[Federal Register Volume 60, Number 238 (Tuesday, December 12, 1995)]
[Rules and Regulations]
[Pages 63613-63615]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-30252]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-236-AD; Amendment 39-9457; AD 95-25-11]


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; Request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to all EMBRAER Model EMB-120 series airplanes. This 
action requires revising the FAA-approved Airplane Flight Manual (AFM) 
to limit the revolutions per minute (RPM) of the propeller during 
ground operation, and removing and installing a new placard. This AD 
also requires revising the FAA-approved maintenance program to limit 
the maximum RPM of the propeller during ground operations. This 
amendment is prompted by reports of failures of in-service propellers 
and subsequent testing, which revealed that operating the propeller at 
or near certain nominal propeller RPM produces high vibration stress. 
The actions specified in this AD are intended to limit exposure to high 
vibration stresses during ground operations under certain weather 
conditions; this situation could accelerate fatigue cracking if 
corrosion is present in the propeller, which could lead to the failure 
of the propeller and subsequent reduced controllability of the 
airplane.

DATES: Effective December 27, 1995.
    Comments for inclusion in the Rules Docket must be received on or 
before February 12, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-236-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    Information concerning this amendment may be obtained from or 
examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, 
SW., Renton, Washington; or at the FAA, Atlanta Aircraft Certification 
Office, Small Airplane Directorate, Campus Building, 1701 Columbia 
Avenue, Suite 2-160, College Park, Georgia.

FOR FURTHER INFORMATION CONTACT: Carla J.W. Worthey, Aerospace 
Engineer, Flight Test Branch, ACE-116A, FAA, Atlanta Aircraft 
Certification Office, Small Airplane Directorate, Campus Building, 1701 
Columbia Avenue, Suite 2-160, College Park, Georgia 30337-2748; 
telephone (404) 305-7364; fax (404) 305-7348.

SUPPLEMENTARY INFORMATION: The FAA has received reports of failures of 
in-service Hamilton Standard 14RF, 14SF, and 6/5500/F series 
propellers. Result of inspections have revealed internal corrosion in 
the taper bore and external damage to the shank section on these 
propellers. Such internal corrosion or external damage reduces the 
design allowable stress levels of the propeller material. Further 
inspections revealed that the corrosion and damage is evenly 
distributed amongst the subject propellers. However, fracturing has 
occurred predominately on the Hamilton Standard 14RF series propellers 
installed on EMBRAER Model EMB-120 series airplanes. This disparity has 
prompted an investigation into operational differences between the 
airplanes utilizing these propellers.
    A vibration/loads survey and analysis was conducted by Hamilton 
Standard on the Hamilton Standard 14RF series propellers installed on 
EMBRAER Model EMB-120 series airplanes. The survey and analysis results 
verified that high vibration stresses could occur on 

[[Page 63614]]
all Hamilton Standard propeller installations during ground operation 
in tail and cross winds (adverse winds) when the propeller is operated 
at or near 73% of the nominal propeller revolutions per minute (RPM). 
For EMBRAER Model EMB-120 series airplanes equipped with Hamilton 
Standard 14RF series propellers, operation at 73% RPM is coincident 
with a propeller natural frequency at exactly twice the RPM (denoted as 
2P), which produces high vibration stresses. For all other airplanes 
equipped with this propeller, the 2P natural frequency is below the 
normal propeller operating speed and, therefore, a resonant vibration 
could not occur.
    Subsequent propeller vibration survey testing on a Model EMB-120 
series airplane revealed a possible small downward shift in the 2P 
frequency RPM on these airplanes relative to the original 1983 
certification test data. Such a shift could increase cyclic stress on 
the propeller blade during normal ground operations. The possible cause 
of such a shift could be attributed to wear and normal changes in the 
propeller mass properties while in-service.
    Operation of Hamilton Standard 14RF series propellers installed on 
EMBRAER Model EMB-120 series airplanes at or near 73% of the nominal 
propeller RPM, if not corrected, could result in high stresses on the 
propeller. Such high stresses subsequently could accelerate fatigue 
cracking at existing internal corrosion pits in the propeller, which 
could lead to the failure of the propeller and subsequent reduced 
controllability of the airplane.
    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.
    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, this AD is being issued to limit ground operation 
of Hamilton Standard 14RF series propellers installed on EMBRAER Model 
EMB-120 series airplanes at or near 73% of the nominal propeller RPM, 
which could result in high stresses on the propeller; this condition 
could accelerate fatigue cracking at existing internal corrosion pits 
in the propeller, which could lead to the failure of the propeller and 
subsequent reduced controllabilty of the airplane. This AD requires 
revising the Limitations and Normal Procedures Sections of the AFM to 
reduce ground operating RPM to MIN RPM (approximately 50%), except for 
brief excursions as needed to maneuver the airplane, which will limit 
exposure to high cyclic stresses on the propeller. This AD also 
requires removal of a placard and installation of a new placard on the 
instrument panel of the cockpit. Additionally, this AD requires 
revising the FAA-approved maintenance program to limit the maximum RPM 
for ground operations.
    This is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.
    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 95-NM-236-AD.'' The postcard will be date stamped and 
returned to the commenter.
    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.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, may be obtained from 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.

Adoption of the Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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

    Authority: 49 U.S.C. 106(g), 40101, 40113, 44701.


Sec. 39.13  [Amended]

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

95-25-11   Embraer:   Amendment 39-9457. Docket 95-NM-236-AD.

    Applicability: All Model EMB-120 series airplanes, certificated 
in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
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 

[[Page 63615]]
requirements of this AD is affected, the owner/operator must use the 
authority provided in paragraph (e) of this AD to request approval 
from the FAA. This approval may address either no action, if the 
current configuration eliminates the unsafe condition; or different 
actions necessary to address the unsafe condition described in this 
AD. Such a request should include an assessment of the effect of the 
changed configuration on the unsafe condition addressed by this AD. 
In no case does the presence of any modification, alteration, or 
repair remove any airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the propeller and subsequent reduced 
controllability of the airplane due to high stresses on the 
propeller at certain nominal propeller revolutions per minute (RPM), 
accomplish the following:
    (a) Within 14 days after the effective date of this AD, 
accomplish the requirements of paragraphs (a)(1) and (a)(2) of this 
AD.
    (1) Revise the Limitations Section (under ``Propeller'') of the 
FAA-approved Airplane Flight Manual (AFM) (in the basic AFM and in 
AFM Supplement 4) to include the following. This may be accomplished 
by inserting a copy of this AD in the AFM.
    ``Condition Levers must be in the MIN RPM position during all 
ground operations, except when cleared for takeoff or during landing 
roll.
    ``Power Levers must remain at or below Flight Idle during all 
ground operations, except for brief (approximately 5 seconds) 
excursions as needed to maneuver the airplane.
    ``CAUTION: Ground operation above Flight Idle significantly 
increases propeller stress under certain adverse wind conditions 
(e.g., tailwinds or rear crosswinds). Operation in this RPM range 
must be avoided to the maximum extent practicable.''
    (2) Revise the Normal Procedures Section (under ``CLEARED INTO 
POSITION'') of the FAA-approved AFM to separate the current 
procedures listed under the ``CLEARED INTO POSITION'' heading into 
two separate headings, as follows, to delay movement of condition 
levers until cleared for takeoff. This may be accomplished by 
inserting a copy of this AD into the AFM.


``CLEARED INTO POSITION                                                 
    Landing Lights Switches...............  ON.                         
    STROBE Light Switch...................  ON.                         
    Transponder...........................  ON.                         
``CLEARED FOR TAKEOFF                                                   
    Condition Levers......................  MAX RPM.                    
    Multiple Alarm Panel Lights...........  CHECK EXTINGUISHED''.       
                                                                        

    (b) Within 14 days after the effective date of this AD, remove 
the placard having part number (P/N) 120-30915-001 on the instrument 
panel of the cockpit.
    (c) Within 30 days after the effective date of this AD, install 
a new placard having P/N 120-61757-001 on the instrument panel of 
the cockpit.
    (d) Within 14 days after the effective date of this AD, revise 
the FAA-approved maintenance program to incorporate the following 
into Chapter 61-00-00, ``Propeller System Operating Limitations,'' 
and Chapter 71-00-00, ``Propeller Operating Limitations,'' of the 
airplane maintenance manual:
    ``To prevent excessive propeller stress, do not operate above 
60% Np UNLESS:

The wind is less than 10 knots, OR
The airplane is headed into the wind +/-45 degrees.

    Wind direction must be monitored locally at the run up site.''
    (e) 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.

    (f) 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.
    (g) This amendment becomes effective on December 27, 1995.

    Issued in Renton, Washington, on December 6, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-30252 Filed 12-11-95; 8:45 am]
BILLING CODE 4910-13-U