PERF CLB AND CRZ: PREDICTIONS, PRESELECTION AND COST INDEX
PERF CLB and PERF CRZ expose speed mode, predictions and altitude references with different meanings. NEXT/PREV PHASE browse preparation pages; they do not simply command the aircraft into the page's named flight phase. Read the active mode and title alongside the FMA. This distinction allows advance preparation without confusing a reviewed future cruise page with an aircraft already in cruise. [66, PDF pp. 108,127,163-179,185-198]
1. Establish the active context. Read ACT MODE and the actual speed mode. The guide distinguishes MANAGED, SELECTED and applicable expedite cases. Compare with the FCU window and FMA. A numerical speed visible on the MCDU can be a prediction, preselection or selected value, so identify its field and present phase before using it as evidence of the commanded target. [66, PDF pp. 108,127,163-179,185-198]
2. Inspect prediction-to-altitude fields. In the source standard, the target used for displayed time/distance may default to the FCU altitude and can be overwritten for a prediction study. Such a study does not change the FCU clearance or guarantee that the aircraft will fly to the entered study altitude. Return the field to its intended reference and inspect what the displayed numbers now describe. [66, PDF pp. 108,127,163-179,185-198]
3. Prepare speed preselection only when needed. The guide supports future climb/cruise speed choices with phase-specific grammar; climb preparation does not accept every Mach input available elsewhere. Read the accepted preselection and its expected phase transition. A preselected cruise speed can change the later speed-mode behaviour. If the intention returns to managed speed, use the documented clearing/managed selection and verify the resulting state. [66, PDF pp. 108,127,163-179,185-198]
4. Reconcile cost index and cruise reference. CI 20 and FL280 remain the teaching assumptions until the plan genuinely changes. Cost index alters economic scheduling; it is not a substitute for a required selected-speed clearance. If the actual cleared final cruise level changes, update the appropriate cruise reference and inspect phase/predictions. A temporary level-off below planned cruise is a different situation from adopting that level as the new cruise. [66, PDF pp. 108,127,163-179,185-198]
5. Review the outcome across displays. Check destination time/EFOB, next T/D or step reference, selected/managed speed and active vertical mode. If ALT appears where ALT CRZ was expected, investigate the planned cruise reference and actual phase rather than changing unrelated keys. Read the aircraft's state as a connected model: page, cruise plan, FCU and FMA each contribute part of the answer. [66, PDF pp. 108,127,163-179,185-198]