[Federal Register Volume 63, Number 141 (Thursday, July 23, 1998)]
[Rules and Regulations]
[Pages 39492-39496]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-19615]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-SW-22-AD; Amendment 39-10675; AD 98-15-26]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Helicopter Systems 
Model 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, 
600N, and OH-6A Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment supersedes an existing priority letter 
Airworthiness Directive (AD) 98-03-15, applicable to McDonnell Douglas 
Helicopter Systems (MDHS) Model 369, 369A, 369D, 369E, 369F, 369FF, 
369H, 369HE, 369HM, 369HS, 500N, 600N, and OH-6 helicopters that 
currently requires an inspection for main rotor blade (blade) cracks 
and for missing or cracked adhesive or paint. This amendment requires 
the same inspections required by the existing priority letter AD but 
deletes the Model 369 (Army YOH-6A), specifies recording torque events 
(TE),

[[Page 39493]]

and establishes a shorter retirement life for certain blades. This 
amendment is prompted by an accident in which a blade failed on a Model 
369D helicopter due to fatigue cracks. The actions specified by this AD 
are intended to detect cracks that could lead to failure of the blade 
and subsequent loss of control of the helicopter.

DATES: Effective August 3, 1998.
    The incorporation by reference of certain publications listed in 
the regulations was approved previously by the Director of the Federal 
Register as of May 29, 1996 (61 FR 24220, May 14, 1996).
    Comments for inclusion in the Rules Docket must be received on or 
before September 21, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Regional Counsel, Southwest Region, 
Attention: Rules Docket No. 98-SW-22-AD, 2601 Meacham Blvd., Room 663, 
Fort Worth, Texas 76137.
    The applicable service information may be obtained from McDonnell 
Douglas Helicopter Systems, Technical Publications, Bldg. M615/GO48, 
5000 E. McDowell Road, Mesa, Arizona 85215-9797, telephone 602-891-
6522. This information may be examined at the FAA, Office of the 
Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663 For 
Worth, Texas; or at the Office of the Federal Register, 800 North 
Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT:
Mr. John L. Cecil, Aerospace Engineer, FAA, Los Angeles Aircraft 
Certification Office, 3960 Paramount Blvd., Lakewood, California 90712, 
telephone (562) 627-5229, fax (562) 627-5210.

SUPPLEMENTARY INFORMATION: On January 29, 1998, the FAA issued Priority 
Letter AD 98-03-15, applicable to Boeing MDHS Model 369, 369A, 369D, 
369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, 600N, and OH-6 
helicopters, which requires an inspection for blade cracks and for 
missing or cracked adhesive or paint. That priority letter AD was 
prompted by an accident in which a blade failed on a Boeing MDHS Model 
369D helicopter due to cracks. The blade that failed had accumulated 
over 2,300 hours time-in-service (TIS). Subsequent investigation 
revealed cracks in two other blades on the same helicopter. 
Additionally, an operator reported finding a blade crack as a result of 
complying AD 98-01-13. The cracks had initiated in the lower doubler 
and propagated in a chordwise direction through the blade skin and 
spar. These fatigue cracks may have been caused by residual stresses 
induced by nonconforming doublers used to construct the blade. A 
fatigue crack in a blade creates an unsafe condition. That condition, 
if not detected, could result in failure of the blade and subsequent 
loss of control of the helicopter.
    The FAA previously issued AD 95-03-13, effective March 21, 1995, 
Docket No. 94-SW-05-AD; AD 96-10-09, effective May 29, 1996, Docket No. 
96-SW-02-AD; Priority Letter AD 98-01-13, issued December 31, 1997, 
Docket No. 97-SW-68-AD, and Priority Letter AD 98-03-15 issued January 
29, 1998, Docket No. 98-SW-06-AD, all of which mandate inspections in 
the same general area. Priority Letter Ad 98-03-15 superseded Priority 
Letter AD 98-01-13. This AD supersedes Priority Letter AD 98-03-15. 
This AD does not supersede AD 95-03-13 or AD 96-10-09.
    Since the issuance of AD 98-03-15, the FAA has determined the need 
for establishing and recording of torque events (TE) plus the lowering 
of the limit lives of the main rotor blades. The FAA has reviewed 
Boeing McDonnell Douglas Helicopter Systems Service Bulletin No. 
SB369H-243R3, SB369E-088R3, SB500N-015R3, SB369D-195R3, SB369F-075R3, 
SB600N-007R2, dated July 13, 1998 (SB). The SB describes procedures for 
a visual inspection of certain main rotor blades using a 10X magnifying 
glass. The inspections are intended to detect cracking of the lower 
surface of each blade starting at the root fitting and the doubler at 
the inboard end of the blade and to detect debonding between the blade 
root end fitting and doubler if missing or cracked adhesive or paint is 
observed. For all affected helicopters except the Model 600N, with 
blades installed that have 600 or more hours TIS, the SB provides that 
these inspections are to be accomplished prior to further flight, and 
thereafter at intervals not to exceed 25 hours TIS. For Model 600N 
helicopters, the SB provides, prior to further flight, removal of 
affected blades due to higher blade stresses on this model as compared 
to other affected models. Additionally, this SB introduces flight hour 
factoring as a means of addressing certain low cycle fatigue by 
providing an alternate retirement life for the affected blades based on 
TE. The manufacturer has determined that this action would not affect 
any Model 369 (Army YOH-6A) helicopters. There are no known Model 369 
helicopters in the U.S. fleet. Further, there were only two Model 369 
helicopters produced as prototype Army YOH-6A. Therefore, the Model 369 
helicopter is deleted from the SB. The FAA has also reviewed McDonnell 
Douglas Helicopter Systems Service Information Notice No. HN-239, DN-
188, EN-81, FN-67, NN-008, dated October 27, 1965, which describes 
procedures for an inspection for debonding between the blade root end 
fitting and doubler if missing or cracked adhesive or paint is 
observed.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other MDHS Model 369A, 369D, 369E, 369F, 369FF, 
369H, 369HE, 369HM, 369HS, 500N, 600N, and OH-6A helicopters of the 
same type design, this AD requires, before further flights, and 
thereafter at intervals not to exceed 25 hours TIS, for affected blades 
that have 600 or more hours TIS, a visual inspection for cracks in the 
lower surface of the blade root fitting and doubler at the inboard end 
of the blade and for missing or cracked adhesive or paint at the root 
end-to-doubler bonding line. The inspections will be accomplished using 
a 10X or higher magnifying glass. Blades will be removed from service 
before or upon the accumulation of a specified number of TE or hours 
TIS, whichever occurs first. Since this same unsafe condition is likely 
to exist on MDHS Model 600N helicopters and develop at a faster rate 
because of higher blade stresses, this AD requires removal of certain 
main rotor blades prior to further flight and replacement with 
airworthy blades.
    The short compliance time involved is required because the 
previously described critical unsafe condition can adversely affect the 
controllability and structural integrity of the helicopter. Therefore, 
inspecting for blade cracks and missing or cracked adhesive or paint, 
removing certain MDHS Model 600N helicopter blades, and reducing the 
service life for the blades are required prior to further flight, and 
this Ad must be issued immediately.
    Since issuance of Priority Letter 98-03-15, the FAA has evaluated 
additional data and has determined that the reduction of the service 
life of the affected blades is appropriate. The actions are required to 
be accomplished in accordance with this AD and Service Information 
Notice No. HN-239, DN-188, EN-81, FN-67, NN-008, dated October 27, 
1995, described previously.
    Since a situation exists that require 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.
    The FAA estimates that 1,030 helicopters of U.S. registry will be 
affected by this AD, and it will take

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approximately 0.5 hours per helicopter to determine whether an affected 
blade is installed, 1 work hour per helicopter with an affected blade 
for the initial inspection, and 2.5 hours to replace a blade at a rate 
of $60 per work hour. Required parts will cost approximately $6200 per 
blade. Based on these figures, the total cost impact of the proposed AD 
on U.S. operators is estimated to be $3,799,980 to inspect the blades 
for cracks and to replace 588 affected blades.

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.
    Comments 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 No. 98-SW-22-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 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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 3913 is amended by adding a new airworthiness directive 
(AD) to read as follows:

AD 98-15-26  McDonnell Douglas Helicopter Systems: Amendment 39-
10675. Docket No. 98-SW-22-AD. Supersedes Priority Letter AD 98-08-
15, Docket No. 98-SW-06-AD.

    Applicability: Model 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 
369HM, 369HS, 500N, 600N, and OH-6A helicopters with main rotor 
blades Part Number (P/N) 369A1100-507 with Serial Number (S/N) D139 
through D203, D209 through D223; P/N 369D21100-517 with S/N H664, 
H665, H667, H669, H671, H672, H674, H676, H679, H680, H683 through 
H724, H726 through H999, J000 through J039, J041 through J055; or P/
N 369D21102-517 with S/N 1976 through 2100, 2106 through 2115, 
installed, certificated in any category.

    Note 1. This AD applies to each helicopter 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 helicopters that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must use the authority 
provided in paragraph (f) 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, alternation, or repair 
remove any helicopter from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    (a) For Model 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 
369HS, 500N, and OH-6A helicopters with any affected main rotor 
blade (blade) that has 600 or more hours time-in-service (TIS), to 
detect cracks that could lead to failure of the blade and subsequent 
loss of control of the helicopter, before further flight and 
thereafter at intervals not to exceed 25 hours TIS, accomplish the 
following:
    (1) With each blade lifted off the droop stop, using a 10X or 
higher magnifying glass, visually inspect the blade for any 
chordwise cracking starting at the root fitting edge on the blade 
lower surface doubler and skin or cracks on the doubler adjacent to 
the root end fitting (Figure 1). If any cracking is discovered, 
remove the blade and replace it with an airworthy blade.

    Note 2: Boeing McDonnell Douglas Helicopter Systems Service 
Bulletin No. SB369H-243R3, SB369E-088R3, SB500N-015R3, SB369D-195R3, 
SB369F-075R3, SB600N-007R2, dated July 13, 1998 (SB), pertains to 
the subject of this AD.

    (2) With each blade lifted off the droop stop, inspect the lower 
surface for missing or cracked adhesive or paint at the root end 
fitting-to-doubler bond line (Figure 1). If any missing or cracked 
adhesive or paint is discovered, remove and inspect the blade in 
accordance with paragraph 3E of Part II of the Accomplishment 
Instructions in McDonnell Douglas Helicopter Systems Service 
Information Notice No. HN-239, DN-188, EN-81, FN-67, NN-008, dated 
October 27, 1995. If there is any disbonding in excess of the 
allowable margins specified in paragraph 3E of Part II of the 
service information notice, replace the blade with an airworthy 
blade.

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    (b) For the Model 600N helicopters, before further flight, 
remove any affected blade from service and replace it with an 
airworthy blade not listed in the applicability section of this AD. 
Blades removed from the Model 600N helicopters are not eligible for 
use on any rotorcraft.

    Note 3: The recurring inspection requirements, contained in 
paragraph (a) of this AD, DO NOT apply to the Model 600N 
helicopters.

    (c) Affected blades are to be removed from service on or before 
reaching either of the applicable new life limits. The new life 
limits are determined by hours TIS or number of torque events (TE). 
A torque event is defined as the transition to a hover from forward 
flight. For this definition of TE, forward flight is considered to 
be flight at any airspeed after attaining translational lift.
    (1) For blades that do not have TE logged, prior to further 
flight, log the TE in the rotorcraft log or equivalent record as 
follows:
    (i) Log the number of TE, if known.
    (ii) For noncargo hook operations, if the number of TE is 
unknown, log 6 TE for each hour TIS.
    (iii) For cargo hook (external load) operations, or for any 
combination of noncargo hook operations and cargo hook (external 
load) operations, if the number of TE is unknown, log 20 TE for each 
hour TIS.
    (2) Make any entry into the component record or equivalent 
record to reflect new life limits for blade P/N's as follows:
    (i) For P/N 369A1100-507, Models 369A, 369H, 369HE, 369HM, 
369HS, and OH-6A, enter 1,750 hours TIS or 10,600 TE, whichever 
occurs first.
    (ii) For P/N 369D21100-517, Models 369D and 369E, enter 2,500 
hours TIS or 15,000 TE, whichever occurs first.
    (iii) For P/N 369D21102-517, Model 369F, 369FF, and 500N, enter 
2,500 hours TIS or 15,000 TE, whichever occurs first.
    (d) After compliance with paragraph (c) of this AD, during each 
operation thereafter, maintain a count of TE performed and 
additional hours TIS accumulated, and, at the end of each day's 
operations, add those counts to the accumulated number of TE and 
hours TIS on the rotorcraft log or equivalent record.
    (e) The blades are no longer retired based upon only hours TIS. 
This AD revises the Airworthiness Limitations Section of the 
maintenance manual by establishing a new retirement life for certain 
blade P/N's based on hours TIS or a number of TE, whichever occurs 
first.
    (f) 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, Los Angeles Aircraft Certification 
Office, FAA. Operators shall submit their requests through an FAA 
Principal Maintenance Inspector, who may concur or comment and then 
send it to the Manager, Los Angeles Aircraft Certification Office.

    Note 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles Aircraft Certification Office.

    (g) Special flight permits will not be issued.
    (h) The inspection required by paragraph (a)(2) of this AD shall 
be done in accordance with McDonnell Douglas Helicopter Systems 
Service Information Notice No. HN-239, DN-188, EN-81, FN-67, NN-008, 
dated October 27, 1995. This incorporation by reference was approved 
previously by the Director of the Federal Register as of May 29, 
1996 (61 FR 24220, May 14, 1996). Copies may obtained from McDonnell 
Douglas Helicopter Systems, Commercial Technical Publications, Bldg. 
M615/G048, 5000 E. McDowell Road, Mesa, Arizona 85215-9797, 
telephone 602-891-3667, fax 602-891-6522. Copies may be examined at 
the FAA, Office of the Regional Counsel, Southwest Region, 2601 
Meachum Blvd., Room 663, Fort Worth, Texas, or at the Office of the 
Federal Register, 800 North Capital Street NW., suite 700, 
Washington, DC.
    (i) This amendment becomes effective on August 3, 1998.

    Issued in Fort Worth, Texas, on July 17, 1998.
Henry A. Armstrong,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 98-19615 Filed 7-22-98; 8:45 am]
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