[Federal Register Volume 62, Number 229 (Friday, November 28, 1997)]
[Proposed Rules]
[Pages 63288-63290]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-31156]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-231-AD]
RIN 2120-AA64


Airworthiness Directives; Empresa Brasileira de Aeronautica, S.A. 
(EMBRAER), Model

EMB-120 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain EMBRAER Model EMB-120 
series airplanes. This proposal would require deactivation of certain 
circuit breakers, and a revision to the Airplane Flight Manual (AFM) to 
provide operational procedures to prevent loss of electrical power 
following an engine flameout. This proposal also would require 
modifications of the electrical system, which would terminate the 
requirement for the AFM revision and allow reactivation of the circuit 
breakers. This proposal is prompted by the issuance of mandatory 
continued airworthiness information by a foreign civil airworthiness 
authority. The actions specified by the proposed AD are intended to 
prevent generator overload conditions that could result in loss of 
electrical power and failure of certain flight and landing control 
systems, and to prevent power interruption to the attitude heading 
reference system (AHRS) that could result in the display of erroneous 
heading information.

DATES: Comments must be received by December 29, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 97-NM-231-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Empresa Brasileira de Aeronautica S/A, Sao Jose dos 
Campos, Brazil. This information may be examined at the FAA, Transport 
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at 
the FAA, Small Airplane Directorate, Atlanta Aircraft Certification 
Office, One Crown Center, 1895 Phoenix Boulevard, suite 450, Atlanta, 
Georgia.

FOR FURTHER INFORMATION CONTACT: John W. McGraw, Aerospace Engineer, 
Systems and Flight Test Branch, ACE-116A, FAA, Atlanta Aircraft 
Certification Office, One Crown Center, 1895 Phoenix Boulevard, suite 
450, Atlanta, Georgia 30349; telephone (770) 703-6098; fax (770) 703-
6097.

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 notice may be changed in 
light of the comments received.
    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 notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 97-NM-231-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-103, Attention: Rules 
Docket No. 97-NM-231-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The Departamento de Aviacao Civil (DAC), which is the airworthiness 
authority for Brazil, notified the FAA that an unsafe condition may 
exist on certain EMBRAER Model EMB-120 series airplanes. The DAC 
advises that it received a report of one instance of substantial 
electrical power loss after flameout of the number 1 engine. The power 
loss was caused by activation of the system overload protection due to 
excessive loads on the remaining number 2 engine generator, which led 
to loss of certain flight and landing control systems. The DAC also 
advises that, due to power interruption for a few milliseconds to the 
attitude heading reference system (AHRS), erroneous heading information 
in both electronic horizontal situation indicators (EHSI) may be 
provided, without warning to the pilots, during an electrical emergency 
or when the electrical emergency switch is set to the ``EMERGENCY'' 
position. This condition, if not corrected, could result in generator 
overload conditions that could result in loss of electrical power and 
failure of certain flight and landing control systems, and power 
interruption to the AHRS that could result in display of erroneous 
heading information.

Explanation of Relevant Service Information

    EMBRAER has issued Service Bulletin 120-24-0008, Change 04, dated 
October 3, 1995, which describes procedures for modification of the 
electrical system.
    This modification involves revising the electrical connections and 
wiring in the relay boxes and circuit breaker panels.
    EMBRAER has also issued Service Bulletin 120-24-0051, Change 04, 
dated March 8, 1995, which also describes procedures for modification 
of the electrical system. This modification involves electrical load 
redistribution and introduction of a contactor to connect a direct 
current (DC) bus to the emergency bus.
    Accomplishment of the actions specified in these service bulletins 
is

[[Page 63289]]

intended to adequately address the identified unsafe condition.
    The DAC classified these service bulletins as mandatory and issued 
Brazilian airworthiness directives (DAE) 93-24-01, dated December 31, 
1993; 94-03-01R1, dated December 10, 1994, and 93-12-01R1, dated 
December 12, 1994, in order to assure the continued airworthiness of 
these airplanes in Brazil.

FAA's Conclusions

    This airplane model is manufactured in Brazil and is type 
certificated for operation in the United States under the provisions of 
section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and 
the applicable bilateral airworthiness agreement. Pursuant to this 
bilateral airworthiness agreement, the DAC has kept the FAA informed of 
the situation described above. The FAA has examined the findings of the 
DAC, reviewed all available information, and determined that AD action 
is necessary for products of this type design that are certificated for 
operation in the United States.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design registered 
in the United States, the proposed AD would require accomplishment of 
the actions specified in the service bulletins described previously.
    The proposed AD also would require a revision to the FAA-approved 
Airplane Flight Manual (AFM) to provide operational procedures in the 
event of loss of electrical power following an engine flameout.

Differences Between the Proposal and Related Brazilian AD

    This proposed AD differs from the parallel Brazilian airworthiness 
directives in the following four respects:
    1. It would not require (as DAE 93-24-01 and DAE 93-12-01R1 
require) that the electrical emergency switch be set to the 
``EMERGENCY'' position prior to takeoff for operations without 
auxiliary power units (APU); rather, it would require electrical loads 
to be reduced to below 400 amps. The FAA has determined that reduction 
of loads to below 400 amps prevents the unsafe generator overload 
condition.
    2. It would require that the APU be operational for all flights 
into known or forecast icing conditions and during takeoff and landing. 
DAE 93-12-01R1 makes no limitation with respect to such icing 
conditions. The FAA has determined that the APU must be operational for 
flights into known or forecast icing conditions to ensure adequate 
electrical power for systems that are necessary for operation in such 
conditions.
    3. It would extend the proposed compliance time for accomplishment 
of the modifications beyond that specified by DAE 93-12-01R1 and DAE 
94-03-01R1. The FAA has determined that the compliance time specified 
in this proposed AD would allow the modifications to be accomplished 
during regularly scheduled maintenance.
    4. It would not require the accomplishment of PART C of DAE 94-03-
01R1, which requires revision of Section 4 (``Normal Procedures'') of 
the AFM. The FAA has determined that Part C has been incorporated by a 
previously approved change to the AFM and need not be mandated.

Cost Impact

    The FAA estimates that 227 airplanes of U.S. registry would be 
affected by this proposed AD.
    It would take approximately 1 work hour per airplane to accomplish 
the proposed AFM revisions, at an average labor rate of $60 per work 
hour. Based on these figures, the cost impact of the AFM revisions 
proposed by this AD on U.S. operators is estimated to be $13,620, or 
$60 per airplane.
    It would take approximately 90 work hours per airplane to 
accomplish the proposed modifications at an average labor rate of $60 
per work hour. Required parts would cost approximately $4,150 per 
airplane. Based on these figures, the cost impact of the modifications 
proposed by this AD on U.S. operators is estimated to be $2,167,850, or 
$9,550 per airplane.
    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 AD were not adopted. However, the FAA has been 
advised that 43 U.S.-registered airplanes are in compliance in 
accordance with the requirements of this proposed AD. Therefore, the 
future economic cost impact of this rule on U.S. operators is now 
$11,040 for accomplishment of the AFM revisions, and $1,757,200 for 
accomplishment of the modifications.

Regulatory Impact

    The regulations proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    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 97-NM-231-
AD.

    Applicability: Model EMB-120, EMB-120RT, and EMB-120ER series 
airplanes; up to and including serial number 120291; certificated in 
any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (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

[[Page 63290]]

been eliminated, the request should include specific proposed 
actions to address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent generator overload conditions that could result in 
loss of electrical power and failure of certain flight and landing 
control systems, and to prevent power interruption to the attitude 
heading reference system (AHRS) that could result in the display of 
erroneous heading information, accomplish the following:
    (a) For airplanes not equipped with an auxiliary power unit 
(APU); except serial numbers 120004, 120006 through 120024 
inclusive, 120026 through 120030 inclusive, 120033 through 120035 
inclusive, 120037, and 120040; on which Part I, II, or III of 
EMBRAER Service Bulletin 120-24-0008, Change 03, dated August 19, 
1994, or Change 04, dated October 3, 1995, has not been 
accomplished: Within 3 days after the effective date of this AD, 
accomplish paragraphs (a)(1), (a)(2), and (a)(3) of this AD.
    (1) Trip (pull open) circuit breakers (CB) 534 (auxiliary 
generator 2 bus control) and CB 535 (auxiliary generator 1 bus 
control) located in the right-hand direct current (DC) relay box and 
left-hand DC relay box, respectively.
    (2) Install circuit breaker collars to prevent the circuit 
breakers from closing.
    (3) Install, near CB 534 and CB 535, a placard or tag with the 
following wording: ``Do not close CB 534 or CB 535.''
    (b) For all airplanes: Within 30 days after the effective date 
of this AD, accomplish paragraphs (b)(1), (b)(2), and (b)(3) of this 
AD.
    (1) Revise the Abnormal Procedures section of the FAA-approved 
Airplanese Gen Flight Manual (AFM) to include the following. This 
may be accomplished by inserting a copy of this AD into the AFM.
    ``Section III--Abnormal Procedures:

Engine Failure

One Engine Inoperative Approach and Landing

    If auxiliary power unit (APU) is not available

Electrical Load--Reduce to Below 400 Amps
    At least the following systems should be turned off: windshield 
heating, propeller de-ice, gasper fans, recirculation fans, logotype 
lights, and taxi lights.

Caution

    Should an unexpected electrical power loss occur during a 
rejected takeoff or landing run, remember:
--Emergency brake will be available
--Below 45 knots (KT), turn anti-skid off to recover one normal 
brake pair (inboard or outboard).

Electrical Failure

Short Circuit in the Relay Box Direct Current (DC) Bus 1

--Gen 1 off Bus, Bus 1 off. Emerg Bus off, Central Bus off, Batt off 
Bus and inverter 2 INOP lights illuminated on the electrical panel.

    Note: In some cases, the Central Bus off light may not 
illuminate.

--ELEC light illuminated on the multiple alarm panel.
--CAUTION light flashing.
    Caution: Do not try to Reset the Electrical System.
Electrical Emergency Switch--Emerg
Altitude--At or Below 25,000 FT

    Airplane is limited to 25,000 ft since the left engine bleed is 
closed due to loss of the electrical power.
    The engines or APU airstart and electrical crossfeed are not 
possible.
    The equipment connected to the relay box DC BUS 1, DC BUS 1, 
radio master DC buses 1B and 1C are out. Land as soon as practical.
    Note:
    <bullet> For airplanes Pre-Mod SB 120-24-0008, the AHRS 1 and 
the equipment connected to the radio master DC BUS 1A are out too.
    <bullet> For airplanes Post-Mod SB 120-33-0033 or S/N 120.273 
and on:

--The emergency lights will be automatically turned on when the 
electrical system is in emergency operating mode.
--The emergency lights must be turned off, in order to save the 
emergency light batteries.
--The emergency lights must be turned on during approach or when 
necessary.''

    (2) Revise the Normal Procedures section of the FAA-approved AFM 
to include the following. This may be accomplished by inserting a 
copy of this AD into the AFM.

``Section IV--Normal Procedures: Before Takeoff

    If APU is available:
APU Generator........................................................ON

    Takeoff must be carried out with APU generator connected to the 
central DC bus, thus providing another source to avoid overload 
should one engine flame out.
    If APU is not available:
Electrical Load................................Reduce to Below 400 Amps

    At least the following systems should be turned off: windshield 
heating, propeller de-ice, gasper fans, recirculation fans, logotype 
lights, and taxi lights.

After Takeoff

    If APU is available:

APU.........................................................As Required

    If APU is not available:

Electrical load--RESTORE
Windshield heating--AS REQUIRED
Emergency lights switch--OFF, then ARM

Approach

    If APU is available:
APU Generator........................................................ON

    Approach and landing must be carried out with APU generator 
connected to the central DC bus.

Before Landing

    If APU is not available:

Electrical Load................................Reduce to Below 400 Amps

    At least the following systems should be turned off: windshield 
heating, propeller de-ice, gasper fans, recirculation fans, logotype 
lights, and taxi lights.

Caution:

    Do not set electrical emergency switch to emergency position 
during approach or landing.''

    (3) Revise the Limitations section (Section II) of the FAA-
approved AFM to include the following. This may be accomplished by 
inserting a copy of this AD into the AFM.
    ``Both starter/generators must operate normally prior to flight. 
The APU generator must operate normally prior to flight in known or 
forecast icing conditions. [Note: This supersedes any relief 
provided by the Master Minimum Equipment List (MMEL).]''
    (c) Within 12 months after the effective date of this AD, 
accomplish paragraph (c)(1) and (c)(2) of this AD, as applicable.
    (1) For all airplanes except serial numbers 120004, 120006 
through 120024 inclusive, 120026 through 120030 inclusive, 120033 
through 120035 inclusive, 120037, and 120040; on which Part I, II, 
or III of EMBRAER Service Bulletin 120-24-0008, Change 03, dated 
August 19, 1994, or Change 04, dated October 3, 1995; has not been 
accomplished: Modify the electrical system in accordance with Part 
IV of EMBRAER Service Bulletin 120-24-0008, Change 04, dated October 
3, 1995. After this modification is accomplished, the modification 
required by paragraph (a) of this AD may be removed and the affected 
circuit breakers reactivated.
    (2) For all airplanes: Modify the electrical system in 
accordance with EMBRAER Service Bulletin 120-24-0051, Change 04, 
dated March 8, 1995. After this modification is accomplished, the 
AFM revisions required by paragraph (b) of this AD may be removed 
from the AFM.
    (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, Atlanta Aircraft Certification 
Office (ACO), FAA, Small Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Atlanta ACO.

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

    (e) 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.

    Note 3: The subject of this AD is addressed in Brazilian 
airworthiness directives 93-24-01, dated December 31, 1993; 94-03-
01R1, dated December 10, 1994; and 93-12-01R1, dated December 12, 
1994.

    Issued in Renton, Washington, on November 20, 1997.
Stewart R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-31156 Filed 11-26-97; 8:45 am]
BILLING CODE 4910-13-U