Cooper-Harper handling quality pilot ratings comparing three different flight control laws to four different display control laws controlling part of the symbology in a helmet mounted display during fixed base helicopter simulation runs where the pilots were tasked to fly to a helicopter pad and hover within a certain distance and altitude span from the pad center for a certain time.
From Hess, Ronald A. and Gorder, Peter James, "Design and evaluation of a cockpit display for hovering flight", NASA-CR-183247
Ronald A. Hess and James Gorder
1988-10-02
<a rel="nofollow" class="external free" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890001529.pdf">https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890001529.pdf</a> fig.14