
* * * * *
(7) A flightcrew alert must be provided whenever the landing gear
position is not consistent with the landing gear selector lever
position.
(f) Protection of equipment on landing gear and in wheel wells.
Equipment that is essential to the safe operation of the airplane and
that is located on the landing gear and in wheel wells must be
protected from the damaging effects of--
(1) A bursting tire;
* * * * *
(3) Possible wheel brake temperatures.
0
3. Amend Sec. 25.773 by revising paragraph (b)(2) and adding
paragraphs (b)(3) and (4) to read as follows:
Sec. 25.773 Pilot compartment view.
* * * * *
(b) * * *
(2) No single failure of the systems used to provide the view
required by paragraph (b)(1) of this section must cause the loss of
that view by both pilots in the specified precipitation conditions.
(3) The first pilot must have a window that--
(i) Is openable under the conditions prescribed in paragraph (b)(1)
of this section when the cabin is not pressurized;
(ii) Provides the view specified in paragraph (b)(1) of this
section; and
(iii) Provides sufficient protection from the elements against
impairment of the pilot's vision.
(4) The openable window specified in paragraph (b)(3) of this
section need not be provided if it is shown that an area of the
transparent surface will remain clear sufficient for at least one pilot
to land the airplane safely in the event of--
(i) Any system failure or combination of failures which is not
extremely improbable, in accordance with Sec. 25.1309, under the
precipitation conditions specified in paragraph (b)(1) of this section.
(ii) An encounter with severe hail, birds, or insects.
* * * * *
Issued in Washington, DC, on December 27, 2011.
Michael P. Huerta,
Acting Administrator.
[FR Doc. 2012-360 Filed 1-10-12; 8:45 am]
BILLING CODE 4910-13-P