Systems 251, and a Passenger Briefing System - PBS 250. Backup/Safety Systems: Honeywell MKXXII Enhanced Ground Proximity Warning System, Penny & Giles MPFR FDRJCVR, 3" Thales Integrated Electronic Standby Indicator (IESI) provides backup attitude, airspeed, altitude, nay cues from NAV 1 or NAV 2, and VHF 2, ELT