F-programs TWT design upgrades [military aircraft radar]

In the early 1990s, Boeing began a systematic program of upgrading the designs of its TWT products that support radars for F-14, F-15 and F-18. The objective was to use technology that was not available when these tubes were originally designed to increase the tube\´s MTBF by an order of magnitude. This improvement would not only provide greater field reliability, but also would greatly reduce tube repair and support costs. The upgrade programs have now been completed for the three F-program designs and are considered to be highly successful. The body currents of the tubes, a key factor in reliability, have been substantially reduced for each design and the power margins have all increased. Finally, the tendency of the tubes to fall out of specification due to "parameter drift," probably the most common cause of tube failures, has been eliminated.