A manufacturer of replacement parts for military aircraft needed an ejection seat header for an older military aircraft. The header was an important replacement component (LRC) of a line replaceable unit (LRU) that controlled the firing of the explosive needed to eject the seat. Our customer at first contracted with another company to make the part but after several months of trying they failed to do so. Our customer turned to us to us to see if we could do it.
We were faced with several challenges in trying to recreate this part. The drawings were over 50 years old and, for some key dimensions, were very hard to read. We had to recreate the drawings in CAD and make a few design changes in order to meet the current robust standards for fit, function, hermeticity and AS9100D standards.
We were also under severe target price constraints so we could not run multiple trials in order to get it right.
The part is composed of nine separate parts of 3 different materials, alumina ceramic, stainless steel and Kovar, all with different expansion coefficients. Through careful design of the many braze joints and the right choice of braze alloy, we were able to create a hermetic seal at all joints in a single braze cycle.
Although it took more than one trial to get it right, we succeeded in providing a replacement part that met all the requirements for their program.