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Flight management systems
Published in Mike Tooley, David Wyatt, Aircraft Communications and Navigation Systems, 2017
The term ‘navigation’ can be applied in both the lateral and vertical senses for aircraft applications. Lateral navigation (LNAV) is effectively the area navigation function described in Chapter 16. Vertical navigation (VNAV) can be used to supplement or replace approach and landings using radio navigation aids; it can also be used to optimise the performance of the aircraft to reduce operating costs. This has been traditionally achieved by the flight crew (particularly the flight engineer) making reference to data contained within charts, tables and performance manuals.
Avionic Systems
Published in Mike Tooley, Aircraft Digital Electronic and Computer Systems, 2023
Vertical flight limits are maintained by a vertical navigation (VNAV) system and the aircraft’s autopilot system. VNAV monitors for correct speed and altitude (as determined in the flight plan) limits and ensures they are maintained at waypoints. By combining these automatic functions, a flight can be made almost entirely automatic, from initial take-off to final touch-down.
Fitts’ law on the flight deck: evaluating touchscreens for aircraft tasks in actual flight scenarios
Published in Ergonomics, 2023
Yubin Xie, Ronggang Zhou, Jianhong Qu
Touchscreens are receiving increasing attention in aviation. Since the use of smartphones, touch technology has made tremendous progress, and touchscreens are ubiquitous in our daily lives (Colle and Hiszem 2004; Giebelhausen et al. 2014). They have now become the mainstream interface for electronic devices from household appliances to smart cars (Harvey et al. 2011). In the aviation sector, a modern flight management system (FMS) was introduced on a Boeing 767 (Bulfer and Gifford 1991) in 1982 to assist pilots in lateral navigation (LNAV) and vertical navigation (VNAV). As the interface of the FMS, the control display unit CDU is still used as the industry standard. For example, when the CDU of a Boeing 787 is replaced with a digital display, the look and feel of the CDU remains unchanged. However, looking forward to the future development of LNAV, the necessity of modernising the FMS interface becomes obvious. Because of the increased degree of intelligence in modern aircraft, the amount of information that a flight computer needs to process has also increased substantially (Rogers et al. 2005). The aviation cockpit requires a more integrated interactive device. In addition, the new generation of pilots has extensive experience with smartphones and smart appliances, and they have a different level of technological competency than those who went before them. In life, the main interaction methods used by these pilots are touchscreens or voice controls. In aviation flight, the cockpit offers traditional click-type and knob-type interaction methods. Thus, there are problems with adaptability and learning.
Plan B for Eliminating Mode Confusion: An Interpreter Display
Published in International Journal of Human–Computer Interaction, 2021
Figure 1 illustrates a potentially confusing interface presentation. It depicts the airplane during a climb with autopilot and autothrottle engaged using LNAV (lateral navigation) and VNAV (vertical navigation) modes, which are complex control modes that take targets from the FMS flight plan. The airplane leveled off at 15,000 feet when Air Traffic Control (ATC) warned of a traffic conflict. The airplane was then cleared to 31,000 feet (Flight Level (FL)310) by ATC. The pilot dialed 31,000 as shown in the MCP altitude window and at the top of the altitude tape on the right-hand side of the PFD. Thus, the interface presents cues – autopilot engaged, correct altitude target – to indicate the airplane should climb to 31,000. However, the intermediate level off at 15,000 forced VNAV to transition to VNAV ALT, which is a submode of VNAV that is used to hold an altitude. In VNAV ALT, the pilot is required to dial the MCP altitude up to 31,000 and also push on the MCP altitude knob (see arrow in Figure 1) to initiate the climb. As it is presented in Figure 1, the pilot has failed to push the altitude knob and will continue flying at the current altitude of 15,000 feet. The interface does not reveal the need for an additional action, and more to the point, it does not reveal its current altitude target. This is a good illustration of how poorly it conveys its state, generally referred to as the gulf of evaluation (Hutchins et al., 1986). Thus, successful use of the autoflight system relies on the pilot’s mode knowledge, especially around VNAV, to make sense of the interface presentation.