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

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.

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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