[Federal Register Volume 66, Number 184 (Friday, September 21, 2001)]
[Proposed Rules]
[Pages 48631-48648]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-23415]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-SW-14-AD]
RIN 2120-AA64


Airworthiness Directives; Model HH-1K, TH-1F, TH-1L, UH-1A, UH-
1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-1P, and Southwest Florida Aviation 
Model SW204, SW204HP, SW205, and SW205A-1 Helicopters, Manufactured by 
Bell Helicopter Textron, Inc. for the Armed Forces of the United States

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes superseding an existing airworthiness 
directive (AD) for Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-
1F, UH-1H, UH-1L, and UH-1P; and Southwest Florida Aviation SW204, 
SW204HP, SW205, and SW205A-1 helicopters manufactured by Bell 
Helicopter Textron, Inc. (BHTI) for the Armed Forces of the United 
States. That AD currently requires establishing retirement lives for 
certain main rotor masts, creating a component history card or 
equivalent record, and identifying and replacing any unairworthy masts. 
That AD also contains certain requirements regarding the hub spring, 
conducting inspections based on the retirement index number (RIN), and 
sending information to the FAA. This action would contain the same 
requirements but would establish a retirement life for the main rotor 
trunnion (trunnion) based on monitoring the number of torque events and 
flight hours rather than flight hours only as currently required. This 
action would also add a note clarifying that the mast serial number (S/
N) is defined by 5 or fewer digits plus various prefixes. This proposal 
is prompted by the determination that monitoring the number of torque 
events and flight hours for the trunnion is more accurate than by 
monitoring flight hours only to establish a retirement life. The 
actions specified by the proposed AD are intended to prevent failure of 
a mast or trunnion, separation of the main rotor system, and subsequent 
loss of control of the helicopter.

DATES: Comments must be received on or before November 20, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Regional Counsel, Southwest Region, 
Attention: Rules Docket No. 2001-SW-14-AD, 2601 Meacham Blvd., Room 
663, Fort Worth, Texas 76137. You may also send comments electronically 
to the Rules Docket at the following address: [email protected]. 
Comments may be inspected at that Office between 9 a.m. and 3 p.m., 
Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Michael Kohner, Aviation Safety 
Engineer, FAA, Rotorcraft Directorate, Rotorcraft Certification Office, 
Fort Worth, Texas 76193-0170, telephone (817) 222-5447, fax (817) 222-
5783.

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 should 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 will 
be considered before taking action on the proposed rule. The proposals 
contained in this document 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 mailed 
comments submitted in response to this proposal must submit a self-
addressed, stamped postcard on which the following statement is made: 
``Comments to Docket No. 2001-SW-14-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, Office of the Regional Counsel, Southwest Region, 
Attention: Rules Docket No. 2001-SW-14-AD, 2601 Meacham Blvd., Room 
663, Fort Worth, Texas 76137.

Discussion

    On November 13, 1998, the FAA issued AD 98-24-15 for BHTI Model

[[Page 48632]]

204B, 205A, 205A-1, 205B, and 212 helicopters, which established a 
retirement life for the main rotor mast (mast) and trunnion based on a 
RIN count. That AD required creating component history cards or 
equivalent records, converting accumulated factored flight hours to a 
baseline accumulated RIN count, establishing a system for tracking 
increases to the accumulated RIN, and establishing a maximum 
accumulated RIN for certain masts and trunnions. Analysis and 
reevaluation of previous fatigue testing conducted by the manufacturer 
of those model helicopters following an accident involving a Model 
205A-1 helicopter confirmed that the remaining lives for the mast and 
trunnion are more accurately assessed by monitoring the number of 
torque events and flight hours rather than monitoring only flight 
hours. Since identical trunnions are installed on the surplus military 
helicopters of similar type design, the FAA has determined that similar 
procedures and limitations need to be imposed on restricted category 
helicopters.
    AD 98-24-15, Amendment 39-10900, Docket 97-SW-20-AD (63 FR 64612, 
November 23, 1998), for BHTI Model 204B, 205A, 205A-1, 205B, and 212 
helicopters, was superseded by Priority Letter AD 2000-08-52, Docket 
2000-SW-20-AD. Priority Letter AD 2000-08-52 was superseded by AD 2000-
15-52, Amendment 39-12042, Docket 2000-SW-28-AD (65 FR 77785, December 
13, 2000). For similar helicopters in the restricted category, AD 2000-
22-51, Amendment 39-12034 (65 FR 77263, December 11, 2000, Docket No. 
2000-SW-42-AD), superseded Priority Letter AD 2000-08-53, Docket 2000-
SW-08-AD, and previous AD 89-17-03, Amendment 39-6251, Docket 88-ASW-33 
(54 FR 31935, August 3, 1989). AD 2000-22-51 required the calculation 
of the retirement life for the trunnion, part number 204-011-105-001, 
installed on those restricted category helicopters based on hours time-
in-service (TIS) only. This document proposes to require that the 
service life of the trunnion on those restricted category helicopters 
be limited to 300,000 RIN or 15,000 hours TIS, whichever occurs first, 
to prevent failure of a mast or trunnion, separation of the main rotor 
system, and subsequent loss of control of the helicopter.
    We have identified an unsafe condition that is likely to exist or 
develop on Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-
1H, UH-1L, and UH-1P; and Southwest Florida Aviation SW204, SW204HP, 
SW205, and SW205A-1 helicopters manufactured by BHTI for the Armed 
Forces of the United States. Therefore, the proposed AD would supersede 
AD 2000-22-51. The FAA has determined that the retirement life for a 
trunnion is more accurate if monitored by the number of torque events 
and flight hours rather than monitoring only flight hours. Therefore, 
this AD would contain the same requirements as AD 2000-22-51 for the 
mast but would establish a retirement life for the trunnions based on 
monitoring the number of torque events and flight hours. This AD would 
also add a note clarifying that the mast S/N is defined by 5 or fewer 
digits plus various prefixes.
    The FAA estimates that this proposed AD would affect 75 helicopters 
of U.S. registry. The FAA also estimates that it would take 10 work 
hours to replace the trunnion, 2 work hours per helicopter to create a 
new component history card or equivalent record for the trunnions and 
that the average labor rate is $60 per work hour. Required trunnions 
would cost approximately $5,300 per helicopter. Based on these figures, 
the total cost impact of the proposed AD on U.S. operators is estimated 
to be $451,500.
    The regulations proposed herein would not have a substantial direct 
effect 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, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    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 removing Amendment 39-12034 (65 FR 
77263, December 11, 2000), and by adding a new airworthiness directive 
(AD), to read as follows:

Arrow Falcon Exporters, Inc. (previously Utah State University); 
Firefly Aviation Helicopter Services (previously Erickson Air-Crane 
Co.); Garlick Helicopters, Inc.; Hawkins and Powers Aviation, Inc.; 
International Helicopters, Inc.; Robinson Air Crane, Inc.; Smith 
Helicopters; Southern Helicopter, Inc.; Southwest Florida Aviation; 
Tamarack Helicopters, Inc. (previously Ranger Helicopter Services, 
Inc.); U.S. Helicopter, Inc.; Western International Aviation, Inc., 
and Williams Helicopter Corporation (previously Scott Paper Co.):  
2001-SW-14-AD. Supersedes AD 2000-22-51, Amendment 39-12034, Docket 
No. 2000-SW-42-AD.

    Applicability: Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, 
UH-1F, UH-1H, UH-1L, and UH-1P; and Southwest Florida Aviation 
SW204, SW204HP, SW205, and SW205A-1 helicopters, manufactured by 
Bell Helicopter Textron Inc. (BHTI) for the Armed Forces of the 
United States, with main rotor mast (mast), part number (P/N) 204-
011-450-007, -105, or -109, or main rotor trunnion (trunnion), P/N 
204-011-105-001, 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 
otherwise 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 request approval for an 
alternative method of compliance in accordance with paragraph (c) 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 been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.

    Note 2: This AD requires using new factors to recalculate the 
FACTORED flight hours and the accumulated Retirement Index Number 
(RIN) for masts installed on certain helicopter models. This AD also 
expands the serial number (S/N) applicability for the one-time 
special inspection of the mast.

    To prevent failure of a mast or trunnion, separation of the main 
rotor system, and

[[Page 48633]]

subsequent loss of control of the helicopter, accomplish the 
following:
    (a) For the mast, P/N 204-011-450-007, -105, or -109:

    Note 3: The next higher assembly level for the affected P/N's 
are the 204-040-366 mast assemblies. Check the helicopter records 
for the appropriate P/N and assembly level.


    (1) Within 10 hours time-in-service (TIS), create a component 
history card or equivalent record for the mast.
    (2) Within 10 hours TIS, determine and record the accumulated 
RIN and revised hours TIS for the mast as follows:
    (i) Review the helicopter maintenance records for the mast. If 
you do not know the helicopter model installation history or hours 
TIS of the mast, remove the mast from service, identify the mast as 
unairworthy, and replace it with an airworthy mast before further 
flight.
    (ii) Calculate the accumulated RIN and the revised hours TIS for 
the mast in accordance with the instructions in Appendix 1 to this 
AD. For those hours TIS the mast has been installed on any other 
helicopter, calculate the RIN for that trunnion in accordance with 
the requirements for those helicopters.
    (iii) Record the accumulated RIN and revised hours TIS for the 
mast on the component history card or equivalent record. Use the 
revised hours TIS as the new hours TIS for the mast.
    (3) Before further flight after accomplishing the requirements 
of paragraph (a)(2) of this AD, remove from service any mast that 
has accumulated 265,000 or more RIN or 15,000 or more revised hours 
TIS and identify the mast as unairworthy. Replace the mast with an 
airworthy mast.
    (4) Within 25 hours TIS, remove any hub spring installed on any 
affected helicopter.

    Note 4: U.S. Army Modification Work Order (MWO) 55-1520-242-50-1 
pertains to the removal of the hub spring and replacement of any 
required parts. U.S. Army Safety of Flight Message UH-1-00-10 dated 
July 19, 2000, also pertains to the subject of this AD.

    (5) Determine whether a mast with a S/N less than and including 
52720, 61433 through 61444, or 61457 through 61465 (regardless of 
prefix), has ever been installed on a helicopter while operated with 
a hub spring.

    Note 5: The mast S/N consists of 5 or less numerical digits and 
may be preceded by one of the following prefixes: NFS, N9, H, AC9, 
CP, FA, H9, N19, RH9, or NC. There may be other prefixes in addition 
to those listed. The prefix and S/N may or may not be separated by a 
dash.

    (i) If a mast has never been installed on a helicopter while 
operated with a hub spring, before reaching 100,000 RIN, inspect the 
upper and lower snap ring grooves in the damper clamp splined area 
for:
    (A) A minimum radius of 0.020 inch around the entire 
circumference (see Figures 1 and 2), using a 100 x  or higher 
magnification. If any snap ring groove radius is less than 0.020 
inch, identify the mast as unairworthy and replace it with an 
airworthy mast before exceeding 100,000 RIN.
    (B) A burr (see Figures 1 through 3), using a 200 x  or higher 
magnification. If a burr is found in any snap ring groove/spline 
intersection, identify the mast as unairworthy and replace it with 
an airworthy mast before exceeding 170,000 RIN.
    (ii) If a mast has ever been installed on a helicopter while 
operated with a hub spring or if you do not know whether a hub 
spring has ever been installed, before reaching 100,000 RIN or 400 
unfactored flight hours, whichever occurs first, inspect the upper 
and lower snap ring grooves in the damper clamp splined area for:
    (A) A minimum radius of 0.020 inch around the entire 
circumference (see Figures 1 and 2), using a 100 x  or higher 
magnification. If any snap ring groove radius is less than 0.020 
inch, identify the mast as unairworthy and replace it with an 
airworthy mast before further flight.
    (B) A burr (see Figures 1 through 3), using a 200 x  or higher 
magnification. If a burr is found in any snap ring groove/spline 
intersection, identify the mast as unairworthy and replace it with 
an airworthy mast before further flight.
    (6) After accomplishing the requirements of paragraph (a)(2) of 
this AD, continue to calculate the accumulated RIN for the mast by 
multiplying all takeoff and external load lifts by the RIN factors 
defined in columns (D) and (G) of Table 1 of Appendix 1 of this AD.
    (7) After accomplishing the requirements of paragraph (a)(2) of 
this AD, continue to count the hours TIS for the mast. Any hours TIS 
for the mast while installed on a helicopter operated with a hub 
spring or those hours during which you do not know whether a hub 
spring was installed must be factored in accordance with the 
instructions in Appendix 1 of this AD.
    (8) This AD establishes a retirement life of 265,000 accumulated 
RIN or 15,000 hours TIS, whichever occurs first, for mast, P/N 204-
011-450-007, -105, and -109.
    (9) Within 10 days after completing the inspections required by 
paragraph (a)(5) of this AD, send the information contained on the 
AD compliance inspection report sample format contained in Appendix 
2 to the Manager, Rotorcraft Certification Office, Federal Aviation 
Administration, Fort Worth, Texas, 76193-0170, USA. Reporting 
requirements have been approved by the Office of Management and 
Budget and assigned OMB control number 2120-0056.

BILLING CODE 4910-13-P

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[GRAPHIC] [TIFF OMITTED] TP21SE01.001


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[GRAPHIC] [TIFF OMITTED] TP21SE01.002

BILLING CODE 4910-13-C

    (b) For the trunnion, P/N 204-011-105-001:
    (1) Within 10 hours TIS, create a component history card or 
equivalent record for the trunnion.
    (2) Within 10 hours TIS, determine and record the accumulated 
RIN and revised hours TIS for the trunnion as follows:
    (i) Review the helicopter maintenance records for the trunnion. 
If the helicopter model installation history or hours TIS of the 
trunnion are unknown, remove the trunnion from service, identify the 
trunnion as unairworthy, and replace it with an airworthy trunnion 
before further flight.
    (ii) Calculate the accumulated RIN and the revised hours TIS in 
accordance with the instructions in Appendix 3 to this AD. For those 
hours TIS the trunnion has been installed on any other helicopter, 
calculate the RIN for that trunnion in accordance with the 
requirements for those helicopters.
    (iii) Record the accumulated RIN and revised hours TIS for the 
trunnion on the component history card or equivalent record. Use the 
revised hours TIS as the new hours TIS for the trunnion.
    (3) Before further flight after accomplishing the requirements 
of paragraph (b)(2) of this AD, remove from service any trunnion 
that has accumulated 300,000 or more RIN or 15,000 or more revised 
hours TIS and identify the trunnion as unairworthy. Replace the 
trunnion with an airworthy trunnion.
    (4) After accomplishing the requirements of paragraph (b)(2) of 
this AD, continue to calculate the accumulated RIN for the trunnion 
by multiplying all takeoff and external load lifts by the RIN 
factors defined in columns (D) and (G) of Table 1 of Appendix 3 to 
this AD.
    (5) After accomplishing the requirements of paragraph (b)(2) of 
this AD, continue to count the hours TIS for the trunnion.
    (6) This AD establishes a retirement life of 300,000 accumulated 
RIN or 15,000 hours TIS, whichever occurs first, for the trunnion, 
P/N 204-011-105-001.
    (c) 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, Rotorcraft 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, Rotorcraft Certification Office.

    Note 6: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Manager, Rotorcraft Certification Office.

    (d) Special flight permits may be issued in accordance with 14 
CFR 21.197 and 21.199 to operate the helicopter to a location where 
the requirements of this AD can be accomplished.

Appendix 1--Instructions for Calculating the RIN and Revised Hours TIS

Definitions for the RIN

    The overall fatigue life of a main rotor mast is a function of 
the number of cycles of torque, lift, and bending loads applied to 
it during the various modes of operation. The mast experiences both 
high cycle fatigue and low cycle fatigue during operation.
    The high cycle fatigue life of the mast is a function of high 
frequency but relatively low level cyclic loads, which are primarily 
induced by rotor rpm. The high cycle fatigue life limit for the mast 
is defined in terms of hours TIS because rotor rpm is basically a 
constant value.
    The low cycle fatigue life of the mast is a function of the 
number of less frequent but relatively high level cyclic loads 
experienced primarily during takeoffs and external load lifts. The 
low cycle fatigue life limit for the mast is expressed in terms of 
the accumulated RIN.
    A load cycle is a power cycle caused by a repeating or 
fluctuating load that alternates from a starting power value, goes 
to a higher power value, and returns to the starting power value.

[[Page 48637]]

    The accumulated RIN is defined as the total number of load 
cycles multiplied by a RIN factor to account for the difference in 
torque levels applied to the same mast (since manufactured) when 
installed in different helicopter models. The level of torque 
applied to the mast is directly proportional to the transmission 
output horsepower.
    The unfactored hours TIS is the time from the moment a 
helicopter leaves the surface of the earth until it touches it at 
the next point of landing with no factors applied.
    The FACTORED flight hours is the unfactored hours TIS multiplied 
by a frequency of event hour factor based on the torque (horsepower) 
of the helicopter model in which it was installed and the usage of 
the helicopter.
    The revised hours TIS is the new hours TIS for the mast as 
determined by following the instructions in this appendix.
    An external load lift is defined as a lift where the load is 
carried, or extends, outside of the aircraft fuselage.

Calculation of RIN and Revised Hours TIS

    There are two methods for calculating the accumulated RIN and 
the revised hours TIS, depending on the available service history 
information for the mast. In some cases, one method will be used for 
a portion of the mast service history, and the other method will be 
used for another portion of the mast service history. Both methods 
require knowledge of all the helicopter models in which the mast was 
installed.

Calculation of RIN and Revised Hours TIS When the Exact Number of 
Takeoffs and External Load Lifts Is Known (Reference Tables 1 and 3)

    Table 1 of Appendix 1 is the worksheet for calculating the 
accumulated mast RIN when the exact number of takeoffs and external 
load lifts is known. Table 3 of Appendix 1 is the worksheet that has 
the frequency of event hour factors to calculate the FACTORED flight 
hours for the unfactored hours TIS for the mast while installed on a 
helicopter operated with a hub spring or the hub spring installation 
history is unknown.
    The RIN factor for each external load lift is twice that 
specified for each takeoff because two torque events are experienced 
during a typical external load lift.
    Using Table 1, calculate accumulated RIN as follows:
    1. Enter the total number of takeoffs for the particular mast 
model/helicopter model combination in column (C).
    2. Multiply the value entered in column (C) by the RIN factor 
listed in column (D), and enter the result in column (E). This is 
the total accumulated RIN due to takeoffs.
    3. Enter the total number of external load lifts for the 
particular mast model/helicopter model combination in column (F).
    4. Multiply the value entered in column (F) by the RIN factor 
listed in column (G), and enter the result in column (H). This is 
the accumulated RIN due to external load lifts.
    5. Add the values from column (E) and column (H) and enter the 
result in column (I). This is the total accumulated RIN to-date for 
the mast for the particular mast model/helicopter model combination.
    6. Add the accumulated RIN subtotals for the various mast model/
helicopter combinations in column (I) and enter the result in the 
space provided. This is the total accumulated RIN for the mast.
    Using Table 3, calculate the revised hours TIS as follows:
    7. Determine the unfactored hours TIS for the mast while 
installed on a helicopter operated with a hub spring or the number 
of hours TIS for which you do not know whether a hub spring was 
installed for each of the particular mast model/helicopter model 
combinations.
    8. Determine the frequency of events per hour for each of the 
particular mast model/helicopter model combinations dividing the 
combined number of takeoffs and external load lifts by the 
corresponding unfactored hours TIS.
    9. Multiply the value for unfactored hours TIS for each of the 
particular mast model/helicopter model combinations by the 
appropriate value in column (E) of Table 3 for the frequency of 
event hour factor. These are the total FACTORED flight hours for the 
particular mast model/helicopter model combinations.
    10. Add the FACTORED flight hour subtotals for each of the 
particular mast model/helicopter model combinations. This is the 
total FACTORED flight hours for the mast while installed on a 
helicopter operated with a hub spring or when you do not know 
whether a hub spring was installed.
    11. Determine the unfactored hours TIS for the mast while 
installed on a helicopter operated without a hub spring.
    12. Add to the total FACTORED flight hours for the mast while 
installed on a helicopter operated with a hub spring or those hours 
during which you do not know whether a hub spring was installed to 
the unfactored hours TIS as determined in step 11. This is the total 
revised hours TIS for the mast when the exact number of takeoffs and 
external load lifts is known.

Calculation of RIN and Revised Hours TIS When Exact Number of Takeoffs 
and External Load Lifts Is Unknown (Reference Tables 2, 3, and 4)

    Tables 2, 3, and 4 of Appendix 1 are the worksheets for 
calculating the FACTORED flight hours and accumulated mast RIN when 
the exact number of takeoffs and external load lifts is unknown.
    Using Tables 2, 3, and 4, calculate the accumulated mast RIN and 
revised hours TIS as follows:
    1. Enter the unfactored hours TIS for the particular mast model/
helicopter model combination in column (C) of Tables 2 and 3.
    2. Using service history for the mast, select the appropriate 
frequency of event hour factor from column (E) of Tables 2 and 3 
based on the total combined number of takeoffs and external load 
lifts per hour shown in column (D).
    3. Multiply the value for unfactored hours TIS entered in column 
(C) by the appropriate value in column (E) for the frequency of 
event hour factor as determined in step 2. Enter the result in 
column (F) of Tables 2 and 3. This is the total FACTORED flight 
hours for the particular mast model/helicopter model combination.
    4. Enter the value for FACTORED flight hours from column (F) of 
Tables 2 and 3 into column (C) of Table 4.
    5. Using Table 4, multiply the value for FACTORED flight hours 
in column (C) by the appropriate RIN conversion factor listed in 
column (D), by the appropriate RIN adjustment factor in column (E), 
and enter the result in column (F). This is the accumulated RIN to-
date for the particular mast model/helicopter model combination.
    6. Add the accumulated RIN subtotals for the various mast model/
helicopter model combinations in column (F) of Table 4 and enter the 
result in the space provided. This is the total accumulated RIN for 
the mast.
    7. Add the factored flight hour subtotals for the various mast 
model/helicopter model combinations as determined in steps 1 through 
4. This is the total revised hours TIS for the mast when the exact 
number of takeoffs and external load lifts is unknown.

Sample Mast Calculation

    Given the following known service history for the mast:
    Mast, P/N 204-011-450'007, was first purchased as a United 
States military surplus part with valid historical records. The mast 
had accumulated 550 hours military TIS on an Army UH-1H with a hub 
spring installed.
    The mast was first installed on a restricted category UH-1H 
former military helicopter for 250 hours TIS. The helicopter had a 
rating of 1100 takeoff horsepower (T.O. hp) at sea level standard 
day conditions (SLS), and the operation of the helicopter without a 
hub spring cannot be determined. The helicopter was used for fire 
fighting operations and the exact number of takeoffs and external 
load lifts is unknown. It is known, however, that the helicopter 
averaged less than 15 combined takeoffs and external load lifts per 
hour.
    The mast was then removed and subsequently installed on a 
restricted category UH-1E former military helicopter (1100 T.O. hp 
SLS rating) without a hub spring for 450 hours TIS. It is known that 
the helicopter was used primarily for aerial surveying for the first 
200 hours of operation. The exact number of takeoffs and external 
load lifts is unknown, but it is known that the helicopter averaged 
less than 16 takeoffs per hour, with no external load lifts. It was 
subsequently used for repeated heavy lift operation for the next 250 
hours of operation and averaged between 25 and 31 combined takeoffs 
and external load lifts per hour during this period of time.
    The mast was then removed and installed on another restricted 
category UH-1H former military helicopter (1100 T.O. hp SLS rating) 
for a total of 150 hours TIS with accurate records indicating that 
it experienced 100 takeoffs and 2,450 external load lifts. A hub 
spring was installed on the helicopter for the first 50 hours of 
operation with a calculated average of 19 combined takeoffs and 
external load lifts per hour (as determined from aircraft records 
for the first 50 hours of operation). The hub spring was 
subsequently removed for the remaining 100 hours TIS.

[[Page 48638]]

    Calculate the FACTORED flight hours and total accumulated RIN 
for the mast as follows:

FACTORED Flight Hours and Accumulated RIN While Installed in U.S. 
Military Model UH-1H

    Calculate FACTORED flight hours from Table 3 as follows:

FACTORED Flight Hours
    = (unfactored hours TIS)  x  (frequency of event hour factor)
    = (column C)  x  (column E)
    = (550)  x  (10)
    = 5,500 hours

    Then using Table 4, calculate the accumulated RIN as follows:

Accumulated RIN
    = (FACTORED flight hours)  x  (RIN conversion factor)  x  (RIN 
adjustment factor)
    = (column C)  x  (column D)  x  (column E)
    = (5,500)  x  (20)  x  (1)

    = 110,000 RIN

FACTORED Flight Hours and Accumulated RIN While Installed in 
Restricted Category Model UH-1H

    Calculate FACTORED flight hours from Table 3 as follows:

FACTORED Flight Hours
    = (unfactored hours TIS)  x  (frequency of event hour factor)
    = (column C)  x  (column E)
    = (250)  x  (14)
    = 3,500 hours

    Then using Table 4, calculate the accumulated RIN as follows:

Accumulated RIN
    = (FACTORED flight hours)  x  (RIN conversion factor)  x  (RIN 
adjustment factor)
    = (column C)  x  (column D)  x  (column E)
    = (3,500)  x  (20)  x  (1)

    = 70,000 RIN

FACTORED Flight Hours and Accumulated RIN While Installed in 
Restricted Category Model UH-1E

    Calculate FACTORED flight hours from Table 2 as follows:

FACTORED Flight Hours (for first 200 hrs.)
    = (unfactored hours TIS)  x  (frequency of event hour factor)
    = (column C)  x  (column E)
    = (200)  x  (5)
    = 1,000 hours

FACTORED Flight Hours (for next 250 hrs.)
    = (unfactored hours TIS)  x  (frequency of event hour factor)
    = (column C)  x  (column E)
    = (250)  x  (10)
    = 2,500 hours

    Then using Table 4, calculate the accumulated RIN as follows:
Accumulated RIN
    = (FACTORED flight hours)  x  (RIN conversion factor)  x  (RIN 
adjustment factor)
    = (column C)  x  (column D)  x  (column E)
    = (1,000)  x  (20)  x  (1) + (2,500)  x  (20)  x  (1)
    = 20,000 + 50,000

    = 70,000 RIN

FACTORED Flight Hours and Accumulated RIN While Installed in 
Another Restricted Category Model UH-1H

    Calculate the accumulated RIN from Table 1 and the given number 
of takeoffs and external load lifts as follows:

Accumulated RIN
    = (number of takeoffs  x  RIN factor per takeoff) + (number of 
external load lifts  x  RIN factor per external load lifts)
    = (column C)  x  (column D) + (column F)  x  (column G)
    = (100)  x  (3) + (2,450)  x  (6)

    = 15,000 RIN

    Calculate the FACTORED flight hours for the mast while installed 
on a helicopter operated with a hub spring or when you do not know 
whether a hub spring was installed using the frequency of event hour 
factors from Table 3 as follows:

FACTORED Flight Hours (w/hub spring)
    = (unfactored hours TIS)  x  (frequency of event hour factor)
    = (column C)  x  (column E)
    = (50)  x  (16)
    = 800 hours

Unfactored Hours TIS (w/o hub spring)
    = (unfactored hours TIS)
    = 100 hours

    Note that the FACTORED flight hours are not used in the 
accumulated RIN calculations when the number of takeoffs and 
external load lifts is known.

Calculate the Total Accumulated RIN and Revised Hours TIS as 
follows

    The total accumulated RIN to-date for the mast is the sum of the 
subtotals from Tables 1 and 4.

Total Accumulated RIN
    = 110,000 + 70,000 + 70,000 + 15,000
    = 265,000

    The total FACTORED flight hours for the mast is the sum of the 
subtotals from Tables 2 and 3 and the total FACTORED flight hours as 
determined in the preceding step 12 when the exact number of takeoff 
and external load lifts is known.

Total FACTORED Flight Hours
    = 5,500 + 3,500 + 1,000 + 2,500 + 800
    = 13,300 hours

    The revised hours TIS to-date for the mast is the sum of the 
total FACTORED flight hours and the additional unfactored hours TIS 
for the mast while installed on a helicopter operated without a hub 
spring and the exact number of takeoffs and external load lifts is 
known.
Revised Hours TIS
    = 5,500 + 3,500 + 1,000 + 2,500 + 800 + 100
    = 13,300 + 100
    = 13,400 hours

    Both the total accumulated RIN and the revised hours TIS need to 
be determined and checked for exceeding the allowable life limits 
for the mast. Also, note that the recalculated total accumulated RIN 
for this sample mast would be 265,000 RIN. Therefore, this mast 
would be removed from service.
    The values for the sample problem are shown in Tables 1-4 for 
illustration purposes only. The FACTORED flight hours TIS shown in 
the brackets in Table 3 are calculated for the mast while installed 
on a helicopter operated with a hub spring or when you do not know 
whether a hub spring was installed and the exact number of takeoffs 
and external load lifts is known. These FACTORED flight hours are 
not used in the accumulated RIN calculations.

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Appendix 2--AD Compliance Inspection Report (Sample Format) P/N 204-
011-450-007/-105/-109 Main Rotor Mast

    Provide the following information and mail or fax it to: 
Manager, Rotorcraft Certification Office, Federal Aviation 
Administration, Fort Worth, Texas, 76193-0170, USA; Fax: 817-222-
5783.

Aircraft Registration No: __________.
Helicopter Model: __________.
Helicopter S/N: __________.
Mast P/N: __________.
Mast S/N: __________.
Mast RIN: __________.
Mast Total TIS: __________.

Inspection Results

Were any radii during inspection of this mast determined to be less 
than 0.020 inch? If yes, what was the dimension measured?
Was a burr found in the inspected snap ring grooves?
Were cracks noted during the inspection?
Who performed this inspection?
Provide any other comments?

Appendix 3--Instructions for Calculating Trunnion the RIN and Revised 
Hours TIS

Definitions for the RIN

    The overall fatigue life of a main rotor trunnion is a function 
of the number of cycles of torque, lift, and bending loads applied 
to it during the various modes of operation. The trunnion 
experiences both high cycle fatigue and low cycle fatigue during 
operation.
    The high cycle fatigue life of the trunnion is a function of 
high frequency but relatively low level cyclic loads, which are 
primarily induced by rotor rpm. The high cycle fatigue life limit 
for the trunnion is defined in terms of hours TIS because rotor rpm 
is basically a constant value.
    The low cycle fatigue life of the trunnion is a function of the 
number of less frequent but relatively high level cyclic loads 
experienced primarily during takeoffs and external load lifts. The 
low cycle fatigue life limit for the trunnion is expressed in terms 
of the accumulated RIN.
    A load cycle is a power cycle caused by a repeating or 
fluctuating load that alternates from a starting power value, goes 
to a higher power value, and returns to the starting power value.
    The accumulated RIN is defined as the total number of load 
cycles multiplied by a RIN factor to account for the difference in 
torque levels applied to the same trunnion (since manufactured) when 
installed in different helicopter models. The level of torque 
applied to the trunnion is directly proportional to the transmission 
output horsepower.
    The unfactored hours TIS is the time from the moment a 
helicopter leaves the surface of the earth until it touches it at 
the next point of landing with no factors applied.
    The FACTORED flight hours is the unfactored hours TIS multiplied 
by a frequency of event hour factor based on the torque (horsepower) 
of the helicopter model in which it was installed and the usage of 
the helicopter.
    The revised hours TIS is the new hours TIS for the trunnion as 
determined by following the instructions in this appendix.
    An external load lift is defined as a lift where the load is 
carried, or extends, outside of the aircraft fuselage.

Calculation of RIN and Revised Hours TIS

    There are two methods for calculating the accumulated RIN and 
the revised hours TIS, depending on the available service history 
information for the trunnion. In some cases, one method will be used 
for a portion of the trunnion service history, and the other method 
will be used for another portion of the trunnion service history. 
Both methods require knowledge of all the helicopter models in which 
the trunnion was installed.

Calculation of RIN and Revised Hours TIS When the Exact Number of 
Takeoffs and External Load Lifts Is Known (Reference Table 1)

    Table 1 of Appendix 3 is the worksheet for calculating the 
accumulated trunnion RIN when the exact number of takeoffs and 
external load lifts is known.
    The RIN factor for each external load lift is twice that 
specified for each takeoff because two torque events are experienced 
during a typical external load lift.
    Using Table 1, calculate the accumulated RIN as follows:
    1. Enter the total number of takeoffs for the particular 
trunnion model/helicopter model combination in column (C).
    2. Multiply the value entered in column (C) by the RIN factor 
listed in column (D), and enter the result in column (E). This is 
the total accumulated RIN due to takeoffs.
    3. Enter the total number of external load lifts for the 
particular trunnion model/helicopter model combination in column 
(F).
    4. Multiply the value entered in column (F) by the RIN factor 
listed in column (G), and enter the result in column (H). This is 
the accumulated RIN due to external load lifts.
    5. Add the values from column (E) and column (H) and enter the 
result in column (I). This is the total accumulated RIN to-date for 
the trunnion for the particular trunnion model/helicopter model 
combination.
    6. Add the accumulated RIN subtotals for the various trunnion 
model/helicopter combinations in column (I) and enter the result in 
the space provided. This is the total accumulated RIN for the 
trunnion.

Calculation of RIN and Revised Hours TIS When Exact Number of Takeoffs 
and External Load Lifts Is Unknown (Reference Tables 2 and 3)

    Tables 2 and 3 of Appendix 3 are the worksheets for calculating 
the FACTORED flight hours and accumulated trunnion RIN when the 
exact number of takeoffs and external load lifts is unknown.
    Using Tables 2 and 3, calculate the accumulated trunnion RIN and 
revised hours TIS as follows:
    1. Enter the unfactored hours TIS for the particular trunnion 
model/helicopter model combination in column (C) of Table 2.
    2. Using service history for the trunnion, select the 
appropriate frequency of event hour factor from column (E) of Table 
2 based on the total combined number of takeoffs and external load 
lifts per hour shown in column (D).
    3. Multiply the value for unfactored hours TIS entered in column 
(C) by the appropriate value in column (E) for the frequency of 
event hour factor as determined in step 2. Enter the result in 
column (F) of Table 2. This is the total FACTORED flight hours for 
the particular trunnion model/helicopter model combination.
    4. Enter the value for FACTORED flight hours from column (F) of 
Table 2 into column (C) of Table 3.
    5. Using Table 3, multiply the value for FACTORED flight hours 
in column (C) by the appropriate RIN conversion factor listed in 
column (D), by the appropriate RIN adjustment factor in column (E), 
and enter the result in column (F). This is the accumulated RIN to-
date for the particular trunnion model/helicopter model combination.
    6. Add the accumulated RIN subtotals for the various trunnion 
model/helicopter model combinations in column (F) of Table 3 and 
enter the result in the space provided. This is the total 
accumulated RIN for the trunnion.
    7. Add the factored flight hour subtotals for the various 
trunnion model/helicopter model combinations as determined in steps 
1 through 4. This is the total revised hours TIS for the trunnion 
when the exact number of takeoffs and external load lifts is 
unknown.

Sample Trunnion Calculation

    Given the following known service history for the trunnion:
    Trunnion, P/N 204-011-105-001, was first purchased as a United 
States military surplus part with valid historical records. The 
trunnion had accumulated 550 hours military TIS on an Army UH-1H.
    The trunnion was first installed on a restricted category UH-1H 
former military helicopter (1100 T.O. hp SLS rating) for 450 hours 
TIS. It is known that the helicopter was used primarily for aerial 
surveying for the first 200 hours of operation. The exact number of 
takeoffs and external load lifts is unknown, but it is known that 
the helicopter averaged less than 16 takeoffs per hour with no 
external load lifts. It was subsequently used for repeated heavy 
lift operation for the next 250 hours of operation and averaged 
between 25 and 31 combined takeoffs and external load lifts per hour 
during this period of time.
    The trunnion was then removed and subsequently installed on a 
restricted category UH-1E former military helicopter (1100 T.O. hp 
SLS rating) for a total of 150 hours TIS with accurate records 
indicating that it experienced 100 takeoffs and 2,450 external load 
lifts.
    Calculate the FACTORED flight hours and total accumulated RIN 
for the trunnion as follows:

FACTORED Flight Hours and Accumulated RIN While Installed in U.S. 
Military Model UH-1H:

    Calculate FACTORED flight hours from Table 2 as follows:
FACTORED Flight Hours

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    = (unfactored hours TIS)  x  (frequency of event hour factor)
    = (column C)  x  (column E)
    = (550)  x  (1)
    = 550 hours

    Then using Table 3, calculate the accumulated RIN as follows:

Accumulated RIN
    = (FACTORED flight hours)  x  (RIN conversion factor)  x  (RIN 
adjustment factor)
    = (column C)  x  (column D)  x  (column E)
    = (550)  x  (20)  x  (1)

    = 11,000 RIN

FACTORED Flight Hours and Accumulated RIN While Installed in 
Restricted Category Model UH-1H

    Calculate FACTORED flight hours from Table 2 as follows:

FACTORED Flight Hours (for first 200 hours)
    = (unfactored hours TIS)  x  (frequency of event hour factor)
    = (column C)  x  (column E)
    = (200)  x  (1)
    = 200 hours

FACTORED Flight Hours (for next 250 hours)
    = (unfactored hours TIS)  x  (frequency of event hour factor)
    = (column C)  x  (column E)
    = (250)  x  (2)
    = 500 hours

    Then using Table 3, calculate the accumulated RIN as follows:

Accumulated RIN
    = (FACTORED flight hours)  x  (RIN conversion factor)  x  (RIN 
adjustment factor)
    = (column C)  x  (column D)  x  (column E)
    = (200)  x  (20)  x  (1) + (500)  x  (20)  x  (1)
    = 4,000 + 10,000

    = 14,000 RIN

FACTORED Flight Hours and Accumulated RIN While Installed in 
Restricted Category Model UH-1E

    Calculate the accumulated RIN from Table 1 and the given number 
of takeoffs and external load lifts as follows:

Accumulated RIN
    = (number of takeoffs  x  RIN factor per takeoff) + (number of 
external load lifts  x  RIN factor per external load lifts)
    = (column C)  x  (column D) + (column F)  x  (column G)
    = (100)  x  (1.5) + (2,450)  x  (3)

    = 7,500 RIN

Calculate the Total Accumulated RIN and Revised Hours TIS as 
follows

    The total accumulated RIN to-date for the trunnion is the sum of 
the subtotals from Tables 1 and 3.

Total Accumulated RIN
    = 11,000 + 14,000 + 7,500
    = 32,500

    The total FACTORED flight hours for the trunnion is the sum of 
the subtotals from Table 2.

Total FACTORED Flight Hours
    = 550 + 200 + 500
    = 1,250 hours

    The revised hours TIS to-date for the trunnion is the sum of the 
total FACTORED flight hours and the additional unfactored hours TIS 
for the trunnion when the exact number of takeoff and external load 
lifts is known.

Revised Hours TIS
    = 550 + 200 + 500 + 150
    = 1,250 + 150
    = 1,400 hours

    Both the total accumulated RIN and the revised hours TIS need to 
be determined and checked for exceeding the allowable life limits 
for the trunnion.
    The values for the sample problem are shown in Tables 1-3 for 
illustration purposes only.

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    Issued in Fort Worth, Texas, on September 12, 2001.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 01-23415 Filed 9-20-01; 8:45 am]
BILLING CODE 4910-13-C