Christian Dimter - Lufthansa Technik AG

Dear Sirs, I have a question concerning AD 2007-26-06 and referenced SB 747-35-2119. The AD note says in the Applicability section that only airplanes as identified in SB 747-35-2119 are affected by the AD note. DLH (and probably many other airlines) are not affected by the SB, because they were not delivered with B/E oxygen masks, but with SCOTT masks. In the aircraft IPC, only PNs of SCOTT masks are given (e.g. 289-601-xxx, 289- 701-xxx,...). Therefore, one might suppose that only SCOTT equipment is installed and no B/E equipment, therefore AD2007-26-07 being not applicable. But after viewing the Boeing Component Maintenance Manuals CMM 35-21-14, 35- 21-24 and 35-21-44, there is an interchangeability for certain SCOTT and B/E PNs. I have attached some pages of these CMMs showing the interchangeability. My question now is: Does this interchangeability information mean that there are probably MANY more airlines affected by the AD note than reflected by the effectivity column of the SB? All airlines using the CMMs for maintenance of the oxygen mask containers or even who purchased a new PSU from Boeing could have B/E Masks instead of SCOTT masks installed in the Oxygen Mask Containers under the same Assy number as installed before. I would be very thankful for clarification in this point. Thank you and best regards, Christian Dimter System Engineer Oxygen System Lufthansa Technik AG