First, my apologizes to nosegear, next time I’ll refresh my computer prior to leave my message. You answered the questions very well.
MJC
1. Differences between ILS cat II and III are basically airport, aircraft, operator and crew certifications and weather minimums. Based on ICAO standards, Cat II is an ILS approach procedure which provides for an approach to a decision height lower than 200ft but not lower than 100ft and RVR not less than 350m. Cat III are divided in 3 categories: IIIA – with a DH lower than 100ft or without a DH and with a runway visual range of not less than 200m, IIIB a decision height lower than 50ft or without a DH not less than 50m and IIIC with no DH and no RVR limitations. Which does the 737 use? Well, it depends on what certification the operator has. B737EFIS and NGs are certified to ILS cat IIIA.
2. Usually, under normal operation there’s no such condition you described. Your procedure to engage the second A/P is operational (maybe there’re some SOP differences among certain carriers), but tell me: First, were both nav receivers tuned to the same ILS frequency? Second, was the same inbound ILS course set on both HSIs? Have you been flying with flaps 5 and speed no faster than 170-180kt prior to intercept the GS?
3. When using VNAV, and no early descent is required pilots just have to set the altitude, using altitude control knob on the FCP. The “Capture” function is used during an early initiation of path or speed descent. VNAV path descent is at 1000 fpm until intercepting the computed path.
Nice flights