# Dassault Service Bulletin F20-676: Revision 1 - Rights: © Dassault Aviation. Filed by the FAA in regulations.gov docket FAA-2017-0908; AD 2018-07-07 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - Document: [Dassault Service Bulletin F20-676](https://openairdocs.org/service-documents/dassault/f20-676.md) - Title as filed: SB F20-676 R1 - Pages: 9 - PDF: https://openairdocs.org/files/sha256/bc/c4/bcc4122fe89cec336a737cc42325751f9ae20c8a17abc02afcf15d0e9cad33f5 - Page: https://openairdocs.org/service-documents/dassault/f20-676/file/bcc4122fe89c ## Text 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) DASSAULT SERVICE BULLETIN IATION FALCON 20 No 676 DECEMBER 23, 1981 REVISION 1, MARCH 4, 1998 ATA 32 - 74 LANDING GEAR LANDING GEAR CONTROL HYDRAULIC PRESSURE MAINTAINED WHEN THE LANDING GEAR IS EXTENDED Copyright © 1981 by Dassault Aviation. All rights reserved. No part of this work may be reproduced or copied in any form or by any means without written permission of Dassault Aviation. FALCON CUSTOMER SUPPORT TEL. 33(0)1.40.83.27.12 TELEFAX 33(0)1.40.83.98.96 TELEX 632633F - FRANCE «NASSAUI T AVIATION Proprietarv Data" ### Page 2 (OCR) DASSAULT SERVICE BULLETIN AVIATION FALCON 20 F20-676 LANDING GEAR LANDING GEAR CONTROL HYDRAULIC PRESSURE MAINTAINED WHEN THE LANDING GEAR IS EXTENDED INITIAL ISSUANCE Date: December 23, 1981 List of effective pages: 1 to 7. COMPLETE ISSUANCE: REVISION 1 Date: March 4, 1998 List of effective pages: 1 to 7. List of modified pages: 1 to 6. REASON: The compliance which was optional becomes recommended. The electrical material is proposed in a modification kit instead of local procurement. This revision has no effect on aircraft complied with the initial issuance of this Service Bulletin. F20-32-74 "DASSAULT AVIATION Proprietary Data" ### Page 3 (OCR) DASSAULT SERVICE BULLETIN AVIATION FALCON 20 F20-676 LANDING GEAR LANDING GEAR CONTROL HYDRAULIC PRESSURE MAINTAINED WHEN THE LANDING GEAR IS EXTENDED 1 . PLANNING INFORMATION A. EFFECTIVITY This Service Bulletin is applicable to FAN JET FALCON Basic and Series D, E, F, G and MYSTERE-FALCON 20-C5, D5, E5 and F5 aircraft, except serial numbers 478 and 485 which have been modified on production line. It covers DASSAULT AVIATION modification F20 M2434 which has been approved by the D.G.A.C. B. REASON (1) To obtain a safier down locking of the landing gear by maintaining the hydraulic pressure on the telescopic bars once the landing gear is extended and down-latched. (2) To prevent pressure surges in the telescopic bars upon engine starts, by connecting the landing gear solenoid selector valve to auxiliary bus A. C. DESCRIPTION A 28 VDC signal maintained on (4G) "L/G down" solenoid of the selector valve when (2G) control switch is in L/G down position, will maintain the pressure while the L/G is extended. The L/G control switch will be replaced or modified in an authorized repair shop in accordance with LABINAL No. 12-337-32-03 Service Bulletin. The wiring is modified as follows: - A shunt and two diodes are added on the switch to allow maintaining the 28 VDC signal. - (1G) landing gear solenoid selector valve circuit breaker is changed from 10 to 4 amperes, to be able to trip in case of short in either of the new diodes. Moreover, this circuit breaker is connected to auxiliary bus A to allow a progressive hydraulic pressure rise in the telescopic bars upon engine start instead of the abrupt rise when the bus in automatically switched on again once start is achieved. It is possible to modify the airplane wiring without having yet received a modified switch because, even installing a non-modified switch in such case will bring about a configuration identical with the configuration before this Service Bulletin i.e., the hydraulic pressure will not be maintained when the landing gear is extended. CAUTION: INADVERTENT INSTALLATION OF A MODIFIED SWITCH IN AN AIRPLANE WHICH DOES NOT INCORPORATE THIS SERVICE BULLETIN WILL RESULT IN AN IMPOSSIBILITY TO RETRACT THE GEAR SINCE THEiLANDING GEAR DOWN" RELEASE SOLENOID OF THE CONTROL SWITCH WILL NOT BE POWERED. March 4, 1998 F20-32-74 Revision 1 Page 1 "DASSAULT AVIATION Proprietary Data" ### Page 4 (OCR) DASSAULT SERVICE BULLETIN AVIATION FALCON 20 F20-676 D. COMPLIANCE Recommended. E. APPROVAL D.G.A.C. approved. F. MANPOWER Estimated manhours: 21 hours. NOTE: These manhours only concern the work described in this Service Bulletin and do not include maintenance work which may be performed on this occasion. G. MATERIAL - PRICE AND AVAILABILITY To obtain the procedure of modification of the landing gear control switch, please contact either address listed below: Western hemisphere: DASSAULT FALCON JET CORP. SPARES DISTRIBUTION CENTER 200 RISER ROAD LITTLE FERRY, NJ 07643 U.S.A. Telephone: CANADA and U.S.A.: 1-800-800-4036 MEXICO: 001-880-800-4036 Other countries: 1-201-541-4809 Fax: CANADA and U.S.A.: 1-800-800-4817 MEXICO: 001-880-800-4817 Other countries: 1-201-440-7021 Other continents: DASSAULT FALCON SERVICE Distribution BOITE POSTALE N° 10 AEROPORT DU BOURGET 93350 - LE BOURGET (FRANCE) Telephone: 33 (0)1.49.34.20.20 Fax: 33 (0)1.49.34.20.90 Price and availability on request. H. TOOLING - PRICE AND AVAILABILITY Normal maintenance tooling. March 4, 1998 F20-32-74 Revision 1 Page 2 "DASSAULT AVIATION Proprietary Data" ### Page 5 (OCR) DASSAULT SERVICE BULLETIN AVIATION FALCON 20 F20-676 I. WEIGHT AND BALANCE Change in weight: None. Change in balance with respect to 0% MAC : None. J. REFERENCES Maintenance Manual: - Chap. 7-10. - Chap. 32-30-00. Maintenance Manual, chap. 12, DTM536G. Service Bulletin LABINAL No. 12-337-32-03. K. OTHER PUBLICATIONS AFFECTED The Illustrated Parts Catalog, Wiring Diagram Manual, Maintenance Manual, Overhaul Manual and Operating Manual will require revision as a consequence of this Service Bulletin. March 4, 1998 F20-32-74 Revision 1 Page 3 "DASSAULT AVIATION Proprietary Data" ### Page 6 (OCR) DASSAULT SERVICE BULLETIN AVIATION FALCON 20 F20-676 2 . ACCOMPLISHMENT INSTRUCTIONS A. PRELIMINARY STEPS (1) Airplane on jacks (Maintenance Manual, chap. 7-10). No ground power unit connected to the airplane. (2) Remove the necessary furnishing to gain access to: - (34) strip panel (aft side). - Wiring between (34) and (2G) landing gear switch, on the RH side. - Circuit breaker panel aft wiring. B. GENERAL INSTRUCTIONS AND CHECKS During the modification, take all necessary precautions: - Not to damage insulation of existing wires. - To prevent filings from being dropped into the components. - To recover any chip or filing which could have been dropped into the components. - To check the solders. All solders must be protected with CELOMER 6060B green varnish. - Route existing wires with existing clamps and tie wraps. - Conduct a wire-by-wire electrical inspection (see fig. 1). C. ELECTRICAL MODIFICATIONS (1) Remove and disconnect (2G) landing gear control switch from the instrument panel. Sent it to an authorised specialized workshop so that LABINAL Service Bulletin No. 12-337-32-03 be applied. (2) Install GA8K20, GA15G18 and GA28E18 new wires between (2G) mobile connector and (34) strip panel. Route these wires in existing cable bundles with existing clamps and tie wraps. (3) Drill one of (34) strip according to fig. 1 (lower strip) to attach the diodes. (4) Crimp AMP 130040 terminal lug (or equivalent for gauge 18 and 20 wire) on GA28E18 wire and on both ends of GA28F20 shunt. (5) Install (47G) and (48G) diodes with GA28E18 wire terminal lugs, one end of GA28F20 shunt (47G cathode) and the other end of GA28F20 shunt (48G cathode). (6) Solder: - GA15G18 wire to (47G) anode. - GA8K20 wire to (48G) anode. Apply a coat of CELOMER 6060B green varnish on the solders (Maintenance Manual, chap. 12, DTM536G). March 4, 1998 F20-32-74 Revision 1 Page 4 "DASSAULT AVIATION Proprietary Data" ### Page 7 (OCR) DASSAULT SERVICE BULLETIN AVIATION FALCON 20 F20-676 (7) In the vicinity of (2G) mobile connector: (a) Cut: - GA1F20 wire coming from terminal N. - GA15E28 wire coming from terminal J. - GA8E20 wire coming from terminal U. (b) Using AMP 320559 permanent splices (or equivalent for gauge 18 and 20 wires) connect: - Both ends of GA1F20 wire to GA1P20 new wire. - Both ends of GA15E18 wire to GA15G20 new wire. - Both ends of GA8E20 wire to GA8K20 new wire. (c) On (2G) mobile connector, connect the new wire: - GA1P20 to terminal K. - GA28E18 to terminal F. (8) After completion of Service Bulletin LABINAL No. 12-337-32-03, connect and install (2G) landing gear switch. (9) Disconnect and scrap (1G) circuit breaker. (10) Install the new 4A circuit breaker. (11) Connect: - One terminal to bus A. - The other to GA1E18 wire. D. TESTS (1) Carry out an operational test of the landing gear extension/retraction according to the Maintenance Manual, chap. 32-30-00. (2) When the landing gear is in down position and downlocked check that there is + 28 VDC on (47G) diode cathode. The recorded voltage should be comprised between 24 and 30 VDC. E . FINAL STEP Reverse procedure to paragraph 2. A. F. RECORDING Record compliance with this Service Bulletin in the appropriate aircraft documents. Fill out the card located at the end of the Service Bulletin and mail or fax it to Dassault Aviation or Dassault Falcon Jet. March 4, 1998 F20-32-74 Revision 1 Page 5 "DASSAULT AVIATION Proprietary Data" ### Page 8 (OCR) DASSAULT SERVICE BULLETIN AVIATION FALCON 20 F20-676 3 . MATERIAL INFORMATION A. MODIFICATION KIT Q INSTRUCTIONS NEW P/N T KEY WORD OLD P/N E Y DISPOSITION M G G2010 2 Diode SILEC See NOTE 1 21506U Circuit breaker ECE See NOTE 2 130040 3 Terminal lug AMP 320559 Splice AMP GA1P20 0,5 m Wire MIL-W-22759 GA8K20 5 m # 20 GA15G18 5 m Wire MIL-W-22759 GA28E18 5 m # 18 NOTE 1: Or equivalent, characteristics of the diodes: • Direct current: 10 A. . Maximum reverse current: 3 mA. . Direct reverse voltage: 200 V. NOTE 2: Or equivalent, characteristics of the circuit breaker: • Monopole thermal (4A), complying with MIL-C-5809C specification. B. LOCAL PROCUREMENT Green varnish CELOMER 6060B (as per Maintenance Manual, chap. 12, DTM536G). C. P/N EVOLUTION Switch P/N 12337-1 becomes 12337-12 after completion of Service Bulletin LABINAL No. 12-337-32-03. March 4, 1998 F20-32-74 Revision 1 Page 6 "nACCA!!! - AVIATION Dropriatary natal ### Page 9 (OCR) Revision 1 March 4, 1998 1G LANDING GEAR L/G SWITCH FALCON 20 "A" BUS LH RH NOSE L/G DOWN • UG UP VIATION DASSAULT 1 25G. -GA26G20 • GA1F20 N - GA4E20 → 17G1 NORMAL, D 6G L/G ELECTRO-DISTRBUTOR • GA1P20 K EMERGENCY 4G1 00 210201 0 9GO-GATSE18 Uplocked J -FIGURE 1- Not locked GA11E20• - DG9F20N UG UP 29G 30G G DOWN GA28F20 - GA15G18 H GA12E20- GA28E18 GA8K20 4G 210GO - -GASE20 Uplocked v - GA18E20- Not locked 6G SERVICE BULLETIN 2190a 11662001 11GO-GABEZO Uplocked - GA19E20-1 Not locked 2G Page 7 F20-32-74 • 91C 47G 48G on 34 lower strip Location of, diodes Diode G2010 F20-676 polarisation --- 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.