# Aircraft Industries Mandatory Bulletin L23/053a ## Copies (2) Copies the FAA filed in AD dockets on regulations.gov, newest revision first. A newer revision may exist. - No revision named ("U.S. DOT/FAA - Service Bulletin"), 4 pages: PDF https://openairdocs.org/files/sha256/c1/32/c13252d69f1bf8348bdfab0d9c31200efed6955da3bc53a3a05850a174018406; text https://openairdocs.org/service-documents/aircraft-industries/l23-053a/file/c13252d69f1b.md. Rights: © Aircraft Industries. Filed by the FAA in regulations.gov docket FAA-2011-0053; AD 2011-02-08 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - No revision named ("U.S. DOT/FAA - Service Bulletin (5)"), 5 pages: PDF https://openairdocs.org/files/sha256/13/08/130863e81c02532e015297adb2a84b270535549c87e8b7d3ed9a074bda13e337; text https://openairdocs.org/service-documents/aircraft-industries/l23-053a/file/130863e81c02.md. Rights: © Aircraft Industries. Filed by the FAA in regulations.gov docket FAA-2011-0053; AD 2011-02-08 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. ## Details - Manufacturer: [Aircraft Industries](https://openairdocs.org/service-documents/aircraft-industries.md) - Type: Service bulletin (Mandatory Bulletin) - Number: L23/053a - Page: https://openairdocs.org/service-documents/aircraft-industries/l23-053a ## ADs that cite it (1) (OpenAirDocs) Newest first, with the revision each names, as OpenAirDocs read it from the AD's text. - [AD 2011-02-08](https://openairdocs.org/ad/2011-02-08.md), effective Feb 14, 2011: No revision named ## Text (4 pages) No revision named, the newest copy. Rights: © Aircraft Industries. Filed by the FAA in regulations.gov docket FAA-2011-0053; AD 2011-02-08 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. This text is OCR from a scan. OCR can misread letters and numbers. Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 (OCR) LET Aircraft Industries MANDATORY BULLETIN MB No.: L23/053a Concerns: All L23 Super-Blanik sailplanes. Subject: Inspection of welded bracket (Drwg. No. A730 420N) located on the fin. Reason: Appearance of cracks on the bracket. To be accomplished by: Immediately after the bulletin receiving. To be performed by: ICAO, Annex 1 AML Holder with L23 Type Qualification. Costs to be covered by: Operator. Necessary material to be delivered by: No material required. Bulletin becomes effective: On the date of its issue. Total No. of sheets: Miroslav Pešák Chief Designer The technical content of this document is approved under the autority of DOA Nr. EASA.21J.119. December 14, 2010 Q 0501 PT. 2 Aircraft Industries, a.s., 686 04 Kunovice, Czech Republic, phone: +420 572 817 660, fax: +420 572 816 112, e-mail: ots@let.cz ### Page 2 (OCR) A. WORKING PROCEDURE 1. Preparatory works • Remove the horizontal tail assembly of the sailplane according to the Maintenance Manual procedure 55-10-00, page No. 401. 2. Bracket check on the fin • Checked area: weld in sleeves areas with special focus to the critical areas marked on the figure in part C of this bulletin. • Perform the check by means of magnifier (6 times magnifying). • Admissibility criteria: No cracks in checked area of the bracket are admissible. • If no cracks are present on the checked bracket, perform record in the Airframe Logbook according to the part I. • If cracks has been detected on the checked bracket, the saiplane further operation is prohibited. Perform replacement of the damaged bracket according to the IB L23/054b. CAUTION In case of cracks detection, send the bracket to the sailplane produ- cer together with basic data of the saiplane (registration mark, S/N, total flight hours and number of take-offs since the sailplane has been put into the operation). 3. Finishing works • Install the horizontal tail assembly on the sailplane according to the Maintenance Manual procedure 55-10-00, page No. 401. B. MATERIAL REQUIRED Not required. L23/053a Page: 2 Pages: 4 ### Page 3 (OCR) C. ILLUSTRATED PART Detail A Critical area BRACKET Detail A BRACKET D. DOCUMENTATION REQUIRED Valid L23 Super-Blanik Maintenance Manual. E. TOOLS REQUIRED Magnifier 6 times magnifying. F. SPARE PARTS IN OPERATION Not affected. G. SAILPLANE MASS Not affected. H. OPERATIONAL DOCUMENTATION Not affected. L23/053a Page: 3 Pages: 4 ### Page 4 (OCR) 1. RECORD IN AIRFRAME LOGBOOK AFTER BULLETIN IMPLEMENTATION Check of the welded bracket for potential cracks appearance has been perfomed according to the MB L23/053a. Identified status: • The bracket A730 420N without defects. The sailplane is released into operation. or • Cracks found on the bracket A730 420N. The sailplane is grounded till the IB L23/054b performance. Date:. Carried out by: .... (legible signature of authorized worker) L23/053a Page: 4 Pages: 4 --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain, except the copies of manufacturers’ service documents, which belong to their rights holders.