20616 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96–CE–01–AD; Amendment 39–

9587; AD 96–09–11]

RIN 2120–AA64

Airworthiness Directives; de Havilland,

Inc. DHC–6 Series Airplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Final rule.

SUMMARY: This amendment adopts a

new airworthiness directive (AD) that

applies to de Havilland DHC–6 series

airplanes. This action requires revising

the Airplane Flight Manual (AFM) to

provide the flight crew with recognition

cues for, and procedures for exiting

from, severe icing conditions, and to

limit or prohibit the use of various flight

control devices. This amendment is

prompted by results of a review of the

requirements for certification of the

airplane in icing conditions, new

information on the icing environment,

and icing data provided currently to the

flight crews. The actions specified by

this AD are intended to minimize the

potential hazards associated with

operating the airplane in freezing rain or

freezing drizzle conditions by providing

more clearly defined procedures and

limitations associated with such

conditions.

EFFECTIVE DATE: June 11, 1996.

ADDRESSES: Information that relates to

this AD may be examined at the Federal

Aviation Administration (FAA), Central

Region, Office of the Assistant Chief

Counsel, Attention: Rules Docket 96–

CE–01–AD, Room 1558, 601 E. 12th

Street, Kansas City, Missouri 64106.

FOR FURTHER INFORMATION CONTACT: Mr.

John Dow, Aerospace Engineer, FAA,

Small Airplane Directorate, 1201

Walnut, suite 900, Kansas City, Missouri

64106; telephone (816) 426–6934;

facsimile (816) 426–2169.

SUPPLEMENTARY INFORMATION: A

proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to

include an AD that would apply to de

Havilland DHC–6 series airplanes was

published in the Federal Register on

January 25, 1996 (61 FR 2175). The

action proposed to require revising the

Airplane Flight Manual (AFM) to

specify procedures that would prohibit

flight in freezing rain or freezing drizzle

conditions (as determined by certain

visual cues), limit or prohibit the use of

various flight control devices, and

provide the flight crew with recognition

cues for, and procedures for exiting

from, severe icing conditions.

Disposition of Comments

Interested persons have been afforded

an opportunity to participate in the

making of this amendment. Due

consideration has been given to the

comments received.

In addition to the proposed rule

described previously, in January 1996,

the FAA issued 17 other similar

proposals that address the subject

unsafe condition on various airplane

models (see below for a listing of all 18

proposed rules). These 17 proposals also

were published in the Federal Register

on January 25, 1996. This final rule

contains the FAA’s responses to all

public comments received for each of

these proposed rules.

Docket No. Manufacturer/airplane model Federal Register citation

96–CE–01–AD de Havilland DHC–6 Series .................................................................................................................. 61 FR 2175

96–CE–02–AD EMBRAER EMB–110P1/EMB–110P2 .................................................................................................. 61 FR 2183

96–CE–03–AD Beech 99/200/1900 Series .................................................................................................................... 61 FR 2180

96–CE–04–AD Dornier 228 Series ................................................................................................................................ 61 FR 2172

96–CE–05–AD Cessna 208/208B .................................................................................................................................. 61 FR 2178

96–CE–06–AD Fairchild Aircraft SA226/SA227 Series ................................................................................................. 61 FR 2189

96–CE–07–AD Jetstream 3101/3201 ............................................................................................................................. 61 FR 2186

96–NM–13–AD Jetstream BAe ATP ............................................................................................................................... 61 FR 2144

96–NM–14–AD Jetstream 4101 ...................................................................................................................................... 61 FR 2142

96–NM–15–AD British Aerospace HS 748 Series .......................................................................................................... 61 FR 2139

96–NM–16–AD Saab SF340A/SAAB 340B/SAAB 2000 Series ..................................................................................... 61 FR 2169

96–NM–17–AD CASA C–212/CN–235 Series ................................................................................................................ 61 FR 2166

96–NM–18–AD Dornier 328–100 Series ........................................................................................................................ 61 FR 2157

96–NM–19–AD EMBRAER EMB–120 Series ................................................................................................................. 61 FR 2163

96–NM–20–AD de Havilland DHC–7/DHC–8 Series ...................................................................................................... 61 FR 2154

96–NM–21–AD Fokker F27 Mark 100/200/300/400/500/600/700/050 Series ................................................................ 61 FR 2160

96–NM–22–AD Short Brothers SD3–30/SD3–60/SD3–SHERPA Series ....................................................................... 61 FR 2151

95–NM–146–AD Aerospatiale ATR–42/ATR–72 Series ................................................................................................... 61 FR 2147

Comment 1. Support for the Proposals

Numerous commenters support the

FAA’s intent to minimize the potential

hazards associated with operating

airplanes of any type design in severe

icing conditions. One commenter states

that the limitation prohibiting the use of

flaps while enroute and during holding

in icing conditions will be a positive

contribution to safety. Additionally,

several commenters support the

requirement of the proposed AD for

Aerospatiale airplanes for installation of

modified deicing boots on the outer

leading edges of the wings. One of these

commenters states that the

incorporation of AFM procedures, in

addition to installation of the modified

boots, provide a substantial margin of

safety for the Aerospatiale fleet.

Comment 2. Requests Concerning

References to ‘‘Freezing Rain/Freezing

Drizzle’’

Raytheon requests that references to a

class of meteorological conditions in the

limitations described as ‘‘freezing rain

or freezing drizzle’’ should be removed

from the proposed rules. Raytheon

contends that instructions for the flight

crew should be restricted to hazardous

conditions that are defined by the

accumulation of ice. The commenter

states that the term ‘‘severe icing’’ has

a specific meaning as defined in the

Aeronautical Information Manual: ‘‘The

rate of accumulation is such that the

icing/anti-icing equipment fails to

reduce or control the hazard. Immediate

diversion is necessary.’’ The commenter

states that, although freezing rain or

freezing drizzle may involve drops

larger than those specified in Appendix

C of part 25 (‘‘Airworthiness Standards:

Transport Category Airplanes’’) of the

Federal Aviation Regulations (14 CFR

part 25), flight into those conditions

does not always result in accumulation
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20617

of ice beyond the capability of the

aircraft nor is severe icing always the

result of freezing rain or freezing

drizzle. Raytheon concludes that the

limitation specified in paragraph (a)(1)

of the proposals which reads, ‘‘Flight in

meteorological conditions described as

freezing rain or freezing drizzle, as

determined by the following visual

cues, is prohibited,’’ is an inference or

conclusion that does not follow from the

premises.

The European Regional Airlines

(ERA) Association states that the

proposals define visual cues to be used

to identify ‘‘freezing rain’’ and ‘‘freezing

drizzle,’’ but these criteria are

inconsistent with the criteria defined by

the International Civil Aviation

Organization (ICAO) and used by

weather observers in aviation

meteorological support services. The

FAA infers from this remark that ERA

requests the use of ICAO terminology

associated with the visual cues.

The FAA concurs partially. The FAA

concurs that most of the references to

‘‘freezing rain/freezing drizzle’’ can be

removed from the final rules. The FAA

has revised the final rules to replace

certain references to freezing rain and

freezing drizzle with the words ‘‘severe

icing.’’ The FAA finds that since the

visual cues contained in paragraph

(a)(1) of these final rules indicate that

icing conditions have exceeded the

limits of the ice protection equipment,

the use of the terminology ‘‘severe

icing’’ is appropriate. As stated by one

commenter, ‘‘severe icing’’ is

terminology used to describe icing

conditions that exceed the capabilities

of the ice protection equipment. The

terminology ‘‘severe icing’’ is commonly

used and understood within the

aviation community. Additionally, there

should be no confusion over the use of

this term in the final rules because the

AFM revisions required by these AD’s

define the terminology ‘‘severe icing’’ by

specifying the visual cues that indicate

when the capabilities of the ice

protection equipment have been

exceeded. However, the FAA would

consider a request for approval of an

alternative method of compliance to use

terminology other than ‘‘severe icing’’ in

an AFM, in accordance with the

provisions of these AD’s, provided that

adequate justification is presented to

support such a request.

Any inconsistencies that may exist

between the criteria used by weather

specialists to define ‘‘severe icing’’ and

the criteria stated in these final rules are

not relevant for these AD’s because

these AD’s do not require the flight crew

to take any action based on information

provided by a weather observer. For

these AD’s, the flight crew must only

take action if certain visual cues are

present on the airplane.

The FAA has determined that

reference to freezing rain and freezing

drizzle should not be removed from the

text of the ‘‘Caution’’ that appears in

paragraph (a)(2) of the proposals. [Note:

The ‘‘Caution’’ appears as the

‘‘Warning’’ in paragraph (a)(1) of the

final rules. An explanation of this

change is contained in the disposition of

Comment 49 of these final rules.]

Reference to freezing rain and freezing

drizzle in that portion of text is made

simply to provide a description of

conditions that may result in ice buildup that exceeds the capabilities of the

ice protection system.

Comment 3. Request for Review of

‘‘Severe Icing’’ Terminology

One commenter, the Civil Aviation

Authority (CAA), which is the

airworthiness authority for the United

Kingdom, requests that use of the

terminology ‘‘severe icing’’ be reviewed.

The CAA does not believe it is

appropriate that this terminology

becomes accepted for supercooled large

droplet (SLD) conditions. The CAA

indicates that a common interpretation

for ‘‘severe icing’’ is that beyond the

limit specified in Appendix C of part 25

of the Federal Aviation Regulations (14

CFR part 25), which is at or just over the

capability of the ice protection system.

The FAA has reviewed the use of the

terminology ‘‘severe icing’’ as related to

SLD. The FAA finds that ice resulting

from SLD conditions may not always

meet the criterion specified in the

common interpretation of ‘‘severe

icing,’’ as described by the commenter.

The FAA notes that while SLD

conditions may result in the formation

of severe icing, severe icing also may

accrue in conditions such as liquid

water content, temperature, or extent of

cloud, when those conditions exceed

the limits specified in Appendix C of

part 25 of the Federal Aviation

Regulations (14 CFR part 25). As

explained previously, most references to

freezing rain and freezing drizzle have

been replaced with the terminology

‘‘severe icing.’’ Additionally, the AFM’s

for the affected airplanes include a

definition of severe icing.

Comment 4. Request To Withdraw the

Proposals: Significant Economic Impact

on Operating Community

A number of commenters request that

the proposals be withdrawn because the

effect of these proposed AD’s will

produce a significant economic impact

on the operating community. The

commenters indicate that many flights

would need to be canceled in order to

make all reasonable efforts to avoid

encounters with freezing rain/freezing

drizzle conditions—i.e., when these

conditions are forecast, airplanes will be

prohibited from flight into those

conditions. One commenter remarks

that, based on the actual weather in

January 1996, nearly 75 percent of its

scheduled flights would have been

canceled due to forecast or actual

freezing rain or freezing drizzle

conditions if the AD’s had been in

effect. The commenters do not believe

that the FAA has considered the

economic factors affected by the

proposed actions, such as the number of

flights lost per day, crew costs,

passenger compensation, misconnected

baggage, etc.

If the FAA does not withdraw the

proposals, one commenter states that

the prohibition of flight in freezing rain

or freezing drizzle, as specified in

paragraph (a)(1) of the proposals, should

be revised. The commenter suggests the

following: ‘‘The aircraft should be

immediately flown clear of icing

conditions if ice is seen forming on the

upper surface of the wing behind the

leading edge deice boots.’’ The

commenter believes that the current

wording in the proposals would cause

flight crews to cancel or delay departure

not only when freezing rain or freezing

drizzle exists, but also when those

conditions are forecast.

The FAA concurs partially. The FAA

finds that some misunderstanding exists

among the commenters concerning the

intent of these AD’s. Many of the

commenters believe that the AD’s will

prevent affected airplanes from flight in

forecast freezing rain and freezing

drizzle. This is not the case. The FAA

agrees that certain language contained

in the AD’s must be clarified to reflect

its intent. The FAA has evaluated the

wording proposed by one of the

commenters and agrees with it in

principal. However, the FAA has

determined that the first limitation in

paragraph (a)(1) of the final rules must

be revised in order to accommodate

visual cues other than that specified by

the commenter, to incorporate

terminology familiar to the flight crew,

and to emphasize that these AD’s

address only in-flight icing encounters.

Additionally, in order to ensure that

appropriate coordination with Air

Traffic Control is accomplished, the

FAA has revised the instruction

following the visual cues in paragraph

(a)(1), and has moved that instruction to

the end of the first limitation in

paragraph (a)(1) of the final rules. The

entire limitation reads as follows:

‘‘During flight, severe icing conditions
20618 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

that exceed those for which the airplane

is certificated shall be determined by

the following visual cues. If one or more

of these visual cues exists, immediately

request priority handling from Air

Traffic Control to facilitate a route or an

altitude change to exit the icing

conditions.’’ (Operators should note

that, in the final rule for Aerospatiale

airplanes, only one visual cue is

specified. That cue involves ice on the

side window of the airplane.)

Several commenters question certain

issues related to dispatch of the airplane

in severe icing conditions. One

commenter states that the procedures

specified in the proposed AD’s fail to

address the conditions that would

prohibit takeoff in freezing rain and

freezing drizzle. The commenter

believes the visual cues provided in the

proposals would only appear on an

airplane during flight. Thus, allowable

conditions for takeoff during times of

forecast freezing rain or freezing drizzle

are left to the individual operator’s

interpretation. Another commenter

believes that the FAA has not

established a basis for prohibiting flight

in all reported freezing drizzle. The

commenter contends that takeoff in

freezing rain should always be

prevented, but takeoff in freezing drizzle

should be possible after applying

appropriate deicing or anti-icing

treatments. One commenter requests

that the FAA clarify how the procedures

for exiting freezing rain/freezing drizzle

conditions would apply to takeoff and

landing. The commenter states that

landing during those conditions might,

in many cases, be the most expeditious

method of avoiding a hazardous

condition. Another commenter suggests

that the AFM for Aerospatiale airplanes

should be revised to reflect standard

dispatch rules; however, the commenter

provides no justification for this request.

The FAA concurs that visual cues that

would prohibit takeoff in freezing rain

or freezing drizzle were not provided

because the FAA’s intent is that these

AD’s address only in-flight icing

encounters. These AD’s do not affect

any existing regulations or FAAapproved operating procedures related

to takeoff, dispatch, or release of an

airplane in icing conditions. These AD’s

only prohibit remaining in icing

conditions when certain visual cues are

present on the airplane; these AD’s do

not prohibit flight into forecast or

reported freezing drizzle. Operators

must comply with existing rules that

require an airplane to be free of ice prior

to takeoff. Further, the FAA finds no

need to revise the AFM for Aerospatiale

airplanes to reflect standard dispatch

rules. The FAA also considers that

landing the airplane when freezing rain/

freezing drizzle conditions are

encountered would, in many cases, be

the most expeditious method of exiting

the conditions. Such landing would be

in compliance with the limitation that

requires the flight crew to exit the

severe icing conditions.

Two commenters indicate that the

first note that appears in paragraph

(a)(1) of the proposed rules could be

interpreted to mean that if freezing rain

or freezing drizzle is forecast anywhere

along the route of flight, the airplane

could not be dispatched. One of the

commenters concludes that forecasting

methodologies are inadequate and

would need to be improved. The other

commenter suggests that the FAA

remove the word ‘‘purely’’ from the

note. The same commenter requests that

the FAA clarify that the airplane may be

dispatched if the forecast may indicate

freezing rain/freezing drizzle

conditions. Another commenter

indicates that the wording of the same

note is unclear as to how the FAA

defines a ‘‘purely’’ inadvertent

encounter. The commenter states that

examples of such purely inadvertent

encounters would be helpful.

One commenter asks the following

questions in regard to the same note:

—What are ‘‘reasonable efforts?’’

—What does ‘‘immediately exit’’ mean?

Are the procedures for immediately

exiting listed in the Air Traffic

Controller’s Handbook or the

Airman’s Information Manual? Can a

pilot operating the airplane in a

holding pattern decide on his/her

own to immediately descend below

the freezing level without regard to

other traffic?

One commenter states that the note

should be placed in the Normal

Procedures Section of the AFM, rather

than in the Limitations Section. The

commenter provides no justification for

this request.

The FAA concurs that clarification of

this note is necessary. The FAA

originally included the note in the AD’s

to clarify the intent of the rules. Since

the first instruction and the limitation

that follows have been revised in these

final rules, the FAA finds that inclusion

of the clarifying note is no longer

necessary. In order to avoid any possible

misinterpretation of the intent of the

limitation on flight in freezing rain or

freezing drizzle, the FAA has removed

the first note that appeared in paragraph

(a)(1) of the proposals. These AD’s do

not prohibit flight into forecast or

reported freezing rain or freezing

drizzle. This means that the aircraft is

not prohibited from takeoff, dispatch, or

release simply because the forecast may

indicate freezing rain or freezing drizzle,

but is prohibited from continued flight

in severe icing conditions.

Comment 5. Request To Withdraw the

Proposals: No Unsafe Condition Has

Been Established

Several commenters request that the

proposals be withdrawn because no

unsafe condition has been established

with respect to airplane handling

characteristics in severe icing

conditions. One commenter states that

the preamble of the proposals does not

provide data that establish an unsafe

condition; the preamble only indicates

that there are inadequate data to

represent all possible conditions.

Another commenter remarks that the

FAA’s dismissal of the significance of

the test results with the specious

comment, ‘‘such airplanes could

develop ice shapes other than those

tested,’’ is wholly speculative, and is an

invalid basis on which to issue an AD

under the provisions of part 39

(‘‘Airworthiness Directives’’) of the

Federal Aviation Regulations (14 CFR

part 39).

The FAA does not concur that these

AD’s should be withdrawn. As stated in

the preamble to the proposals, the FAA

has not required that airplanes be

shown to be capable of operating safely

in icing conditions outside the icing

certification envelope specified in

Appendix C of part 25 of the Federal

Aviation Regulations (14 CFR part 25).

This means that any time an airplane is

flown in icing conditions for which it is

not certificated, there is a potential for

an unsafe condition to exist or develop

and the flight crew must take steps to

exit those conditions expeditiously.

Further, the FAA has determined that

flight crews are not currently provided

with adequate information necessary to

determine when an airplane is operating

in icing conditions for which it is not

certificated or what action to take when

such conditions are encountered. The

absence of this information presents an

unsafe condition because without that

information, a pilot may remain in icing

conditions for which the airplane has

not been proven to be safe. These AD’s

correct the unsafe condition by

requiring AFM revisions that provide

the flight crews with visual cues to

determine when icing conditions have

been encountered for which the airplane

is not certificated, and by providing

procedures to safely exit those

conditions.

Additionally, in the preamble to the

proposed rules, the FAA discussed the

investigation of roll control anomalies to

explain that this investigation was not a
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20619

complete certification program. The

testing was designed to examine only

the roll handling characteristics of the

airplane in certain droplets the size of

freezing drizzle. The testing was not a

certification test to approve the airplane

for flight into freezing drizzle. The

results of the tests were not used to

determine if these final rules were

required, but rather to determine if

design changes were needed to prevent

a catastrophic roll upset. The roll

control testing and the AD’s must be

viewed as two unrelated actions.

Comment 6. Request To Withdraw the

Proposals: Unsafe Condition Is Outside

Certification Limits

One commenter states that the

proposed AD’s should be withdrawn

because the issuance of AD’s to address

the problems of icing encounters

outside of the limits for which the

airplane is certificated is a completely

inappropriate application of part 39 of

the Federal Aviation Regulations (14

CFR part 39). Another commenter

contends that since the Aerospatiale

aircraft passed all present certification

testing, what transpired beyond the

limits of certification should not be held

against that aircraft.

The FAA does not concur that the

AD’s should be withdrawn on the basis

that the unsafe condition is outside the

icing certification envelope. Flight in

icing conditions that are outside the

icing certification envelope occurs

during the normal service life of an

airplane. Apart from the visual cues

provided in these final rules, there is no

existing method provided to the flight

crews to identify when the airplane is

in a condition that exceeds the icing

certification envelope. The appropriate

vehicle for providing this method of

identification is through issuance of an

AD. The FAA acknowledges that the

Aerospatiale airplane has been shown to

comply with existing certification rules;

however, no airplane is certificated for

flight in icing conditions outside of

Appendix C of part 25 of the Federal

Aviation Regulations (14 CFR part 25).

Comment 7. Request To Withdraw the

Proposals: Proposals Unfairly

Discriminate Against TurbopropellerPowered Aircraft

Several commenters state that the

proposed AD’s should be withdrawn

because the AD’s unfairly discriminate

against turbopropeller-powered aircraft.

The commenters contend that by issuing

these proposed rules, the FAA is

creating a public perception that

turbopropeller-powered aircraft are less

safe than other aircraft.

Numerous commenters oppose the

statement contained in the preamble of

the proposals which indicates that since

turbopropeller-powered airplanes are

more likely to operate at low altitudes

and to make more frequent landings,

they are more likely to encounter icing

conditions that are outside the icing

envelope. One commenter states that the

mere fact that turbopropeller-powered

airplanes make more frequent landings

is irrelevant for the following reasons:

—Every flight encounters the same

atmospheric conditions after takeoff

and prior to landing, whether the

airplane is powered by a

turbopropeller or turbojet engine;

—There are numerous airplanes

powered by turbojet engines that

operate on segments equal in duration

to those operated by many

turbopropeller-powered aircraft;

numerous airplanes powered by

turbojet engines make just as frequent

landings; and

—Even if turbopropeller-powered

aircraft do make more frequent

landings, there is no negative

inference to be drawn from that fact;

more opportunities are available to

ensure that ice has not formed on the

aircraft if the aircraft lands more

frequently.

One commenter states that the

altitudes where SLD conditions exist are

the same altitudes at which jets would

encounter those conditions during the

departure and arrival phases of flight.

Flight in SLD conditions that would

have a negative effect on a

turbopropeller-powered airplane would

have the same effect on a jet, since both

are certificated under the same rules

with regard to flight into adverse

weather, and both fly at about the same

speeds during the departure and arrival

phases of flight. Additionally, another

commenter adds that no airplane,

whether it is powered by a

turbopropeller, turbojet, or turbofan

engine, is certificated for operation in

SLD conditions.

Another commenter indicates that

icing encounters take place at altitudes

below the cruising altitudes of most

turbopropeller-powered aircraft used in

scheduled service; this also occurs on

airplanes powered by turbojet engines.

Icing encounters occur during takeoff,

climb, descent, holding, and landing

phases of flight on both types of aircraft.

The commenter adds that operating the

airplane in a holding pattern for a

prolonged period in severe icing

conditions is hazardous for both turbojet

and turbopropeller-powered aircraft.

The commenter explains that, although

the exposure time per flight hour of a

long-haul jet aircraft is less, the

exposure on a per flight basis is exactly

the same. The commenter states that,

like landing gear life limits, the proper

measure of exposure to freezing rain/

freezing drizzle should be the number of

flights, not the number of flight hours.

Another commenter, Saab, states that

Saab Model SAAB 2000 series airplanes

have a unique power-to-weight ratio,

which makes it comparable with

airplanes of the same size and, in some

relevant areas such as climb

performance and single engine ceiling,

even far superior. Operators of those

airplanes can operate the aircraft overthe-weather at flight level (FL) 310. This

means that these Saab airplanes operate

on jet profiles and, therefore, are not

exposed to the icing conditions that are

outside the icing envelope any more

than the airplanes that are excluded

from the proposals.

The FAA does not concur that the

proposals should be withdrawn. The

FAA does not intend to imply through

issuance of these AD’s that

turbopropeller-powered airplanes are

less safe than airplanes having other

types of propulsion systems. As stated

in the preamble of the proposals, the

FAA addressed certain airplanes as a

higher priority for two reasons:

—Turbopropeller-powered airplanes are

more likely to operate at low altitudes

and to make more frequent landings;

therefore, they are more likely to

encounter icing conditions that are

outside the icing envelope specified

in Appendix C of part 25 of the

Federal Aviation Regulations (14 CFR

part 25); and

—The flight crew of an airplane having

an unpowered roll control system

must rely solely on physical strength

to counteract roll control anomalies,

whereas a roll control anomaly that

occurs on an airplane having a

powered roll control system need not

be offset directly by the flight crew.

Since the issuance of the proposed

rules, the FAA has reconsidered this

reasoning. The FAA acknowledges that

simply because an airplane is

turbopropeller-powered and has a

particular flight profile, that airplane

should not be addressed as a higher

priority. However, this does not

diminish the significance of the

necessity of the flight crew of an

airplane having an unpowered roll

control system to rely on physical

strength to counteract roll control

anomalies. The subject airplanes all

have pneumatic deicing boots and

unpowered aileron controls, which have

been common denominators in the

accident and incident history
20620 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

concerning flight in icing conditions

and, in particular, during conditions

when SLD was believed to be present.

Therefore, airplanes having those design

features are of immediate concern to the

FAA and were addressed as a higher

priority. Additionally, these AD’s

primarily address airplanes used in

regularly scheduled passenger service in

the United States.

The FAA finds that the comment

indicating that more frequent landings

provides more opportunity to verify that

ice has not formed is irrelevant. It also

could be said that more frequent

landings gives more opportunity for ice

to form. The FAA agrees with the

statement that holding for prolonged

periods in severe icing conditions is

hazardous for all aircraft types. The

FAA is considering initiating an

assessment of the need to prohibit all

aircraft from continued flight in severe

icing conditions as defined in these

AD’s.

Although Transport Canada Aviation

does not request that the proposed AD’s

be withdrawn, the commenter indicates

that roll control anomalies could exist

for all aircraft whether they have

powered or unpowered roll control

systems. Transport Canada Aviation

adds that some jet-powered aircraft have

unpowered ailerons.

The FAA concurs that roll anomalies

could exist for all aircraft whether they

have powered or unpowered roll control

systems. However, these AD’s address

airplanes having both deicing boots and

unpowered aileron controls. The FAA

acknowledges that other airplanes that

have powered ailerons may be subject to

roll problems in severe icing conditions

due to loss of lift. However, the FAA is

not aware of a mechanism that would

allow ice to produce an uncommanded

control deflection on airplanes having

powered flight control systems. In

addition, airplanes having powered roll

control systems do not have direct

feedback of aerodynamic forces to the

pilot. However, the FAA is considering

initiating an assessment of the need to

apply similar limitations to other

aircraft types.

Comment 8. Request To Withdraw the

Proposals: Affected Airplanes Are Not

Same Type Design as Accident Airplane

Several commenters contend that the

proposals should be withdrawn because

the FAA has not established clearly that

the airplanes addressed in the proposed

rules have the same type design as the

Aerospatiale Model ATR–72 series

airplane that was involved in an

accident in October 1994 that occurred

in severe icing conditions.

One commenter questions the words

‘‘same type design,’’ and asks if those

words refer to high wing, low wing, Ttail, or aircraft of another type design.

Three commenters provide

justification in support of a request that

certain airplanes be exempt from these

AD’s:

• de Havilland Model DHC–7 and

DHC–8 series airplanes: De Havilland

states that the airplanes it manufactures

share a conservative aerodynamic

design philosophy that yields

exceptional low-speed handling

qualities and demonstrated benign

handling qualities in icing conditions.

De Havilland adds that two-thirds of the

roll control authority of these airplanes

is provided by hydraulically powered

roll spoilers. A second commenter adds

that increased testing has been

conducted on these airplanes.

• Fokker F27 Mark 100, 200, 300,

400, 500, 600, 700, and 050 series

airplanes: Fokker states that the leading

edge boots on Fokker Model F27 series

airplanes and Model F27 Mark 050

series airplanes extend to a chord wise

position, 12.5 percent wing chord,

which precludes all but the very largest

droplets impinging on the unprotected

surfaces. Fokker adds that since the

accident airplane has unshielded horn

balances and the affected Fokker

airplanes do not have these unshielded

horn balances, Fokker airplanes will not

experience roll upset problems. Fokker

indicates that aerodynamically

balancing the control surfaces by means

of unshielded horn balances was not

applied because of the bad service

experience of the Vickers Viking aircraft

in 1946.

• Beech Model 200 and 200C

airplanes: Raytheon states that these

particular airplane models are not

normally considered to be commuter

aircraft, and that issuance of an AD

would be contrary to the stated purpose

of the proposals because most of these

airplanes are used in non-revenue

service. Raytheon states that these

airplanes are all low wing aircraft.

Aerospatiale Model ATR–72 series

airplanes (the accident airplane) is 50

percent larger and carries over twice the

number of passengers as these Beech

aircraft. For these reasons, as well as

other differences in the geometry of the

airplanes (i.e., relative aileron span),

Raytheon states that the supposition of

an icing hazard in these aircraft is

purely speculative.

The FAA does not concur that any of

the addressed airplanes should be

exempt from these AD’s. The FAA has

examined the accident and incident

history in icing conditions and, in

particular, those events believed to

involve SLD conditions. Results of this

examination revealed that the type

design characteristics that appear to be

common in these events are pneumatic

deicing boots and unpowered aileron

controls. Airplanes having those type

design characteristics appear to be more

susceptible to control problems in

severe icing conditions. In response to

Fokker’s remark that its airplanes will

not experience roll control problems

since those airplanes do not have

unshielded horn balances, the FAA has

determined that horn balances on the

accident airplane were not the source of

the uncommanded aileron motion.

Design similarities of the wing, tail, or

ailerons do not appear to be a common

denominator among airplanes involved

in accidents or incidents where SLD

conditions may have been present.

Saab asks for removal of the sentence

that reads, ‘‘Since an unsafe condition

has been identified that is likely to exist

or develop on other airplanes of the

same type design * * *.’’ Saab states

that this sentence implies that Saab

Model SF340A and SAAB 340B series

airplanes have a problem and that this

problem is ‘‘likely to develop on other

airplanes of the same type design.’’ Yet,

there have been no reported problems

on those airplanes, which are not of the

same type design as all other

turbopropeller-powered airplanes.

Transport Canada Aviation does not

request that the proposals be

withdrawn; however, the commenter

requests that the FAA revise the same

phrase discussed by Saab. Transport

Canada Aviation requests that the

phrase be reworded as follows: ‘‘Since

an unsafe condition has been identified

where aircraft icing certification is not

adequate to address the conditions that

are outside of Appendix C of FAR part

25 * * *.’’

The FAA does not concur with Saab’s

request. The FAA acknowledges that

there have been no reported problems

involving severe icing conditions on

Saab airplanes. However, Saab Model

SF340A and SAAB 340B series

airplanes have pneumatic deicing boots

and unpowered aileron controls, which

have been determined to be the common

denominators among the airplanes

involved in accidents and incidents in

severe icing conditions. Therefore, the

FAA has determined that when severe

icing conditions are encountered on

these Saab airplanes, those conditions

must be exited.

Although the FAA has no technical

objection to the revised wording

proposed by Transport Canada Aviation,

this sentence does not reappear in the

final rules. Therefore, no change to the

final rule is necessary.
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20621

Comment 9. Request for Explanation of

the Applicability of the AD’s

One commenter requests an

explanation of the methodology used by

the FAA to determine that AD’s should

not be issued for Cessna and Piper

multi-engine aircraft. The commenter

also asks if an AD similar to the

proposed rules exists for Boeing Model

737 series airplanes. The commenter

indicates that Model 737 series

airplanes have demonstrated abnormal

and unexplained roll tendencies.

The FAA provides the following

clarification for this commenter. No

AD’s have been issued for Piper

airplanes or Boeing Model 737 series

airplanes. However, as reflected in the

table above, the FAA has issued an AD

for Cessna Model 208 and 208B

airplanes.

Most of the aircraft affected by these

final rules are used primarily in

regularly scheduled passenger service in

the United States. However, there are

some airplanes affected by the final

rules that are not used in regularly

scheduled passenger service. Two of

these are Cessna Model 208 and 208B

airplanes. Those airplanes were

included in the final rules because of

their accident and incident history in

icing conditions. The FAA is

considering an assessment of the need

to prohibit all aircraft from continued

flight in severe icing conditions.

Comment 10. Request To Withdraw the

Proposals: Service Experience of

Affected Airplanes Is Satisfactory

Several commenters indicate that the

FAA should withdraw the proposed

AD’s in light of the satisfactory service

experience of the airplanes addressed in

the proposals. The commenters believe

that the FAA is singling out

turbopropeller-powered aircraft without

any regard for the operational record of

those aircraft.

Several commenters provide

justification in support of this request:

• One commenter states that de

Havilland airplanes have been

successfully operated for over 30 years

without one instance of roll upset or

flight control problems.

• De Havilland indicates that de

Havilland Model DHC–8 series

airplanes have been in service for 11

years and have accumulated 6 million

flights and 5 million flight hours

without any incidents due to icing.

• De Havilland adds that de

Havilland Model DHC–7 series

airplanes have been in service for 18

years and have accumulated 3.7 million

flights and 2.7 million flight hours

without any incidents due to icing.

• Another commenter has not

experienced any icing related upsets or

control irregularities in its fleet of de

Havilland Model DHC–8 series

airplanes and Beech Model 1900 series

airplanes.

• One commenter operates 21 Beech

Model 1900D airplanes, 32 EMBRAER

Model EMB–120 series airplanes, and

41 Aerospatiale Model ATR–42 and

ATR–72 series airplanes; none of these

airplanes have experienced any icing

incidents this season.

• One commenter indicates that

airplanes produced by Beech,

EMBRAER, and Jetstream Aircraft

Limited (JAL) have no record of

uncommanded roll due to asymmetrical

build-up of ice on surfaces beyond the

deicing boots.

• One commenter notes that it has not

experienced any unusual icing

characteristics on its fleet of EMBRAER

Model EMB–120 series airplanes and

Aerospatiale Model ATR–72 series

airplanes.

• Fairchild notes that in over 26 years

and 15,000,000 flight hours in passenger

service, there has never been a reported

incident where the controllability of

Fairchild Aircraft SA226 and SA227

series airplanes were in jeopardy as a

result of any icing encounters (including

SLD icing encounters).

• The Luftfartsverket (LFV), which is

the airworthiness authority for Sweden,

states that no ice build-up behind the

wing boots has ever been reported on

Saab Model SF340A, SAAB 340B, or

SAAB 2000 series airplanes.

Additionally, the leading edge on these

airplanes can be inspected easily during

flight.

• Saab remarks that no roll anomaly

problems in icing conditions have

occurred during the extensive service

experience of Saab Model SF340A and

SAAB 340B series airplanes.

The FAA does not concur that the

AD’s should be withdrawn. The fact that

an airplane has a perfect safety record

in icing does not negate the fact that no

airplane has been certificated for flight

into SLD. The FAA has determined that

a need exists to provide the flight crew

with useful safety-related information

regarding the limitations of the airplane

concerning flight in severe icing

conditions. The purpose of issuing these

final rules is to provide the flight crew

with such information.

One commenter, Transport Canada

Aviation, requests that the proposals

apply only to those airplanes that have

a demonstrated history of in-service

problems as a priority. The commenter

states that the hazards relating to

operation in icing conditions exist for

all types of aircraft. (The commenter

does not request that the proposed rules

be withdrawn.)

The FAA does not concur with this

request. As explained previously, the

FAA has issued AD’s for airplanes

having pneumatic deicing boots and

unpowered aileron controls as a

priority. Airplanes having these design

features are of immediate concern to the

FAA because these features have been

common denominators in the accident

and incident history concerning flight in

icing conditions and, in particular,

during conditions when SLD was

believed to be present. The FAA is

considering the need for rulemaking to

impose similar limitations on other

aircraft.

Comment 11. Request To Withdraw the

Proposals: Extensive Testing Revealed

No Icing Problems

Several commenters request that the

proposals be withdrawn because

extensive testing revealed no icing

problems on many different

turbopropeller-powered airplanes, even

though those tests likely exceeded any

icing certification tests ever performed

on other civil aircraft types, including

large jet-powered transport category

airplanes. Fokker states that Fokker

Model F27 series airplanes do not

demonstrate unacceptable roll control

characteristics in severe icing

conditions; however, Fokker submits no

data to substantiate this statement.

The FAA does not concur. The FAA

finds that successful completion of the

roll upset evaluation is not a valid

reason for withdrawing the AD’s. On the

contrary, if the evaluation had

demonstrated anomalies, the FAA may

have concluded that action beyond that

required by these AD’s was necessary to

address the demonstrated unsafe

condition. The testing was designed to

examine only the roll handling

characteristics of the airplane in certain

droplets the size of freezing drizzle to

determine if any design changes are

necessary to prevent catastrophic

control surface deflection. The testing

was not a certification test to approve

the airplane for flight into freezing

drizzle since many of the components

and their functions were not tested (e.g.,

pitch control, engine and propeller,

performance, stall warning, windshield,

air data sensors and fuel system vents).

Further, freezing rain was not tested.

Satisfactory demonstration of those tests

does not remove the FAA’s

responsibility to provide a safe

operating environment for the

passengers and crew.

JAL comments that its airplanes are

not subject to the addressed unsafe

condition, and that the FAA had
20622 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

concurred with this contention. JAL

states that the FAA agreed that, by the

controllability evaluation process, all

Jetstream aircraft types had been

demonstrated to be not susceptible to

roll control anomalies in freezing rain or

freezing drizzle conditions.

The FAA does not concur with JAL’s

position concerning its airplanes. All

Jetstream airplanes affected by these

AD’s successfully completed the roll

upset evaluation. However, as stated

previously, no airplanes were tested in

freezing rain conditions. The roll upset

evaluation only addressed conditions

that were believed to have existed

during an accident involving a transport

category airplane that occurred in

October 1994. Therefore, since no

airplane has been tested in all freezing

rain and freezing drizzle conditions, no

airplane has been demonstrated to be

safe for continued flight in these

conditions.

Comment 12. Request To Withdraw the

Proposals: Publish Advisory Materials

and Require Training

Several commenters request that, in

lieu of issuing the proposed rules, the

FAA publish appropriate advisory

materials and require training for

recognition, avoidance, and exit from

severe icing encounters as part of the

required severe weather training for

pilots and dispatchers. Two commenters

suggest that the FAA include such

requirements in the operating rules

specified in 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). Another

commenter indicates that, since jets and

piston-engine aircraft also could

develop ice shapes other than those

tested, training should not be provided

only to pilots of turbopropeller-powered

airplanes, but to pilots of all aircraft.

Some commenters also suggest that the

FAA has successfully addressed other

issues through increased awareness and

training requirements, rather than by

issuing AD’s against every airplane type

design to require revising the

Limitations Section of the AFM. The

commenters cite windshear, ground

deicing, and clear air turbulence as

examples of such issues. The

commenters contend that, except where

configuration changes are needed, such

as in the case of windshear detection

devices, improved awareness and

training programs—not AD’s—have

been highly effective in achieving

needed safety improvements.

The FAA does not concur. The FAA

considers that substituting advisory

material and mandatory training for

issuance of an AD is not appropriate,

nor would this adequately address the

unsafe condition. The FAA fully

supports the development of advisory

materials and training. Part 121

(‘‘Certification and Operations:

Domestic, Flag, and Supplemental Air

Carriers and Commercial Operators of

Large Aircraft’’) and part 135 (‘‘Air Taxi

Operators and Commercial Operators’’)

of the Federal Aviation Regulations (14

CFR parts 121 and 135) require that

appropriate training concerning

limitations such as those contained in

these AD’s be incorporated into air

carriers’ training programs. However,

the FAA’s position is that the

development and use of such advisory

materials and training alone are not

adequate to address the subject unsafe

condition. Currently, the AFM’s specify

that the affected airplanes are

certificated for flight in icing conditions;

however, the AFM’s do not specify a

method of determining whether the

certification limits for those conditions

have been exceeded. Consequently, the

FAA finds that these AFM’s must be

revised to provide limitations for flight

in icing conditions and to provide the

flight crew with a method of

determining when those limitations

have been exceeded.

The FAA does not concur that

amending part 121 of the Federal

Aviation Regulations (14 CFR part 121)

in lieu of issuing these AD’s is

appropriate. The FAA’s position is that

the appropriate place to inform the

flight crew of the limitations of the

airplane is in the AFM. The appropriate

vehicle for mandating such AFM

revisions is through issuance of an AD.

In addition, an AD will ensure that the

incorporation of such AFM revisions is

not left to each operator’s individual

discretion and that flight crews receive

pertinent information. The FAA may

consider an assessment of the need to

provide training to pilots of all aircraft

types for flight in severe icing

conditions.

The commenters reference windshear

as an example of an issue that was

handled successfully without issuance

of an AD to revise the AFM’s. In this

case, the AFM’s for all airplanes having

an onboard windshear system were

revised to provide the flight crew with

procedures for responding when the

system gives an alert. Although no AD

was issued to mandate these AFM

revisions, without revising the AFM,

operators could not comply with the

section of part 121 of the Federal

Aviation Regulations (14 CFR part 121)

that requires installation of the

windshear detection devices. In

conclusion, although AFM revisions

were not required by an AD, AFM

changes were mandated indirectly by a

new part 121 regulation.

The commenters also reference

ground deicing. Part 91 (‘‘General

Operating and Flight Rules’’) of the

Federal Aviation Regulations (14 CFR

part 91) prohibits takeoff of an airplane

unless the airframe is clear of ice;

therefore, there is no need to provide

additional limitations concerning the

amount of ice that would be acceptable

for takeoff. However, in the case of

severe icing conditions addressed by

these final rules, the AFM’s currently

allow flight in icing, but the AFM does

not define when the limits of the

certificated icing operation envelope

have been exceeded.

Concerning the issue of clear air

turbulence, issuance of an AD was not

required because an airspeed limitation

associated with turbulent air

penetration was already in the AFM’s.

Therefore, in this case, the issue was

addressed in the AFM as well as

through awareness and training.

Comment 13. Request To Withdraw the

Proposals: Incorporate Operational

Issues Into a Training Curriculum

Two commenters request that the

proposals be withdrawn because the

proposed AD’s address an operational

issue that should be incorporated into

an operator’s training curriculum. One

commenter states that pilots must be

made aware of the hazards of icing and

that extended operation of an airplane

in any icing encounter that results in

significant airframe accretion of ice is

unacceptable.

The FAA does not concur that the

AD’s should be withdrawn based on the

commenters’ request. The FAA

acknowledges that these AD’s address

an operational issue. When the

requirements of these AD’s are

accomplished and the AFM limitations

are revised, this material will be

incorporated necessarily, as explained

previously, into the training curriculum

for the flight crews and dispatchers, if

applicable, in the operator’s approved

training program. In this manner, pilots

and dispatchers, if applicable, will be

informed of the hazards of icing and

that continued operation of an airplane

in certain icing conditions is prohibited.

Comment 14. Request To Withdraw the

Proposals: Require Training for Air

Traffic Controllers and Weather

Specialists

Two commenters request that the

FAA implement additional policy to

require training for air traffic controllers

and weather specialists in the
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20623

recognition, avoidance, and procedures

to exit severe icing conditions.

The FAA does not concur that these

AD’s should be withdrawn. However,

the FAA acknowledges that

implementation of these AD’s may

necessitate additional training beyond

that which is already required for air

traffic controllers and weather

specialists. The FAA may consider the

need to provide training concerning

recognition, avoidance, and procedures

for exiting severe icing conditions.

However, the intent of these AD’s is to

provide the flight crew with recognition

cues for, and procedures for exiting

from, severe icing conditions. The

appropriate vehicle for requiring that

such information be included in the

AFM’s is through issuance of an AD.

Comment 15. Request To Withdraw the

Proposals: Add a Caution to the AFM

One commenter requests that, in lieu

of issuing the proposed AD’s, a

‘‘Caution’’ should be added to the AFM

to inform pilots to exit icing conditions

if ice was observed to be forming aft of

the protected surfaces of the wings. The

commenter states that information

regarding the use of flaps and the

autopilot in icing conditions could also

be incorporated into the AFM. The

commenter does not indicate which

section of the AFM should include this

material.

The FAA does not concur. The FAA

finds that the requirement to exit severe

icing conditions and information

concerning use of the autopilot during

flight in those conditions must be

included in the Limitations Section of

the AFM. Additionally, information

concerning use of the flaps during those

conditions should be included in the

Procedures Section of the AFM. The

appropriate vehicle for requiring these

changes to the AFM is through issuance

of an AD.

Comment 16. Request To Withdraw the

Proposals: Require Alternative AFM

Limitation

One commenter requests that, in lieu

of an AD, the FAA require an alternative

AFM limitation that reads as follows:

‘‘This aircraft is certified for flight into

icing conditions as specified by

Appendix C of Part 25. Actual icing

encountered may be greater than

Appendix C requirements.’’

The FAA does not concur. The

suggested limitation does not provide

guidance as to how a pilot can identify

and safely exit icing conditions that

have exceeded those specified in the

icing envelope in Appendix C of part 25

of the Federal Aviation Regulations (14

CFR part 25). These AD’s are intended

to provide the flight crew with visual

cues which indicate that icing

conditions have exceeded the

capabilities of the ice protection

equipment, and with procedures to

safely exit those conditions. No change

to the AD’s is necessary.

Comment 17. Request To Withdraw the

Proposals: AFM Revisions Already Are

Required

One commenter requests that the

proposals be withdrawn because section

121.133 (‘‘Manual Requirements:

‘Preparation’ ’’) of the Federal Aviation

Regulations (14 CFR 121.133) already

requires that operators incorporate

revisions into the AFM’s; therefore,

issuance of the proposed AD’s is

unnecessary.

The FAA does not concur. Section

121.133 of the Federal Aviation

Regulations (14 CFR 121.133) does not

specifically require that AFM’s be

updated to current revisions. Section

121.141 (‘‘Airplane or Rotorcraft Flight

Manual’’) of the Federal Aviation

Regulations (14 CFR 121.141) requires

that the current AFM be carried on the

aircraft, but does not require

incorporation of the most current

revisions. Additionally, the commenter

does not address the need to change the

AFM’s for airplanes that operate under

parts 135 (‘‘Air Taxi Operators and

Commercial Operators’’) and 91

(‘‘General Operating and Flight Rules’’)

of the Federal Aviation Regulations (14

CFR parts 135 and 91). The appropriate

vehicle for ensuring that the Limitations

Section of the AFM’s is changed is

through issuance of an AD.

Comment 18. Request To Withdraw the

Proposals: Use Existing AFM Revisions

The General Aviation Manufacturers

Association (GAMA), on behalf of its

members, states that some of the

affected manufacturers have prepared

FAA-approved revisions for the AFM’s

for their products. GAMA indicates that

those revisions incorporate specific

information regarding cues for

recognizing severe icing conditions and

procedures for exiting such conditions,

if encountered. Therefore, if the

proposed AD’s are adopted, the

requirements of the AD’s would

supersede the information operators

have already incorporated into the

AFM’s with less appropriate

information that is not type design

specific.

One commenter, JAL, requests that

certain existing AFM revisions for the

affected Jetstream airplanes be cited in

the proposed AD’s for those airplanes in

lieu of the content of the proposed AD’s.

(However, JAL does not request that the

proposals be withdrawn for this

particular reason.) JAL indicates that the

existing AFM revisions have already

been FAA-approved.

The FAA does not concur with the

commenters’ requests. The FAA

acknowledges that the AFM revisions

required by these final rules will

supersede previously approved AFM

revisions. However, the FAA is unaware

of any AFM that addresses all of the

provisions specified in these final rules,

nor of any AFM that contains specific

visual cues that the FAA has not

included in the final rules. Even if AFM

material currently exists that does

contain all of the provisions of the final

rules, the FAA finds that issuance of an

AD would still be necessary to mandate

the provisions of the AFM revisions.

However, the FAA would consider a

request for approval of an alternative

method of compliance, in accordance

with the provisions of this AD, for those

operators having AFM’s that already

contain all of the provisions of the final

rules.

Another commenter requests that the

FAA withdraw the proposal that applies

to Fairchild Model SA226 and SA227

series airplanes. The commenter states

that the AFM for those airplanes

currently contains visual cues to aid the

flight crew in recognition of weather

conditions conducive to SLD. This AFM

also provides procedures for avoidance

of such conditions. The commenter

adds that these AFM procedures result

in additional operating limitations on

the aircraft with regard to severe

weather conditions. The commenter

believes these AFM procedures address

all current FAA requirements.

The FAA does not concur that the

AFM for Fairchild Model SA226 and

SA227 series airplanes addresses all of

the proposed requirements of the

proposed rule. For example, the

Limitations section of the AFM for those

airplanes does not require the flight

crew to exit severe icing conditions. For

this reason, the FAA does not consider

the AFM for Fairchild Model SA226 and

SA227 series airplanes to be equivalent

to the information specified in these

AD’s.

Comment 19. Request To Withdraw the

Proposals: Develop Rulemaking To

Address Airplane Certification Outside

of Appendix C

Three commenters suggest that

instead of arbitrarily prohibiting

operation of the airplane, the FAA

should undertake a well-designed

research program and, if warranted,

devise a rulemaking plan for

certification of airplanes outside of

Appendix C of part 25 of the Federal
20624 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

Aviation Regulations (14 CFR part 25).

One commenter also suggests possible

retroactive implementation of a new

Appendix C.

The FAA does not concur because of

the length of time that would be

required to implement the commenters’

suggestion. The FAA finds that action is

required prior to the commencement of

the next icing season to prohibit the

continued flight of airplanes in icing

conditions that have been shown to be

unsafe and for which the airplanes have

not been certificated. However, the FAA

is currently considering initiating an

assessment of the need to revise

Appendix C and the possibility of its

retroactive implementation.

Transport Canada Aviation states that

the FAA has determined that there may

be a problem with the certification

requirements for icing on de Havilland

Model DHC–6, DHC–7, and DHC–8

series airplanes, but not the specific

approval or design features of those

airplanes. However, the commenter

does not specifically request that the

proposals be withdrawn.

The FAA does not concur with the

commenter’s statement. The FAA has

only determined that no adequate

means exists for the flight crew to

determine when the icing certification

limits have been exceeded. The purpose

of these AD’s is to provide more clearly

defined procedures and limitations

associated with severe icing conditions.

This does not imply that the

certification requirements for icing are

inadequate.

Comment 20. Request To Withdraw the

Proposals: Issue a ‘‘General AD’’ for All

Airplane Types

One commenter requests that a

‘‘general AD’’ be issued to prohibit all

airplane types from inadvertent flight

into hazardous SLD conditions. Another

commenter adds that if encounters with

freezing rain/freezing drizzle conditions

must be reported to Air Traffic Control,

such reporting also should apply to

flight crews of all airplane types.

The FAA does not concur with the

commenter’s request. For the reasons

discussed earlier in the preamble of this

AD, the FAA has determined that

airplanes having pneumatic deicing

boots and unpowered aileron controls

are of immediate concern and have been

addressed as a higher priority. The FAA

finds that action is required prior to the

commencement of the next icing season

to prohibit the operation of these

airplanes in icing conditions that have

been shown to be unsafe and for which

the airplanes have not been certificated.

However, the FAA is currently

considering initiating an assessment of

the potential adverse effects of SLD on

all airplane types.

Comment 21. Request To Withdraw the

Proposals: Establish a Detailed

Reporting System

One commenter requests that the FAA

establish a detailed reporting system for

inadvertent encounters with severe SLD.

The commenter envisions a system that

would provide a database for better

identification of controllability issues

and visual indications related to these

encounters.

The FAA does not concur with the

commenter’s request. The FAA has been

advised that the Regional Airline

Association (RAA) has already

established an ‘‘Unusual Icing Reporting

Program’’ for the purpose described by

the commenter; therefore, establishing

another reporting program would

duplicate this benefit.

Comment 22. Request To Withdraw the

Proposals: Revise the Master Minimum

Equipment List (MMEL)

Two commenters request that, instead

of addressing an MMEL item in an AD

[i.e., the icing detection lights

referenced in paragraph (a)(1) of the

proposals], the FAA should require that

the MMEL be revised. A third

commenter adds that the decision to

change the MMEL should be made by

FAA Operations Inspectors based on

local conditions. One commenter states

that the prohibition of dispatch with

any inoperative ice detection lights

would preclude any efforts by an

operator to enhance safety by installing

a second set of bulbs. The commenter

adds that under this proposed rule, this

type of action would be penalized by

simply doubling the chances of a

burned out bulb grounding the aircraft.

In practice, if one were to add a fully

redundant set of bulbs, it would

enhance safety by allowing the

equivalent of the current illumination

level even with a bulb burned out.

The FAA does not concur with these

requests. FAA Operations Inspectors are

not authorized to make MMEL

revisions. The FAA has determined that

it is prudent to address the icing

detection lights in these final rules to

ensure uniform and immediate

application of the requirements of the

AD’s. Concerning the example provided

by one of the commenters, if an operator

chooses to add a fully redundant set of

bulbs, that operator should request

approval of an alternative method of

compliance in accordance with the

provisions of this final rule.

Although Transport Canada Aviation

does not request that the proposals be

withdrawn, it requests a revision to the

requirement that all icing detection

lights must be operative. For de

Havilland Model DHC–7 and DHC–8

series airplanes, the commenter requests

that the requirement be changed to

mandate that at least one outboard and

one inboard inspection light be

operative prior to flight into known or

forecast icing conditions at night. Since

the MMEL contains a provision that a

suitable lamp/light of adequate capacity

be available, this is considered

acceptable in conjunction with other

indications of freezing rain or freezing

drizzle. Similarly, for de Havilland

DHC–6 series airplanes, the requirement

should be revised to require a suitable

lamp/light for dispatch at night with

one wing inspection light inoperative.

The FAA does not concur. The FAA

has determined that the justification

provided by the commenter is not

adequate to enable the FAA to

determine if the proposed changes are

acceptable. During severe icing

conditions, the flight crew’s workload

may be high, and there may be no

opportunity to use the portable lamp/

light, which, in itself, may create

disorientation in the cockpit due to

adverse reflections from the glass. The

FAA’s intent in having all inspection

lights be operative at night is to provide

the flight crew the best possible

visibility of the airframe. However, the

FAA would consider a request for

approval of an alternative method of

compliance, in accordance with the

provisions of these AD’s, provided that

adequate justification is presented to

support such a request.

Comment 23. Request To Withdraw the

Proposals: Certify Airplanes for Flight in

Conditions Outside Appendix C

One commenter implies that the

airplanes affected by the proposed rules

must be rectified to a level beyond the

present certification requirements for

flight in icing.

The FAA does not concur. The final

rules do not require certification of the

airplane beyond the current certification

requirements for flight in icing specified

in Appendix C. These AD’s simply

provide the flight crew with visual cues

which indicate that icing conditions

have exceeded the capabilities of the ice

protection equipment, and with

procedures to safely exit those

conditions.

One commenter requests that the

proposal for de Havilland DHC–6 series

airplanes be withdrawn because this

airplane model is type certificated in

Canada, which is a country with a

higher standard than the United States

for operating in icing conditions.
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20625

The FAA does not concur. This

commenter did not submit data to the

FAA to substantiate that the airplane

has been shown to be safe for flight

outside the icing certification envelope

specified in Appendix C. Additionally,

the FAA is unaware of any foreign civil

aviation authority having certification

requirements for icing conditions that

are outside of the icing certification

envelope used in the United States.

Comment 24. Request To Withdraw the

Proposals: Proposals Prohibit Takeoff or

Approach in ‘‘Light Freezing Drizzle’’

Conditions

One commenter requests the

proposals be withdrawn because the

proposed limitation would prohibit

takeoff or approach when ‘‘light freezing

drizzle’’ conditions that are caused by

light precipitation falling through a thin

layer of cold surface air below warmer

air above are reported on the surface.

The commenter maintains that with

accomplishment of the appropriate

ground deicing precautions prior to

takeoff, no hazard to the operation of the

airplane is posed.

The FAA does not concur that the

AD’s should be withdrawn for this

reason. These AD’s do not affect any

existing regulations or FAA-approved

operating procedures related to takeoff,

dispatch, or release of an airplane in

icing conditions, nor do these AD’s

prohibit operation in specific

meteorological conditions. These AD’s

only prohibit remaining in icing

conditions when certain visual cues are

present on the airplane. Operators must

comply with existing rules that require

an airplane to be free of ice prior to

takeoff. Therefore, takeoff in ‘‘light

freezing drizzle’’ would only be

prohibited by existing regulations or

FAA-approved operating procedures,

not by these AD’s. As explained

previously, the FAA considers that

landing the airplane when freezing rain/

freezing drizzle conditions are

encountered would, in many cases, be

the most expeditious method of exiting

the conditions. Such landing would be

in compliance with the limitation that

requires the flight crew to exit the

severe icing conditions.

Comment 25. Request To Withdraw the

Proposals: Proposals Leave Unanswered

Questions

One commenter contends that the

proposals leave unanswered questions.

The commenter alleges that without the

answers to those questions, affected

parties are deprived of the ability to

provide informed comments and,

thereby, are ‘‘denied their rights under

the Administrative Procedures Act

(APA) to comment on the proposed

rules.’’ Specifically, the commenter

asks:

—What is unusual icing?

—Does the pilot, Air Traffic Control,

dispatch, or the FAA determine when

the conditions exist?

—What is splatter effect?

—Where are the operating instructions

incorporated—in the AFM, training

manuals, or some other document?

The FAA infers from the commenter’s

remarks that the commenter requests the

proposed AD’s be withdrawn because

informed comments could not be

provided.

The FAA does not concur that the

AD’s should be withdrawn on this basis.

The FAA does not agree that the public

has been deprived of the ability to

provide informed comments, as

required by the APA. In general, the

APA requires that notice of the terms or

substance of a proposed rule be

published in the Federal Register. The

purpose of this requirement is to ensure

that federal agencies thoroughly

consider all information and opinions

submitted by the public before any

requirements are imposed. Notice is

intended to improve both the quality of

the regulations and their acceptability to

the public. The FAA finds that none of

the questions raised by the commenter

identify areas in which the commenter

has not been provided a reasonable

opportunity to comment. The fact that

the commenter raises questions suggests

that the commenter considers a need for

further clarification. Even if the

commenter is correct in that these

questions require clarification, that fact

in itself is a comment that can be

addressed properly by simply clarifying

terms. The fact that clarification is

necessary does not mean that the public

has been denied reasonable opportunity

to comment.

In response to the commenter’s

questions, the FAA provides the

following clarification. The term

‘‘unusual icing’’ did not appear in the

proposed rules. However, the phrase

‘‘unusually extensive ice’’ is referenced

in paragraph (a)(1) of the final rules.

[This reference appears in paragraph

(a)(2) of the final rule for Aerospatiale

airplanes.] ‘‘Unusually extensive ice’’

accrued on the airframe in areas not

normally observed to collect ice is a

visual cue that is subject to

interpretation by the flight crew;

therefore, a specific definition of

‘‘unusually extensive ice’’ cannot be

provided.

These AD’s address changes to AFM

limitations, which pertain to the pilot

since the pilot is responsible to look for

the visual cues defined in the AD’s.

Therefore, the pilot determines when

severe icing conditions exist.

The terminology ‘‘splatter effect’’ did

not appear in the proposed rules. The

FAA infers from the commenter’s

question that the commenter is

referencing terminology used in

paragraph (a)(2) of the proposed AD’s.

‘‘Droplets that splash or splatter on

impact at temperatures below +5

degrees Celsius OAT’’ is a visual cue

that was included in the proposed AD’s

as a method of identifying severe icing

conditions.

Concerning incorporation of operating

instructions, these final rules specify

that the AFM’s be revised. The AD’s do

not specify that any other manuals or

documents be revised. However,

information that is included in the AFM

as a limitation is necessarily included in

the training program.

Comment 26. Request To Clarify Scope

of Icing Conditions Addressed

Transport Canada Aviation suggests

that the proposals, which address only

freezing rain/freezing drizzle

conditions, are not adequate to cover all

hazards related to operation of aircraft

in icing conditions. The commenter

makes no specific request.

The FAA concurs that these AD’s do

not address all icing related hazards.

The FAA’s intent is to minimize the

potential hazards associated with

operating the airplane in severe icing

conditions by providing the flight crews

with more clearly defined procedures

and limitations associated with such

conditions. However, no change to the

final rules is necessary.

Comment 27. Request To Expand the

Applicability of the AD’s

One commenter, the CAA, suggests

that the ‘‘coverage’’ of the proposals

should be stated clearly. The CAA

believes that a restriction to those

operations in ‘‘regularly scheduled

passenger service’’ is not warranted for

a safety issue as it does not cover cargo,

charter, or private operations. The

commenter does not specify which

airplane models should be addressed.

The FAA infers from the commenter’s

remarks that it requests that the

proposed AD’s be applicable to other

airplane models that are used in cargo,

charter, or private operations that may

have been excluded from the

applicability of these AD’s.

The FAA does not concur that the

applicability of these AD’s should be

expanded to include additional airplane

models used primarily in cargo, charter,

or private operation. The FAA is

currently considering the need for
20626 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

additional rulemaking to address other

airplane models having pneumatic

deicing boots and unpowered aileron

controls that are used in these types of

service that were not addressed by these

AD’s. Additionally, the applicability of

these final rules indicates that the AD’s

apply to ‘‘all’’ of the airplane models

identified, certificated in any category.

This means that the AD’s apply to all of

the affected airplanes, regardless of how

those airplanes are operated (including

passenger service, cargo, charter, or

private operation).

Comment 28. Request for Design

Changes to the Airplanes

One commenter requests that the FAA

require design changes to the airplanes,

which, when accomplished, will allow

elimination of the AFM limitations. The

commenter states that abnormal roll

control anomalies could be eliminated

by design changes that prevent any ice

shapes from forming by using

supplemental ice protection added to

existing pneumatic boots or other ice

protection installations. The commenter

concludes that, given this added

protection, restricting flight in freezing

drizzle could be reduced to allow

exposure to these atmospheric

conditions for a reasonable time and

would not require immediately exiting

these conditions when encountered as

presently stipulated.

The FAA does not concur that it

should require design changes to

airplanes in these AD’s. Currently, the

FAA is unaware of any design changes

that would allow elimination or

reduction of the AFM limitations

specified in these AD’s. However, if

such design changes are developed,

approved, and become available, the

FAA would consider additional

rulemaking to require such changes. The

FAA finds that even if the ice protection

system prevented the formation of ice

shapes in front of the ailerons when the

airframe is exposed to certain freezing

drizzle conditions, other meteorological

conditions still exist (e.g., freezing rain)

for which the airplane would not be

certificated.

Comment 29. Request for More Specific

Visual Cues

One commenter requests that the FAA

provide more specific visual cues for

identification of freezing rain or freezing

drizzle conditions. The commenter

states that the generic visual cues

provided in the proposed AD’s are not

adequate for aircraft types that

frequently operate in and encounter

SLD conditions. For example, ice could

be forming on the upper wing and not

the lower wing; therefore, looking at the

lower wing would not be a reliable

visual cue. Two commenters suggest

that specific visual cues be provided for

each airplane model. One of these

commenters states that subjective cues

may be of limited benefit if the pilot’s

experience with icing is inadequate. The

other commenter adds that subjective

visual cues will result in varying

interpretations (i.e., some unnecessary

course changes in altitudes or service

interruptions caused by overly

conservative interpretations). Transport

Canada Aviation does not request more

specific visual cues; but states that

‘‘unusually extensive ice,’’ ‘‘normally

observed,’’ and ‘‘farther back than

normally observed’’ are all variable

terms that are largely dependent on

flight crew experience. The commenter

contends that limitations and

procedures described using these terms

will not be consistently interpreted. In

addition, Transport Canada Aviation

states that ice on the lower wing surface

aft of the protected area, by itself, is

unlikely to cause a hazard. Moreover,

the presence or absence of such ice

cannot be used as an indication of any

hazardous accumulation on the upper

wing surface or on the horizontal

stabilizer.

The FAA does not concur with the

commenters’ request to provide more

specific (or airplane-specific) visual

cues. The FAA agrees with the

commenters’ assertion that, under

certain circumstances, examination of

the undersurface of a high wing may not

be reliable. The FAA also agrees that

other cues, such as unusually extensive

ice accrued on the airframe in areas not

normally observed to collect ice and

accumulation of ice on the propeller

spinner farther aft then normally

observed, are subjective and that

reliance on pilot judgment and

experience is necessary in such cases.

Additionally, the FAA fully supports

the development and use of airplanespecific cues by operators and

manufacturers. Unfortunately, no

commenter provided airplane-specific

cues during this comment period.

In summary, the FAA finds that the

combined use of the generic cues

provided and the effect of the final rules

in increasing the awareness of pilots

concerning the hazard of operating

outside of the certification icing

envelope will provide an acceptable

level of safety. However, for those

operators that elect to identify airplanespecific visual cues, the FAA would

consider a request for approval of an

alternative method of compliance, in

accordance with the provisions of this

AD.

Transport Canada Aviation states that

the term ‘‘protected area’’ may not be

readily recognizable by the flight crew;

for example, not all of a deicing boot

surface is ‘‘protected area.’’ [This

terminology appears in the second

visual cue (in the proposals for

airplanes other than Aerospatiale

airplanes) and in the autopilot

limitation in paragraph (a)(1) of the

proposals. For Aerospatiale airplanes,

this terminology appears in the

secondary indications in paragraph

(a)(1) of the proposal.] The FAA infers

that the commenter requests that more

specific language than ‘‘protected area’’

be used.

The FAA does not concur that this

terminology should be revised. The

FAA considers that a pilot understands

that a portion of the deicing boot would

be considered to be unprotected.

Therefore, no additional clarification or

definition of the term ‘‘protected area’’

is necessary.

Comment 30. Request To Reference

Clear Icing Conditions and Clear

Component of Mixed Icing Conditions

One commenter also asks that all

references to freezing rain and freezing

drizzle environments and visual cue

identification reference clear icing

conditions and the clear component of

mixed icing conditions. According to

the commenter, mixed icing conditions

can contain areas of freezing rain and/

or freezing drizzle. The commenter

notes that mixed icing has taken on two

different definitions within the aviation

community—the ‘‘engineering’’

definition (which is defined in an FAA

icing handbook) and the definition

pilots use (which includes areas of clear

and rime ice). The commenter states

that a clear definition of these

conditions is needed. The commenter

adds that only pilot reports can show

that freezing rain/freezing drizzle exists

because forecasting of these conditions

is inadequate. The commenter indicates

that while the Aerospatiale airplanes

have side window cues that will

accurately identify freezing rain or

freezing drizzle, pilots of other airplanes

without such a sophisticated cue may

erroneously report mixed icing.

The FAA does not concur. The FAA

acknowledges that freezing rain and

freezing drizzle may be reported as

clear/mixed icing conditions. However,

the flight crew must exit icing

conditions that produce the visual cues

specified in the final rules. Exiting the

icing conditions is not dependent upon

the terminology used to describe the

conditions. Therefore, the FAA has

determined that it is not necessary to

include references to clear icing
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20627

conditions and the clear component of

mixed icing conditions. In addition, the

FAA has determined that including a

discussion in these AD’s of the

phenomenon of mixed icing conditions

as it relates to the current state-of-the-art

weather forecasting would be premature

because no clear definition of this

phenomenon has been agreed upon

among the aviation community. The

FAA is currently considering an

assessment during which various icingrelated subjects, including mixed icing

conditions, would be addressed.

Comment 31. Request for Research and

Use of Wing-Mounted Ice Detectors

One commenter requests that wingmounted ice detectors, which provide

real-time icing severity information (or

immediate feedback) to flight crews,

continue to be researched and used

throughout the fleet. The FAA infers

from this commenter’s request that the

commenter asks that installation of

these ice detectors be mandated by the

FAA.

While the FAA supports the

development of such ice detectors, the

FAA does not concur that installation of

these ice detectors should be required.

The specifications for automatic

detectors having the capabilities to

differentiate among freezing rain,

freezing drizzle, and other icing

conditions have not been determined.

However, if such ice detectors are

developed, approved, and become

available, the FAA may consider further

rulemaking action to require installation

of such equipment.

Comment 32. Request to Limit the

Applicability of the AD’s

One commenter requests that the

applicability of the proposals be limited

to airplanes having NACA 430xx

airfoils. The commenter asserts that the

unusual pressure peak on the NACA

430xx airfoils at 9 percent chord caused

the ice ridge to form at that point, which

resulted in the accident involving a

Aerospatiale Model ATR–72 series

airplane. The commenter states that

‘‘the accident was caused by the poorly

designed, unusual, and fortunately

rarely used NACA 430xx airfoils used

on this airplane.’’

The FAA does not concur with the

commenter’s request to limit the

applicability of the AD’s. First, the

National Transportation Safety Board

(NTSB) has not yet made an official

finding of the probable cause of the

accident referenced by the commenter.

Therefore, the FAA cannot assume that

airplanes having NACA 430xx airfoils

are more susceptible to the addressed

unsafe condition than those airplanes

that do not have this type of airfoil.

Second, the FAA has examined the data

submitted by the commenter, and

disagrees with the commenter’s

assertion concerning the formation of

ice ridges. The formation of ice ridges

depends on many factors. Ice ridges

have been observed to form in areas

where there is no pressure (commonly,

‘‘suction’’) peak. However, the

impingement location of large droplets

is more relevant to the development of

ice ridges than the particular pressure

distribution. The commenter does not

address the fact that, regardless of the

type of airfoil on an airplane, a

substantial sharp edge protuberance in

the vicinity of the suction peak can have

adverse consequences to the

aerodynamic performance of the airfoil.

Regardless of the cause of location of ice

formations, prevention or removal of the

ice is certainly an acceptable remedy for

such conditions, should those

conditions occur. For example,

Aerospatiale extended the deicing boots

to prevent the formation of adverse ice

ridges.

Comment 33. Request for Approval of

Improved Deicing Equipment for

Aerospatiale Airplanes

ATR requests that paragraph (b) of the

proposed rule for Aerospatiale airplanes

be revised to indicate that installation of

any improved version of deicing

equipment that is approved by the FAA

is acceptable for compliance with the

requirements of that paragraph. The

commenter provides no justification for

its request.

The FAA does not concur with the

commenter’s request to revise the AD.

However, if an improved version of

deicing equipment is developed,

approved, and available, the FAA would

consider a request for approval of an

alternative method of compliance, in

accordance with the provisions of the

AD.

Comment 34. Request for Re-Evaluation

of Modified Deicing Boots on

Aerospatiale Airplanes

In response to the proposal for

Aerospatiale airplanes, one commenter

requests that the new, enlarged deicing

boots that are required to be installed on

these airplanes must be re-evaluated

before total confidence in the modified

boots is warranted. The commenter

asserts that no test data exist to show

that the modified boots will preclude

the problem of large droplets outside of

Appendix C. The area of exposure

outside of Appendix C is essentially

open-ended, and only limited testing

within a narrow range of droplet

diameters was conducted. Additionally,

the test conditions that existed during

the tanker testing conducted at Edwards

Air Force Base, which was intended to

be a ‘‘before modification/after

modification’’ validation program, were

not identical. The commenter adds that

no modification will ensure that any

airplane is safe while flying in icing

conditions outside those specified in

Appendix C.

The FAA does not concur with the

commenter’s request for a re-evaluation

of the modified deicing boots. The

modified deicing boots for these

airplanes were subjected to an extensive

certification program by both the FAA

and the Direction Ge ́ne ́rale de l’Aviation

Civile (DGAC), which is the

airworthiness authority for France. FAA

approval of the modified boots was

based on engineering analyses, wind

tunnel testing, flight testing in natural

icing conditions, and a validation

program involving a United States Air

Force icing tanker. This testing verified

that the modified boots continue to

perform the intended function within

the Appendix C icing envelope. In

addition, the extended deicing boots

were shown to adequately protect the

airplane from the larger, supercooled

water droplets that are believed to have

existed in the area at the time of the

accident in October 1994.

It should be noted, however, that it is

not intended that the modified boots

provide protection in all possible icing

conditions, including freezing rain/

freezing drizzle. However, the FAA

considers that the combination of the

enlarged deicing boots, the AFM

operational procedures and restrictions,

and the visual cues which indicate entry

into freezing rain/freezing drizzle

conditions provides for an enhanced

level of safety during inadvertent flight

in these conditions.

Comment 35. Request for Formal

Weather Forecasting System for

Freezing Rain/Freezing Drizzle

One commenter supports a

requirement to establish a formal system

to provide forecasts of freezing rain/

freezing drizzle conditions, as proposed

in paragraphs (b) and (c) of the original

proposed rule for Aerospatiale

airplanes. [This proposed requirement

was removed from the subsequent

supplemental notice of proposed

rulemaking (NPRM) issued for these

airplanes in January 1996.] The

commenter states that such a

requirement should remain in effect

until forecasting tools are developed or

detection methods are established to

prevent dispatch or operations in

conditions outside those specified in

Appendix C. The commenter states that
20628 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

the efficacy of the deicing boots has not

been shown completely nor

documented; therefore, avoidance of

freezing rain/freezing drizzle is

paramount to safety of flight.

The FAA does not concur that such a

requirement is necessary. The FAA

agrees that such a system would

enhance the safety of flight operations.

However, there is no evidence that lack

of a system with such specialized

features would lead to an unsafe

condition. Forecasts of freezing rain/

freezing drizzle are a normal part of preflight weather briefings. The FAA is

aware, however, of serious limitations

for such a system to provide accurate

and timely forecasts of these conditions

during flight in areas that are removed

from weather reporting stations. Quite

often, the only indication of the

existence of severe icing conditions is

from pilot reports or other direct

observations.

Research is underway currently in

industry and the academic community

to address shortcomings in the

forecasting of severe icing conditions.

The FAA may consider further

rulemaking if advancements in weather

forecasting provide for a reliable method

to predict the occurrence of freezing

rain/freezing drizzle conditions during

flight or in areas removed from direct

observations.

Comment 36. Request To Approve

Earlier Service Bulletin Revisions

One commenter to the proposed rule

for Aerospatiale airplanes requests that

the proposed AD be revised to specify

that earlier revisions of service bulletins

are acceptable for compliance with the

requirements of the proposed rule. The

commenter makes this request so as to

eliminate the need to apply for approval

of alternative methods of compliance

when accomplishing service bulletin

revisions other than those specified in

the proposed rule.

The FAA does not concur that earlier

revisions of the referenced service

bulletins should be cited in the final

rule for Aerospatiale airplanes.

However, the FAA would consider a

request for approval of an alternative

method of compliance, in accordance

with the provisions of the AD, provided

that adequate justification is presented

to support such a request.

Additionally, the FAA has revised the

revision levels specified for certain

service bulletins because those revision

levels were omitted inadvertently from

paragraph (b) of the proposed rule for

Aerospatiale airplanes. That final rule

has been revised to indicate that certain

modifications are to be accomplished in

accordance with Revision 1 of

Aerospatiale Service Bulletins ATR42–

57–0043, ATR72–57–1015, and ATR72–

57–1016. The correct date for Revision

1 of those service bulletins (April 10,

1995) was specified in the proposal for

the affected airplanes.

Comment 37. Request To Revise

Referenced Service Bulletins

One commenter to the proposal for

Aerospatiale airplanes suggests that

service bulletin revisions should

contain a statement indicating that the

revision has no effect on previously

modified airplanes. The commenter

provides no justification for this request.

The FAA acknowledges that many

service bulletins do contain the

suggested phrase as an aid to operators

that may already have accomplished an

earlier service bulletin revision. In fact,

if a particular service bulletin is

specified in an AD and that service

bulletin is revised, the FAA routinely

determines whether the service bulletin

revision adequately addresses the

unsafe condition specified in the AD; if

necessary, the FAA amends the AD to

cite the later service bulletin revision.

Comment 38. Request To Revise Visual

Cue: Ice on Side Window

One commenter suggests revised

wording for the first visual cue specified

in paragraph (a)(1) of the proposed rule

for Aerospatiale airplanes, as follows:

‘‘Freezing rain and freezing drizzle are

characterized by ice covering all or a

substantial part of the unheated portion

of either forward side window and/or

water splashing or streaming on the

windshield or the side window when in

freezing or near freezing temperatures.’’

The commenter states that the present

wording implies that ice will always

appear on the side window; however,

this is not the case.

The FAA does not concur with the

commenter’s request. The commenter’s

revised wording suggests that water

splashing or streaming on the

windshield or the side window would

be a primary cue used to determine

when severe icing conditions are

present. The FAA does not concur that

water splashing or streaming on the

windshield or the side window would

be a reliable cue in itself. However, this

cue may be used as a supplemental cue

to the primary cue of ice accruing on the

side window. No change to the final

rule for Aerospatiale airplanes is

necessary.

Comment 39. Request To Remove Visual

Cue: Unusually Extensive Ice Accretion

One commenter, Saab, requests that if

the FAA does not withdraw the

proposed AD’s, paragraph (a)(1) of the

proposal for Saab SF340A and SAAB

340B series airplanes should be revised.

The commenter suggests that the first

visual cue that appears in that

paragraph, which relates to unusually

extensive ice accretion, be removed

from the proposal for those airplanes.

Saab indicates that critical ice is

believed to be ice that builds up beyond

the protected surfaces on the wing. On

Saab Model SF340A and SAAB 340B

series airplanes, the pilot has a good

view of the outer wing and the propeller

spinner. Unusually extensive ice in

other areas may or may not be

significant in determining whether

freezing rain or freezing drizzle is

present; however, the primary visual

cue for these airplanes is ice on the

spinner/outer wing.

In light of Saab’s remarks, the FAA

concurs that the visual cue addressed by

the commenter should be removed from

the final rule for Saab Model SF340A

and SAAB 340B series airplanes. (That

visual cue remains in place for Saab

Model SAAB 2000 series airplanes.)

Paragraph (a)(1) of that final rule has

been revised accordingly.

A second commenter, Raytheon,

requests that the same visual cue be

removed from the proposal for Beech

airplanes. Raytheon indicates that it

does not believe that observation of this

visual cue indicates that the airplane

has exceeded the Appendix C icing

envelope with respect to Beech

airplanes. Therefore, the cue specified

in the proposal would be irrelevant in

an AFM for these airplanes.

The FAA does not concur with

Raytheon’s request. The commenter has

not submitted data to warrant removal

of the visual cue. No change to the final

rule for Beech airplanes has been made.

Comment 40. Request To Remove Visual

Cue: Accumulation of Ice on Wing

Surfaces

JAL requests that the FAA remove the

generic information contained in the

visual cue concerning accumulation of

ice on the wing surfaces from the

proposals for Jetstream airplanes. JAL

indicates that, for its airplanes, the

appropriate visual cue is the accretion

of ice behind the protected area of the

wing upper surface (not the wing lower

surface).

The FAA concurs partially. The FAA

does not agree that the visual cue

should be removed from the final rules

for Jetstream airplanes. However, the

FAA finds that this particular visual cue

should be airplane-specific. Therefore,

the FAA has customized paragraph

(a)(1) of the final rules for all affected

airplanes to specify whether

accumulation of ice is observed on the
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20629

upper or lower surface of the wing,

depending upon whether the airplane is

a high- or low-wing airplane. [Operators

should note that, for Aerospatiale

airplanes, the cue was customized in

paragraph (a)(2) of the final rule.]

Comment 41. Request To Revise Visual

Cue: Accumulation of Ice on Propeller

Spinner

One commenter requests that the FAA

revise the visual cue concerning

accumulation of ice on the propeller

spinner, as specified in paragraph (a)(1)

of the proposals. For consistency, the

commenter requests that the word

‘‘back’’ be replaced with ‘‘aft.’’

The FAA concurs with the

commenter’s request. The final rules

have been revised to change the visual

cue to read as follows: ‘‘Accumulation

of ice on the propeller spinner farther

aft than normally observed.’’ [Operators

should note that, for Aerospatiale

airplanes, this change appears in

paragraph (a)(2) of the final rule.]

Comment 42. Request To Remove Visual

Cue: Accumulation of Ice on Propeller

Spinner

One commenter, JAL, requests that

the FAA remove the visual cue

concerning accumulation of ice on the

propeller spinner from the proposals for

Jetstream airplanes. JAL indicates that

on Jetstream Model ATP airplanes and

Model 748 series airplanes, the

propeller spinner is not visible from the

flight deck. On Jetstream Models 3101,

3201, and 4101 airplanes, the propeller

spinner is visible from the flight deck,

but flight test experience indicates that

there is no unique correlation between

the extent of spinner ice accretion and

the existence of freezing rain/freezing

drizzle conditions.

The FAA concurs partially. The FAA

concurs that since the propeller spinner

is not visible from the flight deck on

Jetstream Model ATP airplanes and

Model 748 series airplanes, the visual

cue can be removed from paragraph

(a)(1) of the final rules for these models.

The FAA does not concur that this

visual cue should be removed from the

AD’s for Jetstream Models 3101, 3201,

and 4101 airplanes. The commenter did

not submit data to substantiate its

assertion that flight test experience

indicates there is no unique correlation

between the extent of spinner ice

accretion and the existence of freezing

rain/freezing drizzle conditions.

Therefore, it is uncertain if the

commenter’s flight test airplane was

equipped with instrumentation that

would allow the detection and/or

measurement of droplets outside the

Appendix C conditions, and if the

airplane had flown into icing conditions

containing freezing rain or freezing

drizzle.

Comment 43. Request To Remove

Limitation to Immediately Exit Freezing

Rain/Freezing Drizzle

Saab requests that the FAA remove a

sentence from paragraph (a)(1) of the

proposals that requires the pilot to

immediately exit freezing rain or

freezing drizzle conditions by changing

altitude or course. This commenter

points out that the first limitation

contained in the proposal for Saab

airplanes (‘‘Flight in meteorological

conditions described as freezing rain or

freezing drizzle, as determined by the

following visual cues, is

prohibited . . .’’) already prohibits

flight in these conditions, and the pilot

should respond accordingly. Raytheon

believes a conflict exists between using

observations of ice accretion, as

required by paragraph (a)(1) of the

proposed rules, and the

‘‘determination’’ of certain

meteorological conditions.

The FAA concurs partially. The FAA

does not agree that the sentence

discussed by Saab should be removed

from paragraph (a)(1) of the final rules.

As explained previously, the first

limitation in paragraph (a)(1) of the final

rules has been revised to read: ‘‘During

flight, severe icing conditions that

exceed those for which the airplane is

certificated shall be determined by the

following visual cues. If one or more of

these visual cues exist, immediately

request priority handling from Air

Traffic Control to facilitate a route or an

altitude change to exit the icing

conditions.’’ (This wording is slightly

different in the final rule for

Aerospatiale airplanes because only one

visual cue is provided.) The FAA finds

that this revision to the final rules

addresses the commenters’ concerns

with regard to the proposed limitations.

One commenter poses various

questions concerning the last sentence

of the first instruction listed in the

procedures for exiting the freezing rain/

freezing drizzle environment in

paragraph (a)(2) of the proposals. (That

sentence reads as follows: ‘‘Asking for

priority to leave the area is fully

justified under these conditions.’’)

—What does the term ‘‘priority’’ provide

a pilot when asking for priority to

leave icing conditions?

—What if there were three simultaneous

requests for ‘‘priority?’’

—What Air Traffic Control procedures

exist for treating an immediate request

for ‘‘priority?’’

—Where is the term ‘‘priority’’ defined?

The commenter states that confusion

over terms that have not been defined

clearly by the FAA has partially resulted

in accidents and incidents. However,

the commenter does not cite a specific

case in which this occurred.

The FAA has re-examined the last

sentence of the first instruction listed in

the procedures for exiting the freezing

rain/freezing drizzle environment in

paragraph (a)(2) of the proposals. The

FAA has reconsidered use of the term

‘‘priority.’’ The FAA finds that more

appropriate language that would be

understood clearly by the flight crew

and Air Traffic Controllers should be

used in that instruction. Existing

training for flight crews and Air Traffic

Controllers addresses priority handling

of airplanes. However, the FAA will

issue additional information for Air

Traffic Controllers to further clarify

priority handling of airplanes in severe

icing conditions. The FAA finds that the

limitations specified in paragraph (a)(1)

of the final rules will result in the pilot

taking appropriate steps to exit the icing

conditions. Therefore, the FAA finds

that the sentence questioned by the

commenter may be removed from the

final rules without affecting safety.

Accordingly, the FAA has removed that

sentence from the final rules.

Additionally, in order to use

terminology in the procedures for

exiting the severe icing environment

that is consistent with the terminology

used in the revised limitation and to

simplify certain language, the FAA has

revised the first instruction of the

procedures. The revised instruction

reads as follows: ‘‘Immediately request

priority handling from Air Traffic

Control to facilitate a route or an

altitude change to exit the icing

conditions in order to avoid extended

exposure to flight conditions more

severe than those for which the airplane

has been certificated.’’

Comment 44. Request To Change the

Note Concerning the Autopilot

One commenter, ATR, requests that

the FAA revise the second note in

paragraph (a)(1) of the proposal for

Aerospatiale airplanes. As proposed,

ATR believes the last sentence of the

note is too restrictive. ATR proposes the

following: ‘‘The autopilot may mask

tactile cues . . . characteristics.

Therefore, when any ice is visible on the

airplane, the pilot should consider

flying manually for short periods in

order to check the absence of any

anomaly.’’

Two commenters request that the

FAA remove a similar note concerning

the autopilot from the proposals for

airplanes other than Aerospatiale
20630 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

models. One of the commenters, JAL,

states that the note contains advisory

information and should not appear in

the Limitations Section of an AFM.

The FAA concurs with ATR’s

comment that the last sentence of the

note is too restrictive; that sentence has

been removed from the final rules for all

airplanes. However, the FAA does not

agree with JAL’s contention that the

explanation of the relationship between

the autopilot and the masking of tactile

cues is inappropriate for insertion in the

Limitations Section of an AFM. On the

contrary, the FAA finds that inclusion

of such information will increase the

level of understanding and,

consequently, will increase the level of

safety.

In light of this, the FAA finds that the

note may be removed from paragraph

(a)(1) of the final rules for all airplanes;

however, the information contained in

the first sentence of that note has been

combined with the autopilot limitation

in paragraph (a)(1) of the final rules. The

final rules have been revised

accordingly.

Comment 45. Requests To Remove

Autopilot Limitation

Saab requests that the FAA revise the

second limitation that appears in

paragraph (a)(1) of the proposal for Saab

airplanes. As proposed, this limitation

indicates that use of the autopilot is

prohibited when any ice is observed

forming aft of the protected surfaces of

the wing, or when unusual lateral trim

requirements or autopilot trim warnings

are encountered. Saab asks that this

autopilot limitation be modified to take

into consideration the autopilot system

design on these airplanes, which

provides out-of-trim warnings;

therefore, the autopilot can be used up

to the point where a warning is

triggered. Saab adds that the triggering

point is early enough for the warning to

be taken, should the reason be ice buildup beyond the protected surfaces.

Additionally, there is no automatic

disconnect if the autopilot servo reaches

its limit torque, which would prevent

any surprise to the pilot during an outof-trim condition.

Another commenter, EMBRAER,

requests that use of the autopilot not be

limited for EMBRAER Model EMB–120

series airplanes. The commenter states

that flight tests have demonstrated the

safe ability of these airplanes to depart

a freezing rain/freezing drizzle

condition with the autopilot on.

Raytheon also objects to the autopilot

limitation. Raytheon suggests that a

better approach is to inform the pilots

of the nature of ice accretion, and then

let the pilots decide when to use the

autopilot. The commenter believes that

prohibiting use of the autopilot when

any ice is observed aft of the protected

surfaces of the wing is a rigid

requirement that takes away a valuable

aid to the flight crew when it may be

needed most. Raytheon states that there

is no evidence that the autopilots on

Beech aircraft would mask an icing

related control problem. The commenter

points out that tests on those aircraft

disclosed no icing related control

problem to mask. The commenter adds

that trying to anticipate every situation

with an absolute prohibition may lead

to other unsafe conditions.

The FAA does not concur that the

autopilot limitation should be modified

or removed from the AD’s for any of the

affected airplanes. The limited amount

of time the pilot is using manual

controls instead of the autopilot would

not result in an unsafe condition. In

normal operational environments and

conditions, the autopilot is a valuable

aid that reduces the workload of the

flight crew. However, under abnormal

conditions (ice aft of the protected

surfaces, unusual lateral trim, or

autopilot trim warnings), the autopilot

will mask the build-up of large or

unusual control forces in one or more

axes. Therefore, for the short period of

time necessary to exit severe icing

conditions, the safest course of action

would be manual pilot control. Even if

an autopilot does not automatically

disconnect, the pilot may choose to

disconnect the autopilot and could then

be faced unexpectedly with unusual

control forces. These reasons also still

hold true with airplanes that have been

flight tested with the ice shapes.

Since the issuance of the proposed

rules, the FAA has re-examined the

autopilot limitation specified in

paragraph (a)(1) of the proposals. The

FAA recognizes that clarification is

necessary with regard to its intent

concerning that limitation. That

limitation, as specified in the proposals,

states that use of the autopilot is

prohibited when any ice is observed

forming aft of the protected surfaces of

the wing, or when unusual lateral trim

requirements or autopilot trim warnings

are encountered. However, the FAA’s

intent concerning that limitation is that

the autopilot be disconnected when the

flight crew observes any of the visual

cues identified in paragraph (a)(1) of the

AD’s. The need to disconnect the

autopilot arises when an amount of ice

accumulates that indicates the limits of

the ice protection equipment have been

exceeded, regardless of the means by

which the flight crew becomes aware of

the accumulation of ice.

Additionally, the FAA acknowledges

that the autopilot limitation, as

proposed, could be misinterpreted to

mean that the autopilot must be

disengaged when unusual lateral trim or

autopilot trim warnings are

encountered, regardless of whether the

airplane is in icing conditions.

However, the FAA only intended that

the autopilot limitation apply while the

airplane is in icing conditions.

In light of this, the FAA has

determined that the autopilot limitation

contained in paragraph (a)(1) of the final

rules must be revised. The FAA has

changed that limitation to read as

follows: ‘‘Since the autopilot may mask

tactile cues that indicate adverse

changes in handling characteristics, use

of the autopilot is prohibited when any

of the visual cues specified above exist,

or when unusual lateral trim

requirements or autopilot trim warnings

are encountered while the airplane is in

icing conditions.’’ (This wording is

slightly different in the final rule for

Aerospatiale airplanes because only one

visual cue is provided.) This revision

more accurately reflects the FAA’s

intent and is, therefore, a logical

outgrowth of the proposed rules.

Comment 46. Request To Insert

Procedures in Limitations or Abnormal

Procedures Section of AFM

One commenter suggests that

operations in icing conditions that

exceed the capability of the airplane

should be described in the Limitations

or Abnormal Procedures Section of the

AFM, rather than in the Normal

Procedures Section, as specified in

paragraph (a)(2) of the proposals.

The FAA concurs partially. The FAA

agrees that the Abnormal Procedures

Section may be an appropriate location

for the procedures for exiting severe

icing conditions. However, the FAA

does not agree that such operational

procedures should appear in the

Limitations Section of the AFM since

such procedures are not limitations.

Additionally, upon further review, the

FAA finds that AFM’s may have neither

an Abnormal Procedures nor a Normal

Procedures Section. Consequently, to

provide operators with flexibility as to

where the procedures specified in

paragraph (a)(2) should be incorporated

in the AFM, that paragraph has been

revised to require that the ‘‘Procedures’’

Section of the AFM be revised. This

means that the procedures may be

inserted in the ‘‘Normal Procedures,’’

‘‘Abnormal Procedures,’’ or other

‘‘Procedures’’ Section of the AFM, as

appropriate.
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20631

Comment 47. Request To Remove

Duplicate Visual Cues

Two commenters indicate that certain

visual cues specified in paragraph (a)(2)

of the proposals are duplicated in the

‘‘Warning’’ that is also contained in that

paragraph. One commenter states that

the duplication of text reduces the

impact of the message. Another

commenter questions whether the visual

cues and procedures for exiting the

icing environment are intended to be

part of the AFM material. The FAA

infers from these remarks that the

commenters request that duplicate text

be removed.

Transport Canada Aviation requests

that the ‘‘Warning’’ be removed because

indications of the possible hazard are

progressive and may not necessarily

require immediate action from the pilot.

The commenter suggests that renaming

this as a ‘‘Caution’’ may be more

appropriate.

The FAA concurs partially. The FAA

agrees that duplicate text should be

removed from the ‘‘Warning’’ section

that appeared in the proposals. The

FAA finds that only one unique

instruction appears in the ‘‘Warning’’ in

paragraph (a)(2) of the proposals: ‘‘If the

flaps are extended, do not retract them

until the airframe is clear of ice.’’

Therefore, the FAA has added that

instruction to the procedures for exiting

the severe icing environment in

paragraph (a)(2) of the AD’s. The

remainder of the ‘‘Warning’’ section that

appeared in the proposals has been

removed from the final rules.

Comment 48. Request for Revision to

Instruction for Flaps Extension

Saab requests that the FAA revise an

instruction contained in the procedures

for exiting the freezing rain/freezing

drizzle environment in paragraph (a)(2)

of the proposals. That instruction

indicates to ‘‘Avoid extending flaps

during extended operation in icing

conditions * * *.’’ Saab suggests the

following: ‘‘Do not extend flaps when

holding in conditions where ice is

accreting on the airframe.’’ Further, the

commenter asks that this instruction be

inserted as a ‘‘caution’’ in the

Limitations Section of the AFM, rather

than into the Normal Procedures

Section, as specified in the proposed

rule. Saab believes that it is imperative

that the flaps not be extended in such

cases. Inserting the instruction into the

Limitations Section, rather than the

Normal Procedures Section, would add

strength to the requirement.

Another commenter states that this

same instruction appears to be in

conflict with previously approved AFM

revisions which state, ‘‘Sustained flight

in icing conditions is prohibited with

flaps extended.’’ However, the

commenter does not provide a

suggestion for rewording this

instruction.

The FAA concurs that the procedures

related to extension of the flaps can be

reworded somewhat. For clarification

purposes, the FAA has replaced the

word ‘‘avoid’’ with ‘‘do not’’ in that

procedure in paragraph (a)(2) of the

final rules. This revision eliminates the

conflict discussed by the second

commenter. However, the FAA does not

agree that revising the remainder of the

instruction, as suggested by Saab,

provides any additional clarification.

The FAA agrees that inserting the

revised wording in the Limitations

Section of the AFM, rather than in the

Normal Procedures Section, would be

acceptable; however, this would expand

the scope of the originally proposed

rules and would necessitate reopening

the comment period to provide

additional opportunity for public

comment. In light of the time required

to complete the rulemaking process in

advance of the upcoming icing season

and in consideration of the safety issues

addressed by these final rules, the FAA

finds that the AD’s should be issued

without additional delay. However, the

FAA would consider a request for

approval of an alternative method of

compliance, in accordance with the

provisions of this AD, to include this

information in the Limitations Section

of an operator’s AFM.

Transport Canada Aviation requests

that this instruction be revised to read

as follows: ‘‘Do not extend flaps during

operation in icing conditions, except for

approach and landing. Operation with

flaps extended will result in a reduced

wing angle-of-attack with the possibility

of ice forming on the upper surface

further aft on the wing than normal,

possibly aft of the protected area.’’

The FAA concurs partially. The FAA

does not concur with the commenter’s

suggested rewording to limit use of the

flaps in all operation in icing conditions

except approach and landing. The

wording proposed in the AD’s would

affect use of the flaps only during

extended operation in icing conditions.

The FAA finds that an amount of ice

sufficient to cause control problems is

more likely to accumulate during

prolonged operations in icing

conditions. Further, the FAA does not

concur that the words ‘‘operation of the

flaps can result in a reduced angle-ofattack * * *’’ should be changed to

‘‘operation of the flaps will result in a

reduced angle-of-attack * * *’’ in this

instruction. Operation with flaps

extended does not always result in a

reduced angle-of-attack. For instance,

during extension of the flaps while the

airplane is slowing, the angle-of-attack

will increase.

The FAA concurs with the suggestion

to include the words ‘‘the possibility of

ice forming on the upper surface further

aft * * *’’ The FAA acknowledges that

under certain conditions the droplets

will not impinge further aft with a

reduced angle-of-attack. The final rules

have been revised to add the words

suggested by the commenter to the sixth

instruction specified in the procedures

for exiting the severe icing environment

contained in paragraph (a)(2) of the

AD’s. That revised instruction reads as

follows: ‘‘Do not extend flaps * * *

with the possibility of ice forming on

the upper surface * * *’’

Comment 49. Requests To Revise

‘‘Caution’’ Paragraph

One commenter asks that the heading,

‘‘Caution,’’ which appears in paragraph

(a)(2) of the proposals, be renamed

‘‘Warning’’ because this section is

intended to prevent loss of life or injury.

Transport Canada Aviation requests that

the ‘‘Caution’’ section be changed to a

note. The commenter provides no

justification.

The FAA concurs partially. The FAA

does not concur that the ‘‘Caution’’

should be changed to a note because

this section is intended to prevent loss

of life or injury. In light of this, the FAA

concurs with the commenter’s request to

rename the ‘‘Caution’’ section

‘‘Warning.’’ The FAA finds that

‘‘Warning’’ is a stronger term and would

be a more appropriate heading for the

paragraph in question. Additionally, the

FAA finds that the ‘‘Warning’’ provides

advisory information that should

precede the first limitation in paragraph

(a)(1) of the AD’s. Accordingly, the FAA

has revised the heading ‘‘Caution’’ to

‘‘Warning’’ in the final rules. In

addition, the ‘‘Warning’’ has been

placed at the beginning of paragraph

(a)(1) of the final rules. The FAA has

determined that including this

information in the Limitations Section

of the AFM will not impose an

additional burden on any operator,

since it is informational only and does

not necessitate providing an additional

opportunity for public comment.

Additionally, the commenter notes

that an undefined term, ‘‘extreme,’’ is

used in a sentence in the ‘‘Caution’’

paragraph of the proposals, as follows:

‘‘Flight in freezing rain, freezing drizzle,

or mixed icing conditions (supercooled

liquid water and ice crystals) may result

in extreme ice build-up on protected

surfaces * * *’’ The FAA infers from
20632 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

this remark that the commenter asks

that the word ‘‘extreme’’ be removed

from the ‘‘Caution’’ paragraph.

The FAA concurs. The FAA finds that

removing the word ‘‘extreme’’ would

not change the intent of the sentence

and may eliminate confusion. The word

‘‘extreme’’ has been removed from this

section of the final rule. In addition, for

clarification purposes, the FAA has

revised the first sentence of the

proposed ‘‘Caution’’ from ‘‘Severe icing

comprises environmental conditions

* * *’’ to ‘‘Severe icing may result from

environmental conditions * * *’’

Comment 50. Request To Remove Visual

Cues: Identification of Freezing Rain/

Freezing Drizzle

One commenter indicates that the

cues provided in paragraph (a)(2) of the

proposals for identifying freezing rain/

freezing drizzle conditions are

duplicated in material that appears in

paragraph (a)(1) of the proposals. The

FAA infers from this remark that the

commenter requests that duplicative

wording be removed from paragraph

(a)(2) of the proposed rules.

The FAA concurs. The FAA finds that

the section entitled ‘‘The following shall

be used to identify freezing rain/freezing

drizzle icing conditions’’ is duplicated

in material that appears in paragraph

(a)(1), and does not enhance the

effectiveness of the AD’s. Therefore, that

section has been removed from

paragraph (a)(2) of the final rules for all

airplanes other than Aerospatiale Model

ATR–42 and ATR–72 series airplanes.

Paragraph (a)(1) of the proposals for

Aerospatiale airplanes specified

secondary indications for identifying

possible freezing rain/freezing drizzle

conditions. The FAA recognizes that the

flight crew could have interpreted that

paragraph to mean that if the secondary

indicators were observed, the airplane

must be flown clear of the severe icing

conditions. However, the FAA’s intent

is that the flight crew must immediately

request priority handling to exit the

icing conditions only when the visual

cue (ice on the side window) specified

in paragraph (a)(1) of the AD is

observed.

Accordingly, the FAA has deleted the

secondary indications of possible severe

icing conditions from paragraph (a)(1) of

the final rule for Aerospatiale airplanes.

In addition, the FAA has removed the

visual cue (ice on the side window)

from paragraph (a)(2) of the final rule.

The FAA has retitled the section

containing the secondary indications of

possible severe icing as follows: ‘‘The

following may be used as secondary

indications of severe icing conditions.’’

Further, the last two secondary

indicators contained in that section are

specified in the final rule in a section

titled: ‘‘The following weather

conditions may be conducive to severe

in-flight icing.’’ (This change is

explained further in Comment 51

below.)

Comment 51. Request To Remove Visual

Cues: Identification of Possible Freezing

Rain/Freezing Drizzle

One commenter states that the word

‘‘may’’ in the following title, which

appears in paragraph (a)(2) of the

proposals, is confusing: ‘‘The following

may be used to identify possible

freezing rain/freezing drizzle

conditions.’’ The commenter indicates

that AFM procedures should provide a

clear sequence of steps that must be

followed and that such procedures

should be explicit; general advice,

regardless of how prudent, should be

published elsewhere. The FAA infers

from this remark that the commenter

asks that the cues that appear under this

section be deleted.

The FAA does not concur that this

section should be removed. The cues

provided for identification of possible

severe icing conditions will alert the

pilot to the possibility that unusual ice

accretion may develop. The FAA finds

that the level of detail provided in the

final rules will increase the level of pilot

awareness and, consequently, will

increase the level of safety over that

which exists currently. Therefore, the

FAA has determined that it is

appropriate to incorporate this section

in the AFM.

However, the FAA finds that

clarification is necessary with regard to

the title of this section. The FAA finds

that operators may misinterpret that

title, as proposed, to mean that this

section contains visual cues that should

be used to identify possible severe icing

conditions prior to takeoff, dispatch, or

release while the airplane is on the

ground. Additionally, the FAA finds

that confusion could result in

differentiating between the weather

conditions specified in this section and

the visual cues provided in paragraph

(a)(1) of the AD’s. For clarification

purposes, the FAA has revised the title

of this section to read as follows: ‘‘The

following weather conditions may be

conducive to severe in-flight icing.’’

Comment 52. Request To Revise Air

Temperature References

Transport Canada Aviation states that

ambient temperature is indicated as

static air temperature (SAT), rather than

outside air temperature (OAT), for de

Havilland Model DHC–8 series

airplanes. The FAA infers from this

remark the commenter requests that the

ambient temperature that appears in the

weather conditions specified in

paragraph (a)(2) of the proposals be

expressed as SAT for those airplanes.

The FAA does not concur. The FAA

does not intend to specify which

specific indicator in the cockpit a pilot

should use to determine the ambient air

temperature. The FAA intends that the

pilot use whatever means necessary to

determine ambient air temperature.

However, since airplanes may have

indicators other than OAT, the FAA has

replaced the words ‘‘outside air

temperature’’ with ‘‘ambient air

temperature’’ in the weather conditions,

and in the procedures for exiting the

severe icing environment, specified in

paragraph (a)(2) of these final rules to

eliminate confusion concerning the

need for a specific type of indicator.

In addition, the FAA has re-examined

the ambient temperature of +5 degrees

Celsius that is specified in paragraph

(a)(2) of the proposals. The FAA has

determined that this temperature is too

high to be used as a reliable indication

of whether severe icing conditions may

exist during flight. The FAA finds that

0 degrees Celsius is a more appropriate

indication. The FAA has revised

paragraph (a)(2) of the final rules for all

airplanes accordingly.

Comment 53. Request To Replace

Reference to Droplets that Splash or

Splatter

JAL requests that the weather

condition that pertains to ‘‘droplets that

splash or splatter’’ be removed from

paragraph (a)(2) of the proposals. JAL

believes that this weather condition

places too much emphasis on subjective

judgment. JAL states that normal rain

conditions will contain droplets that

splash or splatter upon impact with the

windshield. JAL indicates that

information included in its existing

AFM revisions, specified as follows,

adequately addresses the issue:

‘‘Prolonged operation in altitude bands

where temperatures are near freezing

and heavy moisture is visible on the

windscreen should be avoided.’’

The FAA does not concur that this

weather condition should be removed

from the AD’s. This weather condition

must be used in conjunction with the

temperature specified as a means of

identifying severe in-flight icing

conditions. The weather condition also

will alert the pilot to the possibility that

unusual ice accretion may develop. The

FAA finds that the AFM information

submitted by JAL does not provide an

equivalent alert to the pilot.
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20633

Comment 54. Request To Revise

Procedures for Exiting Freezing Rain/

Freezing Drizzle

JAL requests that the procedures for

exiting freezing rain/freezing drizzle

specified in paragraph (a)(2) of the

proposals be restricted to essential

instructions that the flight crew must

follow. JAL contends that the

procedures contained in the proposals

are not written in the appropriate format

for AFM procedures, but are more

representative of advisory material. JAL

also states that the current FAAapproved AFM procedures for exiting

freezing rain/freezing drizzle already

provide this essential information and

conform to the existing style of the

AFM’s. Transport Canada Aviation

requests that the first instruction in

these procedures be revised to state

only: ‘‘Exit the freezing rain or freezing

drizzle conditions immediately.’’ The

commenter also requests clarification of

the terms ‘‘extended exposure,’’ as used

in that instruction.

The FAA concurs partially. The FAA

has reviewed the procedures for exiting

the severe icing environment and finds

that two of the instructions contained in

those procedures do not require the

level of detail provided in the proposed

rules. The FAA finds that the

information concerning masking of

control system forces is already

provided in the Limitations Section of

the AFM. Therefore, the FAA has

revised the third instruction of those

procedures to read as follows: ‘‘Do not

engage the autopilot.’’ Additionally, the

FAA has determined that the flight crew

need not be provided with instructions

for reducing the angle-of-attack because

instructions such as this are considered

to be basic airmanship. Accordingly, the

FAA has revised the fifth instruction in

the procedures for exiting the severe

icing environment to specify only

information that is essential for the

flight crew. The revised instruction

reads as follows: ‘‘If an unusual roll

response . . . reduce the angle-of-attack.’’

The FAA finds that, for the remainder

of the procedures for exiting, the

additional level of details provided in

the final rules will increase the level of

understanding and, consequently, will

increase the level of safety over that

which exists currently. The FAA finds

that these procedures are appropriate for

insertion in the AFM’s.

Regarding the terms ‘‘extended

exposure,’’ the intent of that instruction

is to advise the flight crew that exiting

the severe icing conditions will

minimize the exposure to flight

conditions outside those for which the

airplane has been certificated. The FAA

finds that remaining in such conditions

for a prolonged period may result in

accumulating an amount of ice

sufficient to cause control problems.

The phrase ‘‘to avoid extended

exposure’’ is only intended to explain to

the flight crew why severe icing

conditions should be exited

immediately.

Raytheon questions the necessity to

tell a commercial pilot not to make any

abrupt or excessive maneuvers if the

aircraft is in the position of having

control difficulties. This instruction

appears under the heading ‘‘Procedures

for exiting the freezing rain/freezing

drizzle environment,’’ which appears in

paragraph (a)(2) of the proposals. The

commenter contends that this is a

training issue and is not appropriate for

AFM procedures. The FAA infers from

the commenter’s remark that the

commenter requests that these

instructions be eliminated from the

proposed rules.

The FAA does not concur. The FAA

has determined that such instructions

provide beneficial guidance to the flight

crew, which will enhance the safety of

the aircraft.

Saab requests that the FAA revise one

of the instructions specified in the

procedures for exiting freezing rain/

freezing drizzle specified in the

proposals. The instruction states that if

an unusual roll response or

uncommanded control movement is

observed, the angle-of-attack should be

reduced by increasing the airspeed or

rolling the wings level (if in a turn), and

applying additional power, if needed.

Saab suggests that this instruction be

revised to include the word ‘‘aileron’’ in

the reference to uncommanded control

movement. Saab states further that in

the case of wing ice beyond the

protected surfaces, the application of

power may be appropriate to increase

airspeed/improve airflow. However, if

ice has accrued on the wings beyond the

protected surfaces, there is a possibility

that there also is ice on the horizontal

stabilizers. In this case, a sudden burst

of power may be detrimental. An

uncommanded pitch control movement

is indicative of tail ice, which normally

calls for a different action, both

concerning power as well as the

handling of flaps, if extended. Another

commenter, Transport Canada Aviation,

requests that the same instruction be

revised to include the word ‘‘lateral’’ in

reference to ‘‘uncommanded control

movement,’’ and to change the phrase

‘‘or rolling wings level’’ to ‘‘and rolling

wings level.’’

The FAA concurs partially. The FAA

agrees that the correct procedures for

reducing the angle-of-attack is to

increase the airspeed and roll the wings

level, if in a turn. However, as explained

previously, this portion of the procedure

has been removed from the final rules.

The FAA does not agree that either

‘‘lateral’’ or ‘‘aileron’’ should be used to

specify the type of uncommanded

control movement. The FAA finds that

use of the term ‘‘lateral’’ may not be

understood by the flight crew. The FAA

finds that including the word ‘‘aileron’’

may clarify which control surface is of

concern; however, the FAA has

determined that use of a more general

term, ‘‘roll’’ will correctly specify the

type of uncommanded control

movement that is of concern. The FAA

has revised the fifth instruction in the

procedures for exiting the severe icing

environment in paragraph (a)(2) of the

final rules accordingly. The revised

instruction reads as follows: ‘‘If an

unusual roll response or uncommanded

roll control movement is observed,

reduce the angle-of-attack.’’

In addition, the procedures for exiting

the freezing rain/freezing drizzle

environment contained in the proposals

did not specify to use ‘‘a sudden burst

of power’’ when reducing the angle-ofattack. Rather, the proposed procedure

indicates to apply additional power, if

needed, to provide the desired flight

path. However, as discussed previously,

the FAA has removed this reference

from the final rules. In addition, as

explained previously, the FAA has

revised the final rules to add the word

‘‘roll’’ to describe the type of

uncommanded control movement. This

revised wording addresses Saab’s

concern regarding increasing power for

a pitch anomaly.

Saab also notes that this instruction

recommends a reduction in the angle-ofattack and application of power, if

needed. However, the next instruction

of the procedures indicates that

reducing the angle-of-attack may cause

ice to build up beyond the protected

areas of the wing. Saab concludes that

there is a conflict in that the proposed

AD would require that the angle-ofattack not be reduced or ice will collect

beyond the protected surfaces; however,

the angle-of-attack must be reduced if

there is an unusual roll response or

uncommanded control movement.

The FAA does not concur with the

commenter’s contention that there is a

conflict in the AD’s. Reducing the angleof-attack by increasing airspeed or

rolling the wings level (if in a turn), and

applying additional power, if needed, is

a procedure used to exit severe icing

conditions following an unusual roll

response or uncommanded roll control

movement; whereas the instruction that

involves not extending the flaps during
20634 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

extended operation in icing conditions

is intended to prevent ice build-up

beyond the unprotected surfaces.

Raytheon asks for removal of the

instruction to reduce the angle-of-attack

and apply additional power, if needed,

in response to an unusual roll response

or uncommanded control movement.

The commenter states that these are

normal instructions with respect to

wing stall and are inappropriate for

inclusion in an AFM.

The FAA concurs partially. There

may not be a stall warning associated

with uncommanded control movements

in the case of encounters with severe

icing conditions. Since this is not a

‘‘normal’’ stall, the flight crew may not

recognize that normal stall recovery

procedures should be used. However, as

stated previously, the instruction

referenced by the commenter has been

deleted, in part, from the final rules.

Raytheon also states that it is not

appropriate to require contact with Air

Traffic Control as part of an AFM

procedure since this is already

addressed in the Aeronautical

Information Manual and in section

91.183 of the Federal Aviation

Regulations (14 CFR 91.183). The FAA

infers from this statement that the

commenter requests that the instruction

to contact Air Traffic Control should be

removed from the procedures for exiting

severe icing conditions.

The FAA does not concur. The FAA

is aware that this instruction is

contained in the references provided by

the commenter. However, the FAA finds

that the importance of timely

dissemination of this instruction

warrants its inclusion in the final rules.

Inclusion of instructions of this type is

not without precedent; for example,

similar information also is specified in

certain AFM’s where the forward look

windshear system is addressed.

Comment 55. Request To Revise

Procedures for Exiting the Severe Icing

Environment: Include Airplane- Specific

Instructions

One commenter suggests that any

action that might be necessary to

optimize aircraft performance and

control in conditions of exceptional

icing, and exit from those conditions,

should be determined separately with

each manufacturer; such procedures

should be contained in the AFM for

each airplane model. The FAA infers

from this remark that the commenter

requests that the FAA revise the

procedures for exiting the severe icing

environment in each final rule to

include airplane-specific instructions.

The FAA agrees that procedures

obtained from each individual

manufacturer should be considered and

included in the final rules, if

appropriate. All manufacturers have

been provided with an opportunity to

submit such procedures in response to

the proposed rules. Some manufacturers

requested changes to the final rules. The

FAA has revised the final rules for those

requests that were substantiated

adequately. Following issuance of the

final rules, the FAA would consider a

request to include additional changes to

the AFM revisions, in accordance with

the provisions of these AD’s, provided

that adequate justification is presented

to support such a request.

Comment 56. Revision of Procedures for

Exiting the Severe Icing Environment

The FAA has re-examined the section

titled ‘‘Procedures for exiting the severe

icing environment’’ in paragraph (a)(2)

of the proposals. As proposed, that

section states that if the visual cues used

for identifying ‘‘possible’’ freezing rain

or freezing drizzle conditions are

observed, the flight crew should follow

the procedures specified for exiting

those conditions. The FAA did not

intend that the flight crew use the

procedures for exiting the severe icing

environment when the weather

conditions specified in paragraph (a)(2)

of these AD’s are observed. The FAA’s

intent is that the flight crew use those

procedures only when the visual cues

identified in the Limitations Section of

the AFM are observed.

In order to eliminate any confusion,

the FAA has revised the last sentence of

the first paragraph in the procedures for

exiting the severe icing environment.

The FAA has removed the word

‘‘possible’’ from that sentence, and has

added clarification that the visual cues

are specified in the Limitations Section

of the AFM. The revised sentence reads

as follows: ‘‘If the visual cues specified

in the Limitations Section of the AFM

for identifying severe icing conditions

are observed, accomplish the

following.’’ (Operators should note that,

for Aerospatiale airplanes, the final rule

specifies only one visual cue, which

involves ice on the side window.)

Comment 57. Request to Revise Cost

Estimate

Transport Canada requests that the

FAA provide an operational cost

estimate in the proposed AD’s.

The FAA acknowledges the concern

of the commenter. The FAA recognizes

that, in accomplishing the requirements

of any AD, operators may incur other

costs in addition to the ‘‘direct’’ costs

that are reflected in the cost analysis

presented in the AD preamble.

However, the cost analysis in AD

rulemaking actions typically only

includes such direct costs. In the case of

these AD’s, for example, the

requirements are to revise the AFM to

include certain information. How

operators actually ‘‘implement’’ that

information thereafter (once it is placed

in the AFM) may vary greatly among

them.

Further, because AD’s require specific

actions to address specific unsafe

conditions, they appear to impose costs

that would not otherwise be borne by

operators. However, because of the

general obligation of operators to

maintain and operate aircraft in an

airworthy condition, this appearance is

deceptive. Attributing those costs solely

to the issuance of this AD is unrealistic

because, in the interest of maintaining

and operating safe aircraft, prudent

operators would accomplish the

required actions even if they were not

required to do so by the AD. In any case,

the FAA has determined that direct and

incidental costs are still outweighed by

the safety benefits of the AD.

The FAA points out that it is not

required to do a full cost-benefit

analysis for each AD. AD’s were

explicitly exempted from the Office of

Management and Budget (OMB)

coordination process described in

Section 6 of that Executive Order. As a

matter of law, in order to be airworthy,

an aircraft must conform to its type

design and be in a condition for safe

operation. The type design is approved

only after the FAA makes a

determination that it complies with all

applicable airworthiness requirements.

In adopting and maintaining those

requirements, the FAA has already

made the determination that they

establish a level of safety that is costbeneficial. When the FAA later makes a

finding of an unsafe condition in an

aircraft and issues an AD, it means that

the original cost beneficial level of

safety is no longer being achieved and

that the required actions are necessary

to restore that level of safety. Because

this level of safety has already been

determined to be cost beneficial, and

because the AD does not add an

additional regulatory requirement that

increases the level of safety beyond

what has been established by the type

design, a full cost-benefit analysis for

each AD would be redundant and

unnecessary.

Comment 58. Requests to Delay

Issuance of the Final Rules

Three commenters request that the

FAA extend the comment period for the

proposed rules by 90 days. Each of the

commenters request the extension in

order to complete a comprehensive
Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations 20635

analysis of this issue. The commenters

state their involvement in focusing on

‘‘. . . ther recent rulemaking activity,

including the Commuter Rule, flight

crewmember training requirements, and

proposed rules covering flight crew

flight, duty and test requirements . . .’’

as a reason that did not allow complete

analysis of the proposed AD’s.

One commenter requests that

implementation of the AD’s be deferred

until further discussion with industry

has been undertaken.

The FAA has reviewed these requests

and, in consideration of the importance

and need for dissemination of this

important information to the aviation

community, does not concur that the

comment period should be extended or

issuance of the final rules be deferred

until a later date. Issuing the final rules

will ensure that the information is

available, understood, and implemented

by the aviation community before the

next icing season. For these reasons, the

FAA has determined that it is

imperative that the information and

actions contained in these final rules be

incorporated into the operators’ AFM’s

immediately.

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

The FAA estimates that 169 airplanes

in the U.S. registry will be affected by

this AD, that it will take approximately

1 workhour per airplane to accomplish

the required action, and that the average

labor rate is approximately $60 an hour.

Since an owner/operator who holds at

least a private pilot’s certificate as

authorized by sections 43.7 and 43.11 of

the Federal Aviation Regulations (14

CFR 43.7 and 43.11) can accomplish the

required action, the only cost impact

upon the public is the time it would

take the affected airplane owner/

operators to incorporate the AFM

revisions.

In addition, the FAA recognizes that

this AD may impose operational costs.

However, those costs are incalculable

because the frequency of occurrence of

the specified conditions and the

associated additional flight time cannot

be determined. Nevertheless, because of

the severity of the unsafe condition

addressed, the FAA has determined that

continued operational safety

necessitates the imposition of these

costs.

Regulatory Impact

The regulations adopted herein will

not have substantial direct effects on the

States, on the relationship between the

national government and the States, or

on the distribution of power and

responsibilities among the various

levels of government. Therefore, in

accordance with Executive Order 12612,

it is determined that this final rule does

not have sufficient federalism

implications to warrant the preparation

of a Federalism Assessment.

For the reasons discussed above, I

certify that this action (1) is not a

‘‘significant regulatory action’’ under

Executive Order 12866; (2) is not a

‘‘significant rule’’ under DOT

Regulatory Policies and Procedures (44

FR 11034, February 26, 1979); and (3)

will not have a significant economic

impact, positive or negative, on a

substantial number of small entities

under the criteria of the Regulatory

Flexibility Act. A copy of the final

evaluation prepared for this action is

contained in the Rules Docket. A copy

of it may be obtained by contacting the

Rules Docket at the location provided

under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation

safety, 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 USC 106(g), 40113, 44701.

§ 39.13 [Amended]

2. Section 39.13 is amended by

adding a new airworthiness directive

(AD) to read as follows:

96–09–11 De Havilland: Amendment 39–

9587; Docket No. 96–CE–01–AD.

Applicability: Models DHC–6–1, DHC–6–

100, DHC–6–200, and DHC–6–300 airplanes

(all serial numbers), certificated in any

category.

Note 1: This AD applies to each airplane

identified in the preceding applicability

provision, regardless of whether it has been

modified, altered, or repaired in the area

subject to the requirements of this AD. For

airplanes that have been modified, altered, or

repaired so that the performance of the

requirements of this AD is affected, the

owner/operator must request approval for an

alternative method of compliance in

accordance with paragraph (d) of this AD.

The request should include an assessment of

the effect of the modification, alteration, or

repair on the unsafe condition addressed by

this AD; and, if the unsafe condition has not

been eliminated, the request should include

specific proposed actions to address it.

Compliance: Required as indicated, unless

accomplished previously.

To minimize the potential hazards

associated with operating the airplane in

severe icing conditions by providing more

clearly defined procedures and limitations

associated with such conditions, accomplish

the following:

(a) Within 30 days after the effective date

of this AD, accomplish the requirements of

paragraphs (a)(1) and (a)(2) of this AD.

Note 2: Operators must initiate action to

notify and ensure that flight crewmembers

are apprised of this change.

(1) Revise the FAA-approved Airplane

Flight Manual (AFM) by incorporating the

following into the Limitations Section of the

AFM. This may be accomplished by inserting

a copy of this AD in the AFM.

‘‘WARNING

Severe icing may result from

environmental conditions outside of those for

which the airplane is certificated. Flight in

freezing rain, freezing drizzle, or mixed icing

conditions (supercooled liquid water and ice

crystals) may result in ice build-up on

protected surfaces exceeding the capability of

the ice protection system, or may result in ice

forming aft of the protected surfaces. This ice

may not be shed using the ice protection

systems, and may seriously degrade the

performance and controllability of the

airplane.

• During flight, severe icing conditions

that exceed those for which the airplane is

certificated shall be determined by the

following visual cues. If one or more of these

visual cues exists, immediately request

priority handling from Air Traffic Control to

facilitate a route or an altitude change to exit

the icing conditions.

—Unusually extensive ice accreted on the

airframe in areas not normally observed to

collect ice.

—Accumulation of ice on the upper surface

of the wing aft of the protected area.

—Accumulation of ice on the propeller

spinner farther aft than normally observed.

• Since the autopilot may mask tactile

cues that indicate adverse changes in

handling characteristics, use of the autopilot

is prohibited when any of the visual cues

specified above exist, or when unusual

lateral trim requirements or autopilot trim

warnings are encountered while the airplane

is in icing conditions.

• All icing detection lights must be

operative prior to flight into icing conditions

at night. [NOTE: This supersedes any relief

provided by the Master Minimum Equipment

List (MMEL).]’’

(2) Revise the FAA-approved AFM by

incorporating the following into the
20636 Federal Register / Vol. 61, No. 89 / Tuesday, May 7, 1996 / Rules and Regulations

Procedures Section of the AFM. This may be

accomplished by inserting a copy of this AD

in the AFM.

‘‘THE FOLLOWING WEATHER

CONDITIONS MAY BE CONDUCIVE TO

SEVERE IN-FLIGHT ICING:

• Visible rain at temperatures below 0

degrees Celsius ambient air temperature.

• Droplets that splash or splatter on impact

at temperatures below 0 degrees Celsius

ambient air temperature.

PROCEDURES FOR EXITING THE SEVERE

ICING ENVIRONMENT:

These procedures are applicable to all

flight phases from takeoff to landing. Monitor

the ambient air temperature. While severe

icing may form at temperatures as cold as

¥18 degrees Celsius, increased vigilance is

warranted at temperatures around freezing

with visible moisture present. If the visual

cues specified in the Limitations Section of

the AFM for identifying severe icing

conditions are observed, accomplish the

following:

• Immediately request priority handling

from Air Traffic Control to facilitate a route

or an altitude change to exit the severe icing

conditions in order to avoid extended

exposure to flight conditions more severe

than those for which the airplane has been

certificated.

• Avoid abrupt and excessive

maneuvering that may exacerbate control

difficulties.

• Do not engage the autopilot.

• If the autopilot is engaged, hold the

control wheel firmly and disengage the

autopilot.

• If an unusual roll response or

uncommanded roll control movement is

observed, reduce the angle-of-attack.

• Do not extend flaps during extended

operation in icing conditions. Operation with

flaps extended can result in a reduced wing

angle-of-attack, with the possibility of ice

forming on the upper surface further aft on

the wing than normal, possibly aft of the

protected area.

• If the flaps are extended, do not retract

them until the airframe is clear of ice.

• Report these weather conditions to Air

Traffic Control.’’

(b) Incorporating the AFM revisions, as

required by this AD, may be performed by

the owner/operator holding at least a private

pilot certificate as authorized by section 43.7

of the Federal Aviation Regulations (14 CFR

43.7), and must be entered into the aircraft

records showing compliance with this AD in

accordance with section 43.11 of the Federal

Aviation Regulations (14 CFR 43.11).

(c) Special flight permits may be issued in

accordance with sections 21.197 and 21.199

of the Federal Aviation Regulations (14 CFR

21.197 and 21.199) to operate the airplane to

a location where the requirements of this AD

can be accomplished.

(d) An alternative method of compliance or

adjustment of the compliance time that

provides an acceptable level of safety may be

used if approved by the Manager, Small

Airplane Directorate, FAA, 1201 Walnut,

suite 900, Kansas City, Missouri 64106. The

request shall be forwarded through an

appropriate FAA Maintenance Inspector,

who may add comments and then send it to

the Manager, Small Airplane Directorate.

Note 3: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Small Airplane

Directorate.

(e) All persons affected by this directive

may examine information related to this AD

at the FAA, Central Region, Office of the

Assistant Chief Counsel, Room 1558, 601 E.

12th Street, Kansas City, Missouri 64106.

(f) This amendment (39–9587) becomes

effective on June 11, 1996.

Issued in Kansas City, Missouri, on April

24, 1996.

Henry A. Armstrong,

Acting Manager, Small Airplane Directorate,

Aircraft Certification Service.

[FR Doc. 96–10728 Filed 5–1–96; 3:23 pm]

BILLING CODE 4910–13–P

14 CFR Part 39

[Docket No. 96–CE–02–AD; Amendment 39–

9588; AD 96–09–12]

RIN 2120–AA64

Airworthiness Directives; Empresa

Brasileiro de Aeronautico, S.A. Models

EMB–110P1 and EMB–110P2 Airplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Final rule.

SUMMARY: This amendment adopts a

new airworthiness directive (AD) that

applies to Empresa Brasileiro de

Aeronautico, S.A. (EMBRAER) Models

EMB–110P1 and EMB–110P2 airplanes.

This action requires revising the

Airplane Flight Manual (AFM) to

provide the flight crew with recognition

cues for, and procedures for exiting

from, severe icing conditions, and to

limit or prohibit the use of various flight

control devices. This amendment is

prompted by results of a review of the

requirements for certification of the

airplane in icing conditions, new

information on the icing environment,

and icing data provided currently to the

flight crews. The actions specified by

this AD are intended to minimize the

potential hazards associated with

operating the airplane in freezing rain or

freezing drizzle conditions by providing

more clearly defined procedures and

limitations associated with such

conditions.

EFFECTIVE DATE: June 11, 1996.

ADDRESSES: Information that relates to

this AD may be examined at the Federal

Aviation Administration (FAA), Central

Region, Office of the Assistant Chief

Counsel, Attention: Rules Docket 96–

CE–02–AD, Room 1558, 601 E. 12th

Street, Kansas City, Missouri 64106.

FOR FURTHER INFORMATION CONTACT: Mr.

John Dow, Aerospace Engineer, FAA,

Small Airplane Directorate, 1201

Walnut, suite 900, Kansas City, Missouri

64106; telephone (816) 426–6934;

facsimile (816) 426–2169.

SUPPLEMENTARY INFORMATION: A

proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to

include an AD that would apply to

EMBRAER Models EMB–110P1 and

EMB–110P2 airplanes was published in

the Federal Register on January 25,

1996 (61 FR 2183). The action proposed

to require revising the Airplane Flight

Manual (AFM) to specify procedures

that would prohibit flight in freezing

rain or freezing drizzle conditions (as

determined by certain visual cues), limit

or prohibit the use of various flight

control devices, and provide the flight

crew with recognition cues for, and

procedures for exiting from, severe icing

conditions.

Disposition of Comments

For the disposition of comments on

this rulemaking action, see Docket No.

96–CE–01; Amendment 39–9587; AD

96–09–11, Airworthiness Directives; de

Havilland, Inc. DHC–6 Series Airplanes,

published elsewhere in this issue of the

Federal Register.

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

The FAA estimates that 169 airplanes

in the U.S. registry will be affected by

this AD, that it will take approximately

1 workhour per airplane to accomplish

the required action, and that the average

labor rate is approximately $60 an hour.

Since an owner/operator who holds at

least a private pilot’s certificate as

authorized by sections 43.7 and 43.11 of

the Federal Aviation Regulations (14

CFR 43.7 and 43.11) can accomplish the

required action, the only cost impact

upon the public is the time it would

take the affected airplane owner/

operators to incorporate the AFM

revisions.

In addition, the FAA recognizes that

this AD may impose operational costs.

However, those costs are incalculable