[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
