Before revision: FAA regulation describes that a PFD includes at a minimum, an airspeed indicator, turn coordinator, attitude indicator, heading indicator, altimeter, and vertical speed indicator [14 CFR Part 61.129(j)(1)].
After revision: FAA regulation describes that a PFD includes at a minimum, an airspeed indicator, turn coordinator, altitude indicator, heading indicator, altimeter, and vertical speed indicator [14 CFR Part 61.129(j)(1)].