1.3. Taxi Procedures and Technologies
1.3.6. Human-Machine Interfaces Supporting the Cockpit Crew
dures as well as the mentioned alternative taxi technologies envisage a manual process. The pilot taxiing is in charge to monitor the traffic situation on the sur- face and to apply brakes, throttle, and tiller accordingly. The apron or ground controllers’ taxi instructions need to be memorized or noted manually.9 Although taxi speeds are comparably low and emergency stops are feasible at any location, accidents during parking and taxiing amount for5.5 % of all fatal accidents and hull losses between 1997 and 2016 [Air17, p. 22].
To achieve a higher degree of safety during taxiing especially when visibility is low, newer aircraft offer additional HMIs supporting the pilots by presenting in- formation on built-in displays. Optional EFB applications can provide additional
7 The operational description is based on personal observation by the author and a discussion with involved project engineers.
8 The lower value of 40 % has been communicated in an internal presentation of TaxiBot stake- holders which is not included in the references. The high variations in fuel savings between the different sources are caused by different route and speed profiles as well as by different engine start positions.
9 The description of the general taxi procedures is based on the author’s observation during cock- pit companionships on two medium-haul flights of a German airline and on discussion with pilots.
support to different extents. Regardless of the hardware type, the interfaces com- monly present an airport moving map (AMM) with spatial and operational infor- mation provided by an aerodrome mapping database (AMDB) [Psc+11].
1.3.6.1 Built-In Taxi Interfaces
Modern Airbus aircraft like the Airbus A380, A350 and current versions of A330 and A320 are equipped with an On-Board Airport Navigation System (OANS). As shown in Figure 1.6, the OANS visualizes the airport layout including runways and taxiways as well as the current aircraft position [Cha13]. The visualization is presented on built-in displays placed in front of the pilots [Tha10].
Figure 1.6.: OANS developed by Airbus running on the ND of modern Airbus air- craft (depiction with permission of Airbus Operations GmbH [Air14])
Boeing provides a similar AMM system integrated into the cockpits of Boeing 787 and 747-8 and plans to expand it to all upcoming aircraft models [CT11].
Cockpit system manufacturers like Honeywell or Rockwell Collins also offer in- tegrated solutions displaying airport moving maps on primary displays. In addi- tion to two-dimensional moving charts, the approaches include exo- and egocentric three-dimensional augmented visualizations of the surrounding on ground [Hon15; Hon18; Avi13].
While the extent of information presented on the AMM varies, the industry standard described in RTCA DO-272D/EUROCAE ED-99D [Eur15] provides an overview of current and future functions. These include among others taxi routing, navigation cues and traffic display [Psc+11].
1.3.6.2 Taxi Interfaces on Electronic Flight Bags
Besides the visualization on built-in devices like the ND, the referenced industry standard also considers the implementation on an EFB [Psc+11]. Definitions and regulations regarding EFBs are set by the ICAO Doc 10020 [Int15], the EASA Ac- ceptable Means of Compliance 20-25 [Eur14a], and the FAA Advisory Circular 120- 76D [Fed17]. The FAA defines EFBs as follows:
"An EFB hosts applications, which are generally replacing conventional paper products and tools, traditionally carried in the pilot’s flight bag. EFB applications include natural extensions of traditional flight bag con- tents, such as replacing paper copies of weather with access to near-real- time weather information." [Fed17, p. 2]
An essential requirement for EFB applications is that failures of the application must not result in major hazards or have major safety effects [Fed17]. Having previously defined three EFB classes, the FAA eliminated its class definitions from the regulatory in the most recent Advisory Circular and took over the distinction carried out by EASA and ICAO. Consequently, all three regulations divide EFBs into portable and installed devices [Eur14a; Fed17; Int15]:
Portable EFBs are not part of the certified aircraft configuration and thus can be operated inside and outside the aircraft. It can be mounted to the aircraft if no additional tools for mounting or removing are needed. Installed com- ponents like the mounting unit, an optional aircraft power source, and data ports need to be part of the certified aircraft configuration. If properly se- cured, the portable EFB can be used during all phases of flight. [Eur14a; Fed17]
Installed EFBs are non-removable devices which are considered to be an aircraft part. Consequently, it is part of the certified aircraft configuration and is covered by the aircraft airworthiness approval. With regard to the software, it is also allowed to run non-EFB software10 when running on a separate boot partition. [Eur14a; Fed17]
Generally, both EFB classes are allowed to run Type A and Type B software [Eur14a; Fed17]. The characteristics of the two software types are defined as follows:
10 Non-EFB software was formerly named type C software by the FAA. As this software is no EFB software, FAA eliminated it from the current version of its Advisory Circular. [Fed17]
Type A software has no safety effect if a malfunction occurs [Eur14a; Fed17]. It must “not substitute for or replace any paper, system, or equipment required by airworthiness or operational regulations” [Fed17, p. 3].
Type B software exhibit only minor safety effects if a malfunction occurs [Eur14a; Fed17]. On the contrary to type A software, it may substitute paper products but still must not substitute or replace installed components and systems [Fed17]. In the USA, it requires “specific [FAA] authorization for opera- tional authorization for use” [Fed17, p. 3] while in Europe an operational assessment carried out by the operator is needed [Eur14a].
Concerning airport navigation, the FAA and EASA classify AMMs as type B ap- plications and thus allow them to run on both EFB classes. While installed EFBs running an AMM can be permanently integrated into Aircraft (if not displayed on the primary cockpit screens, see subsubsection 1.3.6.1), several airlines also allow their pilots to carry personal EFBs or provide company EFB devices with pre- installed software [Hil+15]. Common AMM modules for portable devices are in- cluded in Flight Deck Pro of Jeppesen [Jep18] or Lido/eRouteManual of Lufthansa Systems [Luf17]. In addition to the depiction of static airport elements like taxi- ways, runways, and stopbars, the current ownship position as well as desired taxi routes or targets can be visualized on the AMM [Jep18; Luf17].