[Federal Register Volume 66, Number 209 (Monday, October 29, 2001)]
[Rules and Regulations]
[Pages 54418-54421]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-26965]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-SW-28-AD; Amendment 39-12479; AD 2001-22-01]
RIN 2120-AA64


Airworthiness Directives; Enstrom Helicopter Corporation Model F-
28,     F-28A, F-28C, F-28F, 280, 280C, 280F and 280FX Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD) for Enstrom Helicopter Corporation (EHC) Model F-28, F-28A, and 
280 helicopters. That AD currently requires inspecting the main rotor 
shaft (shaft) for a crack or other evidence of damage until 
appropriately modifying or replacing the shaft with an airworthy shaft 
at specified time intervals. This amendment adds EHC Model F-28C, F-
28F, 280C, 280F, and 280FX helicopters and establishes life limits 
after which all unmodified shafts must be retired. This amendment 
requires determining the radius of the shaft fillet, certain visual and 
dye-penetrant inspections before further flight, and replacing certain 
main rotor transmissions. This amendment is prompted by the failure of 
a shaft on an EHC Model F-28A helicopter due to a fatigue crack. The 
actions specified by this AD are intended to prevent shaft failure and 
subsequent loss of control of the helicopter.

DATES: Effective November 13, 2001.
    Comments for inclusion in the Rules Docket must be received on or 
before December 28, 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-28-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].

FOR FURTHER INFORMATION CONTACT: Joseph McGarvey, Fatigue Specialist, 
FAA, Chicago Aircraft Certification Office, Airframe and Administrative 
Branch, 2300 East Devon Ave., Des Plaines, Illinois 60018, telephone 
(847) 294-7136, fax (847) 294-7834.

SUPPLEMENTARY INFORMATION: On August 16, 1976, the FAA issued AD 76-17-
08, Amendment 39-2700 (41 FR 36015, August 26, 1976). On September 16, 
1976, the FAA revised that AD issuing AD 76-17-08 R1, Amendment 39-3043 
(42 FR 51563, September 29, 1977), for EHC Model F-28, F-28A, and 280 
helicopters to establish service time limits after which all unmodified 
shafts must be replaced. That AD was prompted by FAA's determination, 
after a review of the service experience, that shaft crack sites may be 
introduced by allowing the shafts to remain in service for extended 
periods without modification. That condition, if not corrected, could 
result in shaft failure and subsequent loss of control of the 
helicopter.
    Since the issuance of that AD, EHC has issued Service Directive 
Bulletin No. 0094, Revision 1, dated May 31, 2001, specifying certain 
inspections for a crack in certain shafts due to failure of a shaft on 
an EHC Model F-28A helicopter.
    The FAA and the National Transportation Safety Board (NTSB) 
investigated the accident involving the failure of a shaft on the EHC 
Model F28A helicopter. The shaft was designed with a small upper fillet 
radius of 0.13 inch and failed due to a fatigue crack. Such a shaft 
design causes a high stress concentration. That, coupled with the 
occurrence of more frequent than anticipated high flight load 
conditions, can accelerate the development of fatigue cracks. 
Preliminary investigation revealed that the shaft installed in the 
transmission, P/N 28-13101-1-R, failed because of a fatigue crack in 
the fillet area of the shaft directly beneath the main rotor hub. The 
FAA concluded, based on its investigation and after reviewing NTSB 
Report 01-052, dated April 13, 2001, that an inspection should be made 
of such shafts for cracks before further flight. The FAA determined 
that since inspections for cracks are imprecise and detection of all 
existing cracks is uncertain, a shaft with a small radius fillet should 
be replaced with an airworthy shaft with a large radius fillet on 
certain model helicopters within 300 hours time-in-service (TIS).
    We have identified an unsafe condition that is likely to exist or 
develop on other helicopters of the same type designs. This AD 
supersedes AD 76-17-08 and 76-17-08 R1 for EHC Model F-28, F-28A, and 
280 helicopters to add Model F-28C, F-28F, 280C, 280F, and 280FX 
helicopters, to require the following:

     Before further flight, determine the transmission P/N and 
the radius of the shaft fillet.
     For certain models, replace any transmission having a 
shaft with a small radius fillet with an airworthy transmission before 
further flight.
     For certain other models, replace the transmission having 
a small radius shaft fillet that is not P/N 28-13101-1 or -1-R with an 
airworthy transmission before further flight.
     For certain models with transmission, P/N 28-13101-1 or -
1-R, having a small radius shaft fillet installed:
     Before further flight and at recurring intervals, visually 
inspect the shaft for a crack. If a crack is suspected,

[[Page 54419]]

dye penetrant inspect the shaft before further flight.
     Within 5 hours TIS and thereafter at specified intervals, 
dye penetrant inspect the shaft for a crack, and polish out specified 
nicks and scratches.
     If a crack is found or if a nick or scratch exceeds a 
specified limit, replace the transmission with an airworthy 
transmission before further flight.
     Within 300 hours TIS or at the next transmission overhaul 
after the effective date of this AD, whichever occurs first, replace 
transmission, P/N 28-13101-1 or -1-R, with an airworthy transmission 
having a large radius shaft fillet.

Installing a transmission with a shaft, P/N 28-13104-1-1 or -1-R, 
Revision K, L, M, N, P, R, or S or P/N 28-13140-1 or -1-R, any 
revision, is terminating action for the requirements of this AD.
    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, 
determining the transmission P/N and the shaft fillet radius, 
conducting the required inspections, and replacing any unairworthy 
transmission with an airworthy transmission are required before further 
flight, and this AD must be issued immediately.
    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.
    The FAA estimates that 17 helicopters will be affected by this AD, 
that it will take approximately 1.4 work hours to accomplish the 
inspections and that the average labor rate is $60 per work hour. A 
replacement shaft will cost approximately $3,000 per helicopter, and 
overhauling the transmission and replacing the shaft will cost 
approximately $12,000. Based on these figures, the total cost impact of 
the AD on U.S. operators is estimated to be $256,428 assuming 
replacement of the transmission after an inspection of every helicopter 
affected by this AD.

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 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 mailed 
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. 2001-SW-28-AD.'' The postcard will be date 
stamped and returned to the commenter.
    The regulations adopted herein will 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 final rule does not have federalism 
implications under Executive Order 13132.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, may be obtained from the Rules Docket at the 
location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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

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


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing Amendment 39-2700 (41 FR 
36015, August 26, 1976) and Amendment 39-3043 (42 FR 51563, September 
29, 1977), and by adding a new airworthiness directive (AD), Amendment 
39-12479, to read as follows:

2001-22-01  Enstrom Helicopter Corporation: Amendment 39-12479. 
Docket No. 2001-SW-28-AD. Supersedes AD 76-17-08, Amendment 39-2700, 
and AD 76-17-08 R1, Amendment 39-3043, Docket 76-GL-15.
    Applicability: Model F-28, F-28A, F-28C, F-28F, 280, 280C, 280F, 
and 280FX helicopters, 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 (e) 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.
    To prevent main rotor shaft (shaft) failure and subsequent loss 
of control of the helicopter, accomplish the following:
    (a) Before further flight, determine the part number (P/N) of 
the main rotor transmission (transmission) and the radius of the 
upper fillet of the shaft (see Figure 1).

[[Page 54420]]

[GRAPHIC] [TIFF OMITTED] TR29OC01.007

    (b) For EHC Model F-28C, F-28F, 280C, 280F, and 280FX 
helicopters, before further flight, replace any transmission having 
a small radius shaft fillet with an airworthy transmission having a 
large radius shaft fillet as specified in Table 1 of this AD.
    (c) For EHC Model F-28, F-28A and 280 helicopters:
    (1) If the transmission has a shaft with a small radius fillet 
and the transmission P/N is not listed in Table 1, before further 
flight, replace the transmission with an airworthy transmission 
specified in Table 1 of this AD.

                                                      Table 1.--Main Rotor Transmission Effectivity
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                                                                                                          Models effectivity
                                                                   Qty per  ----------------------------------------------------------------------------
            Description                    Transmission P/N          assy     F-28, F-
                                                                                28A        280       F-28C       280C      F-28F       280F      280FX
--------------------------------------------------------------------------------------------------------------------------------------------------------
(i) Main Rotor Gearbox (0.13 in.     28-13101-1 or -1-R.........         1          X          X
 radius fillet M/R shaft).
(ii) Main Rotor Gearbox (0.5 in.     28-13101-5 or -5-R*........         1          X          X          X          X
 radius fillet M/R shaft).
(iii) Main Rotor Gearbox (0.5 in.    28-13101-8 or -8-R.........         1          X          X          X          X          X          X
 radius fillet M/R shaft).
(iv) Main Rotor Gearbox (0.5 in.     28-13101-9 or -9-R.........         1          X          X          X          X          X          X
 radius fillet M/R shaft).
(v) Main Rotor Gearbox (0.5 in.      28-13101-101 or -101-R*....         1          X          X          X          X
 radius fillet, heavy M/R shaft).
(vi) Main Rotor Gearbox (0.5 in.     28-13170-1 or -1-R.........         1          X          X          X          X          X          X
 radius fillet M/R shaft).
(vii) Main Rotor Gearbox (0.5 in.    28-13170-3 or -3-R*........         1          X          X          X          X          X          X
 radius fillet M/R shaft).
(viii) Main Rotor Gearbox (0.5 in.   28-13170-7 or -7-R*........         1          X          X          X          X          X          X
 radius fillet, heavy M/R shaft).
(ix) Main Rotor Gearbox (0.5 in.     28-13101-9 or -9-R*........         1   .........  .........  .........  .........         X   .........         X
 radius fillet, heavy M/R shaft,
 magnetic chip detector, and low
 rotor RPM pick-up).
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Note: ``-R'' indicates an overhauled transmission.
* Transmissions currently available from EHC.


[[Page 54421]]

    (2) If the installed transmission is P/N 28-13101-1 or -1-R and 
has a small radius shaft, before further flight and thereafter at 
intervals not to exceed 25 hours TIS, visually inspect each 
transmission for a crack in the shaft upper fillet using a 10X or 
higher magnifying glass.
    (i) If a crack is suspected, before further flight, a level II 
nondestructive inspector must dye-penetrant inspect the shaft using 
materials approved by MIL-I-25135.
    (ii) If the shaft is cracked, before further flight, replace the 
transmission with an airworthy transmission having a large radius 
shaft fillet.
    (3) If the transmission is P/N 28-13101-1 or -1-R, within 5 
hours TIS, and thereafter at intervals not to exceed 100 hours TIS:
    (i) Dye-penetrant inspect the shaft upper fillet for a crack, a 
nick, or a scratch.
    (ii) Polish out nicks or scratches less than 0.005-inch deep.
    (iii) If the shaft is cracked or has a nick or scratch 0.005 
inch or more deep, replace the transmission with an airworthy 
transmission having a large radius shaft fillet before further 
flight.
    (4) Within 300 hours TIS or at the next overhaul after the 
effective date of this AD, whichever occurs first, replace 
transmission, P/N 28-13101-1 or -1-R, with an airworthy transmission 
having a large radius shaft fillet.
    (d) Installing an airworthy transmission with a shaft, P/N 28-
13104-1 or -1-R, Revision K, L, M, N, P, R or S, or P/N 28-13140-1 
or -1-R, is terminating action for the requirements of this AD.

    Note 2: Enstrom Helicopter Corporation Service Directive 
Bulletin No. 0094, Revision 1, dated May 31, 2001, pertains to the 
subjet of this AD.

    (e) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Chicago, Aircraft Certification 
Office (ACO), FAA. Operators shall submit their requests through an 
FAA Principal Maintenance Inspector, who may concur or comment and 
then send it to the Manager, Chicago ACO.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Chicago ACO.

    (f) 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 provided an 
inspection in accordance with paragraph (c)(2) of this AD reveals no 
crack in the shaft.
    (g) This amendment becomes effective on November 13, 2001.

    Issued in Fort Worth, Texas, on October 16, 2001.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 01-26965 Filed 10-26-01; 8:45 am]
BILLING CODE 4910-13-U