[Federal Register Volume 60, Number 34 (Tuesday, February 21, 1995)]
[Rules and Regulations]
[Pages 9616-9619]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-4001]



-----------------------------------------------------------------------


DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-01-AD; Amendment 39-9152; AD 95-02-51]


Airworthiness Directives; Aerospatiale Model ATR-42 and ATR-72 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

-----------------------------------------------------------------------

SUMMARY: This document publishes in the Federal Register an amendment 
adopting Airworthiness Directive (AD) T95-02-51 that was sent 
previously to all known U.S. owners and operators of Aerospatiale Model 
ATR-42 and ATR-72 series airplanes by individual telegrams. Unless 
modifications are accomplished or alternative procedures and training 
are adopted, this AD prohibits operation of the airplane in certain 
icing conditions, and requires restrictions on the use of the autopilot 
in certain conditions. This AD also provides for an optional 
terminating action, which, if accomplished, would terminate the 
requirements of this AD. This amendment is prompted by an FAA 
determination that, during flight in freezing rain or freezing drizzle 
with the flaps set at the 15-degree position, a ridge of ice can form 
on the wing. This ridge can interrupt the airflow over the ailerons 
when the flaps are retracted to the zero-degree position, and can cause 
an aileron deflection and resultant unusual control forces. The actions 
specified by this AD are intended to prevent a roll upset from which 
the flight crew may be unable to recover.

DATES: Effective March 8, 1995, to all persons except those persons to 
whom it was made immediately effective by telegraphic AD T95-02-51, 
issued January 11, 1995, which contained the requirements of this 
amendment.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 8, 1995.
    Comments for inclusion in the Rules Docket must be received on or 
before April 24, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-01-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056.
    The applicable service information 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; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Sam Grober or Gary Lium, Aerospace 
Engineers, Standardization Branch, ANM-113, FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; 
telephone (206) 227-1187 or (206) 227-1112; fax (206) 227-1320.

SUPPLEMENTARY INFORMATION: On December 9, 1994, the FAA issued 
telegraphic airworthiness directive (AD) T94-25-51, to address an 
unsafe condition related to potential hazards associated with operation 
of Aerospatiale Model ATR-42 and ATR-72 series airplanes in icing 
conditions. That AD requires an operational limitation that prohibits 
operation of the airplane when icing conditions [as defined in the 
Airplane Flight Manual (AFM)] are forecast or reported. It also 
requires restrictions on the use of the autopilot in inadvertent icing 
encounters, when the airplane is operated in moderate or greater 
turbulence, or whenever any unusual lateral trim situation is observed.
    That AD action was prompted by data obtained following an accident 
involving a Model ATR-72 series airplane that occurred when the 
airplane was enroute from Indianapolis to Chicago. The accident 
occurred during the initial descent for approach to Chicago. The 
airplane had been in a holding pattern for more than 30 minutes with 
flaps at the 15-degree position, and there were icing conditions and 
turbulence reported in the area.
    Although the official cause of the accident has not been 
determined, preliminary information from the accident investigation 
indicates that, immediately after the autopilot disconnected, at an 
indicated airspeed of approximately 185 knots, the ailerons abruptly 
deflected in the right-wing-down direction, and the airplane entered an 
abrupt roll to the right, which was not corrected before the airplane 
impacted the ground.
    Prior to the issuance of AD T94-25-51, ATR conducted certain wind 
tunnel and ground tests in Toulouse, France. Following these tests, ATR 
contracted with the United States Air Force to conduct a series of 
flight tests at Edwards Air Force Base, California. The test program 
was developed in conjunction with the National Transportation Safety 
Board (NTSB), National Aeronautics and Space Administration (NASA), 
United States Air Force, representatives from the FAA, and the 
Direction Generale de l'Aviation Civile (DGAC), which is the 
airworthiness authority for France.
    During these tests, a Model ATR-72 series airplane flew in close 
formation behind an ``icing tanker,'' which is a specially modified 
aerial refueling airplane designed to create icing conditions by 
spraying supercooled water droplets on a test airplane during flight. 
Appendix C of part 25 of the Federal Aviation Regulations (14 CFR part 
25) defines droplet diameters, liquid water content, temperature, and 
horizontal extent parameters for testing leading to approval of flight 
in icing conditions. Water droplet diameters specified in part 25 of 
the Federal Aviation Regulations (FAR) for certification of transport 
category airplanes, and larger droplets well outside the diameters 
specified in part [[Page 9617]] 25 of the FAR (commonly referred to as 
``freezing rain or freezing drizzle''), were sprayed onto the outer 
wing leading edges and other airplane surfaces to determine ice 
accretion characteristics of the various diameter droplets. Droplet 
diameters larger than those specified in part 25 of the FAR were tested 
because there is meteorological evidence that the accident airplane 
encountered such large droplets (freezing rain or freezing drizzle) 
prior to the accident.
    Results of data from the numerous flight tests conducted have 
revealed the following significant findings:
    1. Ice accretion characteristics of the normal diameter droplets, 
as specified in the FAR, were entirely satisfactory. This confirms that 
Model ATR-42 and ATR-72 series airplanes comply fully with performance 
requirements relating to the icing envelope specified in part 25 of the 
FAR for certification of these airplanes.
    2. Additional testing was conducted with large water droplets 
(outside certification standards), and it was found to be possible for 
ice to accrete aft of the wing boot surface during a 17-minute exposure 
to the tanker spray when the aircraft operated in a flaps 15-degree 
configuration. Flight tests conducted in this configuration indicated 
that a spanwise ridge could disrupt the flow over the aileron when the 
flaps are retracted to the zero-degree position. This interruption 
caused an uncommanded aileron deflection and resultant unusual control 
forces. However, during the tests conducted, the forces required to 
control the aircraft were within limits specified by the FAR.
    3. Exposure to freezing rain or freezing drizzle on the forward 
side windows of the cockpit produced ice on all or a substantial part 
of the forward side windows. This ice accretion on the forward side 
windows does not appear when the airplane is flying in the icing 
conditions defined in part 25 of the FAR. This characteristic ice 
accretion begins to form within 30 seconds of the beginning of the 
encounter with freezing rain or freezing drizzle. Additionally, test 
data indicate that the crew can observe the accumulation of ice on the 
forward side windows at least several minutes before a significant 
amount of ice accumulates on the wings.
    While the cause of the accident is still under investigation, the 
FAA has determined that if a Model ATR-42 or ATR-72 series airplane is 
in flight with the flaps set at the 15-degree position during freezing 
rain or freezing drizzle, an unusual ridge of ice on the wing (aft of 
the ice protection boots) can occur. This ridge can interrupt the 
airflow over the ailerons when the flaps are retracted to the zero-
degree position. This interruption can cause an aileron deflection and 
resultant unusual control forces. In actual operations, these unusual 
forces may result in a roll upset from which the flight crew may be 
unable to recover.
    In an effort to break the chain of events that may lead to an 
aircraft roll upset, the manufacturer has developed a set of procedures 
to be followed if the airplane should encounter freezing rain or 
freezing drizzle conditions. These procedures are based on results of 
the tests conducted at Edwards Air Force Base. They prohibit dispatch 
into or operation in known or forecast freezing rain or freezing 
drizzle, provide the flight crew with a means to identify inadvertent 
encounters with freezing rain and freezing drizzle conditions, and 
provide procedures to take appropriate corrective action. 
Accomplishment of these procedures will ensure safe operation of the 
airplane while operating in all icing conditions, including inadvertent 
encounters with freezing rain or freezing drizzle.
    The procedures developed by the manufacturer have been incorporated 
into several documents, including the following:
    1. ATR-42 AFM Temporary Revision 18, dated January 10, 1995 (for 
Model ATR-42 series airplanes); and ATR-72 AFM Temporary Revision 14, 
dated January 10, 1995 (for Model ATR-72 series airplanes);
    2. ATR Icing Conditions Procedures Brochure, Version 1.0;
    3. ATR Technical Background Paper, Version 1.0, dated January 6, 
1995; and
    4. Flight Crew Operation Manual, Revision 20, dated January 11, 
1995 (for Model ATR-42 series airplanes); and Flight Crew Operation 
Manual, Revision 12, dated January 11, 1995 (for Model ATR-72 series 
airplanes).
    Additionally, certain modifications have been proposed by the 
manufacturer. The FAA finds that such modification is preferable, as a 
long term solution, to requiring special procedures and special 
training, which can be used for the short term. This is consistent with 
the FAA's general policy that long term continued operational safety 
will be better assured by design changes that will preclude the 
problem, rather than by long term operational limitations. Such 
operational limitations may not have the desired long term effect. 
This, coupled with a better understanding of the human factors 
associated with such limitations, has led the FAA to consider placing 
less emphasis on those limitations and more emphasis on design 
improvements. The optional modification specified in this AD is in 
consonance with these considerations.
    ATR has issued Service Bulletin ATR72-27-1039, dated January 12, 
1995, which describes procedures for installation of ATR Modification 
Number 04213 on Model ATR-72 series airplanes. The modification permits 
movement of the flaps above limit speed in an emergency to give crews 
more operational discretion. Accomplishment of the modification 
eliminates the multi-function computer inhibition against flap 
extension.
    These documents form a basis for providing added information to 
expand the operation of Model ATR-42 and ATR-72 series airplanes beyond 
that defined in AD T94-25-51.
    The FAA finds that these interim procedures may be permitted until 
June 1, 1995, at which time an FAA-approved modification must be 
installed. If such a modification is not installed by June 1, 1995, 
dispatch into or operation in known or forecast icing, freezing rain, 
or freezing drizzle conditions is prohibited.
    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. Pursuant to this 
bilateral airworthiness agreement, the DGAC has kept the FAA informed 
of the situation described above. The FAA has examined the findings of 
the DGAC, reviewed all available information, and determined that AD 
action is necessary for products of this type design that are 
certificated for operation in the United States.
    Since the unsafe condition described is likely to exist or develop 
on other airplanes of the same type design registered in the United 
States, the FAA issued Telegraphic AD T95-02-51 to minimize the 
potential hazards associated with operating in icing conditions, as 
defined in the AFM. This AD supersedes AD T94-25-51. Unless 
modifications are accomplished or alternative procedures and training 
are adopted, this AD continues to require an operational limitation 
that prohibits operation of the airplane when icing conditions (as 
defined in the AFM) are forecast or reported; and restrictions on the 
use of the autopilot in inadvertent icing encounters, when the airplane 
is operated in moderate or greater turbulence, or whenever any unusual 
lateral trim situation is observed.
    This AD permits, as an interim measure prior to installation of an 
FAA-approved modification, operation of the airplane into icing 
conditions, provided [[Page 9618]] that certain actions have been 
accomplished. Those actions include the following:
    1. The FAA-approved AFM must be revised to incorporate the ATR-42 
and ATR-72 AFM revisions described previously.
    2. All Model ATR-42 and ATR-72 flight crew members must attend an 
FAA-approved training course prior to flight in known or forecast icing 
conditions. This training course will provide instruction in the 
recognition of characteristic ice accretion on the cockpit forward side 
windows. This course also will define the procedures designed to escape 
freezing rain and freezing drizzle conditions, and to minimize the 
hazard posed by flight in freezing rain or freezing drizzle.
    3. Operators must establish an FAA-approved system to provide 
forecasts and reports of freezing rain and freezing drizzle at enroute 
altitudes along the route of flight and at all airports considered in 
the flight planning process.
    4. Operators of Model ATR-72 series airplanes must install ATR 
Modification Number 04213 to eliminate the multi-function computer 
inhibition against flap extension.
    This AD also provides for an optional terminating action, which, if 
accomplished, would terminate the requirements of this AD. The optional 
terminating action involves installing a modification that precludes 
the formation of hazardous ice accumulation during flight in freezing 
rain or freezing drizzle conditions. The modification must be approved 
by the FAA. Upon accomplishment of the optional terminating action, ATR 
Modification Number 04213 must be removed from Model ATR-72 series 
airplanes.
    As described previously, the existing AD imposes severe 
restrictions on many airplanes operated in air transportation, causing 
significant cost to the operators, widespread disruption of passenger 
travel, and an undermining of public confidence in the safety of the 
airplane. Based on the results of recent flight tests, if certain 
procedures and training are accomplished, these restrictions are 
unnecessary to ensure an acceptable level of public safety. Therefore, 
the FAA has determined that it would be contrary to the public interest 
to continue these restrictions during the period of time that would be 
necessary to issue a notice to solicit public comment on this action 
and to issue a final rule; such notice is therefore also impracticable. 
This action is considered to be interim action; once the described 
modification has been developed, the FAA may consider further 
rulemaking to mandate that modification.
    Since it was found that immediate corrective action was required, 
notice and opportunity for prior public comment thereon were 
impracticable and contrary to the public interest, and good cause 
existed to make the AD effective immediately by individual telegrams 
issued on January 11, 1995, to all known U.S. owners and operators of 
Aerospatiale Model ATR-42 and ATR-72 series airplanes. These conditions 
still exist, and the AD is hereby published in the Federal Register as 
an amendment to section 39.13 of the Federal Aviation Regulations (14 
CFR 39.13) to make it effective as to all persons.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 95-NM-01-AD.'' The postcard will be date stamped and 
returned to the commenter.
    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, may be obtained from the Rules Docket at the 
location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

95-02-51  Aerospatiale: Amendment 39-9152. Docket 95-NM-01-AD. 
Supersedes telegraphic AD T94-25-51, issued December 9, 1994.

    Applicability: All Model ATR-42 and ATR-72 series airplanes, 
certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To minimize the potential hazards associated with operating in 
icing conditions, as defined in the Airplane Flight Manual (AFM), 
accomplish the following:
    (a) Except as provided in paragraphs (b) and (c) of this AD, 
within 24 hours after [[Page 9619]] receipt of telegraphic AD T94-
25-51: Incorporate the following into the Limitations Section of the 
FAA-approved AFM. This may be accomplished by inserting a copy of 
this AD in the AFM.
    ``(1) Operation of the airplane into forecast or reported icing 
conditions, as such conditions are defined in the AFM, is 
prohibited.
    ``(2) Use of the autopilot is prohibited during inadvertent 
flight in icing conditions, as defined in the AFM, or when the 
airplane is operated in moderate or greater turbulence.
    ``(3) If any unusual lateral trim situations are observed, such 
as excessive trim displacement; illumination of the message `RETRIM 
ROLL R WING DN' or `RETRIM ROLL L WING DN' on the advisory display 
unit (ADU); illumination of the message `AILERON MISTRIM' on the 
ADU; or abnormal flight characteristics of the airplane: Disconnect 
the autopilot and manually fly the airplane prior to adjusting the 
lateral trim. The autopilot may be re-engaged following manual 
adjustment of the lateral trim.''
    (b) Between the effective date of this AD and June 1, 1995, the 
limitations contained in paragraph (a) of this AD may be removed 
from the AFM upon accomplishment of the actions specified in 
paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this AD, as 
applicable. Dispatch into or operation in known or forecast icing 
conditions, as defined in the AFM, may occur if the actions 
specified in paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this 
AD have been accomplished previously. Except as provided by 
paragraph (c) of this AD, the limitation required by paragraph (a) 
of this AD must be reinserted in the AFM no later than June 1, 1995.
    (1) ATR-42 AFM Temporary Revision 18, dated January 10, 1995; or 
ATR-72 AFM Temporary Revision 14, dated January 10, 1995; as 
applicable; shall be incorporated into the Limitations Section of 
the FAA-approved AFM.
    (2) ATR-42 and ATR-72 flight crew members shall receive FAA-
approved training, which consists of the following items.
    (i) ATR Icing Procedures Brochure, Version 1.0.

    Note 1: The ATR Icing Procedure Brochure specified in this 
paragraph also has been published as ``Version 2.0.'' That version 
is acceptable for compliance with this paragraph.

    (ii) ATR Technical Background Paper, Version 1.0, dated January 
6, 1995.
    (iii) ATR-42 AFM Temporary Revision 18, dated January 10, 1995; 
or ATR-72 AFM Temporary Revision 14, dated January 10, 1995; as 
applicable.
    (iv) Flight Crew Operation Manual, Revision 20, dated January 
11, 1995 (for Model ATR-42 series airplanes); or Flight Crew 
Operation Manual, Revision 13, dated January 11, 1995 (for Model 
ATR-72 series airplanes); as applicable.
    (3) Operators of Model ATR-42 and ATR-72 series airplanes shall 
establish an FAA-approved system to provide forecasts and reports of 
freezing rain and freezing drizzle at enroute altitudes along the 
route of flight and at all airports considered in the flight 
planning process. Training concerning the use of these icing 
forecasts and reports shall be accomplished in accordance with 
Flight Standards Information Bulletin ``ATR-42 and ATR-72 
Airworthiness Directive T95-02-51 Compliance Procedures,'' dated 
January 11, 1995.
    (4) For Model ATR-72 series airplanes only: Install ATR 
Modification Number 04213 in accordance with ATR Service Bulletin 
ATR72-27-1039, dated January 12, 1995.
    (c) Installation of a modification that precludes the formation 
of hazardous ice accumulation during flight in freezing rain or 
freezing drizzle conditions constitutes terminating action for the 
requirements of this AD. This modification must be approved by the 
Manager, FAA, Transport Airplane Directorate, Standardization 
Branch, ANM-113. Following installation of such modification, the 
modification required by paragraph (b)(4) of this AD shall be 
removed from Model ATR-72 series airplanes.
    (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. 
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 2: 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.
    (f) Certain actions, when accomplished in accordance with 
paragraph (b) of this AD, shall be done in accordance with ATR-42 
AFM Temporary Revision 18, dated January 10, 1995; ATR-72 AFM 
Temporary Revision 14, dated January 10, 1995; ATR Icing Procedures 
Brochure, Version 1.0; ATR Technical Background Paper, Version 1.0, 
dated January 6, 1995; ATR-42 Flight Crew Operation Manual, Revision 
20, dated January 11, 1995; and ATR-72 Flight Crew Operation Manual, 
Revision 13, dated January 11, 1995; as applicable. Training 
concerning the use of certain icing forecasts and reports [as 
specified in paragraph (b)(3) of this AD] shall be accomplished in 
accordance with Flight Standards Information Bulletin, ``ATR-42 and 
ATR-72 Airworthiness Directive T95-02-51 Compliance Procedures,'' 
dated January 11, 1995. Installation of ATR Modification Number 
04213 [as specified in paragraph (b)(4) of this AD] shall be 
accomplished in accordance with ATR Service Bulletin ATR72-27-1039, 
dated January 12, 1995. This incorporation by reference was approved 
by the Director of the Federal Register in accordance with 5 U.S.C. 
552(a) and 1 CFR part 51. Copies may be obtained from Aerospatiale, 
316 Route de Bayonne, 31060 Toulouse, Cedex 03, France. Copies may 
be inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
    (g) This amendment becomes effective on March 8, 1995, to all 
persons except those persons to whom it was made immediately 
effective by telegraphic AD T95-02-51, issued January 11, 1995, 
which contained the requirements of this amendment.

    Issued in Renton, Washington, on February 13, 1995.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-4001 Filed 2-17-95; 8:45 am]
BILLING CODE 4910-13-U