[Federal Register Volume 62, Number 244 (Friday, December 19, 1997)]
[Rules and Regulations]
[Pages 66512-66521]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-33000]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-46-AD; Amendment 39-10249; AD 97-26-06]
RIN 2120-AA64


Airworthiness Directives; Empresa Brasileira de Aeronautica, S.A. 
(EMBRAER) Model EMB-120 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to all EMBRAER Model EMB-120 series airplanes, that requires 
revising the Airplane Flight Manual (AFM) to include requirements for 
activation of the ice protection systems, and to add information 
regarding operation in icing conditions. This amendment also requires 
installing an ice detector system and revising the AFM to include 
procedures for testing system integrity. This amendment is prompted by 
reports indicating that flightcrews experienced difficulties 
controlling the airplane during (or following) flight in normal icing 
conditions, when the ice protection system either was not activated 
when ice began to accumulate on the airplane, or the ice protection 
system was never activated. These difficulties may have occurred 
because the flightcrews did not recognize that a significant enough 
amount of ice had formed on the airplane to require activation of the 
deicing equipment. The actions specified by this AD are intended to 
ensure that the flightcrew is able to recognize the formation of 
significant ice accretion and take appropriate action; such formation 
of ice could result in reduced controllability of the airplane in 
normal icing conditions.

DATES: Effective January 23, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of January 23, 1998.

ADDRESSES: The service information referenced in this AD may be 
obtained from EMBRAER, Empresa Brasileira De Aeronautica S/A, Sao Jose 
Dos Campos, Brazil. This information may be examined at the Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Small 
Airplane Directorate, Atlanta Aircraft Certification Office, Campus 
Building, 1701 Columbia Avenue, suite 2-160, College Park, Georgia; or 
at the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Carla Worthey, Aerospace Engineer, 
Systems and Flight Test Branch, ACE-116A, FAA, Small Airplane 
Directorate, Atlanta Aircraft Certification Office, Campus Building, 
1701 Columbia Avenue, suite 2-160, College Park, Georgia 30337-2748; 
telephone (770) 703-6062; fax (770) 703-6097.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to all EMBRAER Model EMB-120 series 
airplanes was published in the Federal Register on May 13, 1997 (62 FR 
26258). That action proposed to require revising the Airplane Flight 
Manual (AFM) to include requirements for activation of the ice 
protection systems, and to add information regarding operation in icing 
conditions. That action also proposed to require installing an ice 
detector system and revising the AFM to include procedures for testing 
system integrity.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Support for the Proposal

    Several commenters support the FAA's intent to revise the FAA-
approved AFM procedures for flight in

[[Page 66513]]

icing conditions and/or to require installation of an ice detector 
system.

Compliance Time To Install Ice Detector

    Two commenters request additional time to install the ice detector 
system. One of the commenters states that the manufacturers of the ice 
detector installations (Grimes for the cockpit indications, and 
Rosemount Aerospace for the ice detector) will not have kits available 
for all U.S. operators until the end of January 1998, although at least 
120 kits were available on October 31, 1997. The other commenter states 
that 6 months is an unreasonable schedule for retrofitting their fleet 
of aircraft and requests a 24-month compliance time. Another commenter 
requests additional time to provide operators the opportunity to 
consider other options of ice detection and flightcrew response to such 
conditions, as proposed under the FAA's Inflight Aircraft Icing Plan. 
The commenter did not request a specific period of time for the 
extension.
    The FAA concurs that the compliance time can be extended somewhat, 
since parts will not be available for all aircraft early enough to 
allow completion within 6 months. The FAA finds that, once parts are 
available, operators must comply with the AD prior to the next icing 
season. Therefore, paragraph (b) of the final rule has been revised to 
specify a compliance time of 10 months after the effective date of the 
AD. The FAA does not consider that this extension will adversely affect 
safety. If an operator obtains FAA design and installation approval for 
an alternative to the ice detector, the operator may request approval 
of an alternative method of compliance in accordance with paragraph (c) 
of the final rule.

Master Minimum Equipment List (MMEL) Requirements

    One commenter requests that any ice detection equipment installed 
on an aircraft must be operational prior to dispatch into known or 
forecasted icing conditions. Two other commenters request that the MMEL 
grant relief for dispatch with inoperative ice detector equipment.
    The FAA acknowledges the commenters' requests. However, MMEL 
requirements are determined by the FAA Flight Operations Evaluation 
Board (FOEB). The FOEB has determined that it is permissible to 
dispatch with an inoperative ice detection system provided that all ice 
protection systems are turned on (except leading edge deicing during 
takeoff) and AFM limitations and normal procedures for operating in 
icing conditions are complied with whenever operating in visible 
moisture at temperatures below 10 degrees Centigrade (50 degrees 
Fahrenheit). Revision 5c of the MMEL for EMBRAER Model EMB-120 series 
airplanes, dated October 9, 1997, incorporated this relief.

Additional Analysis

    One commenter states that flight control difficulties of the 
airplanes in icing conditions were reported and known as far back as 
1989, but action is only being taken now. The commenter requests that 
additional analysis be conducted on the previous icing events, and the 
proposal be revised based on the results of that analysis. The 
commenter believes that the proposed AD tends to fall short of what is 
required to preclude subsequent reports of aircraft control problems on 
Model EMB-120 series airplanes.
    The FAA does not concur that additional analysis is required. The 
initial certification test data for flight into known icing approval 
indicate that Model EMB-120 series airplanes meet all of the 
certification requirements specified in Appendix C of part 25 
(``Airworthiness Standards: Transport Category Airplanes'') of the 
Federal Aviation Regulations (14 CFR part 25), provided the ice 
protection systems are activated properly. In addition, available 
information concerning the roll upset event history of the EMB-120 has 
been analyzed thoroughly by the FAA; the Centro Tecnico Aeroespacial 
(CTA), which is the airworthiness authority for Brazil; and the 
airplane manufacturer. That analysis indicates that the flightcrews did 
not activate the de-ice boots prior to the roll upset events. Based on 
this analysis, the FAA has determined that sufficient data exist to 
require that an AD be issued to ensure that the flightcrew is able to 
recognize the formation of significant ice accretion and take 
appropriate action.
    Another commenter requests that roll upset, tailplane icing, and 
uncommanded roll and/or pitch studies be completed prior to issuing the 
final rule. The commenter also suggests that additional research should 
be done regarding the location of ice detectors on the airframe.
    The FAA does not concur that additional research is needed. Roll 
upset, tailplane icing, and uncommanded roll and/or pitch studies have 
been completed, as suggested by the commenter.
    Further review of the event history revealed occurrences of 
controllable departures from normal flight in icing conditions after 
loss in airspeed when the ice protection systems of the lifting and 
control surfaces were not activated. Additionally, operational 
experience and flight testing conducted by the manufacturer indicate 
that maintaining proper airspeeds and the additional action of 
activating the ice protection system at the first detection of airframe 
icing will eliminate future occurrences of roll upset events.
    The FAA finds that supplementing appropriate visual cues for icing 
with dependable detection and annunciation of encountering icing 
conditions by an ice detector will ensure flightcrew recognition of 
icing conditions. In addition, the revision of the FAA-approved AFM, as 
required by this final rule, will help to ensure activation of the ice 
protection system, regardless of whether detection of icing is from 
visual cues or the ice detector, and will require appropriate minimum 
operating speeds.
    The FAA finds that additional research need not be done regarding 
the location of ice detectors. The FAA and CTA have already conducted a 
thorough review of that issue, including analysis of flight test data 
that show that the proposed location of the ice detector will provide 
early and consistent indication of ice accretion on the airframe.

``Bridging'' Phenomenon

    Several commenters express concern that the FAA proposal to mandate 
use of the deicing equipment at the first sign of ice accretion, rather 
than delaying until \1/4\- to \1/2\-inch ice has accumulated, could 
result in ice forming the shape of an inflated boot, which would make 
further attempts to de-ice difficult. These commenters request that 
this phenomenon, commonly referred to as ``bridging,'' be addressed in 
terms of its validity prior to mandating the change to the AFM 
procedures. Another commenter noted that, even though the manufacturer 
already issued Revision 43, dated April 23, 1996, of the AFM to 
indicate the ice protection systems should be activated with the first 
sign of ice accretion, some operators continue to caution pilots about 
``prematurely'' activating the de-ice boots because of the ``bridging'' 
concern.
    The FAA does not concur that it is necessary to withdraw the 
proposal until ``bridging'' is addressed further. The FAA is aware that 
the ``bridging'' condition continues to influence the attitudes of many 
pilots and operators with respect to the use of de-ice boots. However, 
prior to approving Revision 43 of the AFM, the FAA and CTA, along with 
the manufacturer, investigated activating the de-ice boots at the first 
sign of ice to determine whether

[[Page 66514]]

``bridging'' of the de-ice boots was a concern. It was noted that the 
de-ice system is controlled by a timer that inflates the de-ice boots 
in a three-minute cycle in ``light'' mode and in a one-minute cycle in 
``heavy'' mode. Since there are approximately three minutes when the 
boots are deflated in the ``light'' cycle, it is likely that inflation 
cycles have already been occurring in service with less than the 
earlier recommended \1/4\- to \1/2\-inch ice accumulation, with no 
documented indication of ``bridging.''
    The FAA was not able to find documented evidence of ``bridging'' 
occurring on the airplane. The National Transportation Safety Board 
(NTSB) also noted in its response to the proposed rule that it ``* * * 
knows of no documented evidence of `bridging' occurring on current 
generation turbopropeller airplanes.'' Moreover, de-icing system 
technology has improved over the years by using higher pressures, 
smaller chambers, more rapid inflation and deflation, and greater 
coverage of the leading edge, which have increased the system's ability 
to shed smaller accretions.

Unsafe Condition

    Two commenters state that the Model EMB-120 series airplane has 
completed extensive testing in icing conditions and was found to have 
no adverse flight characteristics associated with ice accreted on the 
aircraft. Additionally, it was found to perform well within established 
safety parameters. This testing included natural icing tests within 
icing conditions specified in Appendix C of part 25 of the Federal 
Aviation Regulations (14 CFR part 25) as part of the original icing 
certification, testing of ice contaminated tailplane stall 
characteristics, and subsequent investigations of susceptibility to 
roll control anomalies following flight in supercooled large droplet 
icing conditions. One commenter states that the airplane was properly 
certified for flight into known or forecast icing conditions in 1985, 
and remains in complete compliance with current icing requirements and 
all FAA policies, practices, and procedures.
    Two commenters state that all turbo-prop aircraft are tested to the 
same criteria, and that if the EMB-120 requires an ice detector, then 
all turbo-prop aircraft should be required to install a detector. 
Another commenter states that the justification given for the AD to 
``enable the flight crew to more accurately determine the need to 
activate the ice protection systems on the airplane and to take 
appropriate action'' is insufficient reason to distinguish Model EMB-
120 series airplanes from other airplane models.
    Another commenter notes that another aircraft type with an ice 
detector system installed experienced a recent accident (Roselawn, 
Indiana) where icing conditions were determined to be a contributing 
cause. The commenter states that after the Roselawn accident, the FAA, 
in conjunction with the Brazilian aviation certification authorities, 
conducted an extensive review of the Model EMB-120 series airplanes and 
concluded that the aircraft was safe to fly in inadvertent icing 
environments without adverse handling or flight characteristics.
    The FAA infers that these commenters request the FAA withdraw the 
notice of proposed rulemaking (NPRM), since they believe that an unsafe 
condition has not been established. The FAA acknowledges the previous 
testing and results. However, a review of the service history of Model 
EMB-120 series airplanes reveals that there have been several roll 
upset events in icing conditions, that the flightcrews did not activate 
the de-ice system prior to the events, and that they did not maintain 
proper airspeed. This indicates the flightcrews were either unaware of 
the ice accretion or underestimated the depth of ice accreted and the 
resultant loss in airplane performance, and delayed activation of the 
de-ice system too long. As stated in the NPRM, it is this lack of 
recognition of icing conditions, and the consequent failure to deploy 
the ice protection systems, rather than the performance of the airplane 
once this system is activated, that constitute the unsafe condition 
addressed by this AD. In this regard, the service history of the Model 
EMB-120 is significantly different from that of other turbo-prop 
aircraft. The requirements of the final rule will increase the level of 
pilot awareness, ensure appropriate flightcrew actions, and increase 
the operational level of safety over that which currently exists.
    As further information is obtained, the FAA may consider addressing 
the question of requiring an ice detector to supplement visual icing 
cues for all commercial air transports as a part of future rulemaking 
actions.

Flightcrew Training

    Several commenters request that crew training be instituted to 
increase pilot awareness of the criticality of aircraft performance 
degradation during an icing encounter, in lieu of the proposed rule to 
mandate installation of an ice detector.
    One of these commenters states that the installation of an ice 
detector is not necessary, is overly burdensome, and that proper 
training of the flightcrews to the visual cues associated with ice 
formation on the propeller spinner is the best solution.
    Another commenter, the manufacturer, states that the FAA's review 
of the icing related incidents cited in the proposed rule revealed that 
pilot indecision (as to when to activate the aircraft's de-ice system), 
and the lack of appreciation of the criticality of aircraft performance 
degradation during an icing encounter were the basic causes of the 
reported icing occurrences. The manufacturer concludes that, in 
addition to mandating immediate activation of the de-ice system, 
improved pilot training and recurrent training is needed to ensure that 
the information gained in recent years about icing is passed along to 
line pilots.
    A third commenter agrees with the proposed requirement to install 
an ice detection system, but notes that pilots have been trained for 
years to operate the de-ice boots only after \1/4\- to \1/2\-inch of 
ice has accumulated on the wings. The commenter states that the pilots 
need to be provided training to unlearn old habits and to emphasize the 
new icing procedures.
    The FAA does not concur that substituting training for installation 
of an ice detector is an adequate solution to address the unsafe 
condition. However, the FAA supports the development of advisory 
materials and periodic training to increase awareness of the potential 
for aircraft performance degradation during an icing encounter, 
including ensuring that flightcrews are aware of the visual icing cues 
available to determine if the aircraft is in severe icing conditions. 
The FAA acknowledges that pilot indecision as to when to activate the 
de-ice system may have been a factor in the roll upset events. Training 
to ensure that flightcrews activate the ice protection systems at the 
first sign of ice accumulation will help address this issue. Part 121 
(``Certification and Operations: Domestic, Flag, and Supplemental Air 
Carriers and Commercial Operators of Large Aircraft'') of the Federal 
Aviation Regulations (14 CFR part 121), and part 135 (''Air Taxi 
Operators and Commercial Operators,'') of the Federal Aviation 
Regulations (14 CFR part 135), require that appropriate training 
concerning limitations such as those contained in this AD are 
incorporated into air carriers' training programs.
    However, based on the roll upset event history of Model EMB-120 
series airplanes, the FAA considers that the use of advisory materials 
and training

[[Page 66515]]

alone are not adequate to address the subject unsafe condition. 
Therefore, the FAA has determined that installation of an ice detection 
system is necessary to achieve an acceptable operational level of 
safety.

Availability of Adequate Visual Cues

    Several commenters request that the requirement for an ice 
detection system be removed from the proposal because the visual cues 
of ice accumulation already provide notification of icing conditions. 
One of the commenters further states that the ice detector is simply 
another indicator of the presence of ice, and that it does not have the 
ability to measure ice or alert the crews to icing environments beyond 
the capability of the de-ice system.
    The manufacturer states that the FAA's brief discussion of the 
icing related incidents in the NPRM indicates that the natural visual 
cues of icing accretions are unsatisfactory or insufficient, thus 
necessitating the installation of the additional means of ice 
detection. The manufacturer disagrees with this conclusion because a 
review of the icing related incidents cited in the NPRM indicates that 
the common contributing factor to the icing related incidents was a 
lack of crew attentiveness, rather than a lack of availability of 
visual cues.
    One commenter wrote that there is a definite difference in the 
visual pattern of ice buildup on the propeller spinner between 
supercooled large droplet (SLD) and ``normal'' ice buildup. The 
commenter concludes that the installation of an ice detector system is 
not the best option for dealing with ice on the aircraft.
    Another commenter states that the visual cues for detecting icing 
conditions and operating de-icing equipment are inadequate and must be 
researched further.
    The FAA does not concur with the request to remove the requirement 
for an ice detection system. The FAA acknowledges that natural icing 
testing conducted during the initial certification indicated that the 
visual cues for ice detection were adequate. Later testing revealed 
that the visual cues in freezing drizzle were adequate to provide 
identification of possible severe icing conditions. Nevertheless, a 
review of service history reveals that in several roll upset events in 
icing conditions, the flightcrew did not activate the de-ice system, 
and subsequently allowed the airspeed to decrease prior to the roll 
upset event. The fact that the flightcrews did not activate the de-ice 
system indicates that the flightcrews were either unaware of the ice 
accretion or underestimated the depth of ice accreted, and delayed 
activation of the de-ice system too long.
    The FAA acknowledges the fact that the ice detector system does not 
have the ability to measure the amount of ice or to alert crews when 
icing environments are beyond the capability of the de-ice system. The 
FAA concurs that the visual cues associated with the SLD icing 
conditions, including ice on the propeller spinner farther aft than 
normally observed, are adequate to indicate severe icing conditions. 
Additionally, the FAA finds that the roll control characteristics 
testing in SLD conditions has shown that once the flightcrews are 
alerted that they are in icing conditions and activate the de-ice 
system, the handling characteristics are adequate to allow the crews to 
safely exit the severe icing conditions. Therefore, an adequate level 
of safety will be provided by alerting the crew that they are in icing 
conditions and requiring them to immediately activate the de-ice 
system. (Since the crew will be alerted to the presence of icing 
conditions, they will be able to monitor the aircraft for the visual 
cues associated with severe icing conditions, in accordance with the 
procedures currently provided in the FAA-approved AFM, and take 
appropriate action.)
    The FAA does not concur that further research is warranted before 
issuance of the final rule. The visual cues available for detecting ice 
accumulation have already been defined for both Appendix C of part 25 
of the Federal Aviation Regulations (14 CFR part 25), and SLD icing 
conditions; further research is unlikely to improve these available 
cues. However, the roll upset events indicate that flightcrews relying 
on these visual cues are not consistently activating the de-ice system 
at the proper time. Therefore, installation of an ice detection system 
which provides early and active annunciation to the flightcrew that 
they are in icing conditions, in conjunction with continuous flightcrew 
monitoring of the visual cues available, is necessary to provide an 
acceptable level of safety.

Installation of Ice Evidence Probe

    One commenter indicates that it disagrees with the need to install 
an ice detection system. However, if the FAA requires some additional 
means other than visual cues to assist the crews in identifying icing 
conditions, the commenter suggests installing an ice evidence probe 
similar to the probe installed on Aerospatiale Model ATR series 
airplanes instead of an ice detector. Such a probe would indicate the 
first sign of ice on the airframe and would also be the last location 
to have ice sublimate from the airframe. The commenter states that the 
installation of this type of probe would require a minimum amount of 
time to install, and would take less time to train flightcrews in its 
operation than the proposed ice detection system.
    The FAA does not concur that an ice evidence probe should be 
required to be installed in lieu of an ice detector. The FAA finds that 
the service histories of Model EMB-120 series airplanes and 
Aerospatiale Model ATR series airplanes warrant different approaches to 
satisfy an acceptable level of safety. An ice evidence probe is a 
passive device that would provide another visual indication of ice 
accretion, but would require the flightcrew to monitor and assess the 
appearance of the probe in order to be effective. Conversely, the ice 
detection system is an active system that provides an amber light on 
the multiple alarm panel, an aural warning system chime, and 
illumination of the master caution light. These multiple indications 
provide early and active notification to the flightcrew that they are 
in icing conditions. The ice detection system also provides a high 
level of pilot awareness without constant monitoring, and will increase 
the level of safety over the installation of a passive system such as 
an ice evidence probe. Consequently, the FAA has determined that the 
service history of Model EMB-120 series airplanes warrants installation 
of an ice detector to meet an acceptable level of safety.

Proposed Ice Detection System

    One commenter states that ice detection equipment installed on an 
aircraft must have the capability of detecting all types and severity 
of ice accretions, as specified in Appendix C of part 25 of the Federal 
Aviation Regulations (14 CFR part 25), as well as those types and 
severities of ice accretions outside the scope of Appendix C. The 
commenter further states that such a system must also have the 
capability to differentiate between the two conditions and annunciate 
to the flightcrew which condition is being encountered. Additionally, 
the commenter states that monitoring of icing conditions should be 
conducted at all times during a flight. The commenter also states that 
any ice detection equipment installed on an aircraft should be 
considered an aid to flightcrew recognition and should not be 
considered a primary ice detection method.
    The FAA does not concur with the commenter's suggestion that ice

[[Page 66516]]

detection equipment must have the capability to differentiate between 
the severity and types of ice accretion. The intent of this AD is to 
ensure that the flightcrew is able to recognize the formation of ice 
accretion and to take appropriate action. It is unnecessary to provide 
an ice detector that is capable of distinguishing between icing 
conditions that are defined in Appendix C and those icing conditions 
that are not defined in Appendix C in order to accomplish this intent.
    The FAA has determined that the combination of early ice detection 
and the additional visual cues associated with severe icing conditions 
are adequate to determine if severe icing conditions have been 
encountered and should be exited. Additionally, the roll control 
characteristics testing of the Model EMB-120 series airplane in SLD 
conditions conducted in early 1996 has shown that once the flightcrew 
activates the de-ice system, the handling characteristics are adequate 
to allow the airplane to safely exit the severe icing conditions. The 
installation of an ice detection system, as required by the final rule, 
will provide a clear annunication of the presence of ice that will 
alert the flightcrew to monitor the aircraft for ice accumulation. The 
flightcrew will then be responsible for determining whether the visual 
cues associated with severe icing conditions are present and for taking 
appropriate action in accordance with procedures currently provided in 
the FAA-approved AFM. The FAA finds that reliance on the flightcrew to 
make this determination, in conjunction with the installation of an ice 
detection system, will provide an adequate level of safety.
    The FAA concurs that the flightcrew has the primary responsibility 
for monitoring the icing conditions and for taking appropriate action. 
The FAA also concurs that the ice detection system required by the 
final rule is an aid to the flightcrew for early recognition of icing 
conditions. The FAA considers the definition of a ``primary'' ice 
detection system as one that is sufficiently reliable to serve as the 
sole source of information for flightcrew recognition of icing 
conditions. Primary systems do not require the flightcrew to monitor 
the icing conditions to determine if the ice protection equipment 
should be activated; the FAA does not consider the ice detection system 
required by the final rule as a ``primary'' system. Ice accumulation is 
signaled by either illumination of the ``ICE CONDITION'' light on the 
multiple alarm panel, or by flightcrew observation of other visual 
cues.

Installation of Ice Detector

    One commenter states that compliance with Sec. 25.1419 of the 
Federal Aviation Regulations (14 CFR 25.1419) concerning ice protection 
requirements is optional. The commenter also states that the FAA can 
only mandate operational limitations on the aircraft based on whether 
or not these requirements have been met. The commenter further states 
that such limitations could be so stringent that it would not be 
economical to operate the airplane in scheduled operations. 
Additionally, the commenter states that the need to install ice 
detection systems on the aircraft should be determined solely by the 
operator.
    The FAA does not concur. As described in the NPRM, this AD is based 
on the FAA's finding that an unsafe condition exists on Model EMB-120 
series airplanes, not that the type design does not comply with 14 CFR 
25.1419. The FAA has determined that the operating limitations 
prescribed in this AD are necessary to address the identified unsafe 
condition. Therefore, the FAA is fully authorized under 49 U.S.C. 44701 
and 14 CFR part 39 to impose these limitations by AD. The FAA considers 
these limitations to be highly cost effective, and the commenter has 
provided no information to the contrary.
    Regarding the applicability of 14 CFR 25.1419, although the 
commenter is correct that compliance with this section is optional, the 
decision to comply is made only by applicants for type certificates (in 
this case, EMBRAER), and changes to those certificates, rather than by 
individual operators. EMBRAER chose to show compliance with 14 CFR 
25.1419, and the Model EMB-120 is therefore permitted to operate in 
icing conditions.
    Any operator that does not wish approval to operate into known or 
forecast icing conditions may request approval of an alternative method 
of compliance with the requirements of this AD in accordance with the 
provisions stated in paragraph (c) of the final rule.

Conflict With FAA's Inflight Aircraft Icing Plan

    One commenter requests that the proposed rule be withdrawn because 
the FAA's Inflight Aircraft Icing Plan contains a task to consider a 
regulation to install ice detectors, aerodynamic performance monitors, 
or other means to warn flightcrews of ice accumulation on critical 
surfaces. Therefore, the commenter concludes that the proposed rule is 
in conflict with the FAA's Inflight Aircraft Icing Plan.
    The FAA does not concur that the proposed rule conflicts with the 
FAA's Inflight Aircraft Icing Plan. As the commenter stated, the icing 
plan does identify a task to consider a regulation to require ice 
detectors. However, in the case of Model EMB-120 series airplanes, the 
FAA has identified an unsafe condition and has determined that 
installation of an ice detector is warranted. The potential for future 
adoption of a regulation to require an ice detector neither negates nor 
conflicts with the need to correct the existing unsafe condition.

AFM Procedures

    One commenter requests that the FAA revise paragraph (a)(2) of the 
NPRM which currently requires revision of the ``. . . Normal Procedures 
Section of the AFM by removing any icing procedures that contradict the 
procedures specified in (a)(1) and (a)(3) of this AD. . . .'' The 
commenter requests that the FAA specify which portions of the Normal 
Procedures Section of the AFM should be revised rather than leaving 
this open to interpretation by individual operators.
    One commenter requests that the FAA compare the recently proposed 
AFM changes in NPRM Docket Number 97-NM-46-AD to those AFM changes 
mandated by AD 96-09-24, amendment 39-9600 (61 FR 20677, May 7, 1996), 
as some of the procedures appear to conflict with one another. In 
particular, the commenter is concerned that the procedure in AD 96-09-
24 indicates that flaps should be left wherever they are, whereas the 
current proposed rule indicates that flaps must be left up.
    One commenter states that there is presently no guidance to many 
flightcrews to operate their deicing equipment at the first sign of ice 
accretions. The commenter further states that this guidance must first 
be evaluated for its validity and subsequently generated for flightcrew 
use.
    Another commenter states that all temperature references and 
limitations specified in the proposed rule should be referenced in 
terms of Indicated Outside Air Temperature.
    Two commenters request that the FAA review the language of the 
proposed AD specified in paragraph (a)(1) to validate whether 
continuous ignition should be used for extended periods of time. The 
current proposal is for a new limitation to require ``Turn on . . . 
Ignition Switches . . . When atmospheric or ground icing conditions 
exist.'' One of the commenters states

[[Page 66517]]

that operation of the ignition system on the ground while taxiing may 
mask other engine or fuel control problems. In addition, one commenter 
requests that the FAA review the language of the proposed AD to 
validate whether deicing equipment should be operated on the ground for 
extended periods of time.
    One commenter notes that there is currently no guidance provided in 
the AFM concerning when to use the heavy or light modes of operation of 
the ice protection system.
    One commenter questioned paragraph (a)(3) of the proposed AD, which 
states: ``Daily Checks of the Ice Protection System, add the following: 
Ice Detector System Test Button (if installed) * * * Press. Check 
normal test sequence.'' The commenter states that system reliability on 
similar aircraft do not require daily tests of this system, and that 
the system should be checked prior to dispatch into known or forecast 
icing conditions.
    The FAA concurs that clarification is necessary to specify which 
portions of the Normal Procedures Section of the AFM should be revised. 
Since the issuance of the NPRM, the manufacturer has advised the FAA of 
new, revised procedures of the AFM. Therefore, the FAA has clarified 
and combined the requirements of paragraphs (a)(2) and (a)(3) of the 
proposal into a new paragraph (a)(2) of this final rule. The new 
paragraph (a)(2) of the final rule includes complete information to be 
incorporated into the AFM under the Normal Procedures Section for 
``Operation in Icing Conditions for Flying into Icing Conditions.'' 
However, it should be noted that this information does not replace or 
revise any of the current AFM information provided under the subsequent 
section of the AFM regarding severe icing conditions.
    The FAA does not concur that procedures specified in AD 96-09-24 
conflict with the procedure of this final rule. AD 96-09-24 required 
revising the AFM to provide the flightcrew with recognition cues for 
severe icing conditions and procedures for exiting from severe icing 
conditions, and to limit or prohibit the use of various flight control 
devices, including flaps, in those severe icing conditions. The 
Limitations and Normal Procedures changes included in this final rule 
ensure that the flightcrew will be advised of when to operate the ice 
protection system during any icing condition. Therefore, the FAA finds 
that the change to AFM procedures do not conflict with the earlier AD 
requirements.
    The FAA does not concur that operators (flightcrews) have not been 
provided guidance to operate the deicing equipment at the first sign of 
ice accretion. The FAA has approved Revision 43 of the AFM, dated April 
23, 1996. This revision included a change in the Normal Procedures 
section for flight in icing conditions to indicate that wing and tail 
leading edges, engine air inlet, and windshield ice protection systems 
should be turned on at the first sign of ice formation. The originally 
approved AFM suggested a delay in activation of the wing and tail de-
ice boots until \1/4\- to \1/2\-inch ice had accumulated. However, the 
FAA recognizes that not all EMB-120 operators incorporated this change 
in procedures into their Operators Manuals. Therefore, the final rule 
requires that this procedure be added to the Limitations Section of the 
FAA-approved AFM, as well as in the Normal Procedures Section. As 
previously stated, Federal Aviation Regulations require that all 
operating limitations such as those specified in this AD be 
incorporated into air carriers' training programs and operators' 
manuals. In addition, as explained previously, the FAA has already 
determined the validity of the revised procedure to activate the ice 
protection systems at the first sign of ice accumulation, and has 
determined that this change is required in order to provide an adequate 
level of safety.
    The FAA concurs that the temperature references specified in the 
final rule should be Indicated Outside Air Temperature, and has revised 
the final rule accordingly.
    The FAA does not concur that continuous ignition should not be used 
for extended periods of time or that the operation of the ignition 
system on the ground while taxiing may mask other engine or fuel 
control problems. The FAA has reviewed information indicating that CTA, 
EMBRAER, and Pratt & Whitney have reviewed operation of continuous 
ignition, and the results indicate that extended use of continuous 
ignition does not have a detrimental effect on the operation of the 
engine, although it may decrease the life of the igniters. That 
information also indicated that engine or fuel control problems are 
diagnosed by monitoring other parameters available for the flightcrew. 
In addition, the FAA has reviewed the language of the AD concerning the 
extended operation of deicing equipment on the ground. The FAA has 
determined that operation of the deicing equipment for extended periods 
on the ground will not result in any adverse operating characteristics 
of the deicing equipment.
    The FAA concurs that there is currently no guidance in the AFM 
regarding when, or under what conditions, to use the light or heavy 
modes of the ice protection system. However, the EMBRAER Operators 
Manual recommends that the pilot assess the severity and rate of 
accretion of ice and select the appropriate mode using pilot judgment. 
Paragraph (a)(2) of the final rule has been revised to provide that 
guidance by adding the following procedures in the Normal Procedures 
Section of the FAA-approved AFM under Operation in Icing Conditions for 
Flying into Normal Icing Conditions: ``Visually evaluate the severity 
of the ice encounter and the rate of accretion and select light or 
heavy mode (1 minute or 3 minute cycle) based on this evaluation.''
    The FAA concurs that the ice protection system is required to be 
checked only once a day prior to dispatch into known or forecast icing 
conditions. The AFM change required by paragraph (a) of the final rule 
adds the ice detection system under ``Daily Checks of the Ice 
Protection System.'' Both the CTA and the FAA interpret this AFM 
guidance to mean that the daily checks of the ice protection system 
must be performed once a day before operation into known or forecast 
icing conditions, rather than before every flight into icing. To 
further clarify this procedure, the final rule has been revised to add 
the following procedures of the AFM under ``Daily Checks of the Ice 
Protection System:'' ``The following tests must be performed prior to 
the first flight of the day for which known or forecast icing 
conditions are anticipated.''

Minimum Airspeed in Icing Conditions

    A number of commenters question the validity of the minimum 
airspeed specified in paragraph (a)(3) of the proposed AD that would 
require addition of the following: ``Operation in Icing Conditions for 
Flying Into Normal Icing Conditions: Airspeed * * * 160 KIAS Minimum. 
If buffet onset occurs, increase airspeed.''
    One commenter states that buffet onset is dangerously close to the 
recommended minimum operating speed in icing conditions and should not 
be considered a prerequisite for speed additives. The commenter further 
states that the recommended minimum speed in icing lacks empirical data 
to substantiate its usage, and that any recommended minimum speeds must 
be scientifically determined.

[[Page 66518]]

    Another commenter agrees that setting a clear 160-knot minimum 
airspeed in icing conditions will provide an immediate improvement in 
safety and should be implemented. However, the commenter questions 
whether the language provided in the proposed AD establishes 
appropriate speeds for all conditions (i.e., all flap settings and 
phases of flight) as proposed in the National Transportation Safety 
Board's Safety Recommendation A-97-31. The commenter also notes that 
further tests may show that a higher minimum airspeed is required to 
provide an adequate safety margin.
    Several commenters also questioned the adequacy of the revised 
approach procedure specified in paragraph (a)(3) of the proposed AD 
which states: ``Operation in Icing Conditions for Flying Into Normal 
Icing Conditions: Approach procedure: Increase approach speeds 
(according to flap setting) by 10 KIAS until landing is assured.''
    One commenter recommends the establishment of minimum operating 
speeds for each flap configuration to include no flaps, regardless of 
whether or not the aircraft is operating in icing conditions. With 
flaps up, the commenter recommends the use of 1.4Vs @ 30 deg. bank; for 
approach procedures, the commenter recommends the use of 1.3Vs @ 
30 deg. bank. The commenter further recommends that climb procedures in 
the AFM be revised to reflect the higher speeds required with ice 
accumulation.
    Another commenter asks what approach speed should be utilized since 
an approach speed has not been defined by the manufacturer.
    The FAA concurs that clarification of the justification of the 
minimum airspeed specified in paragraph (a) of the proposal is 
necessary. The 160-knot minimum speed was defined by EMBRAER as the 
recommended holding speed for icing conditions during the original 
icing certification. The simulated ice shapes on unprotected surfaces 
used for the handling qualities and stall testing prior to icing 
approval were defined using the leading edge impingement criteria 
associated with this speed. These tests demonstrated that the aircraft 
can be maneuvered at this speed (160 KIAS) up to 30 deg. of bank angle, 
the normal maximum bank angle for holding, with an adequate stall 
margin to the buffeting boundary, stick shaker, and stick pusher with 
these ice shapes on the aircraft. In addition, natural icing tests were 
conducted at this speed and ice shapes accumulated were recorded and 
compared to the simulated ice shapes to determine their validity. These 
tests demonstrate that the airplane meets the requirements specified in 
part 25 of the Federal Aviation Regulations (14 CFR part 25) during 
flight in icing conditions, provided the ice protection systems are 
properly activated. The flight tests also demonstrated that there is a 
minimum airspeed margin of at least 15 knots indicated airspeed (KIAS) 
in turns and 20 KIAS in level flight between the initial buffeting with 
ice on the unprotected surfaces, and the minimum recommended airspeed 
of 160 KIAS. Therefore, the FAA has determined that the recommended 
minimum speed with flaps up of 160 KIAS in icing conditions has not 
only been scientifically determined, but also has been validated by 
certification flight tests and has shown adequate margin to buffet 
boundary and to stall. Consequently, the FAA has determined that the 
procedure in the proposed rule that stated ``If buffet onset occurs, 
increase airspeed'' is not necessary, and has been removed from the 
final rule.
    The FAA concurs that appropriate speeds for flap settings and 
phases of flight following flight in icing conditions should be 
provided in the final rule. The proposed AD provided a change to the 
Normal Procedures Section of the AFM that stated: ``When flying into 
known or forecast icing conditions, proceed as follows: AIRSPEED * * * 
160 KIAS MINIMUM. If buffet onset occurs, increase airspeed.'' The FAA 
recognizes that this proposed change does not clearly indicate that 
this is the minimum speed for the flaps up, gear up configuration only. 
The FAA also acknowledges that, without clarification, some operators 
may be led to believe this is the minimum speed for all gear and flap 
configurations, even though additional proposed information states: 
``Approach procedure: Increase approach speeds (according to flap 
setting) by 10 KIAS until landing is assured.''
    Therefore, the FAA has revised the wording in paragraph (a) of this 
AD to clarify the procedures for flying into known or forecast icing 
conditions, approach and landing procedures, and go-around procedures.
    The FAA has determined that this revised information will provide 
adequate information regarding minimum speeds to be used for all 
configurations after a continuous maximum icing encounter, which has 
been determined to provide the most severe ice accumulation on the 
airplane. The FAA has further determined that no change to the normal 
takeoff speeds is necessary as ice accumulation during this phase of 
flight with the ice protection system operating should have no impact 
on the flight characteristics of the airplane, provided the takeoff is 
accomplished with a properly de-iced aircraft.
    The FAA does not concur with the commenter's recommendations for 
revision of in-flight minimum operating speeds. Those speeds are 
established by FAA regulations as V2 speed for takeoff, a 
minimum speed of 1.25VS to meet final takeoff climb 
requirements in the cruise configuration, and a climb speed established 
in connection with normal landing procedures, but not exceeding 
1.5VS to meet approach climb gradient requirements. Landing 
speed is required to be not less than 1.3VS or the minimum 
control speed. These speeds, and their associated maneuver margins to 
stall warning, are in part defined by assuming an engine failure. 
Consideration is also given to ensuring adequate maneuver and stall 
warning margins as the wing trailing edge flaps are retracted or 
extended. Experience has shown these minimum speeds to be acceptable. 
Increasing the minimum operating speeds to those suggested would 
improve maneuver and stall warning margins beyond accepted levels. 
Moreover, use of the suggested higher flaps extended minimum 
operational speeds would significantly increase takeoff and landing 
field length requirements, and unnecessarily adversely affect the 
operating economics of the airplane. However, under the provisions of 
paragraph (c) of the final rule, the FAA may consider requests for 
approval of an alternative method of compliance if sufficient data are 
submitted to substantiate that such a design change would provide an 
acceptable level of safety.
    The FAA concurs that the recommended approach speeds for operations 
in non-icing conditions are not clearly defined in the current FAA-
approved AFM. Consequently, the final rule has been revised to include 
the following information in the Approach Checklist for Operation in 
Non-icing Conditions: ``Minimum Airspeed * * * Appropriate to Flap 
Position. Gear Up/Flaps 0, Minimum Recommended Airspeed 150 KIAS. Gear 
Up/Flaps 15, Minimum Recommended Airspeed 130 KIAS.'' The requirements 
of the final rule to increase approach speeds by 10 KIAS following 
flight in icing conditions would, therefore, give minimum approach 
speeds of 160 KIAS and 140 KIAS for flaps 0 and 15, respectively.

Incorporation of AFM Changes Into Operators Manuals

    Several commenters expressed concern that the NPRM does not specify

[[Page 66519]]

how the changes to the Normal Procedures Section of the FAA-approved 
AFM will be implemented in operator flight manuals and training 
programs. This concern stems from the fact that although EMBRAER issued 
revision number 43 to the Normal Procedures Section of its AFM in April 
1996 to require activating the de-ice boots ``at the first sign of ice 
formation,'' this new icing procedure has not yet been implemented by 
several operators.
    The FAA acknowledges that the final rule does not specify how 
changes to the Normal Procedures Section of the AFM should be 
implemented in operator flight manuals and training programs. FAA Order 
8400.10 recognizes that operators may rewrite these AFM procedures to 
tailor them to the operators' operation and to make them more suitable 
for flightcrew use in operation under parts 121 and 135 of the Federal 
Aviation Regulations (14 CFR parts 121 and 135). However, the FAA has 
chartered a team to review the process being used to transfer 
information in the manufacturer's flightcrew operating documents, 
including AFM's, to operators' documents. The team will make 
recommendations to revise the current process, which could lead to a 
higher level of safety. However, this issue is beyond the scope of this 
rulemaking, and no change has been made to the final rule.

Cost Impact Information

    Two commenters state that the cost of retrofit will be 
substantially higher than the estimated cost in the NPRM if aircraft 
down time and canceled/rescheduled equipment are considered.
    One commenter requests an explanation as to why a complete cost-
benefit analysis is unnecessary and redundant. This commenter states 
that the explanation given in the NPRM relates to FAA's position not to 
consider additional costs of accomplishment of the AD after a 
determination has been made by the FAA that an unsafe condition exists 
in a product. Nevertheless, the commenter believes a cost-benefit 
analysis should be used to determine if a rule should be adopted in the 
first place.
    The FAA acknowledges the concerns of the commenters of the cost of 
retrofit required by this final rule. The FAA recognizes that, in 
accomplishing the requirements of any AD, operators may incur other 
costs in addition to the ``direct'' costs that are estimated in the 
cost impact. However, the FAA makes every effort to consider all other 
costs (such as downtime and canceled/rescheduled equipment, etc.) to 
operators in establishing the terms of compliance in a AD. For example, 
the FAA generally establishes AD compliance times that coincide with 
most operators' maintenance schedules, unless safety considerations 
dictate more urgent corrective action. The FAA also frequently revises 
AD's when commenters identify less costly alternatives to address the 
unsafe condition.
    Finally, since the issuance of the NPRM, EMBRAER has issued Service 
Bulletin No. 120-30-0027, dated May 9, 1997, which describes procedures 
for installation of an ice detector that will enable the flightcrew to 
more accurately determine the need to activate the ice protection 
systems on the airplane and to take appropriate action. The service 
bulletin includes specific costs for the installation of the ice 
detector. Those figures have enabled the FAA to provide a more 
realistic estimate in the cost impact section of the final rule.
    The FAA does not concur that further discussion is necessary to 
explain why a complete cost-benefit analysis is unnecessary and 
redundant, since those reasons were stated in the NPRM. Further, the 
FAA does not concur that a cost-benefit analysis should be used to 
determine if a rule should be adopted in the first place. Once an 
unsafe condition is identified, as in this case, it must be corrected 
regardless of cost. When the FAA has determined what actions are 
necessary to correct an unsafe condition, the FAA is obligated to 
require that those actions be accomplished. This obligation arises from 
the statutory requirement that the FAA, not aircraft operators, 
determines the minimum required safety standards for civil aircraft. 
Therefore, it would be inappropriate in issuing AD's for the FAA to 
engage in the same kind of balancing of costs and benefits as when it 
is considering regulations to improve an already high level of safety. 
If an operator has an alternative method of compliance that would ease 
the economic burden for the operator, as well as provide an acceptable 
level of safety, the operator may request approval of that alternative 
method of compliance, as provided by paragraph (c) of the final rule.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Cost Impact

    There are approximately 282 EMBRAER Model EMB-120 series airplanes 
of the affected design in the worldwide fleet. The FAA estimates that 
220 airplanes of U.S. registry will be affected by this AD.
    The FAA estimates that it will take approximately 1 work hour per 
airplane to accomplish the AFM revisions, and that the average labor 
rate is $60 per work hour. Based on these figures, the cost impact of 
the AD on U.S. operators is estimated to be $13,200, or $60 per 
airplane.
    The FAA estimates that it will take approximately 47 work hours per 
airplane to accomplish the proposed installation, and that the average 
labor rate is $60 per work hour. Required parts will cost approximately 
$13,054 per airplane. Based on these figures, the cost impact of the 
proposed AD on U.S. operators is estimated to be $3,492,280, or $15,874 
per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the requirements of this AD 
action, and that no operator would accomplish those actions in the 
future if this AD were not adopted.

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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

[[Page 66520]]

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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

97-26-06 Empresa Brasileira de Aeronautica, S.A., (EMBRAER): 
Amendment 39-10249. Docket 97-NM-46-AD.

    Applicability: All Model EMB-120 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 
otherwise 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 (c) 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 accomplished 
previously.
    To ensure that the flightcrew is able to recognize the formation 
of significant ice accretion, which could result in reduced 
controllability of the airplane in normal icing conditions, 
accomplish the following:
    (a) Within 30 days after the effective date of this AD, 
accomplish paragraphs (a)(1) and (a)(2) of this AD.
    (1) Revise the Limitations Section of the FAA-approved Airplane 
Flight Manual (AFM) to include the following requirements for 
activation of the ice protection systems. This may be accomplished 
by inserting a copy of this AD in the AFM.
    ``TURN ON ICE PROTECTION SYSTEM and IGNITION SWITCHES AS 
FOLLOWS:
     AOA, TAT, SLIP, ENGINE AIR INLET, and IGNITION 
SWITCHES:

--When atmospheric or ground icing conditions exist.

     PROPELLER:

--When atmospheric or ground icing conditions exist, OR
--At the first sign of ice formation anywhere on the aircraft.

    WING and TAIL LEADING EDGES, and WINDSHIELD:

--At the first sign of ice formation anywhere on the aircraft.

    Note: On takeoff, delay activation of the wing and tail leading 
edge de-ice systems until reaching the final segment speed.
    Note: Atmospheric icing conditions exist when:

--Indicated Outside Air Temperature (OAT) during ground operations 
or Total Air Temperature (TAT) in flight is 10 degrees C or below; 
and
--Visible moisture in any form is present (such as clouds, fog with 
visibility of one mile or less, rain, snow, sleet, or ice crystals).

    Note: Ground icing conditions exist when:

--Indicated OAT during ground operations is 10 degrees C or below; 
and
--Surface snow, standing water, or slush is present on the ramps, 
taxiways, or runways.

    Note: For Operation in Atmospheric Icing Conditions:

--Follow the procedures in the Normal Procedures Section under 
Operation in Icing Conditions.''

    (2) Revise the Normal Procedures Section of the FAA-approved 
Airplane Flight Manual (AFM) to include the following additional and 
revised information regarding operation in icing conditions. This 
may be accomplished by inserting a copy of this AD in the AFM.
    ``Under DAILY CHECKS of the Ice Protection System, add the 
following:
    The following tests must be performed prior to the first flight 
of the day for which known or forecast icing conditions are 
anticipated.
Ice Detector System TEST Button (if installed)....................PRESS
    Check normal test sequence.
    Under APPROACH Checklist, add the following:
Minimum Airspeed.........APPROPRIATE TO FLAP POSITION (See Table Below)

------------------------------------------------------------------------
                 Gear/Flap                  Minimum Recommended Airspeed
------------------------------------------------------------------------
UP/0 deg..................................  150 KIAS                    
UP/15 deg.................................  130 KIAS                    
------------------------------------------------------------------------

    Under OPERATION IN ICING CONDITIONS for FLYING INTO ICING 
CONDITION, replace the current AFM section information for normal 
icing conditions with the following:

    --During flight, monitoring for icing conditions should start 
whenever the indicated outside air temperature is near or below 
freezing or when operating into icing conditions, as specified in 
the Limitations Section of this manual.
--When operating in icing conditions, the front windwhield corners 
(unheated areas), propeller spinners, and wing leading edges will 
provide good visual cues of ice accretion.
--For airplanes equipped with an ice between system, icing 
conditions will also be indicated by the illumination of the ICE 
CONDITION light on the multiple alarm panel.
--When atmospheric or ground icing conditions exist, proceed as 
follows:

AOA, TAT, SLIP, and ENGINE AIR INLET.................................ON
IGNITION Switches....................................................ON
AIRSPEED (Flaps and Gear UP)...........................160 KIAS MINIMUM

--When atmospheric or ground icing conditions exist, OR
--At the first sing of ice formation any where on the aircraft, 
proceed as follows:

PROPELLER Deicing Switch.............................................ON
    Select NORM mode if indicated OAT is above -10 deg. C (14 deg. 
F) or COLD mode if indicated OAT is below -10 deg. C (14 deg. F).
--At the first sign of ice formation anywhere on the aircraft, 
proceed as follows:

WINDSHIELD...........................................................ON
WING and TAIL LEADING EDGE...........................................ON

Visually evaluate the severity of the ice encounter and the rate of 
accretion and select light or heavy mode (1 minute or 3 minute 
cycle) based on this evaluation.

    Note: On takeoff, delay activation of the wing and tail leading 
edge de-ice systems until reaching the final segment speed.

    Note: The minimum NH required for proper operation of the 
pneumatic deicing system is 80%. At lower NH values, the pneumatic 
deicing system may not totally inflate, and the associated failure 
lights on the overhead panel may illuminate. If this occurs, 
increase NH.
    Holding configuration:

Landing Gear Lever...................................................UP
Flap Selector Lever..................................................UP
Np...............................................85% MINIMUM

    Increase Np as required to eliminate propeller 
vibrations.
    Approach and Landing procedure:

Increase approach and landing speeds, according to the following 
flap settings, until landing is assured. Reduce airspeed to cross 
runway threshold (50 ft) at VREF. 

Flaps 15--Increase Speed by 10 KIAS (130+10)
Flaps 25--Increase Speed by 10 KIAS (VREF25+10)
Flaps 45--Increase Speed by 5 KIAS (VREF45+5)

    Go-Around procedure:
    Reduce values from Maximum Landing Weight Approach Climb Limited 
charts by:

1500 lbs. for PW 118 Engines
1544 lbs. for PW 118A and 118B Engines
Flaps 15--Increase approach climb speed by 10 KIAS 
(V2+10); Decrease approach climb gradient by:
    3.0% for PW 118 Engines
    2.9% for PW 118A and 118B Engines
Flaps 25--Increase landing climb speed by 10 KIAS 
(VREF25+10)
Flaps 45--Increase landing climb speed by 5 KIAS (VREF+5)

CAUTION: The ice protection systems must be turned on immediately 
(except leading edge de-icers during takeoff) when the ICE CONDITION 
light illuminates on the multiple alarm panel or when any ice 
accretion is detected by visual observation or other cues.


[[Page 66521]]


CAUTION: Do not interrupt the automatic sequence of operation of the 
leading edge de-ice boots once it is turned ON. The system should be 
turned OFF only after leaving the icing conditions and after the 
protected surfaces of the wing are free of ice.
    (b) Within 10 months after the effective date of this AD, 
install an ice detector in accordance with EMBRAER Service Bulletin 
No.: 120-30-0027, dated May 9, 1997.
    (c) 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, Atlanta ACO. Operators shall submit 
their requests through an appropriate FAA Principal Operations 
Inspector, who may add comments and then send it to the Manager, 
Atlanta ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Atlanta ACO.

    (d) 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.
    (e) The installation of the ice detector shall be done in 
accordance with EMBRAER Service Bulletin No. 120-30-0027, dated May 
9, 1997. 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 EMBRAER, Empresa 
Brasileira De Aeronautica S/A, Sao Jose Dos Campos, Brazil. 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.
    (f) This amendment becomes effective on January 23, 1998.

    Issued in Renton, Washington, on December 11, 1997.
Gilbert L. Thompson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-33000 Filed 12-18-97; 8:45 am]
BILLING CODE 4910-13-U