AD 2004-16-15 R1

AD Final Rules - 2004-16-15 R1.pdf
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AD Number:
2004-16-15 R1
Document Type:
AD Final Rules
Docket Number:
FAA-2004-18850
Subject Heading:
Airworthiness Directives; Eurocopter France Model AS-365N2, AS 365 N3, EC 155B, EC155B1, SA-365N, N1...Show more
Subject:
Main gearbox (MGB) base plate
Status:
Current
Citation:
(Federal Register: July 26, 2006 (Volume 71, Number 143))
Citation Publish Date:
07/26/2006
Effective Date:
08/30/2006
Make:
Airbus Helicopters
Model:
AS-365N2 | AS-365N3 | EC 155B | EC155B1 | SA-365N | SA-365N1 | SA-366G1
Product Type:
Aircraft
Product Subtype:
Rotorcraft
Affected AD:
Superseded AD:
2004-16-15
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39
Comments:
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1


[Federal Register: July 26, 2006 (Volume 71, Number 143)]


[Rules and Regulations]


[Page 42254-42258]


From the Federal Register Online via GPO Access [wais.access.gpo.gov]


[DOCID:fr26jy06-5]


–––––––––––––––––––––––––––––––––––-


DEPARTMENT OF TRANSPORTATION


Federal Aviation Administration


14 CFR Part 39


[Docket No. FAA-2004-18850; Directorate Identifier 2004-SW-19-AD; Amendment 39-14694;


AD 2004-16-15 R1]


RIN 2120-AA64


Airworthiness Directives; Eurocopter France Model AS-365N2, AS 365 N3, EC 155B,


EC155B1, SA-365N, N1, and SA-366G1 Helicopters


AGENCY:
 
Federal Aviation Administration, DOT.


ACTION:
 
Final rule.


–––––––––––––––––––––––––––––––––––-


SUMMARY:
 
This amendment revises an existing airworthiness directive (AD) for Eurocopter


France (Eurocopter) Model AS-365N2, AS 365 N3, EC 155B, EC155B1, SA-365N, N1, and SA-


366G1 helicopters that currently requires inspecting the main gearbox (MGB) base plate for a crack


and replacing the MGB if a crack is found. This amendment increases the time intervals for


inspecting the MGB base plate and includes minor editorial changes throughout the AD. This


amendment is prompted by crack growth tests that indicate that the inspection intervals can be


increased without affecting safety. The actions specified by this AD are intended to detect a crack in


an MGB base plate and prevent failure of one of the MGB attachment points to the frame, which


could result in severe vibration and subsequent loss of control of the helicopter.


DATES:
 
Effective August 30, 2006.


ADDRESSES:
 
You may get the service information identified in this AD from American Eurocopter


Corporation, 2701 Forum Drive, Grand Prairie, Texas 75053-4005, telephone (972) 641-3460, fax


(972) 641-3527.


Examining the Docket:
 
You may examine the docket that contains this AD, any comments, and


other information on the Internet at http://dms.dot.gov, or at the Docket Management System (DMS),


U.S. Department of Transportation, 400 Seventh Street, SW., Room PL-401, on the plaza level of the


Nassif Building, Washington, DC.


FOR FURTHER INFORMATION CONTACT:
 
Ed Cuevas, Aviation Safety Engineer, FAA,


Rotorcraft Directorate, Safety Management Group, Fort Worth, Texas 76193-0111, telephone (817)


222-5355, fax (817) 222-5961.


SUPPLEMENTARY INFORMATION:
 
On August 4, 2004, we issued AD 2004-16-15,


Amendment 39-13771 (69 FR 51358, August 19, 2004), to require visually inspecting the MGB for a
2


crack in the MGB base plate, part number (P/N) 366A32-1062-03 or P/N 366A32-1062-06, close to


the attachment hole using a 10x or higher magnifying glass. Stripping paint from the inspection area


is also required, but only before the initial inspection. That action was prompted by the discovery of a


crack in the MGB base plate of an MGB installed in a Model AS-365 N2 helicopter. The crack was


located very close to the attachment points of one of the laminated pads, and it propagated to the


inside of the MGB base plate and then continued into the MGB casing. That condition, if not


detected, could result in failure of one of the MGB attachment points to the frame, which could result


in severe vibration and subsequent loss of control of the helicopter.


When we issued AD 2004-16-15, the cause of crack in the MGB base plate was still under


investigation; therefore, we considered the previously issued AD to be interim action until the cause


of the crack could be determined. The cause of the crack is still under investigation. However, since


issuing AD 2004-16-15, crack growth tests have shown that the inspection intervals can be increased


without affecting safety. We made this determination after Eurocopter conducted crack growth


testing in laboratory bench tests. A cracked base plate was loaded with an alternating torque to


simulate flight loading and cycles. Crack propagation speed was measured and assessed over a longer


duration than the initial inspection interval and this resulted in extending the inspection intervals. The


first inspection interval was determined using crack striations, which was a quick and conservative


method used to ensure airworthiness and allow for timely issuance of service information by the


manufacturer. Based on this additional information, a proposal to amend 14 CFR part 39 by revising


AD 2004-16-15, Amendment 39-13771 (69 FR 51358, August 19, 2004), for the specified


Eurocopter model helicopters, was published in the Federal Register on May 2, 2006 (71 FR 25789).


That action proposed to increase the time intervals between each required inspection and proposed to


include minor editorial changes in the AD.


The Direction Générale de L'Aviation Civile (DGAC), the airworthiness authority for France,


notified the FAA that an unsafe condition may exist on Eurocopter Model SA 365N, N1, SA 366 G1,


AS 365 N2, N3, EC 155 B, and B1 helicopters, all serial numbers. The DGAC advises that a crack


was detected in the MGB base plate of an AS 365 N2 helicopter. The crack was detected in the MGB


base plate web, very close to the attachment of one of the laminated pads, and runs to the inside of


the MGB base plate and then on the MGB casing. In time, the growth of the crack may lead to the


loss of the transfer of rotor torque to the rotorcraft structure.


Eurocopter has issued Alert Service Bulletin (ASB) No. 05.00.45 for Model AS365 N, N1, N2,


and N3 helicopters; ASB No. 05.29 for Model SA366 G1 helicopters; and ASB No. 05A005 for


Model EC155 B and B1 helicopters. All of the ASBs are dated November 8, 2004 and supersede


previously issued Eurocopter Alert Telex No. 05.00.45, No. 05.29, and No. 05A005, all dated


February 5, 2004. The ASBs specify the same actions as the alert telexes–visually inspecting the


MGB base plate for the absence of cracks, using a 10x magnifying glass to facilitate the crack


inspection, and, if in doubt about the existence of a crack, inspecting for a crack using a dye-


penetrant crack detection inspection. However, for the Eurocopter Model AS365 N, N1, N2, N3, and


SA366 G1 helicopters, the 15-flying hour check for the MGB base plate that is specified in the alert


telexes is replaced with check intervals not to exceed 55 flying hours. For the EC155 B and B1


helicopters, the check after the last flight of each day and without exceeding a 9-flying hour check


interval is replaced with check intervals not to exceed 15 flying hours.


The DGAC classified ASB Nos. 05.00.45, 05.29, and 05A005 as mandatory and issued AD No.


F-2004-023 R1, dated November 24, 2004, to ensure the continued airworthiness of these helicopters


in France.


These helicopter models are manufactured in France and are type certificated for operation in the


United States under the provisions of 14 CFR 21.29 and the applicable bilateral agreement. Pursuant


to the applicable bilateral agreement, the DGAC has kept the FAA informed of the situation


described above. We have examined the findings of the DGAC, reviewed all available information,


and determined that AD action is necessary for products of these type designs that are certificated for


operation in the United States.