SYNOPSIS
Three runways were in use for landing at Chicago O’Hare. The Commander, who was the Pilot Flying (PF), briefed the Pilot-Not-Flying (PNF) for an Instrument Landing System (ILS) approach to each landing runway. ATC vectored the aircraft towards an ILS approach to RWY 22R but an unexpected and unusual clearance for a non-precision approach was received shortly before commencing the approach. During the subsequent approach, in fine weather with good visibility, the PF miscalculated the rate of descent required and descended too rapidly. On realising that they were too low, power was increased and subsequently go-around power was selected for a short period. The aircraft climbed to the proper profile and a normal landing ensued. The maximum altitude deviation below the correct flight path was 774 ft. There was no injury or damage.
