[Federal Register Volume 63, Number 187 (Monday, September 28, 1998)]
[Rules and Regulations]
[Pages 51520-51525]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-25774]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-CE-57-AD; Amendment 39-10801; AD 98-20-34]
RIN 2120-AA64


Airworthiness Directives; Twin Commander Aircraft Corporation 
Models 500, 500-A, 500-B, 500-S, 500-U, 520, 560, 560-A, 560-E, 560-F, 
680, 680-E, 680FL(P), 680T, 680V, 680W, 681, 685, 690, 690A, 690B, 
690C, 690D, 695, 695A, 695B, and 720 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
applies to Twin Commander Aircraft Corporation Models 500, 500-A, 500-
B, 500-S, 500-U, 520, 560, 560-A, 560-E, 560-F, 680, 680-E, 680FL(P), 
680T, 680V, 680W, 681, 685, 690, 690A, 690B, 690C, 690D, 695, 695A, 
695B, and 720 airplanes. This action requires revising the FAA-approved 
Airplane Flight Manual (AFM) to specify procedures that would prohibit 
flight in severe icing conditions (as determined by certain visual 
cues), limit or prohibit the use of various flight control devices 
while in severe icing conditions, and provide the flight crew with 
recognition cues for, and procedures for exiting from, severe icing 
conditions. This AD is prompted by the results of a review of the 
requirements for certification of these airplanes in icing conditions, 
new information on the icing environment, and icing data provided 
currently to the flight crew. The actions specified by this AD are 
intended to minimize the potential hazards associated with operating 
these airplanes in severe icing conditions by providing more clearly 
defined procedures and limitations associated with such conditions.

EFFECTIVE DATE: November 3, 1998.

ADDRESSES: This information may be examined at the Federal Aviation 
Administration (FAA), Central Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 97-CE-57-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106.

FOR FURTHER INFORMATION CONTACT: Mr. John P. Dow, Sr., Aerospace 
Engineer, Small Airplane Directorate, Aircraft Certification Service, 
1201 Walnut, suite 900, Kansas City, Missouri 64106, telephone (816) 
426-6932, facsimile (816) 426-2169.

SUPPLEMENTARY INFORMATION:

Events Leading to the Issuance of This AD

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to include an AD that would apply to Twin Commander 
Aircraft Corporation Models 500, 500-A, 500-B, 500-S, 500-U, 520, 560, 
560-A, 560-E, 560-F, 680, 680-E, 680FL(P), 680T, 680V, 680W, 681, 685, 
690, 690A, 690B, 690C, 690D, 695, 695A, 695B, and 720 airplanes was 
published in the Federal Register on September 16, 1997 (62 FR 48549). 
The action proposed to require revising the Limitations Section of the 
FAA-approved Airplane Flight Manual (AFM) to specify procedures that 
would:

[[Page 51521]]

     require flight crews to immediately request priority 
handling from Air Traffic Control to exit severe icing conditions (as 
determined by certain visual cues);
     prohibit flight in severe icing 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; and
     require that all icing wing inspection lights be operative 
prior to flight into known or forecast icing conditions at night.
    That action also proposed to require revising the Normal Procedures 
Section of the FAA-approved 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.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the following comments received.
    In addition to the proposed rule described previously, in September 
1997, the FAA issued 24 other similar proposals that address the 
subject unsafe condition on various airplane models (see below for a 
listing of all 24 proposed rules). These 24 proposals also were 
published in the Federal Register on September 16, 1997. This final 
rule contains the FAA's responses to all public comments received for 
each of these proposed rules.

------------------------------------------------------------------------
                                Manufacturer/Airplane   Federal Register
          Docket No.                    model               citation
------------------------------------------------------------------------
97-CE-49-AD...................  Aerospace              62 FR 48520
                                 Technologies of
                                 Australia, Models
                                 N22B and N24A.
97-CE-50-AD...................  Harbin Aircraft Mfg.   62 FR 48513
                                 Corporation Model
                                 Y12 IV.
97-CE-51-AD...................  Partenavia             62 FR 48524
                                 Costruzioni
                                 Aeronauticas, S.p.A.
                                 Models, P68, AP68TP
                                 300, AP68TP 600.
97-CE-52-AD...................  Industrie              62 FR 48502
                                 Aeronautiche
                                 Meccaniche Rinaldo
                                 Piaggio S.p.A. Model
                                 P-180.
97-CE-53-AD...................  Pilatus Aircraft Ltd.  62 FR 48499
                                 Models PC-12 and PC-
                                 12/45.
97-CE-54-AD...................  Pilatus Britten-       62 FR 48538
                                 Norman Ltd., Models
                                 BN-2A, BN-2B, and BN-
                                 2T.
97-CE-55-AD...................  SOCATA--Groupe         62 FR 48506
                                 Aerospatiale Model
                                 TBM-700.
97-CE-56-AD...................  Aerostar Aircraft      62 FR 48481
                                 Corporation Models
                                 PA-60-600, -601, -
                                 601P, -602P, and -
                                 700P.
97-CE-57-AD...................  Twin Commander         62 FR 48549
                                 Aircraft Corporation
                                 Models 500, -500-A, -
                                 500-B,-500-S, -500-
                                 U, -520, -560, -560-
                                 A, -560-E, -560-F, -
                                 680, -680-E, -
                                 680FL(P), -680T, -
                                 680V, -680W, -681,-
                                 685, -690, -690A, -
                                 690B, -690C, -690D, -
                                 695, -695A, -695B,
                                 and 720.
97-CE-58-AD...................  Raytheon Aircraft      62 FR 48517
                                 Company Models E55,
                                 E55A, 58, 58A, 58P,
                                 58PA, 58TC, 58TCA,
                                 60 series, 65-B80
                                 series, 65-B90
                                 series, 90 series,
                                 F90 series, 100
                                 series, 300 series,
                                 and B300 series.
97-CE-59-AD...................  Raytheon Aircraft      62 FR 48531
                                 Company Model 2000..
97-CE-60-AD...................  The New Piper          62 FR 48542
                                 Aircraft, Inc.
                                 Models PA-46-310P
                                 and PA-46-350P.
97-CE-61-AD...................  The New Piper          62 FR 48546
                                 Aircraft, Inc.
                                 Models PA-23, PA-23-
                                 160, PA-23-235, PA-
                                 23-250, PA-E23-250,
                                 PA-30, PA-39, PA-40,
                                 PA-31, PA-31-300, PA-
                                 31-325, PA-31-350,
                                 PA-34-200, PA-34-
                                 200T, PA-34-220T, PA-
                                 42, PA-42-720, PA-42-
                                 1000.
97-CE-62-AD...................  Cessna Aircraft        62 FR 48535
                                 Company Models
                                 P210N, T210N, P210R,
                                 and 337 series.
97-CE-63-AD...................  Cessna Aircraft        62 FR 48528
                                 Company Models T303,
                                 310R, T310R, 335,
                                 340A, 402B, 402C,
                                 404, F406, 414,
                                 414A, 421B, 421C,
                                 425, and 441.
97-CE-64-AD...................  SIAI-Marchetti S.r.I.  62 FR 48510
                                 (Augusta) Models
                                 SF600 and SF600A.
97-NM-170-AD..................  Cessna Aircraft        62 FR 48560
                                 Company Models 500,
                                 501, 550, 551, and
                                 560 series.
97-NM-171-AD..................  Sabreliner             62 FR 48556
                                 Corporation Models
                                 40, 60, 70, and 80
                                 series.
97-NM-172-AD..................  Gulfstream Aerospace   62 FR 48563
                                 Model G-159 series.
97-NM-173-AD..................  McDonnell Douglas      62 FR 48553
                                 Models DC-3 and DC-4
                                 series.
97-NM-174-AD..................  Mitsubishi Heavy       62 FR 48567
                                 Industries Model YS-
                                 11 and YS-11A series.
97-NM-175-AD..................  Frakes Aviation Model  62 FR 48577
                                 G-73 (Mallard) and G-
                                 73T series.
97-NM-176-AD..................  Fairchild Models F27   62 FR 48570
                                 and FH227 series.
97-NM-177-AD..................  Lockheed L-14 and L-   62 FR 48574
                                 18 series airplanes.
------------------------------------------------------------------------

Comment 1. Unsubstantiated Unsafe Condition for This Model

    One commenter suggests that the AD's were developed in response to 
a suspected contributing factor of an accident involving an airplane 
type unrelated to the airplanes specified in the proposal. The 
commenter states that these proposals do not justify that an unsafe 
condition exists or could develop in a product of the same type design. 
Therefore, the commenter asserts that the proposal does not meet the 
criteria for the issuance of an AD as specified 14 CFR part 39 
(Airworthiness Directives) of the Federal Aviation Regulations.
    The FAA does not concur. As stated in the notice of proposed 
rulemaking (NPRM), the FAA has identified an unsafe condition 
associated with operating the airplane in severe icing conditions. As 
stated in the preamble to the proposal, the FAA has not required that 
airplanes be shown to be capable of operating safely in icing 
conditions outside the certification envelope specified in Appendix C 
of part 25 of the Federal Aviation Regulations (14 CFR part 25). This 
means that any time an airplane is flown in icing conditions for which 
it is not certificated, there is a potential for an unsafe condition to 
exist or develop and the flight crew must take steps to exit those 
conditions expeditiously. Further, the FAA has determined that flight 
crews are not currently provided with adequate information necessary to 
determine when an airplane is operating in icing conditions for which 
it is not certificated or what action to take when such conditions are 
encountered. The absence of this information presents an

[[Page 51522]]

unsafe condition because without that information, a pilot may remain 
in potentially hazardous icing conditions. This AD addresses the unsafe 
condition by requiring AFM revisions that provide the flight crews with 
visual cues to determine when icing conditions have been encountered 
for which the airplane is not certificated, and by providing procedures 
to safely exit those conditions.
    Further, in the preamble of the proposed rule, the FAA discussed 
the investigation of roll control anomalies to explain that this 
investigation was not a complete certification program. The testing was 
designed to examine only the roll handling characteristics of the 
airplane in certain droplets the size of freezing drizzle. The testing 
was not a certification test to approve the airplane for flight into 
freezing drizzle. The results of the tests were not used to determine 
if this AD is necessary, but rather to determine if design changes were 
needed to prevent a catastrophic roll upset. The roll control testing 
and the AD are two unrelated actions.
    Additionally, in the preamble of the proposed rule, the FAA 
acknowledged 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, in 1996, the FAA found that the specified unsafe condition 
must be addressed as a higher priority on airplanes equipped with 
pneumatic deicing boots and unpowered roll control systems. These 
airplanes were addressed first because the flight crew of an airplane 
having an unpowered roll 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. The FAA also placed a 
priority on airplanes that are used in regularly scheduled passenger 
service. The FAA has previously issued AD's to address those airplanes. 
Since the issuance of those AD's, the FAA has determined that similar 
AD's should be issued for similarly equipped airplanes that are not 
used in regularly scheduled passenger service.

Comment 2. AD is Inappropriate to Address Improper Operation of the 
Airplane

    One commenter requests that the proposed AD be withdrawn because an 
unsafe condition does not exist within the airplane. Rather, the 
commenter asserts that the unsafe condition is the improper operation 
of the airplane. The commenter further asserts that issuance of an AD 
is an inappropriate method to address improper operation of the 
airplane.
    The FAA does not concur. The FAA has determined that an unsafe 
condition does exist as explained in the proposed notice and discussed 
previously. As specifically addressed in Amendment 39-106 of part 39 of 
the Federal Aviation Regulations (14 CFR part 39), the responsibilities 
placed on the FAA statute (49 U.S.C. 40101, formerly the Federal 
Aviation Act) justify allowing AD's to be issued for unsafe conditions 
however and wherever found, regardless of whether the unsafe condition 
results from maintenance, design defect, or any other reason.
    This same commenter considers part 91 (rather than part 39) of the 
Federal Aviation Regulations (14 CFR part 91) the appropriate 
regulation to address the problems of icing encounters outside of the 
limits for which the airplane is certificated. Therefore, the commenter 
requests that the FAA withdraw the proposal.
    The FAA does not concur. Service experience demonstrates that 
flight in icing conditions that is outside the icing certification 
envelope does occur. Apart from the visual cues provided in these final 
rules, there is no existing method provided to the flight crews to 
identify when the airplane is in a condition that exceeds the icing 
certification envelope. Because this lack of awareness may create an 
unsafe condition, the FAA has determined that it is appropriate to 
issue an AD to require a revision of the AFM to provide this 
information.
    One commenter asserts that while it is prudent to advise and 
routinely remind the pilots about the hazards associated with flight 
into known or forecast icing conditions, the commenter is opposed to 
the use of an AD to accomplish that function. The commenter states that 
pilots' initial and bi-annual flight checks are the appropriate 
vehicles for advising the pilots of such hazards, and that such 
information should be integrated into the training syllabus for all 
pilot training.
    The FAA does not concur that substituting advisory material and 
mandatory training for issuance of an AD is appropriate. The FAA 
acknowledges that, in addition to the issuance of an AD, information 
specified in the revision to the AFM should be integrated into the 
pilot training syllabus. However, the development and use of such 
advisory materials and training alone are not adequate to address the 
unsafe condition. The only method of ensuring that certain information 
is available to the pilot is through incorporation of the information 
into the Limitations Section of the AFM. The appropriate vehicle for 
requiring such a revision of the AFM is issuance of an AD. No change is 
necessary to the final rule.

Comment 3. Inadequate Visual Cues

    One commenter provides qualified support for the AD. The commenter 
notes that the recent proposals are identical to the AD's issued about 
a year ago. Although the commenter supports the intent of the AD's as 
being appropriate and necessary, the commenter states that it is 
unfortunate that the flight crew is burdened with recognizing icing 
conditions with visual cues that are inadequate to determine certain 
icing conditions. The commenter points out that, for instance, side 
window icing (a very specific visual cue) was determined to be a valid 
visual cue during a series of icing tanker tests on a specific 
airplane; however, later testing of other models of turboprop airplanes 
revealed that side window icing was invalid as a visual cue for 
identifying icing conditions outside the scope of Appendix C.
    The FAA does not concur with the commenters' request to provide 
more specific visual cues. The FAA finds that the value of visual cues 
has been substantiated during in-service experience. Additionally, the 
FAA finds that the combined use of the generic cues provided and the 
effect of the final rules in increasing the awareness of pilots 
concerning the hazard of operating outside of the certification icing 
envelope will provide an acceptable level of safety. Although all of 
the cues may not be exhibited on a particular model, the FAA considers 
that at least some of the cues will be exhibited on all of the models 
affected by this AD. For example, some airplanes may not have side 
window cues in freezing drizzle, but would exhibit other cues (such as 
accumulation of ice aft of the protected area) under those conditions. 
For these reasons, the FAA considers that no changes regarding visual 
cues are necessary in the final rule. However, for those operators that 
elect to identify airplane-specific visual cures, the FAA would 
consider a request for approval of an alternative method of compliance, 
in accordance with the provisions of this AD.

Comment 4. Request for Research and Use of Wing-Mounted Ice Detectors

    One commenter requests that wing-mounted ice detectors, which 
provide real-time icing severity information (or immediate feedback) to 
flight crews, continue to be researched and used

[[Page 51523]]

throughout the fleet. The FAA infers from this commenter's request that 
the commenter asks that installation of these ice detectors be mandated 
by the FAA.
    While the FAA supports the development of such ice detectors, the 
FAA does not concur that installation of these ice detectors should be 
required at this time. Visual cues are adequate to provide an 
acceptable level of safety; therefore, mandatory installation of ice 
detector systems, in this case, is not necessary to address the unsafe 
condition. Nevertheless, because such systems may improve the current 
level of safety, the FAA has officially tasked the Aviation Rulemaking 
Advisory Committee (ARAC) to develop a recommendation concerning ice 
detection. Once the ARAC has submitted its recommendation, the FAA may 
consider further rulemaking action to require installation of such 
equipment.

Comment 5. Particular Types of Icing

    This same commenter also requests that additional information be 
included in paragraph (a) of the AD that would specify particular types 
of icing or particular accretions that result from operating in 
freezing precipitation. The commenter asserts that this information is 
of significant value to the flightcrew.
    The FAA does not concur with the commenter's suggestion to specify 
types of icing or accretion. The FAA has determined that supercooled 
large droplets (SLD) can result in rime ice, mixed (intermediate) ice, 
and ice with glaze or clear appearance. Therefore, the FAA finds that 
no type of icing can be excluded from consideration during operations 
in freezing precipitation, and considers it unnecessary to cite those 
types of icing in the AD.

Comment 6. Restrictions on Use of Autopilot Could Have Adverse Impact

    One commenter specifically addressed the Twin Commander 690 series 
airplanes. This commenter stated that the restriction against use of 
the autopilot in certain conditions of severe icing would have an 
adverse impact on certain 14 CFR part 135 single-pilot IFR operations, 
and thus should be revised to provide only information. Further the 
commenter stated it is counterproductive to and does not materially 
contribute to the safety of flight.
    The FAA does not concur. Federal Aviation Regulation, part 135 (14 
CFR part 135, section 135.103), ``Exceptions to second in command 
requirements: IFR operations'', addresses weather conditions that must 
exist in order to operate without a second in command. Federal Aviation 
Regulations part 135 (14 CFR part 135, section 135.105): ``Exception 
for second in command requirements: Approval for use of autopilot 
systems'', addresses certain conditions that have to be met in order to 
rely upon an autopilot in lieu of a second in command.
    The regulation only specifies the installation of a functioning and 
operable autopilot that meets the operations specifications. The pilot-
in-charge determines the appropriate use of the autopilot, unless 
mandated by other regulation, i.e., airworthiness directive. In the 
case of the proposed AD, the autopilot could not be used in certain 
conditions of severe icing. The autopilot would still be operable and 
would meet the operations specifications, and could then be utilized 
once the pilot-in-charge exited these severe icing conditions.
    The regulations do not address icing conditions, and the AD does 
not revise or amend the above referenced sections of 14 CFR part 135. 
Therefore, as long as the airplane meets all the autopilot restrictions 
of 14 CFR 135.105 and the weather requirements of 14 CFR 135.103 are 
met, restricting use of the autopilot in certain icing conditions would 
not contradict the current regulations.
    Additionally, the FAA does not concur with the commenter's 
statement that the masked symptoms caused by the use of autopilot in 
severe icing is a ``hunch''. The FAA has carefully examined data from 
aircraft types involved in various modes of upset in icing conditions. 
This data includes flight data recorder information obtained from 
revenue flights, flight test instrumentation, radar data, interviews 
with flight test pilots and review of anecdotal information on multi-
engine airplanes, including the Commander 690 series airplanes.
    This examination shows a reduction of aircraft control or 
performance is imminent and upset may occur with continued flight in 
severe icing conditions, and in certain infrequent cases of icing 
conditions within the design limits. This upset may occur without 
substantial natural or artificial warning in advance of aerodynamic 
stall, and at higher speed than without ice contamination. In these 
cases, there is clear and compelling evidence of three important 
benefits that arise from hand flying the airplane.
    Benefit one is prevention. The pilot is usually able to feel the 
onset of adverse changes to the handling characteristics of the 
airplane by changes in the way the airplane responds to control input. 
Essentially, the airplane ``feel'' is different. The different ``feel'' 
or handling characteristics should alert the pilot that an immediate 
decrease in angle-of-attack, change in course, or altitude is needed to 
prevent possible upset. Some of these handling characteristics could be 
increased or decreased force to change the control surface position, 
vibration or buffeting of the control surface, or greater control 
surface deflection to obtain the desired airplane response.
    Benefit two is reducing the severity of an upset. By disconnecting 
the autopilot early in a potential upset sequence, extreme trim inputs 
will be prevented. Delayed disconnect of the autopilot could increase 
the potential for cross trimmed flight controls at aerodynamic stall 
(most likely at higher than normal airspeeds), and may lead to a spiral 
spin entry, or unusual attitude. In past incidents, autopilot trim 
inputs reached trim surface limits prior to aerodynamic stall, 
complicating recovery by resulting in higher control forces that the 
pilot had to apply.
    Benefit three is the potential for faster recovery. With ``hands-
on'' the controls, the pilot is able to recover immediately should an 
upset occur. It is important to remember that the response 
characteristics of an ice contaminated airplane may differ dramatically 
from that of the uncontaminated airplane. Severe icing implies even 
more adverse changes than tested within normal icing conditions. This 
final rule will not change as a result of this comment.

The FAA's Determination

    After careful review of all available information related to the 
subject presented above, the FAA has determined that air safety and the 
public interest require the adoption of the rule as proposed except for 
minor editorial corrections. The FAA has determined that these minor 
corrections will not change the meaning of the AD and will not add any 
additional burden upon the public than was already proposed.

Cost Impact

    The FAA estimates that 811 airplanes in the U.S. registry will be 
affected by this AD, that it will take approximately 1 workhour per 
airplane to accomplish this action, and that the average labor rate is 
approximately $60 an hour. Since an owner/operator who holds at least a 
private pilot's certificate as authorized by sections 43.7 and 43.9 of 
the Federal Aviation Regulations (14 CFR 43.7 and 43.9) can accomplish 
this action, the only cost impact upon the public is the time it will 
take the affected airplane

[[Page 51524]]

owners/operators to incorporate this AFM revision.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of this requirements of this AD 
action, and that no operator will accomplish those actions in the 
future if this AD were not adopted.
    In addition, the FAA recognizes that this action may impose 
operational costs. However, these costs are incalculable because the 
frequency of occurrence of the specified conditions and the associated 
additional flight time cannot be determined. Nevertheless, because of 
the severity of the unsafe condition, the FAA has determined that 
continued operational safety necessitates the imposition of the costs.

Regulatory Impact

    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.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final 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.

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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding a new airworthiness directive 
(AD) to read as follows:

98-20-34 Twin Commander Aircraft Corporation: Amendment 39-10801; 
Docket No. 97-CE-57-AD.

    Applicability: Models 500, -500-A, -500-B, -500-S, -500-U, -520, 
-560, -560-A, -560-E, -560-F, -680, -680-E, -680FL(P), -680T, -680V, 
-680W, -681, -685, -690, -690A, -690B, 690C, -690D, -695, -695A, -
695B, and 720 airplanes (all serial numbers), 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 request approval for an 
alternative method of compliance in accordance with paragraph (d) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless already accomplished.
    To minimize the potential hazards associated with operating the 
airplane in severe icing conditions by providing more clearly 
defined procedures and limitations associated with such 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 should 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.

``WARNING

Severe icing may result from 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 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.

     During flight, severe icing conditions that exceed 
those for which the airplane is certificated shall be determined by 
the following visual cues. If one or more of these visual cues 
exists, immediately request priority handling from Air Traffic 
Control to facilitate a route or an altitude change to exit the 
icing conditions.

 Unusually extensive ice accumulation on the airframe and 
windshield in areas not normally observed to collect ice.
 Accumulation of ice on the lower surface of the wing aft of 
the protected area.
 Accumulation of ice on the engine nacelles and propeller 
spinners farther aft than normally observed.

     Since the autopilot, when installed and operating, may 
mask tactile cues that indicate adverse changes in handling 
characteristics, use of the autopilot is prohibited when any of the 
visual cues specified above exist, or when unusual lateral trim 
requirements or autopilot trim warnings are encountered while the 
airplane is in icing conditions.
     All wing icing inspection lights must be operative 
prior to flight into known or forecast icing conditions at night.

    [Note: This supersedes any relief provided by the Master Minimum 
Equipment List (MMEL).]''

    (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.

``THE FOLLOWING WEATHER CONDITIONS MAY BE CONDUCIVE TO SEVERE IN-FLIGHT 
ICING

     Visible rain at temperatures below 0 degrees Celsius 
ambient air temperature.
     Droplets that splash or splatter on impact at 
temperatures below 0 degrees Celsius ambient air temperature.

PROCEDURES FOR EXITING THE SEVERE ICING ENVIRONMENT

    These procedures are applicable to all flight phases from 
takeoff to landing. Monitor the ambient 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 Limitations Section of the AFM for identifying severe icing 
conditions are observed, accomplish the following:
     Immediately request priority handling from Air Traffic 
Control to facilitate a route or an altitude change to exit the 
severe icing conditions in order to avoid extended exposure to 
flight conditions more severe than those for which the airplane has 
been certificated.
     Avoid abrupt and excessive maneuvering that may 
exacerbate control difficulties.
     Do not engage the autopilot.
     If the autopilot is engaged, hold the control wheel 
firmly and disengage the autopilot.
     If an unusual roll response or uncommanded roll control 
movement is observed, reduce the angle-of-attack.
     Do not extend flaps when holding in icing conditions. 
Operation with flaps extended can result in a reduced wing angle-of-
attack, with the possibility of ice forming on the upper surface 
further aft on the wing than normal, possibly aft of the protected 
area.
     If the flaps are extended, do not retract them until 
the airframe is clear of ice.

[[Page 51525]]

     Report these weather conditions to Air Traffic 
Control.''
    (b) Incorporating the AFM revisions, as required by this AD, may 
be performed by the owner/operator holding at least a private pilot 
certificate as authorized by section 43.7 of the Federal Aviation 
Regulations (14 CFR 43.7), and must be entered into the aircraft 
records showing compliance with this AD in accordance with section 
43.9 of the Federal Aviation Regulations (14 CFR 43.9).
    (c) 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.
    (d) An alternative method of compliance or adjustment of the 
compliance time that provides an equivalent level of safety may be 
approved by the Manager, Small Airplane Directorate, FAA, 1201 
Walnut, suite 900, Kansas City, Missouri 64106. The request shall be 
forwarded through an appropriate FAA Maintenance Inspector, who may 
add comments and then send it to the Manager, Small Airplane 
Directorate.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Small Airplane Directorate.

    (e) All persons affected by this directive may examine 
information related to this AD at the FAA, Central Region, Office of 
the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, 
Missouri 64106.
    (f) This amendment becomes effective on November 3, 1998.

    Issued in Kansas City, Missouri, on September 18, 1998.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 98-25774 Filed 9-25-98; 8:45 am]
BILLING CODE 4910-13-P