High-fidelity simulators, replicating full scale cockpits and with realistic visual systems surrounding the pilot FOV, discussed in Section 2.3.2, are normally used to provide DMO training [50], which was previously introduced in Section 1.1.1. However, such high-fidelity simulators (Figure2.6(a)) are restricted by their cost, size and infrastructure to deploy on either a large scale or to field locations [51]. Low-fidelity simulators (Figure2.6(b)) can also provide equivalent training benefits without the extra cost if used appropriately [52]. The primary difference between full-mission simulators and low-fidelity trainers is the significant reduction in the visual scene FOV. This requires fundamental research into methods as presented later in Section2.4of overcoming the challenges a narrow FOV presents in order to achieve the same level of training effectiveness without compromising normal task behavior. To fully comprehend the differences and commonalities between these simulator types, a census overview is given next for both civilian and military flight simulators in use today.
(a) High-fidelity dome simulator (b) Low-fidelity trainer Figure 2.6: Comparison between a) high-fidelity and b) low-fidelity simulators
2.2.1
Civil Flight Simulators
In the civil aviation world, airline operators, training organizations, and flight training centers use flight simulators, known as Flight Simulation Training De- vices (FSTD), as a highly effective and economical method of training, testing and checking aircrew. These FSTDs are regulated by the National Aviation Au- thorities (NAA). That is, the FAA in the US and the CAA in the UK. Other NAAs have developed their own standards for the complete range of FSTDs, for both aeroplane and helicopters [36]. FSTDs range from instrument trainers with
no visual displays, PC based desktop flight training devices to large motion-based full flight simulators commonly known as Level D simulators for airline checkrides. Figure 2.7 shows two examples of desktop FSTDs which are FAA approved. An illustration of a static FSTD and full motion simulator is shown in Figure 2.8. With a variety of names and capabilities assigned to simulators by individual aviation authorities, it is difficult to correlate their attributes at a worldwide level. This may cause inefficiencies for pilot licensing, ratings and checks for all but the top-level, highest-fidelity simulators (Level D). This lack of harmonization occurs even between the two largest aviation bases of North America and Europe [53].
(a) PC/Basic (b) Advanced
Figure 2.7: Examples of FAA approved desktop training devices [54]
(a) Static flight training device (b) Level D full motion flight simulator Figure 2.8: Flight training devices
Morrison [55] named five reasons behind the need to update the FSTD standards: 1) regulatory changes, 2) lack of harmonization, 3) new aircraft types, 4) new training types and 5) new technologies. The aviation industry’s frustration due to the above mentioned reasons led to to an International Working Group (IWG) by the Royal Aeronautical Society (RAeS) in 2006 to review FSTD technical cri- teria. The IWS decided that a fundamental review was necessary to establish the simulation fidelity levels required to support each of the required training tasks
for each type of pilot licence, qualification, rating or training type [36]. This task analysis process to support the updated flight simulator qualification standard is covered in Section 3.2.2.
2.2.2
Military Flight Simulators
The number of military flight simulators has been increasing yearly due to high cost of aircraft programmes and budget constraints. There are around 1,912 known military training devices worldwide according to a 2011 census [56]. The charac- teristics of these simulators and FSTDs are related to the role of the aircraft for which they are used as trainers. These devices have either an outside-the-window (OTW) visual system or a motion system, or both, full-size cockpit controls and mostly full-size replica cockpits. They also range from Unit Level Trainers with only one visual channel to full mission rehearsal simulators which are similar to a civilian Level D simulator. With over 1,050 simulators for fighter aircraft types, g- force cueing is an additional concern when compared to civilian simulators. Nearly 580 military simulators can be networked and only 60 out of the total amount are designed to be transportable as the survey showed [56]. Despite common termi- nology and designations across operators, there is no documentation of simulator standards because usually each simulator is a bespoke piece of equipment.
2.2.3
Research Flight Simulators
Regarding research simulators, Rehmann states:
“The essential feature of simulator experimental investigations is to introduce the pilots into a closed-loop control situation, so that account is taken of their capabilities and limitations regarding the performance measure being evaluated. The expectation is that within the bounds of the experimental conditions, behaviour in the simulator will match their behaviour in the flight situation. Hence, the primary goal for a flight simulation researcher is to produce experimental conditions that elicit behaviour that would occur under similar circumstances in the real world.” [57]
In research, other factors are of importance in addition to physical realism, such as the level of realism perceived by the pilot (perceptual fidelity) discussed in Section 3.2.1. Since non-research FSTDs do not have to consider this aspect, their classification system is not applicable to research simulators. This lack of classification for research simulators has lead to confusion when specifying what type of simulation is necessary for a particular research task, and is the major reason for performing analysis of fidelity requirements for simulation research.