Document ID: FAA-2008-0173-0001
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Empresa Brasileira de Aeronautica S.A. (EMBRAER) Model EMB-120, -120ER, -120FC, -120QC, and -120RT Airplanes
Posted Date: 2008-02-08T05:00Z

[Federal Register: February 8, 2008 (Volume 73, Number 27)]
[Proposed Rules]               
[Page 7494-7498]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr08fe08-19]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2003-NM-33-AD]
RIN 2120-AA64

 
Airworthiness Directives; Empresa Brasileira de Aeronautica S.A. 
(EMBRAER) Model EMB-120, -120ER, -120FC, -120QC, and -120RT Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), applicable to all EMBRAER Model EMB-120 series 
airplanes, that would have required revising the airplane flight manual 
to include operational limitations for use of the autopilot, and 
installing two placards that advise the flight crew to check the pitch 
trim before descent. This new action would retain the original 
requirements, but with revised placard language. This new action would 
also require modifying the elevator trim system, which would terminate 
the requirements of the AD. The actions specified by this new proposed 
AD are intended to prevent pitch trim upsets if the pitch trim 
actuators jam or freeze, which could result in reduced controllability 
of the airplane. This action is intended to address the identified 
unsafe condition.

DATES: Comments must be received by March 4, 2008.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2003-NM-33-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98057-3356. Comments may be inspected at this 
location between 9 a.m. and 3 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must 

contain ``Docket No. 2003-NM-33-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 or 2000 or 
ASCII text.
    The service information referenced in the proposed rule may be 
obtained from Empresa Brasileira de Aeronautica S.A. (EMBRAER), P.O. 
Box 343--CEP 12.225, Sao Jose dos Campos--SP, Brazil. This information 
may be examined at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Dan Rodina, Aerospace Engineer, 
International Branch, ANM-116, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
227-2125; fax (425) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this action may be changed in 
light of the comments received.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the proposed 
AD is being requested.
     Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2003-NM-33-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 2003-NM-33-AD, 1601 Lind Avenue SW., Renton, Washington 
98057-3356.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to all 
EMBRAER Model EMB-120 series airplanes, was published as a notice of 
proposed rulemaking (NPRM) in the Federal Register on April 1, 2003 (68 
FR 15684). That NPRM would have required revising the airplane flight 
manual to include operational limitations for use of the autopilot, and 
installing two placards that advise the flight crew to check the pitch 
trim before descent. That NPRM was prompted by pitch trim upsets during 
the autopilot-coupled descent phase of flight, which have been 
attributed to jammed or frozen pitch trim actuators. That condition, if 
not corrected, could result in reduced controllability of the airplane.

New Relevant Service Information

    The original NPRM cited EMBRAER Service Bulletin 120-25-0262, dated 
October 15, 2001, and Change 01, dated September 3, 2002, as the 
appropriate sources of service information for installing the placards. 
Since we issued the original NPRM, EMBRAER revised the service 
bulletin. Change 02, dated October 30, 2003, recommends revised

[[Page 7495]]

placard language that clarifies that the pitch trim system is to be 
checked only before the initial descent.
    EMBRAER has issued Service Bulletins 120-27-0095 and 120-27-0096, 
both dated February 16, 2007, which describe procedures for modifying 
the elevator trim system. Service Bulletin 120-27-0095 describes 
procedures for replacing the elevator trim tab actuators with new ones 
that have been developed using corrosion-resistant internal materials 
and other improvements, including a damper coupled to one of the two 
actuators. Service Bulletin 120-27-0096 describes procedures for 
replacing some segments of the elevator trim tab control cables. The 
replacement segments have a different diameter, and have been developed 
to contribute to the new actuator dampening function specified in 
Service Bulletin 120-27-0095.
    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition. The Ag[ecirc]ncia 
Nacional de Avia[ccedil]o Civil (ANAC), which is the airworthiness 
authority for Brazil, mandated the service information and issued 
Brazilian airworthiness directive 2001-06-01R4, effective August 23, 
2007, to ensure the continued airworthiness of these airplanes in 
Brazil.

Comments

    Due consideration has been given to the comments received in 
response to the original NPRM.

Support for Original NPRM

    SkyWest Airlines concurs with the proposed requirement to revise 
the Limitations section of the Collins APS-65B Autopilot AFM 
Supplement. The Air Line Pilots Association (ALPA) concurs 
(conditionally, based on its comments as discussed below) with the 
proposed actions.

Request for Appropriate Solution for Mechanical Problem

    ALPA asserts that the original NPRM would implement an operational 
fix to address a mechanical problem, and requests that we revise the 
original NPRM to adequately correct the unsafe condition. ALPA notes 
that the original NPRM addresses pitch trim actuators that freeze in 
position when moisture accumulates at colder temperatures. ALPA 
requests that the FAA and EMBRAER identify the extent of water 
intrusion in this area and look into a mechanical means to preclude the 
actuators from jamming. ALPA also notes that the original NPRM does not 
identify the cause of the jammed pitch trim actuators. ALPA explains 
that pitch trim actuators have become mechanically jammed on other 
EMBRAER aircraft due to insufficient power available from the actuator. 
If the cause of the jamming can be mechanical, ALPA requests that the 
FAA and the manufacturer identify a means to preclude such a failure.
    We agree. In this supplemental NPRM, we consider the AFM revisions 
and placards to be interim solutions, and propose to also mandate the 
modifications described in Service Bulletins 120-27-0095 and 120-27-
0096, which would terminate the proposed requirements to revise the AFM 
and install the placards.

Assertion Regarding Jamming Conditions

    The commenter, Thomas Kuhlman, states that the original NPRM 
apparently assumes that all or most of the jamming occurs during cruise 
flight. Mr. Kuhlman instead asserts, based on the supportive data that 
accompany his comment, that the pitch trim actuator jamming can and 
does occur when moisture is present in freezing conditions.
    Although Mr. Kuhlman makes no specific request regarding the 
original NPRM's proposed requirements, we agree with his rationale. 
When actuator internal frictions are within their normal specified 
ranges, the system can manage normal envelope load increases attributed 
to events such as speed variations and cold soak environment icing, so 
a jam attributable solely to a cold soak environment is unlikely. If 
contamination is gradually occurring inside the actuators, the proposed 
manual checks of the pitch trim systems on initial descent on every 
flight will inform the flight crew of degraded system performance, and 
affected actuators would then be removed before they reach a condition 
that could lead to a complete jam. In any event, as stated previously, 
we have revised this supplemental NPRM to require modifications that 
will adequately address the commenter's concerns.

Request To Allow Autopilot Re-Engagement Under Certain Conditions

    SkyWest concurs with the proposed requirement in the original NPRM 
to revise the elevator trim jamming procedure specified in the flight 
controls failure paragraph of the AFM abnormal procedures section, but 
requests that we allow the flight crew to re-engage the autopilot once 
pitch trim is recovered. The commenter asserts that SkyWest's 
experience suggests that, once normal elevator trim operation was 
restored, continued use of the autopilot did not result in any abnormal 
operation.
    We disagree. When free pitch trim is restored after jamming, the 
appropriate approach is to continue the flight manually without the 
autopilot and report the issue to maintenance, rather than re-engaging 
the autopilot, so the cause of the jam can be evaluated and corrected 
before further use of the autopilot. We have not changed the 
supplemental NPRM regarding this issue.

Request To Revise AFM Normal Procedures

    SkyWest reports that its EMB-120 SOP already includes an advisory 
to check the pitch trim before initiating a descent if trim jamming is 
suspected. The commenter requests that we revise the original NPRM to 
include these revised procedures in the descent checklist in the AFM's 
normal procedures section.
    We acknowledge that conducting such checks whenever a trim system 
jam is suspected is a reasonable practice. But conducting such manual 
checks of the pitch trim system at every flight before initial descent 
on autopilot is a more effective approach because it will detect 
jamming before it is suspected. We have not changed the supplemental 
NPRM regarding this issue.

Request To Revise Placard Language

    SkyWest asserts that the placard language proposed in the original 
NPRM, which specifies a check before any (all) descents, will 
compromise the safe operation of Model EMB-120 airplanes. The commenter 
reports that it is not unusual to level off at intermediate altitudes 
four to eight times during descent from cruise altitude and approach, 
depending on cruise altitude, terminal area requirements, and type of 
approach. As a result, the proposed limitation would require the pilot 
to disconnect the autopilot during flight an equal number of times, 
including just before ILS glide slope intercept. The commenter requests 
that we change the proposed placard language to the following: 
``Perform pitch trim system check prior to initial descent and anytime 
elevator trim jamming is suspected.'' According to the commenter, 
limiting the checks in this way would ensure that the check is 
completed at least once per flight (consistent with EMBRAER's 
recommendations from the 2002 World Wide Operators Conference), but 
mandating a check before every descent would create a distraction,

[[Page 7496]]

unnecessarily increase pilot workload, and compromise safety.
    We partially agree. EMBRAER has revised the placard language to 
require trim system checks only before initial descent. Manually 
checking the system when jamming is suspected would be a natural 
reaction, so it is not necessary to add the extra requested words to 
the placard. We have revised paragraph (c) in this supplemental NPRM to 
mandate Change 02 of the service bulletin.

Request To Remove Placard Requirement: Potential Pilot Distraction

    The commenter, Thomas Kuhlman, feels that the proposed requirement 
to test the trim system before every descent could result in little 
effect, or even decreased safety due to pilot distraction, during 
arrival procedures with multiple descents. He also notes that most 
precision approaches have a level flight segment just before glide 
slope intercept. The AD as proposed would require an elevator trim test 
at the critical glide slope intercept.
    We infer the commenter wants us to remove the proposed requirement 
to install the placards. We partially agree. We agree with the 
manufacturer's recommendation to check the system manually before 
initial descent only. As we stated previously, the placard language has 
been revised in Change 02 of Service Bulletin 120-25-0262, and in 
corresponding paragraph (c) of this supplemental NPRM, to clarify that 
such checks are necessary only before the initial descent of every 
flight. Limiting the number of checks in this way would maintain the 
safety of the fleet and still address the commenter's concern about 
potential pilot distraction during critical phases of flight.

Request To Remove Placard Requirement: Inadequate Solution

    The commenter, SkyWest Airlines, states that merely installing the 
placards as proposed in the original NPRM would not adequately address 
the problem of elevator trim jamming. The commenter notes that this 
procedure would be inconsistent with its findings: In the 18 months 
before the original NPRM was issued, there were ten incidents involving 
elevator trim jamming; of these, four occurred in the descent phase of 
flight, four occurred in the cruise phase of flight, and two occurred 
during climb to cruise altitude. The commenter concludes that advising 
the flight crew to perform a pitch trim check only during descent will 
not prevent problems associated with pitch upset.
    We infer that the commenter wants us to require revised procedures 
during other phases of flight. We partially agree. We agree that the 
pitch trim can jam during any phase of flight. But while the data 
provided by SkyWest might reflect results for SkyWest, the fleet data 
suggest that most of the reported events occurred during the descent 
phase or during transition from cruise to descent. The possibility that 
a pitch trim jam can occur during any flight phase does not render the 
proposed approach ineffective. The multiple system checks will assist 
in reducing the possibility of a pitch oscillation event due to 
actuator performance degradation. Since the comment was submitted, we 
revised this supplemental NPRM to add the modifications of the elevator 
trim system, which will address the identified unsafe condition and 
eliminate the need for the placards.

Explanation of Additional Changes to Original NPRM

    We have revised the applicability identified in the original NPRM 
to identify model designations as published in the most recent type 
certificate data sheet for the affected models.
    To correspond with the ANAC AD, we have revised paragraph (b) of 
this supplemental NPRM to specify that the revised AFM language in that 
paragraph also be included in the Normal Procedures section (in 
addition to the Limitations section) of the autopilot system 
supplement.

Conclusion

    Since certain changes described above expand the scope of the 
originally proposed rule, the FAA has determined that it is necessary 
to reopen the comment period to provide additional opportunity for 
public comment.

Cost Impact

    The following table provides the estimated costs for U.S. operators 
to comply with this supplemental NPRM.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                        Number of
                                               Average                    Cost per        U.S.-
           Action              Work hours    labor rate       Parts        product     registered    Fleet cost
                                              per hour                                  airplanes
----------------------------------------------------------------------------------------------------------------
AFM revisions...............             1           $80            $0           $80           103        $8,240
Placard installation........             2            80           182           342           103        35,226
Actuator replacement........             7            80        16,670        17,230           103     1,774,690
Cable replacement...........            14            80         1,050         2,170           103       223,510
----------------------------------------------------------------------------------------------------------------

    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the proposed requirements 
of this AD action, and that no operator would accomplish those actions 
in the future if this proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

[[Page 7497]]

Regulatory Impact

    The regulations proposed herein would not have a substantial direct 
effect 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, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec.  39.13  [Amended]

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

Empresa Brasileira De Aeronautica S.A. (Embraer): Docket 2003-NM-33-
AD.

    Applicability: All Model EMB-120, -120ER, -120FC, -120QC, and -
120RT airplanes, certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent pitch trim upsets if the pitch trim actuators jam or 
freeze, which could result in reduced controllability of the 
airplane, accomplish the following:

Revision of Airplane Flight Manual (AFM): AFM-120/794

    (a) Within 100 flight hours after the effective date of this AD, 
revise the FAA-approved AFM, EMBRAER AFM-120/794, as specified in 
paragraphs (a)(1) and (a)(2) of this AD. These actions may be 
accomplished by inserting a copy of this AD into the AFM.
    (1) Revise the FLIGHT CONTROLS FAILURES paragraph of the 
Abnormal Procedures section by replacing the existing ELEVATOR TRIM 
JAMMING procedure with the following:

                         ``ELEVATOR TRIM JAMMING

 Control Wheel......................  Hold Firmly.
Autopilot...........................  Disengage.
Airspeed............................  Reduce.

 NOTE: Minimum airspeed with flap 0 [deg]--160 KIAS

 Pitch trim command.................  Check all switches and elevator
                                       trim wheel.

 If pitch trim is recovered:
    Re-trim the airplane and continue the flight with the autopilot
     disengaged, not exceeding the airspeed when the trim was recovered.
     .
If pitch trim is not recovered:
    Land at the nearest suitable
     airport.
Approach and landing configuration:
    Landing gear....................  Down.
    Flaps...........................  25.
    Airspeed........................  Vref25.

 CAUTION: DO NOT TRY TO RE-ENGAGE THE AUTOPILOT.''
(2) Revise the Normal Procedures section of the AFM, after the current
 checklist item for activating the FASTEN BELTS switch, by inserting the
 following:

      ``PITCH TRIM SYSTEM CHECK

 Control Wheel......................  Hold firmly.
Autopilot...........................  Disengage.
Power Levers........................  As required.
Elevator Trim Wheels................  As required.

 CAUTION: MANUALLY SET THE ELEVATOR TRIM WHEELS TO THE REQUIRED DESCENT
 ATTITUDE.

If any trim system binding (if trim wheel rotates more than one trim
 wheel index mark after being released), or abnormal trim operation is
 observed:
    Elevator Trim Jamming Procedure.  Perform.

 CAUTION: DO NOT TRY TO RE-ENGAGE THE AUTOPILOT.

 If no abnormal trim operation is
 observed:
    Flight Director Vertical Mode...  As required.
    Autopilot.......................  Reengage.''

AFM Revision: Collins APS-65B Autopilot AFM Supplement

    (b) Concurrently with the AFM revisions required by paragraph 
(a) of this AD, revise the Limitations section of the Collins APS-
65B Autopilot System Supplement to include the following (this may 
be accomplished by inserting a copy of this AD into the AFM 
Supplement):

``(1) The autopilot must not be used during descent unless a trim check
 has been performed successfully prior to descent, as follows:

       PITCH TRIM SYSTEM CHECK

Control Wheel.......................  Hold firmly.

[[Page 7498]]

Autopilot...........................  Disengage.
Power Levers........................  As required.
Elevator Trim Wheels................  As required.

 CAUTION: MANUALLY SET THE ELEVATOR TRIM WHEELS TO THE REQUIRED DESCENT
 ATTITUDE.
If any trim system binding (if trim wheel rotates more than one trim
 wheel index mark after being released), or abnormal trim operation is
 observed:
    Elevator Trim Jamming Procedure.  Perform.

 CAUTION: DO NOT TRY TO RE-ENGAGE THE AUTOPILOT.
If no abnormal trim operation is observed:
    Flight Director Vertical Mode...  As required.
    Autopilot.......................  Reengage.

 ``(2) If an elevator trim jamming is detected during flight and the
 pitch trim system resumes normal operation on ground, only a ferry
 flight using a special permit may be performed to return the aircraft
 to a maintenance base for replacement of the actuators. In this case,
 the use of autopilot is prohibited.''

Placard Installation

    (c) Within 300 flight hours after the effective date of this AD, 
install two placards on the glareshield, advising the flight crew to 
check the pitch trim before initial descent, in accordance with Part 
II of the Accomplishment Instructions of EMBRAER Service Bulletin 
120-25-0262, Change 02, dated October 30, 2003.

Elevator Trim System Modification

    (d) Within 36 months after the effective date of this AD, modify 
the elevator trim system, in accordance with the Accomplishment 
Instructions of EMBRAER Service Bulletin 120-27-0095 and 120-27-
0096, both dated February 16, 2007. Accomplishment of the 
modification terminates the requirements of paragraphs (a), (b), and 
(c) of this AD, and the corresponding AFM revisions and placards may 
be removed.

Parts Installation

    (e) As of 36 months after the effective date of this AD, no 
person may install, on any airplane, an elevator trim tab actuator 
or control cable having a part number identified in Table 1 of this 
AD.

                       Table 1.--Prohibited Parts
------------------------------------------------------------------------
                   Part                               Part No.
------------------------------------------------------------------------
Elevator trim tab actuator................  120-19685-001
                                            120-19685-003
                                            120-19685-007
                                            120-38650-001
                                            120-39205-001
                                            5299
                                            5299-1
Control cable.............................  120-27729-095
                                            120-27729-097
                                            120-31370-095
                                            120-31370-097
------------------------------------------------------------------------

Alternative Methods of Compliance

    (f)(1) The Manager, International Branch, ANM-116, Transport 
Airplane Directorate, FAA, has the authority to approve AMOCs for 
this AD, if requested in accordance with the procedures found in 14 
CFR 39.19.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.

    Note 1: The subject of this AD is addressed in Brazilian 
airworthiness directive 2001-06-01R4, effective August 23, 2007.

    Issued in Renton, Washington, on February 1, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-2356 Filed 2-7-08; 8:45 am]

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