[Federal Register Volume 60, Number 8 (Thursday, January 12, 1995)]
[Rules and Regulations]
[Pages 2877-2880]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-633]



=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-ANE-59; Amendment 39-9113; AD 95-01-02]


Airworthiness Directives; Hartzell Model HC-B4 Series Propellers 
Installed on Mitsubishi MU-2 Series Aircraft

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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

SUMMARY: This amendment supersedes three existing airworthiness 
directives (AD), applicable to Hartzell Model HC-B4TN-5(D,G,J)L/
LT10282(B,K)-5.3R and HC-B4TN-5(D,G,J)L/LT10282N(B,K)-5.3R propellers 
installed on Mitsubishi MU-2 series aircraft. These AD's currently 
require replacement of existing LT10282(B,K)-5.3R propeller blades with 
LT10282N(B,K)-5.3R improved ``N'' configuration propeller blades, and 
repetitive inspection and rework when required of the inner hub arm 
bore. This amendment requires new repair limits, shot peening 
procedures, and retirement at 10,000 hours time in service for the 
``N'' configuration blades. Additionally, this action requires 
replacement of existing propeller hubs with new improved fatigue 
strength steel hubs and requires inspection, and specified rework as 
necessary, of the new steel hubs at a repetitive interval of 3,000 
hours time in service. This amendment is prompted by a determination 
that the current hub design and blade repair limits do not adequately 
protect against initiation of fatigue cracks in the propeller hub arm 
bore and do not prevent the resonant speed of the propeller from 
shifting into the permitted ground idle operating range. The actions 
specified by this AD are intended to prevent initiation of fatigue 
cracks in propeller assemblies and subsequent progression to propeller 
failure, with departure of the blade, or hub arm and blade, that may 
result in loss of aircraft control.

DATES: Effective January 27, 1995.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of January 27, 1995.
    Comments for inclusion in the Rules Docket must be received on or 
before March 13, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 94-ANE-59, 12 New England 
Executive Park, Burlington, MA 01803-5299.
    The service information referenced in this AD may be obtained from 
Hartzell Propeller Inc., One Propeller Place, Piqua, OH 45356-2634; 
telephone (513) 778-4200, fax (513) 778-4391. This information may be 
examined at the FAA, New England Region, Office of the Assistant Chief 
Counsel, Burlington, MA; or at the Office of the Federal Register, 800 
North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Tomaso DiPaolo, Aerospace Engineer, 
Chicago Aircraft Certification Office, FAA, Small Airplane Directorate, 
2300 East Devon Avenue, Room 232, Des Plaines, IL 60018; telephone 
(708) 294-7031, fax (708) 294-7834.

SUPPLEMENTARY INFORMATION: Airworthiness directive (AD) 93-01-09, 
Amendment 39-8463, effective April 20, 1993, applicable to Hartzell 
Model HC-B4TN-5(D,G,J)L/LT10282(B,K)-5.3R propellers installed on 
Mitsubishi MU-2 series aircraft was published in the Federal Register 
on March 26, 1993 (58 FR 16347). That action was prompted by three 
reports of propeller blades separating during flight. The 
manufacturer's investigation of the failed blades revealed that fatigue 
cracks could initiate at the radius end of the blade bearing bore. That 
condition, if not corrected, can result in fatigue cracks initiating 
and progressing to failure resulting in departure of the blade and 
possible loss of aircraft control.
    That AD requires initial and repetitive inspections for fatigue 
cracks at the blade bearing bore. All affected propeller blades showing 
evidence of cracks or propeller blades not meeting acceptable rework 
criteria are required to be replaced with serviceable blades prior to 
further flight. Additionally, as a terminating action to the repetitive 
inspections, AD 93-01-09 requires replacement of existing LT10282(B,K)-
5.3R propeller blades with LT10282N(B,K)-5.3R improved ``N'' 
configuration propeller blades at the next overhaul, or within 15 
months of the effective date of that AD (July 31, 1994), whichever 
occurs first. Propeller blades modified to the ``N'' configuration have 
design improvements in the blade bearing bore that reduce the 
susceptibility to corrosion and localized stresses. The modified blades 
also have additional thickness added to the blade inboard stations to 
reduce operating stresses. The FAA determined that long term continued 
operational safety would be better assured by actual modification of 
the propeller to remove the source of the problem rather than 
continuing with repetitive inspections.
    On April 28, 1993, the FAA issued priority letter AD 93-09-04, 
applicable to both Hartzell Model HC-B4TN-5(D,G,J)L/LT10282(B,K)-5.3R 
and Model HC-B4TN-5(D,G,J)L/LT10282N(B,K)-5.3R propellers installed on 
Mitsubishi Model MU-2B-60 aircraft. That AD was published in the 
Federal Register on July 22, 1993 (58 FR 39139). That AD action was 
prompted by two reports of propeller hub arm assembly fatigue failures 
and subsequent hub arm and blade separation from aircraft in flight. 
Preliminary data indicated that fatigue cracks can originate in the 
propeller hub arm assembly.
    That AD requires initial and repetitive removals from service of 
affected propeller hub assemblies for inspection and specified rework 
procedures before returning to service. That AD was an interim action 
until more data became available on the cause of propeller hub arm 
assembly failures.
    On June 10, 1993, the FAA issued priority letter AD 93-12-01, also 
applicable to both Hartzell Model HC-B4TN-5(D,G,J)L/LT10282(B,K)-5.3R 
and Model HC-B4TN-5(D,G,J)L/LT10282N(B,K)-5.3R propellers installed on 
MU-2B-26A, -36A, and, -40 aircraft. That AD was published in the 
Federal Register on September 29, 1993 (58 FR 50840). That action was 
prompted by a report of a hub assembly with a crack indication in the 
hub arm that was found during the inspection and rework required by AD 
93-09-04. In addition, although not stated in AD 93-12-01, the FAA 
based AD 93-12-01 on flight strain survey investigations. Airworthiness 
Directive 93-12-01 cites the same safety concerns and requirements as 
AD 93-09-04 and was also an interim action until more data became 
available on the cause of propeller hub arm assembly failures.
    Since the issuance of AD 93-09-04 and AD 93-12-01, the FAA 
determined that fretting can cause a fatigue crack to initiate in the 
propeller hub arms of the affected propellers. The fatigue crack 
[[Page 2878]] initiates in the propeller inner hub arm bore. The 
fretting fatigue can be caused by a high stress loading condition that 
occurs two times per revolution when operating in a propeller ground 
resonance condition known as the ``reactionless mode.'' The propeller 
resonance condition can be experienced in MU-2 series aircraft when 
Hartzell HC-B4 series propellers, with blades at or near the previous 
thickness repair limits, are operated at the originally certified 
engine ground idle speed when a quartering tail wind is present.
    The FAA has also issued AD 94-11-04, Amendment 39-8920, effective 
on June 10, 1994, applicable to Mitsubishi Model MU-2B-26A, -36A, -40, 
-60, and MU-2B-36 aircraft Modified by Supplemental Type Certificate 
(STC) SA2413SW. That AD restricts the engine ground idle speed to a 
range of 76.5 percent to 78.5 percent to prevent the possibility of 
operating the propeller too close to the ground idle resonant speed. 
The requirements of AD 94-11-04 are not affected by this action.
    Since the issuance of AD's 93-01-09, 93-09-04, and 93-12-01, the 
manufacturer has developed an improved fatigue strength steel propeller 
hub that has a compressive rolled internal bearing bore in the hub 
arms. Additionally, to further assure propeller operation will not 
occur in the reactionless mode, the manufacturer has developed new 
repair limits and shot peening procedures, and has established a 
retirement life limit of 10,000 hours time in service for the ``N'' 
configuration propeller blades. This AD will mandate phase in of the 
new steel hub design and the new ``N'' configuration propeller blade 
repair limits, shot peening procedures, and retirement life.
    The FAA has reviewed and approved the technical contents of the 
following service documents:
    Hartzell Alert Service Bulletins (ASB's) No. A182A and A183A both 
dated March 11, 1994, that describe procedures for installation, 
inspection, and rework as required for an improved fatigue strength 
steel hub applicable to propellers installed on Mitsubishi MU-2B-60 
aircraft and MU-2B-26A, -36A, -40 or other MU-2 model aircraft, 
respectively; and
    Hartzell ASB No. A188 dated February 25, 1994, applicable to 
affected propellers installed on all Mitsubishi MU-2 series aircraft 
that describes new repair limits and procedures for shot peening the 
LT10282N(B,K)-5.3R blade surfaces for optimum service life when 
installed on Mitsubishi MU-2 series aircraft.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other propellers of this same type design, the FAA 
is superseding AD's 93-01-09, 93-09-04, and 93-12-01; and adopting a 
new AD which requires replacement of any remaining LT10282(B,K)-5.3R 
propeller blades with LT10282N(B,K)-5.3R improved ``N'' configuration 
propeller blades, requires shot peening of all ``N'' blades, and 
establishes a new life limit of 10,000 hours time in service for ``N'' 
blades used on Mitsubishi MU-2 series aircraft; and requires 
replacement of Part Number (P/N) 840-139 or P/N 840-91 propeller hubs 
with new improved fatigue strength steel hubs which require inspection, 
and specified rework as necessary, at a repetitive interval of 3,000 
hours time in service. The actions are required to be accomplished in 
accordance with the alert service bulletins described previously.
    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 should 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 notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 94-ANE-59.'' 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 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, Incorporation by 
reference, Safety.

Adoption of the Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-8463 (58 FR 
16347, March 26, 1993); amendment 39-8583 (58 FR 39139, July 22, 1993); 
and amendment 39-8642 (58 FR 50840, September 29, 1993); and by adding 
a [[Page 2879]] new airworthiness directive to read as follows:

95-01-02  Hartzell Propeller Inc.: Amendment 39-9113. Docket 94-ANE-
59. Supersedes AD 93-01-09, Amendment 39-8463; AD 93-09-04, 
Amendment 39-8583; and AD 93-12-01, Amendment 39-8642.

    Applicability: Hartzell Propeller Inc. Models HC-B4TN-5(D,G,J)L/
LT10282(B,K)-5.3R, HC-B4TN-5(D,G,J)L/LT10282N(B,K)-5.3R, and HC-
B4TN-5(D,G,J)L/LT10282NS(B,K)-5.3R propellers installed on 
Mitsubishi MU-2B-26A, -36A, -40, -60; MU-2B-30 Modified by 
Supplemental Type Certificate (STC) SA336GL-D & SA339GL-D; MU-2B-36 
Modified by SA2413SW; and any other MU-2 Series aircraft which have 
the affected propellers installed.

    Note: The parentheses indicate the presence or absence of an 
additional letter(s) which vary the basic propeller hub and blade 
model designation. This Airworthiness Directive (AD) still applies 
regardless of whether these letters are present or absent on the 
propeller hub and blade model designation.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent initiation of fatigue cracks in propeller assemblies 
and subsequent progression to propeller failure, with departure of 
the blade, or hub arm and blade, that may result in loss of aircraft 
control, accomplish the following:
    (a) Before further flight replace Hartzell Model HC-B4TN-
5(D,G,J)L/LT10282(B,K)-5.3R propeller blades with serviceable 
Hartzell HC-B4TN-5(D,G,J)L/LT10282N(B,K)-5.3R or HC-B4TN-5(D,G,J)L/
LT10282NS(B,K)-5.3R ``N'' configuration propeller blades. 
Airworthiness Directive 93-01-09, which is superseded by this AD, 
required this action to be completed by July 31, 1994.
    (b) For propeller hub assemblies that experience a blade strike, 
as defined in paragraph (g) of this AD, after the effective date of 
this AD, before further flight, accomplish the following as 
applicable:
    (1) Replace propeller hub unit, Part Number (P/N) 840-139 or P/N 
840-91, with a hub that has compressive rolled internal bearing 
bores, which is identified with the addition of a third letter ``A'' 
in the hub serial number prefix (e.g. ``CDA1234''). Propeller hub 
assemblies removed from service in accordance with this AD paragraph 
are to be permanently retired and may not be returned to service on 
any aircraft; and
    (2) Thereafter, at intervals of 3,000 hours time in service 
(TIS) or 60 calendar months, whichever occurs first, remove the 
compressive rolled internal bore hub assembly, identified with the 
addition of a third letter ``A'' in the hub serial number prefix 
(e.g. ``CDA1234''), for inspection and specified rework in 
accordance with Hartzell Alert Service Bulletins (ASB's) No. A182A 
or A183A, both dated March 11, 1994.
    (3) For compressive rolled internal bearing bore hub assemblies, 
identified with the addition of a third letter ``A'' in the hub 
serial number prefix (e.g. ``CDA1234''), that experience a blade 
strike, remove the hub assembly for inspection and specified rework 
procedures, in accordance with Hartzell ASB Nos. A182A or A183A, 
both dated March 11, 1994, Thereafter, at intervals of 3,000 TIS or 
60 calendar months, whichever occurs first, repeat this inspection 
and required rework.
    (c) Before further flight for propeller hub assemblies that have 
never been inspected; or within 750 hours TIS since the last 
inspection for those propeller hub assemblies inspected in 
accordance with Hartzell ASB's Nos. A182A, or A183A, both dated 
March 11, 1994; or ASB No. A182, dated April 28, 1993, or ASB No. 
A183, dated June 1, 1993; but in no case later than 12 calendar 
months from the effective date of this AD; accomplish the following:
    (1) Replace propeller hub unit P/N 840-139 or P/N 840-91, unless 
already accomplished, with a hub that has compressive rolled 
internal bearing bores, which is identified with the addition of a 
third letter ``A'' in the hub serial number prefix (e.g. 
``CDA1234''). Propeller hub assemblies removed from service in 
accordance with this AD paragraph are to be permanently retired and 
may not be returned to service on any aircraft; and
    (2) Thereafter at intervals of 3,000 hours TIS or 60 calendar 
months, whichever occurs first, remove the compressive rolled 
internal bearing bore hub assembly, identified with the addition of 
a third letter ``A'' in the hub serial number prefix (e.g. 
``CDA1234''), for inspection and specified rework in accordance with 
Hartzell ASB's No. A182A or A183A both dated March 11, 1994.
    (d) Perform a propeller blade thickness inspection, rework if 
necessary, shot peen, and mark the blades, in accordance with 
Hartzell ASB No. A188, dated February 25, 1994, in accordance with 
the following schedule and requirements:

------------------------------------------------------------------------
   Propeller blade time since new                                       
(TSN) on the effective date of this          Compliance required        
                 AD                                                     
------------------------------------------------------------------------
Greater than or equal to 2,900       Within 100 hours TIS after the     
 hours TSN.                           effective date of this AD, or     
                                      during compliance with paragraphs 
                                      (b) or (c) of this AD, as         
                                      applicable, whichever occurs      
                                      first.                            
Less than 2,900 hours TSN but        Prior to reaching 3,000 hours time 
 greater than 2,200 hours TSN.        TSN or during compliance with     
                                      paragraphs (b) or (c) of this AD, 
                                      as applicable, whichever occurs   
                                      first.                            
Less than or equal to 2,200 hours    Within 800 hours TIS after the     
 TSN.                                 effective date of this AD or      
                                      during compliance with paragraphs 
                                      (b) or (c) of this AD, as         
                                      applicable, whichever occurs      
                                      first.                            
------------------------------------------------------------------------

    (1) If blade thickness requires rework of blades comprising 
thickness reduction of inboard stations then shot peening is also 
required prior to returning to service.
    (2) If the blade thickness inspection is satisfactory and no 
rework is required, shot peening may be deferred until the next 
overhaul, but not to exceed 3,000 hours TSN of the propeller blades, 
or within 60 calendar months since the last overhaul, whichever 
occurs first.
    (3) Propeller Model LT10282N(B,K)-5.3R ``N'' configuration 
blades that have been satisfactorily shot peened and inspected and 
must be metal impression stamped in the blade butt as well as ink 
stamped externally on the blade shank with the suffix letter ``S'' 
in the blade model designation, per Hartzell ASB No. A188, dated 
February 25, 1994.
    (e) Any blade repairs made after the effective date of this AD 
shall be accomplished in accordance with the procedures specified in 
Hartzell ASB No. A188, dated February 25, 1994.

    Note: Airworthiness Directive (AD) 94-11-04 restricts Mitsubishi 
Model MU-2B-26A, -36A, -40, -60, and MU-2B-36 Aircraft Modified by 
(STC) SA2413SW to an engine ground idle speed range of 76.5 to 78.5 
percent to prevent the possibility of operating the propeller too 
close to the ground idle resonant speed (``reactionless mode''). The 
purpose of Paragraphs (d) and (e) of this AD are to insure that the 
resonant speed does not shift into the permitted engine ground idle 
range during operation.

    (f) Propeller blade Model LT10282N(B,K)-5.3R and LT10282NS(B,K)-
5.3R configuration blades now have a retirement life limit of 10,000 
hours TIS and are to be permanently retired from service, and 
replaced with serviceable blades, upon reaching this limit.
    (g) A blade strike is defined as a propeller having any blade 
that has been bent beyond the repair limits specified in Hartzell 
Propeller Inc. Standard Practices Manual, Revision 1, Pages 1104-
1105, dated June 1994.
    (h) The ``calendar month'' compliance times stated in this AD 
allow the performance of the required action up to the last day of 
the month in which compliance is required.
    (i) 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, FAA, Chicago Aircraft Certification 
Office. The request should be forwarded through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, FAA, Chicago Aircraft Certification Office.

    Note: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the FAA, Chicago Aircraft Certification 
Office.

    (j) Except when propeller hub arm assemblies have experienced a 
blade strike, 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 aircraft to a location 
where the requirements of this AD can be accomplished.
    (k) The actions required by this AD shall be done in accordance 
with the following Hartzell Propeller Inc. service documents:

                                                                        
[[Page 2880]]                                                           
------------------------------------------------------------------------
               Document No.                 Pages           Date        
------------------------------------------------------------------------
ASB No. A182A............................      1-3  Mar. 11, 1994.      
    Total pages: 3.......................                               
ASB No. A183A............................      1-3  Mar. 11, 1994.      
    Total pages: 3.......................                               
ASB No. A188.............................      1-4  Feb. 25, 1994.      
    Total pages: 4.......................                               
Hartzell Propeller Standard Practices       1104-5  June 1994.          
 Manual, Revision 1.                                                    
    Total pages: 2.......................                               
------------------------------------------------------------------------

    This incorporation by reference was approved by the Director of 
the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR 
part 51. Copies may be obtained from Hartzell Propeller Inc., One 
Propeller Place, Piqua, OH 45356-2634; telephone (513) 778-4200, fax 
(513) 778-4391. Copies may be inspected at the FAA, New England 
Region, Office of the Assistant Chief Counsel, 12 New England 
Executive Park, Burlington, MA; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
    (l) This amendment becomes effective on January 27, 1995.

    Issued in Burlington, Massachusetts, on December 22, 1994.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 95-633 Filed 1-11-95; 8:45 am]
BILLING CODE 4910-13-P