AD 94-09-07

This amendment adopts a new airworthiness directive (AD), applicable to certain Teledyne Continental Motors (TCM) IO-346, IO-520, and IO-550 series piston engines, that requires initial and repetitive inspections of the engine mount brackets for cracks, and if found cracked, replacement with improved design engine mount brackets. All engine mount brackets require replacement with improved design engine mount brackets at the next engine removal after the effective date of this AD. This amendment is prompted by reports of cracks in engine mount brackets on engines that have completed at least one overhaul cycle. The actions specified by this AD are intended to prevent engine separation from the aircraft due to cracks in the engine mount brackets.

Final rule.

94-09-07 Teledyne Continental Motors: Amendment 39-8896. Docket 92-ANE-50.

Applicability: Teledyne Continental Motors (TCM) engine models IO-346A, IO-346B, IO-520C, IO-520CB, and IO-550C; rebuilt engine model IO-520C with serial numbers (S/N) 287051-R and lower; rebuilt engine model IO-520CB with S/N 282226-R and lower; rebuilt engine model IO-550C with S/N 271742-R and lower; and all factory overhauled IO-520C, IO-520CB, and IO-550C engines with a build date prior to August 6, 1992. These engines are installed on but not limited to Beech model A23, A23A, 95-C55, 95-C55A, D55, D55A, E55, E55A, 58, and 58A airplanes.

Compliance: Required as indicated, unless accomplished previously.

To prevent engine separation from the aircraft due to cracks in the engine mount brackets, accomplish the following:

(a) For engines with engine mount brackets that have completed at least one engine overhaul cycle, or have accumulated 2,500 or more hours time in service (TIS) onthe effective date of this AD, inspect the lower left engine mount bracket, Part Number (P/N) 630695, for cracks using the dye penetrant techniques specified in this paragraph and in accordance with TCM Service Bulletin (SB) No. M92-13, dated September 4, 1992, within the next 50 hours TIS after the effective date of this AD.

(1) Perform the dye penetrant inspection as follows: NOTE: Military Specification MIL-I-6866 and American Society of Testing Materials specifications ASTM E1417-93 and E165-9 contain additional information on dye penetrant inspection processes.

(i) Preparation: clean and dry all parts in such a manner as to leave the surfaces free from grease, oil, soaps, alkalies, and other substances which would interfere with inspection. Vapor degreasing is generally suitable for this purpose.

(ii) Penetrant Application Procedure: after preparation, spray or brush the parts with the penetrant, and allow to stand for not less than 5 minutes. The effectiveness of the penetrant increases if left standing for a longer time, as the penetrant will reach finer discontinuities.

(iii) Penetrant Cleaning: clean the parts thoroughly using a medium which will remove penetrant from the surfaces of parts; wash with water when the penetrant is water soluble. When other than water soluble penetrants are used, the penetrant shall be removed with a suitable cleaner. Avoid excessive cleaning which would remove the penetrant from discontinuities.

(iv) Drying: dry the parts as thoroughly as possible. Drying of parts may be accomplished by evaporation at room temperature or by placing the parts in a circulating warm air oven or in the air stream of a hot air dryer. Avoid excessive drying time or drying temperatures above 75oC (165oF) to prevent excessive evaporation of the penetrant. If heat is used for drying parts, cool parts to approximately 50oC (120oF) before proceeding to the developing procedure.

(v) Developing: apply the developer to the dry parts as lightly and as evenly as possible, using as thin a coating of developer as is possible. A translucent film is adequate. Mix wet developer by agitation immediately prior to applying it. After applying the developer, take care that no penetrant indication is disturbed or obliterated in subsequent handling.

(vi) Examination: examine the developed penetrant indications in accordance with the dye penetrant manufacturer's instructions. Examine parts for indications of discontinuities open to the surface.

(vii) Final cleaning: clean the parts following the inspection to remove penetrant and developer.

NOTE 1: Caution: because of differences among penetrants, take care to ensure that the final cleaner, the penetrant, the penetrant remover, and the developer are suitable for use with each other.

NOTE 2: Caution: all penetrant materials should be kept as free from moisture as possible.

NOTE 3: Caution: most penetrants, cleaning agents, and developer suspensions are low flash point material; use caution to prevent fires.

(2) If no crack is detected, inspect in accordance with paragraph (a) of this AD at intervals not to exceed 500 hours TIS since the last inspection.

(3) If a crack is detected, prior to further flight replace both the lower left engine mount bracket, P/N 630695, and lower right engine mount bracket, P/N 630694, with improved design engine mount brackets, P/N 653306 and 653305, respectively.

(b) For all engines, replace both the lower left engine mount bracket, P/N 630695, and lower right engine mount bracket, P/N 630694, with improved design engine mount brackets, P/N 653306 and 653305, respectively, at the next engine removal after the effective date of this AD.

(c) Installation of the improved design engine mount brackets, P/N 653306 and 653305, constitutes terminating action to the inspection requirements of this AD.

(d) 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, Atlanta Aircraft Certification Office. The request should be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Atlanta Aircraft Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Atlanta Aircraft Certification Office.

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

(f) The inspection and replacement shall be done in accordance with the following service bulletin:

Document No.
Pages
Revision
Date
TCM SB M92-13
1-2
Original
September 4, 1992
Total Pages: 2.

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Teledyne Continental Motors, P.O. Box 90, Mobile, AL 36601; telephone (205) 438-3411. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street NW., suite 700, Washington, DC.

(g) This amendment becomes effective on July 5, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to Teledyne Continental Motors (TCM) IO-346, IO-520, and IO-550 series piston engines was published in the Federal Register on October 20, 1993 (58 FR 54072). That action proposed to require initial and repetitive dye penetrant inspections for cracks in certain lower left engine mount brackets, Part Number (P/N) 630695. If the lower left engine mount bracket is found cracked, that proposed rule would require replacing both the lower left and lower right engine mount brackets with improved design engine mount brackets, P/N 653306 and 653305, respectively. If a crack is not detected, the lower left engine mount bracket would require repetitive inspections at intervals not to exceed 500 hours time in service (TIS) until the next engine removal, at which time engine mount brackets, P/N 630694 and 630695, would be replaced with improveddesign engine mount brackets, P/N 653306 and 653305. Installation of these improved design engine mount brackets would constitute terminating action to the inspection requirements of that AD. The actions would be required to be accomplished in accordance with TCM Service Bulletin (SB) No. M92-13, dated September 4, 1992.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the one comment received.

The commenter supports the proposed rule but states that the interval for the repetitive inspections should be reduced from 500 hours TIS to 100 hours TIS. The commenter states that if the bracket is found broken, the airframe engine mount and surrounding areas should be inspected for damage and the upper brackets and all bolts and nuts should be replaced as they may be overstressed. The commenter further states that the pilot should visually inspect the brackets on each preflight.

The FAA does not concur with the recommendation to reduce the repetitive inspection interval to 100 hours TIS. Data provided from the manufacturer indicates that the repetitive inspection interval of 500 hours TIS is sufficient once the initial inspection is satisfactorily completed.

The FAA does not concur with the commenter's recommendation to inspect the airframe engine mount and surrounding areas for damage and to replace all bolts and nuts if the bottom brackets are found broken. Once the bottom brackets are broken, there is essentially no load being transmitted to the lower airframe structure. In addition, a structural analysis of the bolt strength indicates that with only the two upper mounts securing the engine, safety factors exceed required values for normal category "g" loading. Therefore, none of the bolts and nuts should be overstressed.

The FAA does not concur with the commenter's recommendation to require the pilot to visually inspect the brackets on each preflight. Based on the data presented above, the FAA has determined that it is not necessary to inspect the brackets on each preflight.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

There are approximately 9,750 TCM IO-346, IO-520, and IO-550 series piston engines of the affected design in the worldwide fleet. The FAA estimates that 8,300 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per inspection, and if the engine mount brackets must be replaced, an additional 4 work hours will be required. The average labor rate is $55 per work hour. Required parts will cost approximately $320 per engine. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $5,395,000.

The regulations adopted herein will not have substantial directeffects 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.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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 14 CFR part 39 of the Federal Aviation Regulations as follows:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new airworthiness directive: