EVS Approaches: Is a HUD really Required for Operational Credit?

Kurzfassung

In the currently existing rules for the use of EVS in combination with operational benefits (FAA rule on Enhanced Flight Visibility or the respective JAA approach published in the NPA OPS 41 Subpart E All Weather Operations) do not allow an EVS head-down display. The rule requires that EFVS include a head-up display rather than the alternative of a head-down display because the pilot is conducting an instrument approach procedure in lower visibility conditions, but with no change in the prescribed instrument approach minima and must accomplish several visually-related judgments and control tasks in quick succession. While the regulatory requirements for the use of EFVS are analogous to the conventional requirements for descent and operation below DH or MDA, the pilot needs to use the imagery, the flight reference information, and eventually the outside view, at the same time. The pilot must be able to look for the outside visual references in the same location as they appear in the EFVS image and readily see them as soon as visibility conditions permit, without any delays or distraction due to multiple head-up/ head-down transitions. When scanning between the head-up and head-down views, it takes additional time for the pilot to reacquire the information in each view and for the pilot’s eyes to readjust for differences in light level and changes in focus between optical infinity and the distance to the instrument panel. Repeated scanning between the head-up and head-down views would be distracting, increase pilot workload and potentially degrade path performance during a critical phase of flight. However, our proposal for the use of EVS does allow for a head-down display to continue the descent below DH/MDA. The above mentioned concerns against head-down display can be overcome by an introduction of an adequate crew procedure and display design The task sharing between Pilot-Flying and Pilot-Not-Flying has to be arranged such that multiple head-up/head-down transitions can be avoided. The Pilot-Flying is using the head-down display for acquisition of the necessary visual cues in the EVS image. The pilot flying is monitoring the instruments and looking for the outside visual cues. The use of reduced RVR (as described in the JAA NPA OPS 41) will help the crew to define the point when one can expect the runway to become visible. Thus, this aspect is included in the approach briefing. In addition, the approach briefing covers the aspect of who will conduct the visual landing once visual contact to the runway is established and how - in case there will be no hand-over of the controls – the pilot-not-flying can support the pilot-flying in immediately detection the runway after his transition from head-down to head-up. This contribution focuses on the results of simulation trials with pilots using DLR’s cockpit simulator GECO. The simulation trials compares the currently used head-up display design with the new head-down display in combination with the defined crew procedure. Results are given in terms of performance and workload assessments.