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Personal Plane: Assessment and Validation of Pioneering Concepts for Personal Air Transport Systems

Personal Plane: Assessment and Validation of Pioneering Concepts for Personal Air Transport Systems

Final Report Summary - PPLANE (Personal plane: assessment and validation of pioneering concepts for personal air transport systems)

Executive summary:

The PPLANE project was proposed to the European Commission (EC) in 2008, aimed at stimulating radical and novel ideas for air transport through a systematic approach. This innovative project, selected and subsequently launched in October 2009, was designed to investigate, define and evaluate a Personal air transport system (PATS), inspiring breakthrough system ideas that enable public, personal, air transport in the future.

The PPLANE project aims to investigate, define and evaluate a PATS, offering a viable alternative to the current transport system in European Member States. The definition of promising new concepts for future PATS was undertaken, followed by an assessment phase that considered important selection criteria such as security and safety, automation and control (A&C), human factors and environment and leading to a set of recommendations on the most advantageous PATS concepts for implementation throughout Europe.

The methodology adopted in the project enabled the identification of future customer needs for a PATS fully compliant with the expectations of European citizens, while taking into account developing new technologies expected to reach maturity by the post-SESAR deployment phase (including appropriate socio-economic considerations that may arise). The system definition process led to the proposal of a comprehensive personal air transport solution as an organisational, regulatory and technical concept that enables a variety of fully-automated (no pilot on-board), electrically-powered vehicles to perform on-demand personal and ground supported flights. A wide-selection of compliant air vehicles of varying sizes are included in the system. Its ground support infrastructure is integrated into the global Air transport system (ATS), providing efficient and conflict-free, highly-automated flight service, controlled by SESAR derived, 4D contract-based Air traffic management (ATM).

The PPLANE system feasibility benefits from the increasingly-automated air traffic system, which continues to strive for the integration of remotely-piloted aircraft systems in European Union (EU) airspace.

It is anticipated that PPLANE vehicles will be managed by operators providing vehicles, maintenance, handling and flight planning that will market their services directly to consumers. Since the planes will be fully-automated, remote pilots stationed on the ground will be hired by the operators to take responsibility for PPLANE flights. PPLANE vehicle passengers will not require specific competency or training, just a basic pre-flight briefing. This proposed system will address most environmental concerns, including air and noise pollution. The PPLANE system will utilise a network of airports, PPLANE ports (PPorts), fully-integrated in the system and properly equipped to handle PPLANE traffic. No potential Show-stoppers have been identified. PPLANE's vision is in-line with EC roadmap stating that: Automation has changed the roles of both the pilot and the air traffic controller. Their roles are now as strategic managers and hands-off supervisors, only intervening when necessary.

The PPLANE system will be one segment of a multi-modal European transport system providing the European citizen with a wide variety of transport options. Furthermore, optimised planning will make the system highly-efficient, reducing to a minimum the number of empty seats. PPLANE would serve as an excellent, complementary addition to existing means of transportation, reducing road congestion and making air travel more accessible to the average European citizen. PATS would also serve a key strategic role in European industry since it calls for maintaining adequate, European-based skills and research infrastructure for the emerging market of highly-automated aircraft and ATM systems. Integrated with other modes of transportation, PPLANE will serve to link European countries to one another and to the rest of the world. However, further technological and social research is necessary in order to solidify the European role in pioneering the air transport of the future.

Project context and objectives:

Project context
Introduction

Pioneering the air transport of the future is not a simple issue. Nowadays, a few years after the first flight centennial celebration, the ATS is far from having reached a stable and definitive state. This is even more obvious for general aviation and personal transport aircraft, a field that has not been investigated as deeply and developed as much as the commercial transport field. Of course, the business perspectives of conventional airlines and of personal transport cannot be easily compared nowadays since the scales are different.

However, technology, mostly automation, is maturing making safe personal aircraft closer to reality. Personal transport could thus become a significant element of a future multi-modal transport system.

In the United States, National Aeronautics and Space Administration (NASA) has launched an initiative aimed at utilising emerging aviation technologies that can be integrated into operations in a small airport environment. The output of this initiative was the introduction of novel aircraft on the market such as the Cirrus.

In Europe, the Commission has recently started to pave the way to better understanding about a future personal air transportation system. Two tangible results have emerged from that investigation. The first one is the EPATS coordinated action that has set up a network of experts aiming to analyse these issues. The second one is the out-of-the-box project aimed at stimulating radical and novel ideas for air transport through a systematic approach. This project was built around a desire to encourage more innovative, radical and farsighted ideas than conventional, evolutionary research. Initially, 100 ideas were defined. Using a weighted set of criteria, the project finally ended with the selection of 6 ideas for follow-up projects. One of these ideas are PATS.

Compared to conventional airlines and business jets or to general aviation, (PATS) is a new paradigm in air transport. The personal air vehicle is analogous to the private car in terms of accessibility and ease of operation, yet delivers the benefits of speed and routing efficiencies that are only possible via direct-to-destination flight. It differs from general aviation aircraft by making the air vehicle usable by non-pilot passengers. It is anticipated that air transport will continue to evolve towards smaller aircraft exhibiting personal, rather than commercial, properties.

PATS are not a near-term system. Considerable progress beyond the current state-of-the-art will have to take place before personal aircraft will be taking off and landing in abundance from airfields only a short distance away from the passengers' destination. This technological progress will have to be accompanied by progress in aspects such as regulation, licensing, infrastructure, controlling, synergies with existing forms of transportation (co-modality), etc.

PPLANE has taken this concept one step further. The preliminary assumption was that automation should be developed to allow a regular Joe? to use a personal aircraft, in various weather conditions, without any command and control difficulties, using a human friendly navigation interface.

A systematic and innovative approach has been developed and implemented within the PPLANE project in order to understand and analyse customers' needs and to propose novel ideas for a PATS. This system would satisfy the end users' need, will be affordable, and will respect all environmental and social constraints.

The PPLANE consortium is coordinated by ONERA (France), administratively supported by Intergam Communications (Israel), and includes leading organisations from 11 European countries and associate states from different aviation domains in industry, research and academy. The team members are: ONERA (France), IAI (Israel), AIR (Slovenia), UNIBO (Italy), BUT (Czech Republic), CIRA (Italy), ITG (Israel), WUT (Poland), DLR (Germany), INTA (Spain), NLR (Netherlands), UPAT (Greece), and REA (Hungary).

1.2 Surface transport

Gridlocked highways increasingly burden our society. Currently, the doorstep-to-doorstep average speed for cars in the United States is 35 mph and is further decreasing year by year. Statistics show that, on average, cars carry only 1.3 people, even with High occupancy vehicle (HOV) lanes in place.

The situation in Europe is not better. European surface transport is not homogenous and highly depends on local road system. For example the total length of highways in Poland is equal approximately to 600 km (with respect to the country area equal to 312 000 km2), whereas Germany has 13 000 km of highways (with respect to area of 356 000 km2). From the one side this disproportion is a barrier for higher economic growth in New Member States, but from the other side it creates a chance for rapid growth of door-to-door transportation system (PATS).

Personal transportation today consists of on-surface vehicles (cars) limited by low speed (up to 130 km / h on highways when the traffic is low), high fuel consumption, major safety hazards and the need for costly maintenance of roads and infrastructure. These factors limit the distance one can live conveniently from work, worsening the core-periphery syndrome in which employment centres become residential centres (core) leaving remotes areas unexploited for employment or residence (periphery).

Travelling larger distances usually requires using public mass transportation like trains or commercial airplanes. Trains today travel between 100 to 300 km / h and are very limited to specific railways and stations, therefore limiting the traveller to few destinations only. Additional constraints are the fixed timetables, forcing passengers to adjust their plans according to an external schedule, and issues of demand and supply which reflect on the vacancy or non-vacancy of trains.

1.3 Public air transport

Although regional airlines airplanes fly faster, over 300 km / h, they are large and require long distance speed increase and decrease intervals. Public air-transportation, much more than trains, is also very limited to specific airline destinations, large commercial airports and pre-set timetables. In the United States, the average door-to-door speed for automobiles is 55 km / h and 90 km / h for airliners on trips of up to 400 km. The burden due to security inspections is also a reason for a reduction of this speed even further as travellers must, in some cases, arrive at the airport 3 hours prior to take-off.

A growing inconvenience accompanies the experience of flying. The terminals at most major airports are crowded and noisy. There is reluctance to check baggage for fear of losing it, having it damaged by Security Inspectors or having to wait a significant amount of time to get them back once arrived at destination. At the security gate security agents exhort travellers to unload their pockets, jackets and tote-bags. Travellers must remove shoes, belts with metal buckles, and wristwatches. They must empty all pockets of small change, key fobs, and other personal items. Then they have to re-dress in a hurry-up, awkward fashion while an aura of fear and urgency reigns over the entire area.

After landing, travellers find more delays in the form of freeways toward town that are gridlocked with rush-hour traffic, overloaded trains or overpriced taxis.

For these reasons, the public air-transport available today is not efficient for mid-range distances of under 800 km.

1.4 General aviation

General aviation is not currently considered as a transport means due to several reasons. The primary one is that piloting an aircraft is not as easy and accessible as driving a car. Flying a plane brings new challenges to humans. The instrumentation needed to fly is more complex than surface transport and the efforts to learn how to use it are time consuming and skill demanding.

Furthermore, preparing a flight is far more complex than preparing a travel by car. There are no road signs in the air, there is no possibility to stop and consult a map and the weather has bigger influence on an aircraft that it has on a car.

The last reason is cost. A plane is technologically more complex than a car, its acquisition cost is higher, and flying is more energy demanding than using the ground means of transportation. The utilisation cost of an aircraft is consequently higher than for cars, except for the cases when car travel is impossible such as sea, rivers, and mountains obstacles.

Most general aviation aircraft are poorly equipped and only a small part of this fleet is able to be flown using instrumental flight rules. This limits their flight capabilities to good weather conditions.

Consequently general aviation is mostly used today for leisure when weather conditions are fine, for training and, marginally, as a transport means by some business man having their own aircraft and using it when this option is possible.

1.5 Personal air transport

The state-of-the-art regarding PATS in Europe is not highly developed for historical, economic and technological reasons. These are 2 to 6 passengers aircraft that are mostly used for leisure but can also be used by business travellers.

This category of PATS cannot exist if the user needs a pilot to fly the air vehicle (too expensive) or he or she have to be themselves a well-educated and trained pilot (too much time and money demanding). Thus, the solution is to make an air vehicle able to fly without a pilot on board.

Technology progresses have to be made in aircraft design to make aircraft safe in a large flight envelope. Automatisms have to be developed to allow a regular Joe to use his own aircraft without any difficulties in various weather conditions, both from the command and control aspects and for its integration into the airspace with the other sky users.

This is not simple, but the emerging Unmanned aircraft system (UAS) technology shows that an aircraft is able to fly even with no pilots on board. As a consequence, it should be possible to fly an aircraft with a low proficiency driver, providing he has the means to ask for a destination, monitor the flight until reaching that destination and get help and information from a ground component of the system.

2. Project objectives

Main objective

The PPLANE project aims to investigate, define and evaluate a PATS, stimulating breakthrough system ideas that enable public, personal air transport in the future. The objective of such a system is to avoid the ever increasing congestion on European roads and to offer a viable alternative for the current transport system in European Member States.

Promising new concepts for future PATS were undertaken, followed by an assessment phase that considered important selection criteria such as security and safety, A&C, human factors and environment; and leading to a set of recommendations on the most advantageous PATS concepts for implementation throughout Europe.

2.2 Specific objectives

- Define, evaluate and select promising new concepts for future PATSs (PATS).
- Assess these concepts taking into account the following main selection criteria: Security and safety (including regulatory issues), A&C, human factors and environment.
- Analyse and recommend the most beneficial concepts.
- Provide a road-map for implementation of PATS across Europe.

2.3 Approach

The main issues that have been addressed are divided into five domains: security and safety, A&C, environmental impact, energy constraints, human factors and social acceptance. In each domain, areas such as technologies, social acceptance, regulation, and affordability are considered resulting in the design of viable systems ideas.

During the first phase of the project, a comprehensive methodology was implemented in order to select and prioritise the concepts of operations and the attributes of the PPLANE system. The methodology consists of two complementary means: a Delphi survey and a design engineering tool named House of Quality (HoQ). The Delphi Survey was conducted among several hundred external experts in aeronautics and related fields such as regulation, air traffic control, aircraft design and manufacture, safety and security. The experts were asked to suggest and rank operational parameters, technical features and attributes of future PAT systems from the end-user perspective. The survey resulted in a comprehensive set of customer needs. The top rated attributes: safety, door to door time and accessibility. Other parameters: expected flight Range 300 - 540 km, capacity 4 - 6 seats cruise speed 230 - 340 km / h, cost 1.5 - 2.6 times terrestrial.

The HoQ method (tier 1 and tier 2) was used to prioritise and select the desired system. PPLANE system attributes were listed and ranked resulting in multiple concepts of operations and scenarios. Parameters that were listed and weighted included aircraft characteristics, recovery systems, mission, type of runway, guidance, class of airspace, visibility, wind and many more. This methodology enabled to identify and classify the most promising system concepts and scenarios for further analysis.

2.4 Main results and recommendations

PPLANE vehicle should be fully automated, used by a 'regular Joe' with no specific competency or training, and only a pre-flight briefing will be required (emergency procedures); passengers only will be on board, and with a pilot on the ground (GP). Safety and security will be the highest priority including development of a new type of highly reliable Flight control system (FCS) and autopilot. PPLANE is fully-compliant with the expectations of European citizens, while taking into account developing new technologies expected to reach maturity by the post-SESAR deployment phase (including appropriate socio-economic considerations that may arise). The system concept enables a variety of fully-automated (no pilot on-board), electrically-powered vehicles to perform on-demand personal and ground supported flights. A wide-selection of compliant air vehicles of varying sizes is included in the system. Its ground support infrastructure is integrated into the global ATS, providing efficient and conflict-free, highly-automated flight service, controlled by SESAR derived, 4D contract-based ATM.

PPLANE's vision is in-line with EC roadmap: automation has changed the roles of both the pilot and the air traffic controller. Their roles are now as strategic managers and hands-off supervisors, only intervening when necessary.

The PPLANE system will be one segment of a multi-modal European transport system providing the European citizen with a wide variety of transport options. However, further technological and social research is necessary in order to solidify the European role in pioneering the air transport of the future.

Project results:

Description of the main scientific and technical results

WP1: Operational concepts

1.1 Definition of operational and technical parameters and requirements for PPLANE systems

The PPLANE definition and the system selection phases have first been obtained thought a Delphi Survey sent to a list of stakeholders. It allowed the team to defined and build the customer interest, i.e. Voice of Customers (VoC). The HoQ method was then chosen to transform user demands into design guidelines in two successive tiers. The first tier was structured to analyse the relationship between VoC and a wide set of technical feature coming from different authorities (airworthiness) and design disciplines like aerodynamics, flight dynamics, propulsion, and aircraft design.

The second tier answered the question of how the technical parameters from the first tier can be realised in order to satisfy the customer needs. A list of enabling technologies and system features has been proposed to do so. This data enabled the team to finally recommend a number of possible scenarios i.e. types of vehicles and operations modes.

This systematic and innovative approach developed and implemented in WP1 'Operational concepts' for the system definition phase enabled to capture future customers' needs and to propose novel ideas for a PATS. Dealing with the user requirements and with a high-level description of PPLANE system elements, this approach made WP1 central to the overall project work, implementing the methodology of defining and selecting the PPLANE scenarios that were analysed by the other WPs. The activity of WP1 started with an internal brainstorming amongst partners in order to mutually form a baseline understanding of the roles and the structure of the futuristic PPLANE system. It was stimulated by an internal 'What is PPLANE' survey which revealed different views in the group. Then a Delphi survey was used to extract experts' opinions about the envisaged PATS system. It was circulated among 450 European experts and mind setters in aviation, mass transportation and related fields, and eventually helped us creating a concise representation of future customer needs.

Based on 160 responses (26 % reply rate), the main conclusions of the survey are as follows:

- PATS will not reduce total number of cars in Europe
- PATS are more important in locations where present day roads and rails network is underdeveloped
- PATS will reach locations that are not serviced by ground transportation
- PATS is more important for rural areas and small cities than major urban areas
- Range 300 - 540 km
- Flight time 80 - 140 min
- Capacity 4 - 6 seats, 13 - 19 kg luggage
- Cruise speed 230 - 340 km / h
- Altitude 11 000 ft
- Landing / take-off distance (LTOD) 180 - 300 m
- Cost 1.5 - 2.6 times terrestrial.
- Cancellation ratio 1:50 to 1:300.
- Tolerable departure delay 31 - 63 min
- Fully automated flight will not gain public acceptance before 2025 (36 %), but it will eventually be accepted (98 %). Majority of the respondents believe that electric propulsion will be widely used only between 2025-2035
- The expected energy storage device for the electric propulsion is batteries or hydrogen with no clear winner hybrid technologies are not seen as very feasible.
- Roadable airplanes are seen as distant or non-feasible technology by the majority (80 %).

In parallel, two notions were defined to materialise the PPLANE system vision:

- Concept of operation: A high level formal description of how system elements operate and interact in order to safely carry people and luggage from an origin point to a destination point without any on-board human piloting skills.
- Scenario: A formal description of a concept of operation with a specific suitable vehicle i.e. scenarios are simple combinations of ConOps and compatible air-vehicles.

Four main ConOps paradigms have been defined:

- roadable vehicles that carry you from door to door (ground and flight phases combined;
- non-roadable vehicles that fly urban paths and are being operated wherever the vehicles are, from city centre to city centre (thus most likely suitable for VTOL or STOL air vehicles);
- non-roadable vehicles that fly urban paths but being operated from PPLANE ports (PPorts) in city centres â?“ thus most likely suitable for VTOL or STOL air vehicles;
- flying from small PPorts on the outskirts of towns, as a complementary transportation means (not a direct door to door solution).

For all the above mentioned paradigms, the flight could be executed in a single leg, or in a series of hops (i.e. with stopover or without).

Several vehicles have been proposed for the study, with various engineering features, such as single or multi engine, 2 seats up to 6 seats, electrical prolusion, reciprocating engines or a hybrid solution, roadable vehicle or non roadable, etcâ?¦ Twenty nine main scenarios have been generated.

In order to analyse the various options and isolate the most promising ConOps the HoQ methodology has been selected as a Quality function deployment (QFD) process.

QFD is a method to transform user demands into design quality, to deploy the functions forming quality, and to deploy methods for achieving the design quality into subsystems and component parts, and ultimately to specific elements of the manufacturing process. Such a method allows to find the relationships between the customers' needs and product capabilities and to evaluate them based on mutual professional knowledge and expertise of the project partners.

In the project, the HoQ method has been run in two successive tiers. As mentioned previously, the first tier was structured to analyse the relationship between VoC and a wide set of technical feature coming from different authorities (airworthiness) and design disciplines like aerodynamics, propulsion, etc. The second Tier answered the question of how the technical parameters from the first tier can be realised in order to satisfy the customer needs.

The first tier analysis leads to a prioritisation vector showing the most rated parameters in relation to the customers need (i.e. what parameters can satisfy the customers).

The top five priorities were fully automated, consideration of the aerial vehicle as a system, consideration of emergency situations, smart automation and automated PPorts.

In order to answer the tier2 question of how the technical parameters derived in tier 1 could be satisfied, a list of 75 technology enablers and system features has been proposed. The top five technology enablers and system features identified through the tier 2 analysis were advanced avionics, high level of system awareness, redundancy of systems, fault detection and isolation methods and advanced on-board 4D flight management system.

After this identification, 29 representative scenarios (16 with a non-roadable aircraft and 13 with a roadable aircraft) were analysed; the main conclusions were that roadable aircraft have to be disregarded due to the necessary trade-off between roadability requirements and aircraft performance that brings unsustainable efficiency penalties. Conventional take-off and landing (horizontal) vehicle configurations were preferred with electric or hybrid propulsion. The selected number of passengers per vehicle ranged from two to six people.

1.2 PPLANE system architecture

Regarding the overall PPLANE system architecture, the vehicles are only one part of a global system integrated in a network centric architecture? including many other entities contributing to the operation of the PPLANE vehicles.

The actors of the system are the PPLANE manufacturers to be called up in case of severe emergency and for failure management the PPLANE System operation management centre (PSOMC) and other entities such as aircraft, the Remote pilot station (RPS), the Air Traffic Control (ATC), the PPLANE operator centre (POC) and the PPorts. Two redundant data link networks are used, a ground to air one (in blue) linking all PPLANE system entities and providing ground to air nominal communications and an air to air one providing a means to exchange 4D contracts information between aircraft.

The operation phases of a PPLANE flight can be defined with conventional flight phases: before departure, departure, en-route and arrival. The main difference is into the definition of a 4D contract, based on a 4D proposal from POC by the PSOMC. Any 4D contract must be completed in the right manner respecting the time and the flight path accurately. Any modification of a 4D contract (due to weather or other) will necessarily trigger an update request; it will be negotiated / coordinated by PSOMC. The same coordination must be applied for emergency procedures.

1.3 Main conclusions regarding the PPLANE ConOps and requirements

The major conclusions of the definition of operational and technical parameters and requirements for PPLANE systems are that the PPLANE project is about a comprehensive automated system of public but personal air transportation and not about the operation of independent vehicles. However, it was natural for the project group to give a lot of thinking about the vehicle. Concentrating on vehicle was just a way of thinking for our engineering minds in the complete design process of a full system.

The PPLANE system will be an organisational, regulatory and technical solution that enables various conforming vehicles to perform on demand, personal, automated and ground supported flights. Many types of vehicles can be included in the system as long as they comply with the standards imposed by the PPLANE system.

The PPLANE system will include a virtually uniform distributed ground support array providing a conflict free automated flight service, emergency support and information services. The PPLANE vehicles will be operated by organisations (PPLANE operators) providing, maintaining and handling the vehicles, allocating them into service and market their services to the wide public of passengers.

The remote piloting functionality is the entity that takes the responsibility over PPLANE flights and serves as the interface between the PPLANE system and the on-board passengers during the flight. The flight is fully automated with minimal human intervention during operation. Such approach would turn redundant the need to communicate with the aircraft in order to land it safely, when it loses all communications with the outer world.

The most feasible solution for the automated flight seems to be 4D contracting where the vehicle and the system agree on the conflict-free path in time, and as long as both parties are capable of sustaining the contract there is no need for any further clearances, negotiations and control of the flight. When necessary, due to unexpected contingencies, the contracts would be swiftly negotiated and updated to allow the safe continuation of all flights. The PPLANE system will use its own network of airports PPorts that are well defined in the system and properly equipped to handle the PPLANE traffic. A wide variety of PPorts' layout and architecture is currently envisaged.

The concept of roadable airplanes will not fit into the PPLANE system structure. In addition to the efficiency issues of roadable vehicles, the transportation system will be managed by operators who are capable of handling the required multimodality including ground transport segments making roadable aircraft useless.

The combined Delphi and HoQ process enabled the project team to focus on the most promising scenarios. It can be observed from the results, that the preferred ConOps is a conventional take-off / landing vehicle that is being normally operated from PPorts that are located outside the cities. Urban flights are not recommended at all, as they are not listed among the leading top ten scenarios.

Energy efficiency, low environmental impact and good availability seem to be necessary conditions for the PPLANE system to ever succeed. This leads the design concept of the vehicle into the electrical propulsion as the primary concept from the today's technology perspective. Electrically driven vehicles are predominant among the leading scenarios. This result can be predicted as future propulsion is expected to be more environmentally friendly, and modern day GA airplanes show some initial progress in the implementation of electrical propulsion in aerial platforms. The relatively high confidence in electrical engines is also evident among the experts participating in the Delphi survey. But the question of propulsion is not the central question of the PPLANE system, so we are only taking this as a model to develop the PPLANE system and not focus on the vehicles or their propulsion systems.

WP2: Safety and security issues

2.1 Safety objectives

A significant decision factor for the definition of future PPLANE concept is the current state-of-the-art in aircraft categories close to the defined PPLANE aircraft. Therefore, an extensive study of existing aircraft was done with particular attention on typical systems and equipment. The outcome of the study was a database of aircraft representing current situation in different categories of aircraft.

Additionally, PPLANE concept and scenarios were defined within PPLANE project to provide vision of future transportation system. As a basic rule, same safety standard for the PPLANE concept as for current commercial transport of passengers should be established.

2.1.1 Current aircraft in similar categories

The fixed wing aircraft are mostly powered by single piston engine driven by three-blade constant-speed propeller. Structure is either composite or all-metal (but it can also be combined).

Aircraft systems used in the aircraft evolved into reliable products, often with back-up. The usual electrical power system is 28 V DC with one alternator and one battery. Modern trend is to use dual electric system with two alternators and two batteries. FCS in most current GA aircraft is conventional and manual mechanical. The main control surfaces (e.g. aileron, rudder, elevator) are mechanically controlled via cables and pushrods. Flaps and trims are controlled electrically in modern aircraft.

The aircraft are standardly equipped with two electronic navigation systems, one mechanical back-up navigation system, two or three communication receivers and transmitters and one mode S transponder. The most of the new aircraft are also equipped with the two-axis autopilot.

Safety requirements (aircraft systems):
- no catastrophic failure condition should result from the failure of a single component;
- maximum allowable probabilities of events are connected to their effects (Minor with probability < 10-3 per flight hour, major < 10-4, hazardous < 10-5, catastrophic < 10-6).

2.1.2 PPLANE system

PPLANE vehicle is a manned, light aircraft with fully automated operation supplemented by emergency remote control. Controllability by the occupants is deliberately unavailable. No direct control of the vehicle is available.

Control of the PPLANE vehicle can be done using other PPLANE system elements i.e. remote pilot station. In case of emergency, RPS (with ground pilot) can utilise redefinition of trajectories and control over selected systems is possible.

Concept of personal plane has following characteristics (in compliance with described WP1 scenarios #1 to #6):
- 1-4 seats;
- single electric engine (multiengine concept also analysed);
- IFR operation;
- operation from PPorts (small airports close to the cities);
- flights in all types of airspaces at altitudes from 0 up to FL100 (10 000 ft equal to 3 048 m).

Type of use: different types of business use, private flights

Proposed safety requirements (aircraft systems):

- PPLANE system should ensure same safety standard for users as commercial airliners, use of CS 25;
- no catastrophic failure condition should result from the failure of a single component;
- maximum allowable probabilities of events are connected to their effects.

Recommended levels: Minor with probability < 10-3 per flight hour, major < 10-5, hazardous < 10-7, catastrophic < 10-8 or 10-9.

2.2 Simplified list of critical PPLANE functions

Definition of most important safety problems in aviation needs well organised, structured analysis identifying all potential hazards for given operational concept. As a base for identification of critical functions for different PPLANE operational concepts, well defined Functional hazard assessment (FHA) was selected. FHA is commonly used for aviation purposes and is also well defined in regulation requirements and industrial documents. FHA created for PPLANE is based on WP1 scenario #1 (with consideration of scenarios #2 to #6). It describes failure conditions for 100 functions including respective classifications.

Furthermore, several additional aspects were taken into account. These include especially:
- weather aspects;
- urban flights restrictions;
- propulsion configuration aspects.

Most important additional aspect in the definition of critical PPLANE functions proved to be propulsion configuration. Significant effort was given to the study of emergency procedures for the Single engine (SE) aircraft, as well as to the survey of current accident records related to propulsion failures.

Summary of results established the base for final recommendations. In particular, key decision factors were:

- emergency landings of GA SE aircraft due to propulsion failure 6x10-6 (per 1 flight hour);
- initiation rate of Ballistic recovery system (BRS) (emergency parachute) 6.98x10-6 (per 1 flight hour);
- probability of electric engine failure 8.7x10-6 (per 1 flight hour);
- fatal accident rates of small SE active aircraft 8.5x10-4 (per 1 flight hour);
- fatal accident rates of small multi engine active aircraft 1.7x10-3 (per 1 flight hour);
- fatal accident rates of current commercial airliners 10-7 (per 1 flight hour).

These results were supplemented by FHA results, indicating that twin-engine compared to single-engine configuration has 10 functions with lower criticality out of 15 FHA functions (and only 1 function with higher criticality).

If more strict reliability requirements are met, PPLANE can be single-engine (with BRS). Current engines (and perspective engines identified today) do not meet such requirements multiple-engines are needed today.

2.3 Safety conclusions and recommendations

The most critical functions (and systems) of proposed PPLANE system include especially:

- Flight and FCS functions related to maintaining flight parameters (attitude, speed, altitude, etc.) and direct control of the vehicle. Loss of such functions is highly critical and should be the subject of major design focus. Higher criticality of functions at PPLANE (compared to existing aircraft) leads to the need to develop new type of highly reliable FCS and autopilot, if possible integrated in the single system. Totally different design of FCS is expected (FBW instead of mechanical system). Higher degree of redundancy compared to existing autopilots in similar aircraft categories is required. Design of FCS system could be based on existing designs for higher category aircraft. Some elements could be based on existing technology.

- Emergency second most critical group of functions is related to emergency systems (performing emergency procedures). Since some of today's existing and commonly used procedures would be difficult to adopt in PPLANE system (i.e. emergency landing out of airstrips, sense and avoid), new systems and procedures have to be developed. A key element in emergency equipment is BRS utilising emergency parachute. It is recommended to keep means for users on-board to manually initiate BRS in case of predefined emergency conditions (means to prevent deliberate use should be applied).

It is also recommended to keep means for users on-board to manually initiate fire extinguishing equipment in case of fire.

Many elements could be based on existing technology: monitoring (central maintenance system) high degree of automation in PPLANE system (and especially in vehicle operation) leads to dependency on Central maintenance system (CMS) and especially on on-board monitoring. This system is therefore highly critical and misleading indications can lead to the loss of critical systems.

Combination of two major approaches is recommended to be applied: Back-up of on-board monitoring CMS functions. Redundancy will help to prevent simultaneous misleading indication of given function. Use of different sensors (based on different physical laws) is highly recommended. This option adds significant complexity, number of components and therefore weight and cost of the system. Compared to existing approach, it reduces maintenance effort and costs.

Development of maintenance practices based on human effort (checks of PPLANE vehicles by maintenance personnel): Adopting purely this approach is for many reasons not practical for the PPLANE system. For example, current practices include pre-flight check done by pilots prior to every flight (series of flights) this check gives sufficient overall picture on condition of most of the aircraft systems. This practice is not desirable for the PPLANE system.

In addition:

- PPLANE needs improvement in design compared to current aircraft: Currently 1.01 fatal accidents per 100 000 flight hours (approximately 10-5 per flight hour) occur for general aviation aircraft (both, single-engine and multi-engine). However, only approximately 15 % is related to mechanical / maintenance problems (0.155 fatal accidents per 100 000 flight hours). At the same time, accident rate of large air carriers is 0.01 fatal accidents per 100 000 flight hours (10-7 per flight hour) for Northern America region. Worldwide, 0.049 fatal accidents per 100 000 flown hours (4.9x10-7 per flight hour) were tracked in the period 1997-2006. To reach the same fatal accident rate for PPLANE sised aircraft may not be realistic (due to cost escalation for development and certification). However, compared to other transportation means, target safety statistics should be comparable (i.e. to 0.05 per 100 000 flight hours).

- PPLANE can be SE aircraft, but after careful analysis, an important conclusion for PPLANE project is that number of engines is not decisive factor for safety of current PPLANE sized aircraft. More decisive is the use of additional emergency equipment. If more strict reliability requirements are met, PPLANE can be single-engine. Current engines (and perspective engines identified today) do not meet such requirements multiple-engines are needed today. Arguments supporting multi-engine aircraft include: Risk induced by an engine loss seems to be higher for a remotely piloted aircraft than for a manned one; Current engines do not meet new strict reliability (safety) requirements proposed for PPLANEs.

Arguments against use of multi-engine aircraft: Additional complexity leading to additional failure states requiring very fast and precise system response; Weight vs. performance issue for small aircraft.

- Electric propulsion is expected to be reliable: It can be expected that use of electric propulsion will not lead to degradation of reliability of the propulsion system. Generally, it is expected that future electric engines should have higher reliability compared to piston engines (because of significantly less complex design). Since no commercial (and long-time) electric propulsion applications are currently available in aviation, this has to be confirmed.

- Increased reliance on electronic / avionic systems should not itself constitute hazard: The study indicated also relatively low percentage of accidents caused by instruments and electrical systems (0.11 % of all accidents, and 0.67 % of fatal accidents). Therefore, higher level of automation should lead to lower accident rate. This conclusion is also supported by operational experience with recent Technologically advanced aircraft (TAA). However, a sounded reliability analysis will be required to demonstrate that the target safety objectives are reached.

2.4 Security requirements

According to the literature, personal / small aircraft could be seen as much vulnerable as general aviation, which has basically two security targets:
- protecting the passengers and the aircraft from attack;
- protecting the aircraft from being used for unlawful acts as a weapon at sensitive targets on the ground.

PPLANE must be protected from being turned into a weapon by someone on-board / in the remote ground station that overtakes the control, or being used for a sabotage act with a bomb or other explosive material on-board.

However, various authorities and industry players believe that such aircraft category is not an attractive source for being turned into a weapon, since characteristically it differs in many points from the large commercial aircraft. Some of the major differences include the followings:

- lower mass, resulting in less kinetic energy to make damage, once it is turned into a weapon;
- considerably less fuel capacity that could be to burned in an unlawful act ;
- limited kinetic energy that is not enough to damage the reinforced concrete of nuclear power plants since those are generally the most hardened industrial facilities;
- limited carrying capability, which is not the ideal platform for conventional explosives;
- according to the Aircraft owners and pilots association (AOPA), operators almost know everyone who boards the aircraft unlike transporting strangers in commercial aviation.

2.5 Safe integration of PPLANE into the traffic

This issue is comprehensively studied and analysed worldwide to make Remotely piloted aircraft system (RPAS) operation a routine. As the operational principle of the PPLANE system is quite close to the RPAS one, the project team is quite confident in the availability of solutions in the 2030 - 2050 timeframe. Solutions will likely impact standards to which PPLANE aircraft will have to be designed.

WP3: A&C issues

The objective of WP3 was twofold:
- to analyse and define automation (and autonomy) levels to be implemented in PATSs, and to propose preliminary designs and assessment modules;
- to provide some basic performance estimations for vehicles recommended by WP1, in several typical missions: after having selected candidate configurations from existing conventional aircraft and using WP1 recommendations, generic aeromechanic and energetic models were specified and a basic simulation of typical IPAVs missions was developed.

3.1 Operational and environmental constraints

A preliminary list of operational and environmental constraints of the PPLANE system related to the A&C functionalities was established. It was held in strong cooperation with WP1 (in order to take into account the recommended scenarios and vehicle configurations) and with WP4 (for the human factors related design recommendations).

3.1.1 Environmental constraints

Two main categories of environmental constraints were considered: landing sites on one hand, ATC and weather forecasting on the other hand.

3.1.1.1 Landing sites

From the assessment of the advantages and disadvantages of infrastructure adaptations of existing airports to PPLANE operations, compared to creating aerodromes totally devoted to the PPLANE system (PPorts), it turned out that the most promising concept was the PPort one, with a special emphasis on:

- PPorts location, taking into account the availability of public transport links;
- possibility to locate the RPS (Remote Pilot Station) inside or in the vicinity of the PPort;
- take-off and landing assisting devices, that allow to spare energy on board, thus leading to lighter and more efficient air vehicles.

A special focus was made on maintenance facilities and procedures, where automated procedures with low level of human involvement could help accomplishing the required level of safety.

3.1.1.2 ATC and weather forecasting

After having considered several possible solutions for the integration of the PPLANE system in what could be the ATC of the future whole ATS, it was assumed that the conventional ATC remains in the future ATS and that the PPLANE system has a connection with this ATC similar to the one of the other components of the ATS.

Due to the rather high sensitivity of a PPLANE vehicle to meteorological conditions, the high dependency of the PPLANE system availability and efficiency on reliable and precise weather forecasting services was pointed out; hence the needs to develop dynamic real time weather forecasts to feed both mission planning and aircraft FCS functions, with the possibility to include PPLANE themselves as a source of meteorological information by means of integrated sensors.

3.1.2 Operational constraints

3.1.2.1 Requested passenger interaction level

Two categories of interactions were considered: between the passengers and the automated system on one hand, between the passengers and the ground pilot on the other hand (including audio communication channel). Some general rules were established in order to select the nature of the pieces of information to be displayed to the passengers, as choosing information likely to increase their confidence in the system.

Concerning the emergency requests (taxiing, take-off or landing interruption requests or, to the contrary, emergency landing requests), the possibility to put at passengers' disposal some kind of "red button" was considered, with the possibility for the system either to process this request automatically or to submit it to the ground pilot validation.

3.1.2.2 Communication needs and dealing with communication loss

An analysis was conducted that consisted in describing the kind and contents of messages to be exchanged by the different communication links between a given aircraft and the other system components, and strategies were proposed in order to deal with communication losses.
The way of using the inter PPLANE communication link was also analysed: transmitting flight data in nominal conditions, used as a secondary link in case of degraded situations.

3.2 A&C technologies and preliminary architecture designs

The main A&C technologies that could be used in order to enable the realisation of the selected PPLANE scenarios have been investigated and preliminary designs of control architectures were proposed.

3.2.1 Supervision

In order to manage the whole flight progress and to coordinate the various on-board A&C functions, the supervision architecture is meant to achieve the following tasks:
- performing the global PPLANE situation assessment;
- sequencing the various phases of the mission;
- dealing with abnormal situations;
- managing communications with other system components (RPS, ATC, other PPLANE aircraft).

The Petri net based ProCoSA tool was used to develop a preliminary design of a PPLANE supervision system, both at the aircraft and RPS levels.

3.2.2 On-board 4D trajectory management

In order to cope with the 4D contracts based traffic management assumption, a 4D automatic navigation algorithm was proposed, including advanced navigation functionalities allowing the automatic capture of 4D waypoints, while meeting assigned constraints related to the orientation of the inertial speed vector at each waypoint and to the free flight volume assigned to the vehicle. Moreover, the algorithm minimises the True air speed (TAS) reference variations during the flight and it can explicitly consider the performance limitations of the vehicle, so to cope with both nominal and degraded flight conditions.

3.2.3 Automatic collision detection and avoidance methods and separation management

Even with an extended use of non-conflicting 4D contracts and assuming that every aircraft should be cooperative, it seems difficult to totally exclude the possibility of interfering flying object or non-foreseen ground obstacles. The case of a communication loss has also to be taken into account, where the aircraft has to take care of it by itself: even if the behaviour of the non-communicating aircraft has to be predictable to others, collision avoidance systems can prove to be necessary.

In the context of separation management, an algorithm for a conflict detection system for PPLANE was proposed as a back-up for the 4D contracts. This system focuses on 4D contract monitoring based on short-term trajectory prediction, including appropriate actions for emergency management.

3.2.4 Fault detection and identification

In order to avoid the drawbacks of multiple redundancies to achieve continued safe operation (such as the cost resulting from the additional weight and volume), model-based FDI approaches were considered.

A model-based FDI architecture was proposed for PPLANE based on stochastic input-output or output only models being estimated in real-time via flight data; the system is constantly monitored and new models representing it are estimated on-line. These models are compared to the baseline healthy ones to detect possible faults; once a fault is detected, the current model is compared to the baseline faulty model to identify this fault.

3.2.5 Automatic take-off and landing

Three main categories of ATOL systems belonging either to existing or prospective devices were investigated: those using dedicated ground equipment, those relying on accurate Global positioning system (GPS)-based localisation systems, and those based on on-board equipment only.

In order to reach a higher degree of autonomy than the one offered by a radar based ground equipment, a combined European Geostationary Navigation Overlay Service (EGNOS)-based and vision-based system, associated to efficient data fusion algorithms, was considered, together with the possibility of using specific ground assistance devices for the take-off phase, as a way to ensure the guidance stability during the roll phase and other safety aspects.

3.2.6 Automation, autonomy and human machine function allocation

An analysis of various authority sharing approaches was conducted in order to tackle conflicting situations that may happen between the automated PPLANE aircraft flight management systems, the on-board passengers, the RPS ground pilots and other possible human or artificial agents. A structure for an authority dynamics controller meant to monitor online the general behaviour of the system and to detect possible conflicts was proposed: associated to the design of recovery strategies, such as situation awareness reinforcement towards the ground staff, such a controller would enable solving and eliminating conflicting situations, thus increasing the PPLANE system safety level. However, the PPLANE team has taken note of the current requirements given by ICAO regarding automation in UAS: autonomous flights are forbidden for the time being due to the unclear responsibility for the autonomous portion of the flight. Authority sharing raises also responsibilities issues as the pilot may not be able to act as a pilot in command as he may not be able to make the decision.

3.2.7 Swarms guidance architecture

Swarming was eventually investigated as a procedure of clustering aircraft with similar goals and intentions to a group that can be controlled by a single RPS. An associated coordination system would enable not only to ensure a steady state safe flight mission of the swarm but also to manage splitting and merging aircraft or groups of aircraft.

Single link and multiple links swarm communication types were compared, together with the different ways to address collision detection and resolution, giving preference to a cooperative decentralised method.

3.3 PPLANE behaviour evaluation

Instead of designing some new and improbable concepts of vehicle, a preferred approach consisted in starting from existing conventional aircraft, covering if possible or being sufficiently close to the different categories chosen in WP1.

After having established a list of candidate existing aircraft, the first step consisted in evaluating their basic aerodynamics characteristics from their main geometric features; then, combining those aerodynamics characteristics with propulsion and mass ones, basic performances like range, ceiling, cruise speed, rate of climb, TO/L distances were calculated; then a mission simulation tool enabled to derive the key performances of each vehicle along a complete generic mission.

The last stage consisted in extrapolating those performance figures to quite similar vehicles, but including features required for the envisaged scenarios: full electric propulsion (or at least hybrid), and mass reduction resulting from an extended use of composite materials.

WP4: Human factors issues

4.1 Human factors issues identification

A preliminary working PPLANE operational concept was adopted within WP4 to serve as a basis for the discussion with the experts and potential end users. Workshops and interviews were held to identify from different perspectives the HF issues that need to be addressed.

The HF issues analysis identified and prioritised a number of HF related issues:
- allocation between function and machine;
- information requirement;
- system reliability;
- competence requirements.

The HF impacts of the HF issues on human performance were found to be:
Regarding the PPLANE passenger, a high level of automation was favoured in order to allow the use by people with no particular flight preparation and execution experience. The role of the passenger will be limited to destination input and landing request, for example in case of an emergency. Main HF impacts are:

- non acceptance of the (limited) information presented on board the PPLANE;
- non acceptance of the (limited) role of the PPLANE passenger;
- lack of trust in the (automation of the) PPLANE;
- lack of comfort on board the PPLANE;
- lack of situation awareness of the PPLANE passenger.

Regarding the RP, not much experience is actually available as the role is quite new, although similar with the RPS of unmanned aircraft. S/he will endorse the responsibility of the flight. The role will be critical and requires very careful attention. The HF impacts are:
- cognitive processes too demanding for the RP;
- workload too demanding for the RP;
- human error by the RP;
- lack of situation awareness of the RP;
- stress by the RP concerning the task at hand.

The following mitigation initiatives were identified:
For the PPLANE passenger:
- adequate information presentation on board the PPLANE;
- intuitive and user-friendly user interface for the passenger;
- emergency button available at all times;
- high comfort on board the PPLANE;
- comfortable ergonomics on board;
- adequate training for the passenger (focus on awareness instead of flight capabilities);
- trustworthy system automation.

For the RP:
- adequate information presentation in the RPS;
- intuitive and user-friendly user interface for the RP;
- adequate emergency procedures;
- adequate selection process for the RP;
- adequate training for the RP (and proper licensing) / adequate knowledge acquisition programme;
- RP communicates with ATCo;
- acceptable (in terms of cognitive processes, workload, and situation awareness) allocation between RP function and machine.

An artist impression of PPLANE user interface on board vehicle is provided in the full report. In order to help the project team to understand what could be a PPLANE, the WP4 team has created an artist impression of a possible user interface of the PPLANE vehicle. The WP4 team has presented a set of slides named NLR meets PPLANE as a first artist impression of a possible user interface on board the PPLANE vehicle. The aim of creating this artist impression was to give our creative minds a positive impulse.

The artist impression was built on the premise that the PPLANE system will not have a pilot on board the vehicle, but a RP with a supervisory role. The presented user interface provides us with an impression of the type of high level tasks that the passengers on board the vehicle could have.

4.2 Human factor issues evaluation

Different actions were undertaken to resolve each identified HF Issue. HF actions included an online survey and two experimental studies using a simulated PPLANE operational environment; one focused on the RP and one on the PPLANE passenger. The online survey was held prior to the experiments and the results of the survey were fed into the experimental set-up.

4.2.1 Action 1: Online survey (253 invitations to participate, 120 full and 23 partial responses)

The objectives of the online survey were two-fold. From a HF perspective the objective was to evaluate whether or not the PPLANE operational concept impacts performance of the PPLANE Passenger with regard to acceptance, trust, comfort, and situation awareness. Another objective of the online survey was to explore the required (level of) competencies of the involved RP. Following these two objectives, the survey consisted of two parts focusing on (1) HF impacts on PPLANE passenger, and (2) required competences of RP. The survey was preceded by an introduction of the PPLANE system. Great effort was put into creating an introductory movie so participants had a good sense of the context in which the survey questions were asked. This was considered important as a large group of participants, all with different background, were to understand the concept of personal planes as designed within the PPLANE project.

Online survey results on HF impact on PPLANE passenger

Despite the uncertainties linked to an innovative concept like PPLANE, some trends emerged from the survey. The main results are summarised below.
The participants generally considered the PPLANE system as potentially useful, they felt that a high level of automation would be needed, they would like to use a proven PPLANE as a passenger, and they think they would be able to do so.

At the same time, they had more reserved opinions regarding the current reliability of a PPLANE-like system and accordingly, their global confidence level towards such a system was moderate: only a minority (25 %) would accept flying a PPLANE now, while a large majority (70 %) would accept to do so in 25 years.

A majority of participants considered that it would not be stressful to use a PPLANE as passenger, they thought that some kind of training would be required -even as a passive passenger- and they declared to be interested first by the weather conditions during the flight.

Online survey results on required competences of RP

A first competence profile draft of the RP was used in the PPLANE survey. In the survey participants were asked to select 5 competences (sustain and divide attention, handle emergencies, prioritise, absorb and process information quickly, recognise and resolve problems) and 3 attitudes (responsible, accuracy and stress resistant) that are critical for the RP. The results of the survey were used to define the second draft of the PPLANE competence profile.

List of websites: http://www.PPLANE-project.org

Project information

Grant agreement ID: 233805

Status

Closed project

  • Start date

    1 October 2009

  • End date

    31 October 2012

Funded under:

FP7-TRANSPORT

  • Overall budget:

    € 4 402 658,54

  • EU contribution

    € 3 279 005

Coordinated by:

OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AEROSPATIALES