pdf Gfa ad 665 Cancelled 2018-09-14 Popular

WATER BALLAST SYSTEM FIN TANK VALVE, SPRING REPLACEMENT

CANCELLED Refer EASA AD  2011-0009

Stress corrosion has been found in the zinc plated compression springs removed from the fin ballast tank valve, installed on an LS10-s  sailplane.  The  investigation  has  shown  that  if  one and/or both fin tank valve springs fail, the water tank valve might not open or not open completely. This could cause a displacement of the sailplane centre of gravity. The design of the fin tank valve springs is common to both the LS10-s and LS10-st sailplanes. This condition, if not detected and corrected, could result in loss of control of the sailplane due to the centre of gravity being too far aft.  DG Flugzeugbau Technical Note No. LS10-01 dated 22 October 2010. To correct this unsafe condition, DG Flugzeugbau have developed a modification which consists of the replacement of the fin ballast tank valve zinc plated springs, with a springs made of stainless steel. For the reasons described above, this AD requires the replacement of the both fin tank valve springs with stainless steel springs, P/N 45000699.