Learjet 40/5; Honeywell Upgrade Gets STC A Honeywell upgrade (featuring the Primus Elite Advanced Features) for the LearJet 40/45 model has been given a Supplemental Type Certificate (STC) by the Federal Aviation Administration (FAA). It now allows for the original CRT monitors in the cockpit to be replaced by DU-875 LCD screens. There are many advantages to upgrading to the new displays. The old CRT monitors are very heavy, the LCD screens will save seven pounds of weight per screen over the old technology. The LCD screens provide clarity and are brighter.