Literature Review on Single Pilot Operations

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18th May 2020 Example Literature Review Reference this

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Collective literature focus their research on one particular perspective towards single pilot operations.  While the attention to detail in this approach is somewhat precise, there is some credit to surveying the landscape and adopting a holistic approach in seeking for a finetuned solution.  We examine the fundamental Single Pilot Operations (SPO) concepts found in literature and then further extend our investigation by analysing with frameworks designed to provide analyst a measurement tool to assess the feasibility of SPO.  Presented are seven categories of SPO concepts and of the seven, the option of a single pilot on board and the displacement of the second pilot to a ground station has been recognised as the most achievable.  To better understand this concept and sociotechnical systems, we model alternative SPO using the Cognitive Work Analysis (CWA) and Social Network Analysis (SNA).  The analysis identified the functional loading and interactions between the agents and formulation of the systems architecture for future SPO. 

1.       Introduction

For any pilot, the Avionics and systems are the brains and guts of the modern aircraft.  Once the aircraft aligns itself to the earth (longitude and latitude) and the critical flight information, such as the departure and destination are entered into the Flight Management Computer (FMC), the aircraft can mostly fly there itself.  The current regulations require 2 crew for all regular public transporting aircraft. This has vastly changed from the times where flight engineers where required where there were 3 to 5 crew.  The logical path to full automation may be a phased approach [Trumble 2017], firstly by transitioning to single-pilot operations (SPO) with the support of a ground control station. With further advancements in systems and understanding the limitations of human-machine interfaces, could it then transition to single-pilot operations.  The motivation towards SPO’s or the less fathomed pilotless aircraft are purely economic benefits.  A Swiss Bank, UBS conducted a survey [Financial Times 2017], suggested that the development of new technology could bring “material economic benefits” and would assist airlines in improving safety.  The analysis claimed that airliner could save more than 35bn per year, through the reduction of a pilot, lower insurance premiums and even fuel costs.  The onset of “Baby Boomer” retirements and continual growth in the demand for air travel compared to the lack of available qualified pilots have really created a shortage of pilots. In the recent years, we have seen the airlines absorb much of the experienced pilot workforce, leaving the tiers below, such as smaller regionals and General Aviation (GA) population with very little resources.  To alleviate this shortage, several changes to the recruitment model have been adapted by the airlines, such as cadet programs and lowering the entry requirements.  With growing demand for air travel, according to Airbus, in a Global Market Forecast 20182037, anticipates that air traffic will grow at 4.4% annually, requiring some 37,400 new passenger and dedicated freighter aircraft at a value of US$5.8 trillion over the next 20 years [Airbus 2018].  The forecast also addresses the long-term growth in the aircraft manufacturing industry and estimates that the worlds fleet will more than double in the next 20 years.  Many researchers have pondered the possibility of single pilot aircraft, however many challenges need to be resolved before commercial aircraft are single piloted. 

Figure 1 Source: Airbus Global Market Forecast 2018-2037

2.      Concepts and the Roadmap

The concept of SPO or the Reduction of Crew Operations (RCO) has been a popular topic for some time, dating back to the 1970’s [Neis et al 2018].  It is a common sight in general aviation, as well as military aircraft to see a single pilot at the controls.  In today’s commercial aviation sector and under the classification of Regular Public Transport, an aircraft must have two pilots on board.  This has come a long way from the days we saw five to four flight crew in the cockpit, where the requirement was at a minimum, the Captain, First Officer and the Flight Engineer.  depending on the nature and length of the flight.

In this section, we will discuss academic conceptual frameworks for Commercial SPO, the possible design interfaces of the SPO cockpit and the role of the human operator for ROC operations.  It is not the aim for this paper to go into great depth with each topic, but an overview of the topic.

The implementation and progress of SPO in commercial airlines has always been hindered by issues with human factors, operational technicalities and public perception.  Operating in a sociotechnical system, the transition from today’s two crew cockpit to SPO while maintaining if not exceeding todays safety records can be complex.  Just adding further automation to current operations as many researchers have suggested have only adds further complications.  Advanced automation only exacerbates the human in the loop issues [Sprengart et al 2018] and other issues surrounding pilot incapacitation need to be resolved, not to mention the potential of high workloads.

Due to the inherent complexities, the research has rarely provided any comprehensive or tangible solutions, rather the approaches remain broad and pertain generally to conceptual frameworks.  Motivated by safety the general consensus is the removal of a pilot is not even in realms of possibility.  While it was possible to remove the flight engineer with automation and technology, the further reduction to a single pilot has stirred up a lot of interest and has been extensively explored.

Despite the many concepts in literature, they are derived following two seemingly logical steps from the current two-crew requirements.  The philosophies can be summarised as follows: [Neis et al 2018]

  1. Replacement design approach (aircraft centric)

The replacement of the second pilot with more technologically advanced automation.  Applying physiological monitoring of human performance and systems designed to assist the remaining pilot are intended to decrease the probability of errors.  These design concepts is to circumvent making major changes to the current operational environment.

  1. Displacement design concept (air to ground centric) The philosophy will not require the second pilot to be replaced, rather displaced located on the ground.  These ground stations can be strategically positioned on the ground with advanced communication systems linked to the aircraft.  This approach comes with a multitude of new issues such as security, reliability and high bandwidth required for these communication systems to function, situational awareness and reaction times between the multiple agents on the ground and in the air as well as the allocation of responsibility and authority.

Based on either of the philosophies, it was possible to derive further SPO concept categories [Neis et al 2018].

  1. Removal of second pilot

This will involve the removal of a pilot without any changes to the correct operational environment [Graham et al 2014].  With only one pilot on-board, this will inherently increase workload and consequently jeopardise safety.  Not mention the violation of current regulation and airworthiness requirements.

  1. Removal of the second pilot, with a capable person for relief when required.

In this concept, the key word is “capable person”.  When the SPO needs assistance such as situations involving pilot incapacitation, a capable person is granted access to the cockpit to assist during times of high workload.  These people may consist of flight attendants, commuting pilots or air marshals.  This was discussed in research by the European Advanced Cockpit for Reduction of Stress (ACROSS) through an Emergency Aircraft Control System [Malik and Gollnick 2016].

  1. Virtual pilot in an aircraft in the vicinity. Very similar to the above, in the case of pilot incapacitation, a “trained person”, likely another single pilot in a support aircraft could rendezvous in a virtual cockpit scenario to take over control [Comerford et al 2013].
  2. Displacement of the second pilot to the ground, Much like some of the military drones, this concept involves a pilot displaced to the ground and via a reliable and secure data link, control the plane remotely [Discroll et al 2017].  For this method to be feasible, both pilot must be clear on the control allocation protocol and know what and why the other pilot is doing and who is in control at any point in time to avoid any control conflict.  The potential workload issues which come along with this is discussed by many in research literature.
  3. Replacement of the second pilot with on-board automation

This concept would be the next logical step and possibly the path towards pilotless aircraft.  This de-crewing trend and the relationship between man and machine or human in the loop issues must be resolved for it to be feasible [Malik and Gollnick 2016]. Many manufacturers like Embraer, who are closer to the realm of single pilot operations in general aviation are already developing technologies at various automation levels.

  1. Replacement of the second pilot with on-board and ground automation.

As an extension to the V scenario, to enhance safety and provide for additional redundancy, this concept involves additional automation on the ground.

  1. Displacement of the second pilot with one or multiple (redundant) ground operator(s), additional on-board and ground automation.

A project undertaken by NASA’s Ames Research Centre, is essentially a combination of the elements in the previously mentioned concepts.  In the many pieces to this puzzle, it comprises an on-board single pilot, Ground Operator(s), ground automation as well as wingmen (pilots in the vicinity).  The benefits to this change will only be seen when it is implemented throughout the air transportation system.  Again, the on-board pilot functions will be on a macromanagement level, tasked to manage the risks and resources to complete the mission [Lathceter 2017].  Whereas automation, at a micro-management level will be used to manage tasks such as engine management, aircraft’s trajectory and adhering to air traffic instructions [Bilmoria et al 2014].

An important element to this concept is the role of the Ground Station (GS) whether this be one or multiple stations.  This has been the nature of current research conducted by NASA [Dao et al 2015].  The concept is based on the pilot on-board during high workload times, requesting “dedicated assistance”.  The functions of the Ground Operator (GO) include providing flight monitoring services and decision-support functions, which current dispatchers in airlines already perform. As suggested in the literature, there are four main roles which may or may not consist of all four.

The remote pilot already covered in IV, involves remote controlling from the GS.  As mentioned, all the implications with secure and reliable data links and protocols for authority must exist.

The Harbor Pilot concept as discussed by [Koltz et al 2015] and was developed to combat the high workload phases of flight during take-off, approach and landing.  The advantage of this concept is a single harbour pilot has an intimate knowledge of the local terminal airspace, procedures and operations.  The harbour pilot will be providing dedicated assistance to all departing and arriving aircraft and may do so for multiple nominal aircraft.

As the name suggests, the Hybrid GOconcept will do mostly all the support of the Harbour Pilot, but also dedicated pilot support to a single off-nominal aircraft.  When a single pilot requests for the dedicated assistance, the other nominal aircraft will be handing off all other aircraft   The services of this Hybrid G is not restricted to any one airline.  Once the issues with the off-nominal aircraft have been resolved, the will resume its previous Hybrid GO role. 

Lastly, the Specialist GO, have defined the different roles between a Ground Associates (GA) and Ground Pilot (GP).  Essentially, when an on-board pilot requests for dedicated assistance, the GP will take over the control of the aircraft from the GA.  Before handing over, the GA will provide the GP with a briefing of the situation and will continue to support the off-nominal aircraft with dispatch or possibly other airlines control centre support.

With the exception of category I, an evaluation of the category concepts can be summarised in the table 1.   As the literature suggested by [Graham et al 2014], for safety reasons, this concept would not be feasible for future implementation.  The removal of a pilot would not involve any change to the current operational environment but would radically change the workload, especially in the case of pilot incapacitation where implications would impair the safety of the flight.  As each of the conceptual design approaches have their merit, they also bring about new challenges.  A feasibility study is only possible when all the facets of such a complex system have been considered.  Furthermore, other considerations such as social acceptance; public perception and whether they would accept the single pilot operating on their flight; legal implications such as certification, responsibility and liability; and finally economical; training, development casts, installation of modifications to current fleet, running costs and insurance premiums, all need to be reviewed individually.

Some worthy observations during the research was the tendency for the focus to be on the extreme cases during nominal and nonnominal periods.  When in reality, day-today pilot activities are rarely considered as perfect nor are there constant emergencies situations.  More commonly, pilots are faced with challenges that require them to manage circumstances presented to them during the flight such as weather, traffic and delays.  Academic in nature, the temptation of just bundling up solutions to solve the multifaceted challenges of SPO operations can only complicate the issue.  This not only convolutes arguments, but it also over complicates conceptual designs.  The most feasible approach would provide a concise, consistent measures in the allocation of responsibility and perhaps working from a “clean slate”.  While literature offer many conceptual frameworks, there has yet to be a concept which alters to minds of the public but to leave them with more unanswered questions than practical solutions.



Removal of the second pilot, with a capable person for relief when required

•      The additional crew members on board, potentially offset the benefits of SPO

•      Redesigning of the flight deck will be necessary to enable capable persons can adapt intuitively

•      Security of the flight deck may become an issue


Virtual pilot in an aircraft in the vicinity

•      Virtual pilots required offset the benefits of SPO

•      Redesigning of the flight deck will be necessary to enable capable persons can adapt intuitively

•      Security of the flight deck may become an issue


Displacement of the second pilot to the ground


•      Development and implementation cost of any remote pilot technologies, through personnel training and secure lines of communication may initially deem these options unfeasible

•      Minimal cost savings and can only be realised through a reduction of accommodation costs, when the number of pilot required for each fleet would not change

•      This concept may be used as a steppingstone to further complex concepts


Replacement of the second pilot with on-board automation


•      As mentioned, there are already versions of advanced automation in existence today, however issues arise between the man and machine.  Final authority and decision making are protocols which must be in place

•      Issues such as mode awareness and inadequate trust towards automation may lead to self-induced issues and must be resolved


Replacement of the second pilot with on-board and ground automation


• The complications of this categories are highlighted in E along with high development costs for ground stations


Displacement of the second pilot with one or multiple (redundant) ground operator(s), additional onboard and ground automation


•      Development and implementation cost of any remote pilot technologies, through personnel training and secure lines of communication may initially deem these options unfeasible

•      The complications of this categories are highlighted in E along with high development costs for ground stations

Table 1 Summary of Concept Categories – Feasibility Assessment

3.      The Big Boys

In a many recent online media sources state the two largest aircraft manufacturers, Airbus and Boeing are contemplating the conception of designing their next masterpiece with a single crew member at the controls.

Ultimately, safety is paramount, especially in the eyes of the airline’s customer.  The aftermath of the disappearance of Malaysian Airlines flight MH2370 and the suicidal mission of the First Officer on Germanwings flight 9525, draw some concerns to human performance limitations in which wouldn’t exist in technology.  So, are these two examples along with other similar cases substantial enough for the aircraft designers reduce the input of the human pilot?  Then again, the opposing question still remains, can the advancements in technology be safer than the human pilot?  Certainly, in the cases of QANTAS flight QF72 and US Airways flight 1549, both quite different in the root cause, nevertheless the Captain of each flight have been held as living hero’s, as they saved the lives of everyone on board their flight.  Sullenberger said, “Having only one pilot in any commercial aircraft flies in the face of evidence and logic. Every safety protocol we have is predicated on having two pilots work seamlessly together as an expert team cross-checking and backing each other up.” [Flight Safety Australia 2018].

Where is the motivation to reduce flight crew numbers?  It is quite simple, it’s the saving the airlines amounting to billions in pilot salaries and training.  In a study by the Swiss bank UBS stated that the transition would provide a cost saving of at least 15 billion for the industry and could possibly see single pilot aircraft as soon as 2022 to 2023 [CNBC 2017].

Furthermore, the direction of SPO could really alleviate the current and foreseen issue with the global pilot shortage issues.  This would be the motivation would be both Airbus and Boeing flesh out their SPO concepts at the Singapore Airshow in February 2018.  The manufacturers recognise the challenges of public perception, however, have stated that this direction would be implemented first in cargo transport.  In fact, the Chief Operating Officer, Jeffrey Lam at Singapore’s ST Aerospace has stated, “The interest is global…I think some (cargo operators) are watching each other; quite certainly if one jumps on board, you would expect the others to not want to fall behind because there’s a lot of cost savings here.”  With the Director General of Singapore’s Civil Aviation Authority saying flight technology was advanced enough to create a one-pilot cockpit in as little as five years.  Also adding, that it would be a matter of human factors, mentioning pilot incapacitation, and fatigue are amongst the biggest problems the concept faces. [Guardian 2018].  The concept will have the regulators up in arms, especially after the Germanwings crash, when the European regulators introduced new rules requiring two people in the flight deck, only assessing two years later had to lift the decision as it added little value to security while introducing new risk.  Whilst some members in the aviation community have very little appetite for the SPO concept, others remain hopeful and believe it will take some time for it to sink into the perception of the travelling public.

4.      Modelling Future Flight Decks

Considering again the Hudson case, human error have contributed to approximately 60% of accidents.  So, the question is, will the elements which SPO concepts be at a minimum be safer than the current system of two pilots?   Commercial airliners operate in environments where a number of agencies are required to infuse their work efforts to make a mission successful.  This type of complex system is commonly referred to as a sociotechnical system.  To assess such a complex system, many research literature have used alternative methodological approaches to analyse the effects of RCO, such as workload evaluations.  To better understand the complexity of a sociotechnical system, this next section will be examining concepts using Cognitive Work Analysis (CWA).  Combining the efforts, we will examine the conceptual models using the Social Network Analysis (SNA) to analyse these models.

As discussed in category V, many developing concepts such as Cognitive Adaptive Man-Machine Interface (CAMMI) project [Keinrath et al 2010], use adaptive artificial intelligence in the automation technology.  This concept predicates the notion of incorporating systems particularly direct voice input/output systems, data linking and synthetic vision systems to provide further pilot automated support.  The arguments surrounding the second pilot on board is based on the workload factor, especially during non-nominal situations, such as pilot incapacitation.  The assertions be easily defied practically when the current commercial airliner are not only certified to be operated by a single pilot, but the fact that reducing one member in the cockpit will not equate to halving the workload.  Since the reduction in crew members to two, the current level of automation has already considerably reduced the workload for the crew.  Even though the presumption is the second member shares the workload, there have been instances where ineffective Crew Resource Management (CRM have resulted in accidents.  A study conducted by the [Civil Aviation Authority 2008], this has been classified as being a contributory factor to 23% of aircraft accidents.  Other findings found that 39% of accidents were a result of the second pilot failing to check the incorrect application of procedures.  It was also found in 27% of cases, the causal factor for position awareness.  The study may exhibit a rudimentary analysis and it does not account for the many occasions where the effective distribution of the work tasks have prevented an accident from occurring.   The data for these commendable cases are not available, however relevant observational data from [Thomas 2003], reports that 47% of error committed by Captains were intentional and 38.5% were unintentional procedural non-compliance.  Hence, the argument that the removal of the second pilot narrows the scope for accidents resulting in the ineffective communications. 

The question begs to be answered, so is there really a need for a second pilot?  The biggest predicaments for the SPO is pilot incapacitation and pilot death.  A study of US airline pilots by [DeJohn et al 2004] found there were only 39 occasions of incapacitation and 11 occasions where the pilot was impaired.  There were only seven instances recorded where the safety of the flight was significantly impacted.  If these results hold the test of time, then perhaps there are no feasible justifications to assume that technology is the issue.  It is conceivable, the focus should be placed in understanding the complex environment airliners operate and designing pilot interfaces to ensure safe operations in nominal and non-nominal situations.  In one of the more plausible concepts (concept VII), there are three elements in which need to be considered in terms of design, the functionality of each element have already been described in the above and hence there are only small variations listed in the table below [Stanton et al 2014].

These elements will provide a base to which the cognitive work analysis can be made in order to assess the proposals efficacy and conjecture the required technology for future development.  As the previous text stated, besides minimal changes to the architecture of the interfaces of the flight deck, there will be little difference to the current designs.  The qualification for the pilot on board shall be at the Air Transport Pilot Licence (ATPL) level. 

It is envisioned that the procedures with regard to Air Traffic Management will not be recreated, using the current protocols.   So long as this does not jeopardise the safety of the flight.



Pilot in Ground Station






A. Single pilot aircraft

C. Single pilot aircraft with additional pilot on the ground


B. Single pilot aircraft with additional automation mirror on the ground

D. Single pilot aircraft with additional automation mirror on the ground and additional pilot on the ground

Table 2 Comparison of four potential versions of SPO

Sociotechnical systems are complex due to the number of moving parts, for Flight Operations, this consists of the interweaving interactions between human and machine operating in a dynamic and fast paced environment.  Significant challenges arise when modelling for such complex systems and requires Systems Ergonomics approaches to adequately design the future of these systems.  [Wilson and Crayon 2014].  The Cognitive Work Analysis (CWA) provides a structured framework so that complex systems can be developed and analysed.  CWA has been found to be beneficial to designing complex systems or integrating new systems to exiting technology.  It provides a framework towards system design and supports analysis at all segments of the systems life-cycle [Naikar and Saderson 2001].  CWA comprises of five phases:

  1. Work Domain Analysis (WDA)
  2. Control Task Analysis (CTA)
  3. Strategies Analysis (STA)
  4. Social Organisation and Cooperation Analysis (SOCA) and;
  5. Worker compensation Analysis (WCA)

In this paper we will focus on the WDA, ConTA and SOCA, commonly used to examine some of the effects of RCO in the commercial aviation.  Using the CWA framework complemented by the Social Network Analysis (SNA), this will allow us to investigate the effects of reducing crew in this complex system.  The schemes can guide the analyst to refine the question of why the system exists in the first place and what work can be achieved within the parameters and which agent is best to execute them, at the same time ascertaining the aptitudes required to achieve them.  The following will be demonstrations of how CWA has been used to explore various options for system configurations in a number of operating scenarios.  The  literature then further analyses these scenarios complemented by a Social Network Analysis (SNA) to provide an indication of the resilience of each operational system [Barber et al 2013].  The outcomes of these analysis can provide a basis for systems architecture for the Single Pilot Operation (SPO), as well as assist in defining the assembly of future automation requirements and support roles of the Ground Station.  The baseline example used [Stanton et al 2016] is a very common airliner the Airbus A320 as a two-crew operated aircraft.  This is then compared to the same aircraft (certified to be flown by a single pilot) operated by a single pilot.  This is then followed by a comparative analysis of four feasible configurations presented in table 3. 

To formulate CWA and SNA, credible material was drawn from several sources, such as the Airbus Operations Manuals, Standard Operating Procedures, as well as experienced Captains.  [McIlroy and Stanton 2011] uses the most commonly used component of CWA, the Work Domain Analysis (WDA) to identify the domain of work.  They identified the constraints to worker behaviour within the problem space and is predicated more so towards the functionality rather than the behavioural level.  Once the environment in which the work is conducted has been defined, the better we can understand the constraints for any work actions within any component in the system.  Therefore, providing a fundamental foundation to aircraft design.  The following are five levels (top to bottom) are generally used in the thought process.  It is not the objective of this paper to go into detail, however a general description of each level has been provided [McIlroy and Stanton 2011]:

•          Function purposes – Purely just the overall purpose of the system and the reason the system exists. In the case studied, this is to safely transport passenger or freight from A to B, and to ensure the aircraft is operated at it optimal to provide increases to shareholder dividends.

•          Values and Priority Measures – The next level down, further constraints have been identified, such as maximizing passenger comfort, minimising operational risk, maximizing the utilization of aircraft, all at the same time reducing operating costs.  Certain measures used to determine how well the system reached its functional potential.  This is the way configuration of future aircraft systems can be designed to fulfil its potential.

Design Interfaces

The aircraft (including the pilot)

• The majority of the components which exist in todays cockpit will be in large be intact and be able to function the current air traffic system.  

Ground Station (GS) (including the second pilot and real-time navigation/flight planning and engineering support)

•      As mentioned, the main role for this element is to support the pilot without necessarily duplicating the functions.  These roles will be Subject Matter Experts in the role.

•      Ground support will have the ability to control the aircraft remotely, via data links to manipulate the aircraft automation.  The control of the aircraft manipulating the primary flight control manually will only be used in dire situations.

•      Re-designing the cockpit will be required, however the emphasis should also be towards changing the overall philosophy of operating the aircraft.

•      The GS will also be crewed with similarly qualified pilots which can be rotated to enhance the mutual situational awareness between the functions of the ground and air roles.

System ‘mirror’ (including real time representation of the of the aircraft’s main systems

•      This independent system will be a mirror and represent the aircrafts system states.  These will include the Flight Management Computer (FMC), autothrust and the general aircraft configuration.

•      During nominal times, the aircrafts automation will be mirrored and transparent to all operators in the system In the unlikely event of a datalink failure, the aircraft systems will mirror the last configuration and provide system updates when available.

Table 3 Design Interfaces

Figure 2 Source: Example of a Work Domain Analysis showing the five levels (Source: Neis S.M., Klingauf U., 2018)

•          Purpose-related Functions – These are listed and have the ability to impact one or more Values and Priority measures.  They are linked to object related processors and can be any of the following; aviate, navigate, communicate, manage and warn.  Using the figure 1, from the top, you can follow the links down and have answers to questions, ‘why is this needed?’ Therefore, to ‘maximise passenger comfort’ and ‘maximise the utilization of the aircraft’.  Furthermore, the links down from ‘aviate’ the allows the question of how this is achieved can be aircraft ‘airspeed and rate of climb.

•          Object-related Processes – At this level the related mechanisms, capture the processes operated by physical objects used to perform the related design functions.  Most importantly, they can describe the affordances of physical objects independently of the designed intent.

•          Physical Objects – at the bottom level is a list of physical objects which have direct relevance to the operations of SPO.  Examples are, throttle, rudder pedals, brakes, nav/comms, flight management system, electrical system, fuels system and the list goes on.

In the next phase of CWA framework, the Control Task Analysis (ConTA) all analysts to find a way to represent the activity within these work systems and characterize them by both work situations and functions.

•          Work functions – are associated with manipulating the controls and managing of the aircraft

•          Work situations – can be broken down from recurring schedules or specific localities (phases of flight as designated by ICAO)

The use of the Contextual Activity Template (CAT) is commonly used to represent the relationship between work functions and work situations and can be plotted on two axes for analysis.  Figure 3 is an example of CAT and the circles represent work functions and the bars indicate extent of which the work activity occurs.  Whereas, the dotted boxes around each circle present all work situations where a work function could occur.  The template is indicative of all the phases of a flight.  However, it is important to note that the purpose of this paper is to provide an overall explanation the CWA, with the full details in the research literature.

Moving to the third phase of the analysis the Social Organisational Cooperation Analysis-Contextual Activity Template is applied to allocate the functions of personnel to the functions across the situation.  The SOCA-CAT describes how key roles are distributed between the diverse resources of social and technical agents.  This template is mainly focused on team communications and cooperation and is used extensively when considering the dynamic allocation of resources within the network [Schmid et al 2019].

Lastly, Social Network Analysis (SNA) is used to evaluate and represent the relationship between the agents and objects.  As defined by [Driskell and Mullen 2005], a social network is a set or a team of agents that share a relationship with one another. In the case study, the social network expanded to incorporate agencies such as Air Traffic Control and Dispatch.

Considering when new technology is introduced into the system, this could introduce new hazardous situations, leading to constant changes in aircraft operational architecture.  SNA is predicated on the notion that the relationship between the agent’s has substantial effect to the actions executed and performance achieved by the network.  Social networks can be best represented by the use of mathematical and graphical presentations.  The degree of betweenness and closeness (measures of centrality) and the overall density of the network can be calculated.  The measure of centrality will allow us to identify which agent plays the key role and the classification of the network structure.  The data consists of a number of metrics associated with the study of entire networks.  The network size can also determine the complexity of the network.  First, we must first define the aircraft operating network required to be analysed.  Once this has been specified, the people and objects also need defining.  In the case of SPO, the agents to name a few would consist of the Pilot Flying, the Pilot Monitoring, air traffic control/management, Dispatch and engineering.  The contrast can only be made if the baseline operations is provided so a comparison can be made against the concept of single piloted aircraft.  In table 4, the matrix represents the frequency of communication with each of the identified agents.  This will  determine whether or not a particular agent can be associated with the proposed single pilot concept, particularly the frequency of communications.

Network agents: From/to









Pilot flying (PF)








Pilot monitoring (PM)








Aircraft automation (AA)
















Dispatch (D)








Flight planning (FP)








Ground handling (GH)








Fuellers (F)








Table 4 Association matrix (Source: Neis S.M., Klingauf U., 2018)

Figure 3  Example of a Work Domain Analysis showing the five levels (Source: Neis S.M., Klingauf U., 2018)

In figure 4, is an example of an aircraft during taking off.  The Social Network diagram visually portrays the network in a mesh like fashion.  These mesh-like formations are generally considered to quite robust [Stanton et al 2008].

The data in the matrix is derived from counting the frequency of collaborative/cooperative associations.  This ultimately will form the basis of numerical analysis using SNA statistics figure 3.  The analysis can take form from a number of perspectives either the overall network or analyse specified parameters.

The SNA was used in the case of the four feasible configurations.  The networks dipicted a mesh like formation, with fewer connections in Option A, comparable to more connections in Option D.  As suggested in [Stanton et al 2016], generally the more connections the more robust the network.  This is not to say that everything must be connected, in fact of unnecessary connection can mean irrelevant information within the network.  The analysis of SOCA-CAT displays some disparities in the functional loading when comparing single pilot to current flight operations.

In table 6, it illustrates that the removal of a single pilot has a significant impact to the functional loading to the remaining pilot, as well as reducing the density of the network.  It also shows in single pilot operations with a pilot on the ground mostly resembles the current operations.  With Option D, demonstrating the most density would be considered the most robust of all the networks, with less dependency of the single pilot being in the centre of the network.  [Walker et al 2009].

Figure 4  Example of a Network diagram for baseline aircraft generic operational (Source: Neis S.M., Klingauf U., 2018)

5.       Conclusion

There has been extensive research on Single Pilot Operations in commercial airliners by many stakeholders in the past decades. The two largest commercial aircraft manufacturers Airbus and Boeing have publicly stated, “We are studying that, and where you will first see that is probably in cargo transport, so the passenger question is off the table,” Boeing research and technology vice-president Charles Toups said of one-pilot operations at the Singapore Airshow last year.  The popularity is widespread and different theories and quantitative models have been applied to measure the feasibility.  Most literature brush over the topic by fashioning their interpretation of concept models without truly understanding the nature of the many facets involved in one flight.  The typical commercial airliner in its quest to safely transport passengers or freight for that matter operate in a complex system, commonly referred to as a sociotechnical system.

In this paper, uncovers most of the research to provide the reader some understanding to the subject and presented the most feasible solution.  The first instance, the scrutiny of many SPO concepts are revealed beginning with the notion of just removing a crew member in the cockpit.  The argument of impracticability is easily rebutted with the inquiry of what the options are in the case of pilot incapacitation.  After identifying two main design approaches, the discretion of either replacing or displacing the second pilot.  Whether the approach was incorporated an advanced automation system, ground stations with a pilot, we identified a further seven concept categories.  These were just an amalgamation of different agents.  Consideration was based alongside multiple criteria’s and a logical evaluation was given.  In general, the displacement of the second pilot with one or multiple ground operator(s) additional on-board and ground automation became obviously a prominent solution.  In the course of research, there some observations requiring attention for further investigations.  An in depth understanding of human factors and the human interfaces with machines is still noticeably lacking.  Exposing issues of ultimate authority and responsibility allocation, as well as human interface designed flight decks all require further study.  Nevertheless, purely judging from the literature, the most feasible concept would be category VII

This then brings about controversy with reason whether the issue lies in human factor issues or the limitations in technology.  Many approaches have placed focus on advanced automation to replace the second pilot, only to achieve mixed success.  Some demising statistic have reasonably deflated approaches with solutions which involve advanced technology and by solving the human factor requirements, the surfacing of SPO would be not be unrealistic within the very near future.  Similarly, the literature supports the conceptual conclusion of displacing the pilot with ground stations.  In fact, facts have been drawn to the readers and evidently have proven that in many cases, the assistance provided from the ground may be of higher quality when better targeted when compared to the traditional two crew.  Cognitive Work Analysis in combination with Social Work Analysis can provide a platform to which a formative systems approach where the function allocation between agents and subsequent functional loading can be better understood.  The SNA contends to the same option as mentioned above, with the additional mirrored system approach and has found this more resilient to current operations.  This research will be reliable with real-time simulations.  In closing, as much as the option of displacing the second pilot to a ground station is combining all these agents in phased approach is the most feasible solution.  Consideration to taking the revolutionary approach and start with a clean slate, with the “pilotless aircraft” concept being the end goal could also be a possibility.


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