[Federal Register Volume 61, Number 17 (Thursday, January 25, 1996)]
[Proposed Rules]
[Pages 2147-2151]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-1170]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 95-NM-146-AD]
Airworthiness Directives; Aerospatiale Model ATR-42 and ATR-72
Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Supplemental notice of proposed rulemaking; reopening of
comment period.
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SUMMARY: This document revises an earlier proposed airworthiness
directive (AD) that is applicable to all Aerospatiale Model ATR-42 and
ATR-72 series airplanes. That proposal would have superseded an
existing AD to prohibit operation of the airplane in certain icing
conditions unless modifications are accomplished or alternative
procedures and training are adopted, and to require restrictions on
[[Page 2148]]
the use of the autopilot in certain conditions. That proposal also
would have added requirements for modification of the deicing boots on
the leading edge of the wing and various follow-on actions. That
proposal was prompted by an FAA determination that, during flight in
certain icing conditions, and with the airplane in a specific flight
configuration, a ridge of ice can form on the wing and cause an
interruption in the airflow over the ailerons, aileron deflection, and
resultant lateral control forces. This action revises the originally
proposed rule by removing certain limitations and procedures. The
actions specified by this proposed AD are intended to prevent a roll
upset from which the flight crew may be unable to recover.
DATES: Comments must be received by March 7, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 95-NM-146-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056. Comments may be inspected at this
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except
Federal holidays.
The service information referenced in the proposed rule may be
obtained from Aerospatiale, 316 Route de Bayonne, 31060 Toulouse, Cedex
03, France. This information may be examined at the FAA, Transport
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.
FOR FURTHER INFORMATION CONTACT: Gary Lium, Aerospace Engineer,
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate,
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206)
227-1112; fax (206) 227-1149.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the
proposed rule by submitting such written data, views, or arguments as
they may desire. Communications shall identify the Rules Docket number
and be submitted in triplicate to the address specified above. All
communications received on or before the closing date for comments,
specified above, will be considered before taking action on the
proposed rule. The proposals contained in this notice may be changed in
light of the comments received.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the proposed rule. All
comments submitted will be available, both before and after the closing
date for comments, in the Rules Docket for examination by interested
persons. A report summarizing each FAA-public contact concerned with
the substance of this proposal will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 95-NM-146-AD.'' The postcard will be date stamped and
returned to the commenter.
Availability of NPRMs -
Any person may obtain a copy of this NPRM by submitting a request
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules
Docket No. 95-NM-146-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion -
A proposal to amend part 39 of the Federal Aviation Regulations (14
CFR part 39) to add an airworthiness directive (AD), applicable to all
Aerospatiale Model ATR-42 and ATR-72 series airplanes, was published as
a notice of proposed rulemaking (NPRM) in the Federal Register on
October 18, 1995 (60 FR 53883). That NPRM would have superseded an
existing AD to prohibit operation of the airplane in certain icing
conditions unless modifications are accomplished or alternative
procedures and training are adopted, and to require restrictions on the
use of the autopilot in certain conditions. That proposal also would
have added requirements for modification of the deicing boots on the
leading edge of the wing and various follow-on actions. That NPRM was
prompted by an FAA determination that, during flight in certain icing
conditions, and with the airplane in a specific flight configuration, a
ridge of ice can form on the wing and cause an interruption in the
airflow over the ailerons, aileron deflection, and resultant lateral
control forces. That condition, if not corrected, could result in a
roll upset from which the flight crew may be unable to recover.
Further Examination of Atmospheric Conditions -
Since the issuance of that NPRM, the FAA has further examined the
atmospheric conditions that may have contributed to an accident
involving a Model ATR-72 series airplane that encountered severe icing
conditions (believed to be composed of freezing drizzle size droplets)
while the airplane was enroute from Indianapolis to Chicago. Those
atmospheric conditions (freezing drizzle) are outside the icing
envelope specified in Appendix C of part 25 of the Federal Aviation
Regulations (14 CFR part 25) for certification of the airplane.
Freezing rain is an atmospheric condition that also is outside the
icing envelope. Such icing conditions are not defined in Appendix C,
and the FAA has not required that airplanes be shown to be capable of
operating safely in those icing conditions.
Information Currently Provided to Flight Crews -
The FAA finds that, in general, flight crews are not currently
provided with adequate information necessary to determine when the
airplane is operating in icing conditions for which the airplane is not
certificated or what action to take when such conditions are
encountered. Therefore, the FAA has determined that flight crews must
be provided with such information and must be made aware of certain
visual cues that may indicate the airplane is operating in atmospheric
conditions that are outside the icing envelope.
Effect of Unsafe Condition on Other Airplanes -
Since such information is not available to flight crews, and no
airplane is certificated for operation in freezing drizzle conditions,
the FAA finds that the potentially unsafe condition (described
previously as control difficulties following operation of the airplane
in icing conditions outside of the icing envelope) is not limited to
airplanes having the same type design as that of the accident airplane.
-
The FAA recognizes that the flight crew of any airplane that is
certificated for flight in icing conditions may not have adequate
information concerning flight in icing conditions outside the icing
envelope. However, the FAA finds that the specified unsafe condition
must be addressed as a higher priority on airplanes that are
turbopropellerpowered and have unpowered control systems. Many of these
airplanes carry passengers in regularly scheduled revenue service in
the United States. Since turbopropellerpowered airplanes are more
likely to operate at low altitudes and to make more frequent landings,
they are more likely to encounter icing conditions that are outside the
icing envelope. Additionally, the flight crew of an airplane having an
unpowered roll
[[Page 2149]]
control system must rely solely on physical strength to counteract roll
control anomalies, whereas a roll control anomaly that occurs on an
airplane having a powered roll control system need not be offset
directly by the flight crew.
Review of Other Turbopropeller-Powered Airplanes -
Subsequent to the accident, the FAA, in conjunction with certain
foreign airworthiness authorities and airplane manufacturers, conducted
reviews of certain transport and small category airplanes to determine
if any airplanes might experience control difficulty should a ridge of
ice form aft of the deicing boots and forward of the ailerons. The
review focused on turbopropeller-powered airplanes having unpowered
roll control systems, since those airplanes are similar in design to
the accident airplane and because they are frequently exposed to icing
conditions. -
During the reviews of these airplanes, an artificial ice shape was
used in the demonstration of roll control characteristics. This ice
shape was chosen as representative of a shape that might form if an
airplane were operated in freezing drizzle. Results of these reviews
revealed that certain airplanes demonstrated acceptable roll control
forces. However, the dynamics of ice accretion in freezing drizzle are
not well understood, and the FAA recognizes that such airplanes could
develop ice shapes other than those tested during the review. Upon
further review, the FAA may consider additional rulemaking.
Relevant Service Information Issued -
Aerospatiale has issued Service Bulletins ATR42-57-0043, ATR72-57-
1015, and ATR-72-57-1016, all dated April 10, 1995. These service
bulletins describe procedures for modification of the deicing boots on
the outer leading edges of the wing. The modification entails replacing
the existing leading edges with leading edges having wider deicers.
Accomplishment of this modification will provide increased protection
against severe icing conditions by increasing the effective area of the
deicing boots.
Conclusion -
Following examination of all relevant information, the FAA has
determined that certain procedures and requirements specified in the
original NPRM for Model ATR-42 and ATR-72 series airplanes are
unnecessary. Further, the FAA finds that the limitations and procedures
listed below adequately address the unsafe condition associated with
inadvertent flight into freezing rain or freezing drizzle: -
Aerospatiale Model ATR-42 and ATR-72 series airplanes must
be prohibited from flight in freezing rain or freezing drizzle
conditions (as determined by certain visual cues); and
flight crews must be provided with information that would
minimize the potential hazards associated with operating the airplane
in freezing rain or freezing drizzle conditions.
The FAA has determined that such limitations and procedures currently
are not defined adequately in the AFM for these airplanes. These same
limitations and procedures are the subject of additional rulemaking
actions that affect several other turbopropeller-powered airplanes.
This airplane model is manufactured in France and is type
certificated for operation in the United States under the provisions of
section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and
the applicable bilateral airworthiness agreement.
Explanation of the Provisions of this Proposed AD -
Since an unsafe condition has been identified that is likely to
exist or develop on other airplanes of the same type design, the
proposed AD would require revising the Limitations Section of the AFM
to specify procedures that would: -
Prohibit flight in freezing rain or freezing drizzle
conditions (as determined by certain visual cues); -
Prohibit use of the autopilot when ice is formed aft of
the protected surfaces of the wing, or when an unusual lateral trim
condition exists; -
Require that all icing detection lights be operative prior
to flight into icing conditions at night; and -
Require that the ice detector be operative for flight into
icing conditions. -
The prohibition on flight in freezing rain or freezing drizzle is
not intended to prohibit purely inadvertent encounters with the
specified atmospheric conditions. However, pilots should make all
reasonable efforts to avoid such encounters and must immediately exit
the conditions if they are encountered. -
This proposed AD also would require revising the Normal Procedures
Section of the AFM to specify procedures that would: -
Limit the use of the flaps and prohibit the use of the
autopilot when ice is observed forming aft of the protected surfaces of
the wing, or if unusual lateral trim requirements or autopilot trim
warnings are encountered; and -
Provide the flight crew with recognition cues for, and
procedures for exiting from, severe icing conditions. -
This proposed AD also would require modification of the deicing
boots on the outer leading edges of the wing. -
Since these changes revise the scope of the originally proposed
rule, the FAA has determined that it is necessary to reopen the comment
period to provide additional opportunity for public comment.
Cost Impact -
The FAA estimates that 158 airplanes of U.S. registry would be
affected by this proposed AD, that it would take approximately 1 work
hour per airplane to accomplish the proposed actions, and that the
average labor rate is $60 per work hour. Based on these figures, the
cost impact of the proposed AD on U.S. operators is estimated to be
$9,480, or $60 per airplane. -
For Model ATR-42 series airplanes, Modification 4216 (or 4222), as
proposed in this AD, would take approximately 52 work hours per
airplane to accomplish, at an average labor rate of $60 per work hour.
Required parts would be supplied by the manufacturer at no cost to
operators. Based on these figures, the cost impact on U.S. operators
for this proposed modification is estimated to be $492,960, or $3,120
per airplane. -
For Model ATR-72 series airplanes, Modification 4215 (or 4221), as
proposed in this AD, would take approximately 96 work hours per
airplane to accomplish. Required parts for this modification would be
supplied by the manufacturer at no cost to operators. Modification
4213, as proposed in this AD, would take approximately 4 work hours to
accomplish. Required parts would cost approximately $200 per airplane.
The average labor rate for accomplishment of both modifications is $60
per work hour. Based on these figures, the cost impact on U.S.
operators for these proposed modifications is estimated to be $979,600,
or $6,200 per airplane. -
The cost impact figure discussed above is based on assumptions that
no operator has yet accomplished any of the proposed requirements of
this AD action, and that no operator would accomplish those actions in
the future if this AD were not adopted. -
In addition, the FAA recognizes that this proposed AD may impose
operational costs. However, those costs are incalculable because the
frequency of occurrence of the specified conditions and the associated
additional
[[Page 2150]]
flight time are indeterminable. Nevertheless, because of the severity
of the unsafe condition addressed, the FAA has determined that
continued operational safety necessitates the imposition of these
costs.
Regulatory Impact
The regulations proposed herein would not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment.
-For the reasons discussed above, I certify that this proposed
regulation (1) is not a ``significant regulatory action'' under
Executive Order 12866; (2) is not a ``significant rule'' under the DOT
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);
and (3) if promulgated, will not have a significant economic impact,
positive or negative, on a substantial number of small entities under
the criteria of the Regulatory Flexibility Act. A copy of the draft
regulatory evaluation prepared for this action is contained in the
Rules Docket. A copy of it may be obtained by contacting the Rules
Docket at the location provided under the caption ``ADDRESSES.''
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration proposes to amend
part 39 of the Federal Aviation Regulations (14 CFR part 39) as
follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 USC 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Aerospatiale: Docket 95-NM-146-AD.
Applicability: All Model ATR-42 and ATR-72 series airplanes,
certificated in any category.
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
modified, altered, or repaired in the area subject to the
requirements of this AD. For airplanes that have been modified,
altered, or repaired so that the performance of the requirements of
this AD is affected, the owner/operator must use the authority
provided in paragraph (d) of this AD to request approval from the
FAA. This approval may address either no action, if the current
configuration eliminates the unsafe condition; or different actions
necessary to address the unsafe condition described in this AD. Such
a request should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any airplane from the applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To minimize the potential hazards associated with operating the
airplane in freezing rain or freezing drizzle icing conditions,
accomplish the following:
-(a) Within 30 days after the effective date of this AD,
accomplish the requirements of paragraphs (a)(1) and (a)(2) of this
AD.
Note 2: Operators must initiate action to notify and ensure that
flight crewmembers are apprised of this change.
(1) Revise the FAA-approved Airplane Flight Manual (AFM) by
incorporating the following into the Limitations Section of the AFM.
This may be accomplished by inserting a copy of this AD in the AFM.
`` Flight in meteorological conditions described as
freezing rain or freezing drizzle, as determined by the following
visual cue, is prohibited:
Freezing rain and freezing drizzle are characterized by ice
covering all or a substantial part of the unheated portion of either
forward side window, possibly associated with water splashing and
streaming on the windshield.
The following also may be used as secondary indications of
possible freezing rain/freezing drizzle conditions:
--Unusually extensive ice accreted on the airframe in areas not
normally observed to collect ice.
--Accumulation of ice on the upper or lower surface of the wing aft
of the protected area.
--Accumulation of ice on the propeller spinner farther back than
normally observed.
If the airplane encounters conditions that are determined to
contain freezing rain or freezing drizzle, the pilot must
immediately exit the freezing rain or freezing drizzle conditions by
changing altitude or course.
Note: The prohibition on flight in freezing rain or freezing
drizzle is not intended to prohibit purely inadvertent encounters
with the specified meteorological conditions. However, pilots should
make all reasonable efforts to avoid such encounters and must
immediately exit the conditions if they are encountered.
Use of the autopilot is prohibited when any ice is
observed forming aft of the protected surfaces of the wing, when
unusual lateral trim requirements or autopilot trim warnings are
encountered, or when the side window visual cue described in the
Limitations Section of the AFM is observed.
Note: The autopilot may mask tactile cues that indicate adverse
changes in handling characteristics. Therefore, the pilot should
consider not using the autopilot when any ice is visible on the
airplane.
All icing detection lights must be operative prior to
flight into icing conditions at night. [Note: This supersedes any
relief provided by the Master Minimum Equipment List (MMEL).]
The ice detector must be operative for flight into
icing conditions.
(2) Revise the FAA-approved AFM by incorporating the following
into the Normal Procedures Section of the AFM. This may be
accomplished by inserting a copy of this AD in the AFM.
``WARNING
``If ice is observed forming aft of the protected surfaces of
the wing, if unusual lateral trim requirements or autopilot trim
warnings are encountered, or if the side window visual cue described
in the Limitations Section of the AFM is observed:
If the flaps are extended, do not retract them until
the airframe is clear of ice.
The flight crew should reduce the angle-of-attack by
increasing speed as much as the airplane configuration and weather
allow, without exceeding design maneuvering speed.
If the autopilot is engaged, hold the control wheel
firmly and disengage the autopilot. Do not re-engage the autopilot
until the airframe is clear of ice.
Exit the icing area immediately by changing altitude or
course.
Report these weather conditions to Air Traffic Control.
CAUTION
Severe icing comprises environmental conditions outside of those
for which the airplane is certificated. Flight in freezing rain,
freezing drizzle, or mixed icing conditions (supercooled liquid
water and ice crystals) may result in extreme ice build-up on
protected surfaces exceeding the capability of the ice protection
system, or may result in ice forming aft of the protected surfaces.
This ice may not be shed using the ice protection systems, and may
seriously degrade the performance and controllability of the
airplane.
THE FOLLOWING SHALL BE USED TO IDENTIFY FREEZING RAIN/FREEZING DRIZZLE
ICING CONDITIONS:
Freezing rain and freezing drizzle are characterized by ice
covering all or a substantial part of the unheated portion of either
forward side window, possibly associated with water splashing and
streaming on the windshield.
The following also may be used as secondary indications of
possible freezing rain/freezing drizzle conditions:
Unusually extensive ice accreted on the airframe in
areas not normally observed to collect ice.
Accumulation of ice on the upper or lower surface of
the wing aft of the protected area.
Accumulation of ice on the propeller spinner farther
back than normally observed.
[[Page 2151]]
Visible rain at temperatures below +5 degrees Celsius
[outside air temperature (OAT)].
Droplets that splash or splatter on impact at
temperatures below +5 degrees Celsius OAT.
PROCEDURES FOR EXITING THE FREEZING RAIN/FREEZING DRIZZLE ENVIRONMENT:
These procedures are applicable to all flight phases from
takeoff to landing. Monitor the outside air temperature. While
severe icing may form at temperatures as cold as -18 degrees
Celsius, increased vigilance is warranted at temperatures around
freezing with visible moisture present. If the visual cues specified
in the AFM for identifying possible freezing rain or freezing
drizzle conditions are observed, accomplish the following:
Exit the freezing rain or freezing drizzle severe icing
conditions immediately to avoid extended exposure to flight
conditions outside of those for which the airplane has been
certificated for operation. Asking for priority to leave the area is
fully justified under these conditions.
Avoid abrupt and excessive maneuvering that may
exacerbate control difficulties.
Do not engage the autopilot. The autopilot may mask
unusual control system forces.
If the autopilot is engaged, hold the control wheel
firmly and disengage the autopilot.
If an unusual roll response or uncommanded control
movement is observed, reduce the angle-of-attack by increasing
airspeed or rolling wings level (if in a turn), and apply additional
power, if needed.
Avoid extending flaps during extended operation in
icing conditions. Operation with flaps extended can result in a
reduced wing angle-of-attack, with ice forming on the upper surface
further aft on the wing than normal, possibly aft of the protected
area.
Report these weather conditions to Air Traffic
Control.''
(b) Within 6 months after the effective date of this AD, modify
the deicing boots on the leading edges of the wing by accomplishing
either paragraph (b)(1) or (b)(2) of this AD, as applicable.
(1) For Model ATR-42 series airplanes: Accomplish Aerospatiale
Modification 4216 (during retrofit) or 4222 (during production), as
applicable. Modification 4216 shall be accomplished in accordance
with Aerospatiale Service Bulletin ATR42-30-0059, Revision 1, dated
April 10, 1995; and ATR42-57-0043, dated April 10, 1995.
Modification 4222 shall be accomplished in accordance with
Aerospatiale Service Bulletin ATR42-57-0043, dated April 10, 1995.
(2) For Model ATR-72 series airplanes: Accomplish Aerospatiale
Modification 4215 (during retrofit) or 4221 (during production), as
applicable. Modification 4215 shall be accomplished in accordance
with Aerospatiale Service Bulletin ATR72-30-1023, Revision 1, dated
April 10, 1995; ATR72-57-1015, dated April 10, 1995; and ATR72-57-
1016, dated April 10, 1995. Modification 4221 shall be accomplished
in accordance with Aerospatiale Service Bulletin ATR72-57-1015,
dated April 10, 1995; and ATR72-57-1016, dated April 10, 1995.
(c) For Model ATR-72 series airplanes: Within 6 months after the
effective date of this AD, install Aerospatiale Modification 4213,
``Flaps Extension Inhibition above VFE 15 deg.,'' in accordance with
Aerospatiale Service Bulletin ATR72-27-1039, dated January 12, 1995.
(d) An alternative method of compliance or adjustment of the
compliance time that provides an acceptable level of safety may be
used if approved by the Manager, Standardization Branch, ANM-113,
FAA, Transport Airplane Directorate. Operators shall submit their
requests through an appropriate FAA Principal Operations Inspector,
who may add comments and then send it to the Manager,
Standardization Branch, ANM-113.
Note 3: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Standardization Branch, ANM-113.
(e) Special flight permits may be issued in accordance with
sections 21.197 and 21.199 of the Federal Aviation Regulations (14
CFR 21.197 and 21.199) to operate the airplane to a location where
the requirements of this AD can be accomplished.
Issued in Renton, Washington, on January 19, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-1170 Filed 1-24-96; 8:45 am]
BILLING CODE 4910-13-U
