FAA issues Emergency AD on CFM56-7B engines
Last Update: May 4, 2018 / 13:25:40 GMT/Zulu time
Incident Facts
Date of incident
Jan 1, 1970
Classification
News
This emergency AD was prompted by a recent event in which a Boeing Model 737-700 airplane powered by CFM56-7B model engines experienced an engine failure due to a fractured fan blade, resulting in the engine inlet cowl disintegrating. Debris penetrated the fuselage causing a loss of pressurization and prompting an emergency descent. Although the airplane landed safely, there was one passenger fatality. Fan blade failure due to cracking, if not addressed, could result in an engine in-flight shutdown (IFSD), uncontained release of debris, damage to the engine, damage to the airplane, and possible airplane decompression.
See Accident: Southwest B737 near Philadelphia on Apr 17th 2018, uncontained engine failure takes out passenger window for details of the accident referenced by the EAD.
The FAA reports that CFM Service Bulletin CFM56-7B S/B 72-1033 dated April 20 (SB) 2018 provides action for engines with fewer than 30,000 flight cycles, however, the EAD affects engines with 30,000 or more flight cycles only. In addition the SB requires reporting of the inspection results, the EAD does not require reporting. Otherwise there is no difference between the SB and the EAD.
The EAD requires all 24 fan blade dovetail concave and convex sides of CFM56-7B engines to undergo ultrasonic inspection to detect cracking within 20 days. If any unservicable fan blades are being found, they are to be removed from service before further flight.
On May 2nd 2018 the FAA released another Airworthiness Directive 2018-09-10 that based on the same reasoning as the previously released EAD introduces a more generic inspection scheme requiring inspections of fan blades as follows:
(1) Perform an ultrasonic inspection (USI) or eddy current inspection (ECI) of the concave and convex sides of the fan blade dovetail as follows:
(i) Perform an initial inspection on each fan blade before the fan blade accumulates 20,000 cycles since new, or within 113 days from the effective date of this AD, whichever occurs later.
(ii) If cycles since new on a fan blade is unknown, perform an initial inspection within 113 days from the effective date of this AD.
(iii) Thereafter, repeat this inspection no later than 3,000 cycles since the last inspection.
(iv) Use the Accomplishment Instructions, paragraphs 3.A.(3)(a) through (i), of CFM Service Bulletin (SB) CFM56-7B S/B 72-1033, dated April 20, 2018, to perform a USI or use the instructions in subtask 72-21-01-220-091, of task 72-21-01-200-001, from CFM CFM56-7B Engine Shop Manual, Revision 57, dated January 15, 2018, to perform an ECI.
(2) If any unserviceable indication, as specified in the applicable service information in paragraph (g)(1)(iv) of this AD, is found during the inspections required by paragraph (g) of this AD, replace the fan blade before further flight with a part eligible for installation.
The FAA estimates that 3,716 engines under US registration will be affected by the AD.
Incident Facts
Date of incident
Jan 1, 1970
Classification
News
This article is published under license from Avherald.com. © of text by Avherald.com.
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