OPTIONAL SERVICE BULLETIN NO. OSB-42-050

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Diamond Aircraft Industries GmbH N. A. Otto-Straße 5 A-2700 Wiener Neustadt DAI OSB-42-050 Page 1 of 4 13-Aug-2007 OPTIONAL SERVICE BULLETIN NO. OSB-42-050 I TECHNICAL DETAILS I.1 Category Optional I.2 Airplanes Affected Type: DA 42 Serial Numbers: all I.3 Time of Compliance At owners discretion. I.4 Subject Installation of additional ECU Backup Batteries to supply electric power solely to the ECU in the course of high transient causing a short term voltage drop in case of insufficient main battery power. The ECU Backup Battery capacity is sufficient for at least 30 minutes engine operation. ATA-Code: 72 I.5 Reason On one occasion after starting the engines using ground power due to fully depleted main battery without following the procedures published in the AFM the airplane experienced a dual engine failure and total loss of electrical power. In the course of the investigation ground tests on production aircraft in a similar scenario were carried out without showing the same results. Testing done by the engine manufacturer and subsequent further analysis revealed a potential for experiencing the above mentioned failures under the circumstances of failed or fully depleted main battery and non adherence to the published AFM procedures. According to the Thielert Aircraft Engines Installation Instructions, the alternator of the engine is viewed as the engine s own electrical power source. The battery is the source of electric power in the electrical system of the aircraft. The alternator is certified as part of the engine. The FADEC, alternator and battery are wired in such a way that the FADEC electrical power supply is provided by the alternator in the event of a failure of the battery as required by the Thielert Aircraft Engines Installation Instructions. It has been observed, that the alternator is not able to provide adequate electric power under Diamond Aircraft Industries GmbH N. A. Otto-Straße 5 A-2700 Wiener Neustadt DAI OSB-42-050 Page 2 of 4 13-Aug-2007 such circumstances. Inrush currents of electric consumers may cause short term voltage drops (3 to 5 ms) which trigger a FADEC reset. During such a reset which lasts about 1.28 seconds the FADEC gives no commands to the fuel injectors or the propeller control system. This leads to a sudden engine RPM drop due to no combustion and a propeller auto feather command with subsequent insufficient electrical power generation if the engine RPM are below a certain limit. This results in a total loss of engine thrust and electric power. I.6 Concurrent Documents none I.7 Approval The technical information or instructions contained in this document relate to the Design Change Advisory No. OÄM 42-129, which has been approved under the authority of EASA Design Organization Approval No. EASA.21J.052. The technical content of this document has been approved und the authority of DOA No. EASA.21J.052. I.8 Accomplishment/Instructions Comply with WI-OSB-42-050, latest effective issue. Incorporate TR-OÄM-42-129 Incorporate AMM-TR-OÄM 42-129 I.9 Mass (Weight) and CG Update the Weight and Balance report of the aircraft in accordance with AMM Airplane Maintenance Manual, Doc. No. 7.02.01, latest effective issue. II PLANNING INFORMATION II.1 Material & Availability See WI-OSB-42-050, latest effective issue. II.2 Special Tools See WI-OSB-42-050, latest effective issue. II.3 Labor Effort Approx. 10 to 13 hours, depending on airplane configuration Diamond Aircraft Industries GmbH N. A. Otto-Straße 5 A-2700 Wiener Neustadt DAI OSB-42-050 Page 3 of 4 13-Aug-2007 II.4 Credit For credit contact Diamond Aircraft. II.5 Reference Documents Diamond Aircraft DA 42 Airplane Maintenance Manual, Doc. No. 7.02.01, latest effective issue. WI-OSB-42-050, latest effective issue. AMM-TR-OÄM 42-129 TR-OÄM-42-129 III REMARKS 1. Due to the complexity of the installation all measures may only be carried out by certified Diamond Aircraft Service Centers. 2. Accomplishment of the measures must be confirmed in the log book. 3. In case of any doubt, contact Diamond Aircraft Industries. Diamond Aircraft Industries GmbH N. A. Otto-Straße 5 A-2700 Wiener Neustadt DAI OSB-42-050 Page 4 of 4 13-Aug-2007 EXECUTION REPORT for OSB 42-050 AIRPLANE DATA Airplane Serial Number: _________________ Airplane Registration: _________________ Airplane Operator: _________________ Hours of operation of airplane: _________________ No. of landings: _________________ Hours of operation-engine LH: _________________ RH: _________________ Typical operation of airplane: private, club, training, other ______________ __________________________________ Date, Name, Sign Please fax the completed form to Fax No. **43-2622-26700-369 or e-mail to airworthiness@diamond-air.at