A320 SEC PERF unavailable
HI all,
As part of my arrival preparation, I'll enter a different runway on the secondary flightplan. At some point, the PERF prompt at R2 on the SEC FPLN page disappears, and I can't change any of the data without copying the active fpln, or rebuilding the secondary.
Why does it disappear?
When exactly does it disappear?
How do I change the data on the SEC PERF pages with the prompt missing?