In respect of the Army pilots' height keeping, how relevant might it be that the
FAA Airman Certfication Standards for helicopter instrument ratings (IH.IV.A.S1 and elsewhere) specify a required accuracy of plus or minus 100 feet? An argument that the pilots were negligent for deviating by less than that would surely be open to challenge, even before considering that they were flying visually and therefore would have been expected to spend more time looking outside than scanning instruments (leading to less accurate height keeping). This would bring the focus squarely back onto the FAA's airspace management and control. Was it reasonable to expect pilots to fly at precisely 200 feet, plus or minus zero?