WO2025186547A1

WO2025186547A1 - Apparatus

Info

Publication number: WO2025186547A1
Application number: PCT/GB2025/050419
Authority: WO
Inventors: Stephen Mark Husband; Tom FEEHALLY
Original assignee: GKN Aerospace Services Ltd
Current assignee: GKN Aerospace Services Ltd
Priority date: 2024-03-04
Filing date: 2025-03-03
Publication date: 2025-09-12
Anticipated expiration: 2026-09-04
Also published as: WO2025186547A8; GB202403095D0; GB2639177A

Abstract

The present invention relates to an electrical aircraft propulsion arrangement comprising: at least one electrically operated prime mover for providing thrust for the aircraft; at least one source of electrical energy arranged to provide electrical energy to at least one electrically operated prime mover; a controller arranged to control production, storage and provision of electrical energy from the at least one source of electrical energy; a sensor arrangement arranged to provide data to the controller, the data relating to flight condition, aircraft condition, and electrical energy source condition.

Description

Apparatus

Technical Field

The present invention is concerned with energy management for green propulsion systems for aircraft.

According to most estimates, airline traffic is set to double every fifteen years providing a significant increase in the operation of land-based and, subsequently, airborne propulsion systems and therefore the production of associated emissions. Emissions are known to be harmful whether produced at ground level or at altitude.

In order to meet targets for reduction of emissions set by the International Air Transport Association, the use of alternate fuels has been identified as a possible avenue of exploration. Alternate fuels include biofuels, synthetic kerosene, compressed natural gas. In addition, the ACARE roadmap for 2050 identifies the need and sets objectives for significant reductions for a range of emissions. It is widely recognised that the opportunities to come close to or achieve these targets are limited.

T o solve these issues a number of propulsion systems have been employed in different aircraft. Most systems use fossil fuel sources for economic reasons and also due to their very high energy density and specific energy. The prevalence of the gas turbine has also led to fossil fuels being a desirable propulsion mechanism for aircraft. This has led to developments for improving the performance of fossil fuel burning gas turbines.

Some aircraft use electrical systems to provide propulsion. For example, electrical energy can be provided to a propulsor from an energy store or energy source and used to generate thrust.

Management systems for energy sources are important to regulate and maintain performance. This may be in the form of ensuring there is sufficient energy to maintain all required systems at an operational level.

During safety events for combustion-propelled aircraft, typically the fuel is dumped overboard to reduce weight and improve flying or gliding capability. Immediate analogues for electrically- propelled aircraft are not in practice and are not obvious. Summary of the Invention

Aspects of the invention are set out in the accompanying claims.

Viewed from first aspect there is provided an electrical aircraft propulsion arrangement comprising: at least one electrically operated prime mover for providing thrust for the aircraft; at least one source of electrical energy arranged to provide electrical energy to at least one electrically operated prime mover; a controller arranged to control production, storage and provision of electrical energy from the at least one source of electrical energy; a sensor arrangement arranged to provide data to the controller, the data relating to flight condition, aircraft condition, and electrical energy source condition.

The present arrangement is able to ascertain whether a safety event has occurred, is occurring or is about to occur. In light of this, the arrangement is then able to provide a suitable safety event response that accounts for the severity of the safety event and a power capacity of an aircraft. This accounts for fuel loads, energy stores and health of aircraft elements.

The present arrangement therefore provides a bespoke solution for a very large array of safety events. Alongside this, the present arrangement may be used in a system using environmentally friendly fuels. The present arrangement is also arranged such that component health can be compromised in the designing of safety event responses. This allows the arrangement to prioritise landing the aircraft over the inherent safety concerns on a per component basis.

In examples, the at least one source of electrical energy comprises at least one of an electrical energy source and an electrical energy store. The arrangement may include a source of electrical energy (such as a converter from chemical energy to electrical energy). This may be for example a fuel cell or a series of fuel cells or fuel cell stacks or the like. The arrangement may include a store of electrical energy. This may be one or more of for example a battery, batteries, a capacitor, capacitors, a super-capacitor, and super-capacitors. In this way, the response has an option to select between provision of stored electrical energy or the production of further electrical energy provided there is time to safely do so and that the production of electrical energy is required.

In examples, the at least one source of electrical energy is at least partially cryogenically operated. This may be from a cryogenic fuel source or the like that may have been used in thermal exchange processes prior to use. For example, fuel cells or the like. Such fuel is environmentally friendly and is therefore desirable in air travel.

In examples, flight condition comprises: stage of flight; and, details of flight; aircraft condition comprises: prime mover condition; and, aircraft integrity; electrical energy source condition comprises: charge status; fuel status; operational status; and electrical status. Each of these can be used to provide a full understanding of the condition of the aircraft. Each of these are also useable to provide a bespoke response to the safety event based on the condition of the aircraft by the controller. As such, taking this data improves the suitability of a response to a safety event by the controller.

In examples, the controller is an intelligent electrical system controller. In examples, the controller is arranged to detect safety events from the data provided by the sensor arrangement.

In examples, the controller is arranged to, in response to detecting a safety event, at least one of: calculate a likelihood of return to normal flight conditions; calculate a requirement to jettison a fuel source for the at least one source of electrical energy; calculate a requirement of a deep discharge event of at least one source of electrical energy; calculate a failure state of the aircraft; and, calculate an energy need for a failure state of the aircraft.

These data are advantageous in providing an overview of the condition of the aircraft and the condition of and resolution for the safety event.

In examples, at least one electrically operated prime mover is an electrically operated propulsor. In examples, at least one electrically operated prime mover is an electrically operated thrust producer. In examples, at least one electrically operated prime mover is at least partially cryogenically operated. These synergistically combine with the use of environmentally friendly fuels, that may be stored as e.g. liquid and then used in gaseous form. In examples, there may be a liquid hydrogen fuel that is used in heat exchanger purposes before being provided to fuel cells as gaseous hydrogen for use in production of electrical energy.

In examples, the sensor arrangement comprises at least one of: a status sensor configured to detect a status condition of the at least one source of electrical energy, wherein at least one status condition is one of voltage, current, temperature, coolant input temperature, coolant input flow rate, coolant output temperature and coolant output flow rate; and, a state of health sensor configured to detect a state of health of components within the electrical aircraft propulsion arrangement.

These data are advantageous in providing an overview of the condition of the source of electrical energy and the condition of and resolution for the safety event. Noting state of health of elements allows for a more demanding approach to be used where the health of elements is good as opposed to when the health of elements is poor.

Viewed from another aspect there is provided an aircraft comprising the electrical aircraft propulsion arrangement of any above embodiment or example;

The electrical aircraft propulsion arrangement is advantageously provided within an aircraft. An aircraft may utilise each of the elements and may house each of the elements. While the controller may be held remotely it may be preferable for response times to hold each element of the arrangement on an aircraft. In use, therefore the at least one electrically operated prime mover provides thrust for the aircraft, the at least one source of electrical energy provides electrical energy to the prime mover (from which thrust is generated), the controller acts as per the above and the sensors are arranged proximal to the relevant components of the aircraft.

In examples, the sensor arrangement comprises at least one of: a status sensor configured to detect a status condition of the at least one source of electrical energy, wherein at least one status condition is one of voltage, current, temperature, coolant input temperature, coolant input flow rate, coolant output temperature and coolant output flow rate; a state of health sensor configured to detect a state of health of components within the electrical aircraft propulsion arrangement; a fuel sensor configured to detect a condition of a fuel source for use in the aircraft; and, an aircraft condition sensor configured to detect an aircraft condition wherein an aircraft condition is one of altitude, aircraft speed, orientation, projected landing profile, stage of flight, estimated remaining flight time, elapsed flight time, and landing gear deployment status, and wherein a portion of the sensor arrangement is arranged proximal to the at least one source of electrical energy.

These data are advantageous in providing an overview of the condition of the source of electrical energy and the condition of and resolution for the safety event. Noting state of health of elements allows for a more demanding approach to be used where the health of elements is good as opposed to when the health of elements is poor. Furthermore, data on the aircraft itself is highly advantageous in devising a suitable response when the response includes an indication of time of glide, speed, altitude, etc. for the aircraft. It is advantageous for at least some sensors to be arranged proximal to some relevant components of the aircraft.

Viewed from another aspect there is provided a method of operating an electrically operated aircraft comprising: receiving at a controller data from a sensing unit relating to: flight condition; aircraft condition; and, electrical energy store condition; calculating, by the controller, the presence or not of safety events based on the data; in response to detecting a safety event, calculating at least one of: a likelihood of return to normal flight conditions; a requirement to jettison a fuel source for at least one source of electrical energy; a requirement of a deep discharge event of at least one source of electrical energy; a failure state of the aircraft; and, an energy need for a failure state of the aircraft, and, controlling, by the controller, production, storage and provision of electrical energy from at least one source of electrical energy according to the calculations in response to detecting a safety event.

The method is able to detect safety events and differentiate between the severity of differing safety events, The method also provides accurate and careful control over the production, storage and provision of electrical energy in response to safety events. The production, storage and provision of electrical energy may vary based on the severity of differing safety events.

In examples, controlling, by the controller, production, storage and provision of electrical energy from at least one source of electrical energy according to the calculations in response to detecting a safety event comprises at least one of: jettisoning a fuel source; purging an electrical energy generation system of fuel; activating a deep discharging event of at least one source of electrical energy; providing electrical energy to essential glide systems; and, activating electrical energy dumping.

Each of the steps of this example are additional steps that can be taken and may be instigated in response to the severity of the safety event occurring at the time. For example, in response to highly severe safety events, jettisoning of fuel may be advantageous to reduce the potential energy on the aircraft prior to landing. In a similar mind set, it may be advantageous to deeply discharge the batteries on board to increase the glide time of an aircraft prior to landing to reduce the rate of descent. Each of these optional steps advantageously improve the overall safety of landing, however it is most advantageous that a controller can optimise the response by performing those steps that are suited for the safety event in question. The present invention is an improvement over that which has occurred previously as it assesses the safety event and provides a bespoke solution for the event based on the severity of the event. This response may even include damaging hardware to provide a more robust response to the safety event. Damaging hardware may occur during, for example, deep discharge of the electrical energy stores. The arrangement of the controller being above the normal aircraft hardware controller allows for these decisions to be made and enacted in a novel and inventive approach.

Brief Description of the Drawings

One or more embodiments of the invention will now be described, by way of example only, and with reference to the following figures in which:

Figure 1 shows a schematic view of an electrical aircraft propulsion arrangement according to examples of the present disclosure;

Figure 2 shows a schematic view of an electrical aircraft propulsion arrangement according to examples of the present disclosure;

Figure 3 shows a schematic view of an electrical aircraft propulsion arrangement according to examples of the present disclosure;

Figure 4 shows a schematic of a pair of graphs illustrating a use example of the electrical aircraft propulsion arrangement according to examples of the present disclosure;

Figure 5 shows a schematic of a pair of graphs illustrating a use example of the electrical aircraft propulsion arrangement according to examples of the present disclosure; and,

Figure 6 shows a flow diagram of a method according to examples of the present disclosure.

Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”. The invention is further described with reference to the following examples. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples. It will also be recognised that the invention covers not only individual embodiments but also combination of the embodiments described herein.

The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc, other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

Detailed Description

An invention described herein relates to energy control for an electrically powered aircraft.

Safety events can occur during aircraft travel. In systems containing typical aircraft fuels such as kerosene, fuel may be dissipated to the environment whether in a controlled manner or by passive leakage. In the present disclosure, more environmentally friendly fuels are considered and therefore solutions are devised for safety events in such aircraft. In particular, with cryogen fuels that may be converted into gaseous phase prior to use, the gaseous phase fuel may leak from its container. Furthermore, the gasification of liquid cryogen results in significant volumetric expansion. This presents a significant containment challenge during failure events. As such, processes and systems are proposed herein to overcome issues associated with use of environmentally friendly fuels. In the disclosure, fuels may be referred to in general or may be referred to by example fuels, such as hydrogen.

Safety events may occur in many different ways. Safety events may include loss of prime movers for providing thrust for the aircraft. In examples, a prime mover may be a propulsor or the like. The prime mover receives electrical energy and converts this into kinetic energy for use in propelling the aircraft. An aircraft may contain one or more prime movers and a safety event may be the loss of one or more of these prime movers. A safety event may be the loss of fuel in either liquid or gaseous form (cryogenic or otherwise). As noted above, in examples this may be hydrogen fuel though could also be ammonia, methanol, natural gas this may be in gas, liquid or solid state storage.

In these instances, there are considerations regarding how to provide power for any emergency actions that are to be taken alongside improving the safety of the aircraft prior to taking emergency actions such as glide and landing. Improving the safety may include purging fuel. Purging fuel reduces the likelihood of cascading safety events on landing. Fuel may be present in fuel containers and may be present in other locations such as in fuel cells or the like. Fuel may be used in the aircraft to provide heat exchanger functions (e.g. cooling of electrical equipment to improve electrical efficiency or the like) and used in the conversion from chemical energy to electrical energy (e.g. during use in a fuel cell).

In instances wherein the fuel is purged, the fuel cell (or other similar chemical energy to electrical energy converter) may be unable to provide additional power during e.g. landing. Purging of the fuel may be purging from the fuel containers and all other locations or may be from select elements within the aircraft (e.g. conduits and the fuel cells but not the containers).

Proposed herein is an electrical aircraft propulsion arrangement that includes a source of electrical energy for use in such safety events. The energy source may be a fuel cell (e.g. a source of electrical energy that is provided via conversion of chemical energy from a fuel) and/or a battery, capacitor or super-capacitor or the like (e.g. a store of electrical energy that can be released when required). It may be preferable to reduce the energy stored in these systems to reduce likelihood of cascaded failure during safety events and therefore this is a further consideration. This may occur for example via discharge of energy from a store of electrical energy (e.g. battery) or for example via lack of production of electrical energy from a converter (e.g. fuel cell) from chemical to electrical energy. This lack of production may occur from a cessation of provision of fuel to the converter (e.g. fuel cell).

In detail, the present system includes cryogen fuel storage, which may in part be handled with some similarity to common fuels, alongside significant electro-chemical energy storage. The combination of these two energy sources offers challenge and opportunity. The present system provides an arrangement that accounts for the challenges while maximising the benefits. For example, the present system in examples uses deep discharge to reduce cascaded failure and provide additional propulsive power.

The present system allows for a highly robust response to safety events and allows improved safety alongside use of more environmentally friendly fuels. Improved safety may arise from use of information to ascertain the required energy for safe landing and utilising that information alongside the electrical energy sources in the aircraft arrangement.

Referring now to Figure 1 there is shown a schematic view of an electrical aircraft propulsion arrangement 100 according to examples of the present disclosure.

In the example shown, the arrangement 100 comprises at least one electrically operated prime mover 110 for providing thrust. The thrust may be suitable for use in propelling an aircraft. The arrangement 100 comprises at least one source of electrical energy 120. The source of electrical energy 120 is arranged to provide electrical energy to at least one electrically operated prime mover 110. The arrangement 100 comprises a controller 130 arranged to control production, storage and provision of electrical energy from the at least one source of electrical energy 120. The arrangement 100 comprises a sensor arrangement 140 arranged to provide data to the controller 130. The data may relate to flight condition, aircraft condition, and/or electrical energy source condition.

In use, the arrangement 100 provides propulsion for an aircraft by providing electrical energy from the at least one source of electrical energy 120 to the electrically operated prime mover 110. The prime mover 110 acts to provide kinetic energy that drives the aircraft in which the arrangement 100 is arranged.

The prime mover 110 may be a propulsor or a motor and propulsor combination. The prime mover 110 may be any form of electrical to kinetic energy converter. Broadly, the electrical energy received from the electrical source 120 is converted in such a way that an aircraft can be propelled by the prime mover 110.

The at least one source of electrical energy 120 may comprise an electrical energy source. The source of electrical energy 120 may comprise a fuel cell for converting chemical energy into electrical energy. A fuel cell (equally a fuel cell stack) is seen herein to be an electrical energy source. The source of electrical energy 120 may additionally or alternatively comprise an electrical energy store. The electrical energy store may be at least one of a battery, a capacitor and a super-capacitor. The source of electrical energy 120 may comprise photovoltaic cells or the like.

In practice, the aircraft may hold cryogenic fuels. In this way, liquid cryogen may be held in a container or the like. This cryogenic material may be used in thermal exchange and move into gaseous phase fuel. This gaseous phase fuel may be used in a fuel cell or the like. In this way, the source of electrical energy 120 may be at least partially cryogenically operated. Cryogenic operation may arise from direct use of cryogenic fuel or use of fuel that was once cryogenic and has been warmed via thermal exchange. The electronics of the source of electrical energy 120 may benefit from use of low temperatures (for example an electrical energy store may benefit from low temperatures). In this way, a battery may be maintained at a low temperature by thermal exchange from the cryogenic fuel.

The controller 130 controls production, storage and provision of electrical energy from the at least one source of electrical energy 120. In particular, during safety events (unlike with kerosene-powered aircraft) energy and fuel may need to be “jettisoned” for improved safety on approach to and during landing. In examples, the at least one source of electrical energy comprises a battery (or a plurality of batteries) and the battery (or batteries) are to be deeply discharged during the safety event. This reduces the likelihood of battery fire during a hard landing or possible crash. In examples, the at least one source of electrical energy comprises a fuel cell (or plurality of fuel cells) and the fuel for the fuel cells may be jettisoned. This reduces the likelihood of fires occurring during the safety event and also reduces passenger exposure to the fuel.

As noted above, the fuel may be hydrogen. Hydrogen is highly combustible and a mix of hydrogen with ambient air requires only a small amount of thermal energy to combust. As such, it is advantageous for the controller to control jettisoning of fuel and charge in the arrangement prior to and/or during landing. Furthermore, the fuel (which may be hydrogen) may be contained in container or the like which may crack or undergo deformation during the safety event. As such, if this occurs, compressed hydrogen may rapidly expel into the air around the aircraft (increasing risk of combustion of said air). As such, the controller can control jettisoning of the hydrogen (or other fuel) at a distance from the aircraft prior to landing so that the hydrogen is of a lower risk. The fuel may be jettisoned in liquid or gaseous form.

The controller 130 is connected to a sensor arrangement 140. The controller 130 may be connected in a wired or wireless manner with the sensor arrangement 140. The controller 130 controls the operation of the arrangement 100 following receipt of data from the sensor arrangement 140. In operation, the sensor arrangement 140 may permanently provide data to the controller 130 or may provide data on an intermittent or on-request basis. The controller 130 may receive data relating to flight condition, aircraft condition, and electrical energy source condition.

In particular, these data are advantageous as the controller 130 can ascertain the working status of the arrangement 100 and the working requirements of the aircraft (in which this arrangement is located). Noting these, the controller 130 can broadly optimise a response to safety events based on both the working status and the working requirements.

In particular, the sensor arrangement 140 is able to obtain data based on a suitable array of sensors within the sensor arrangement 140. The sensor arrangement 140 detects data relating to flight condition, aircraft condition, and electrical energy source condition. In examples, flight condition data may comprise data on stage of flight and details of flight. In examples, aircraft condition data may comprise data on prime mover condition and aircraft integrity. In examples, electrical energy source condition data may comprise data on charge status, fuel status, operational status, and electrical status.

In more detail, a stage of flight may be any of taxi, take off, climb, cruise, descent (or the like). The stage of flight is relevant for preparing a response to a safety event. If for example a safety event is detected during taxi, the response may differ to a response to a safety event detected during cruise. In particular, during taxi there is no need to calculated or estimate required power needs for the aircraft to land safely as such the controller 130 will respond differently depending on the stage of flight.

Details of flight may include any of altitude, velocity, stability of aircraft, speed, time elapsed in flight, distance of flight, geographic position, geographic conditions and meteorological conditions. Each of these may be salient in the preparation of a response to a safety event. In particular, if the stage of flight is cruise and the details of flight note that altitude is rapidly dropping and for example stability of the aircraft is low, this indicates that the aircraft is not in comfortable cruise (rather the aircraft may be dropping out of cruise). The response to such a set of data may be to control production and provision of electrical energy such that sufficient thrust can be provided to stabilise the aircraft prior to jettisoning fuel and discharging batteries (and/or capacitors and/or super-capacitors, etc). If there is a suitable amount of electrical energy in the electrical energy stores, the controller 130 may choose to deeply discharge the electrical energy stores and with that electrical energy stabilise the aircraft. In this way, the controller 130 is able to provide a somewhat optimised response to safety events.

Prime mover condition may be the operational status of the prime movers. If, for example, it is noted that one or more of the propulsors is non-operational, the controller 130 may design a different safety event response than in an instance where all propulsors are operational. In particular, the controller 130 may adapt the response for an asymmetric thrust profile to be provided from the remaining propulsors. This may include provision of greater electrical energy for propulsors near the non-operational propulsor to account for the lack of thrust from that non-operational propulsor. In examples, this may additionally or alternatively include provision of greater electrical energy for propulsors on the other wing of the aircraft to account for lack of thrust from the non-operational propulsor. In the present disclosure, the propulsors may be electrically operated propulsors. The fuel used herein may be stored in a cryogenic form. The fuel may be warmed prior to use in e.g. fuel cells for providing electrical energy. This energy is the energy that therefore activates the propulsors. As this energy stems from a cryogenic fuel it is deemed herein that the propulsors are at least partially cryogenically operated. Furthermore, the cryogenic fuel may be used to cool the propulsors and/or electronics associated with the propulsors. It is therefore deemed herein that the propulsors are at least partially cryogenically operated.

Aircraft integrity may be the condition of the aircraft in general or for elements within the aircraft. For example, the condition of the tanks containing fuel. As noted above, during safety events liquid or gasous tanks may crack or become deformed. This may be detected using a pressure sensor in the tank. By noting the integrity of the tank within the aircraft, the controller 130 can design a more suitable response. In particular, if fuel is rapidly exiting the fuel tank, the controller 130 may opt to provide all remaining fuel to the fuel cells to provide electrical energy sufficient to stabilise the aircraft and simultaneously store any remaining produced electrical energy in the batteries (or capacitors, super-capacitors). The energy in the batteries may then be used for further landing processes or the like. Aircraft integrity includes conditions of the cabin and potential locations for depressurization or leaks or the like. This may also include whether an engine or the like is non-operation (e.g. has blown) or the like.

Data on electrical energy source condition may include data on the charge status of the electrical energy source. This may be as to whether the electrical energy source is charging or is capable of being charged or not. If there is an error in the storing of electrical energy in the electrical energy source, the controller 130 may opt to not provide electrical energy to the store for storage. Instead, the controller 130 utilises other working components in the design of the safety event response, for example providing electrical energy to the propulsors (or the like). Charge status may indicate a current available charge level from the electrical energy store and whether it is operating as expected.

Data on electrical energy source condition may include fuel status. This may relate to the amount of fuel presently available for use in the fuel cells for production of electrical energy. This may include volume and pressure and the like. This may include temperature of fuel. Where an error has occurred and the fuel is being warmed from cryogenic to gaseous (for example due to an issue that has impacted the container [e.g. breaking of the vacuum in the container]) the controller 130 may opt to send high volumes of fuel immediately to the fuel cells rather than attempt to use the fuel in heat exchanger functions. If the fuel is already warm, there will be lower or no advantage provided in heat exchanger functions. Fuel status may also indicate whether the fuel cells have fuel in them that may be purged in a safety event response. Fuel status may also provide data on the time required for a purge to be completed. This data can be used to best design a response to a safety event by the controller 130. Data on electrical energy source condition may include operational status and electrical status. Operational status may broadly relate to whether components are operating in a manner that is expected. Where components are not operational (or not fully operational) the controller 130 may opt to design a safety event response that does not use such components or only uses such components at a much reduced operational capacity. In this way, the risk of using a partially operational component can be reduced. Electrical status may include charge levels and viability for use in a safety event response. Electrical status may also include data on whether the electrical energy store is in a charging regime, a non-charging regime, a discharge regime or a deep discharge regime.

The controller 130 receives this data and prepares a response based on the calculated safety event and the calculated total operational capacity of the aircraft. This controller 130 may therefore be referred to as an intelligent electrical system controller. The controller 130 may be part of a controller arrangement comprising a series of control elements.

The controller 130 may act to provide a solution to the safety event. The controller is therefore arranged to detect safety events from the data provided by the sensor arrangement. The response to the safety event may be designed by the controller 130 in response to the safety event and the overall condition of the aircraft. This response may follow a sequence of considerations and actions such as:

(1) Provide power to facilitate the safe shutdown of the fuel cell system.

(2) Provide power for control systems to provide sufficient operability of the aircraft towards a safer outcome.

(3) Deep discharge batteries prior to contact with the ground.

Step (1) may include purging of gaseous fuel. Step (3) may include provision of electrical energy from the batteries to the propulsors for final thrust allowing for control on landing.

Referring now to Figure 2, there is shown a schematic view of an electrical aircraft propulsion arrangement 200 according to examples of the present disclosure. The arrangement 200 of Figure 2 is similar to the arrangement 100 of Figure 1. Features with the same or similar function are shown with reference numerals increased by 100. For example, at least one electrically operated prime mover 210 in Figure 2 provides thrust in the same manner that at least one electrically operated prime mover 110 in Figure 1. Figure 2 shows some elements in greater detail than in Figure 1.

The arrangement 200 of Figure 2 differs to the arrangement 100 of Figure 1 by the presence of at least one electrical energy source 222 and at least one electrical energy store 224. In the arrangement 200 of Figure 2, the at least one source of electrical energy 220 comprises at least one of an electrical energy source 222 and an electrical energy store 224.

In particular, as noted above, the arrangement 200 may have both a chemical-to-electrical energy converter 222 and an electrical energy store 224. In an example, the chemical-to- electrical energy converter 222 may be a fuel cell (or a series of fuel cells, or fuel cell stacks) 222. In an example, the electrical energy store 224 may be at least one of a battery, a capacitor and a super-capacitor.

In this way, the arrangement 200 of Figure 2, has a method by which electrical energy can be stored prior to or during flight (excess electrical energy generated by the fuel cell 222 could be stored in the battery 224) and used where desired. Similarly, electrical energy can be generated during flight by the fuel cell 222. As such, the controller 230 has greater control over the provision of electrical energy from the at least one source of electrical energy 220. In this way, the controller 230 can provide a greater number of resolution options for any one safety event. Where the at least one source of electrical energy 220 is only e.g. a fuel cell, the controller 230 has fewer options for remedies (in that the fuel cell cannot rapidly discharge a large amount of electrical energy that may be used to e.g. stabilise the aircraft).

Referring now to Figure 3, there is shown a schematic view of an electrical aircraft propulsion arrangement 300 according to examples of the present disclosure. The arrangement 300 of Figure 3 is similar to the arrangement 200 of Figure 2. Features with the same or similar function are shown with reference numerals increased by 100. For example, at least one electrically operated prime mover 310 in Figure 3 provides thrust in the same manner that at least one electrically operated prime mover 210 in Figure 2. Figure 3 shows some elements in greater detail than in Figure 2.

Figure 3 shows an arrangement 300 with at least one electrically operated prime mover 310. In particular, the at least one electrically operated prime mover 310 comprises a plurality of motors 311 , 313 and a plurality of propulsors 312, 314. In the specific example shown, a first motor 311 is connected to a first propulsor 312 and a second motor 313 is connected to a second propulsor 314.

The arrangement 300 comprises at least one source of electrical energy 320. In particular, the at least one source of electrical energy 320 comprises a plurality of fuel cells 321 , 322, 323 and an energy storage system 324 (ESS). In the specific example shown, the arrangement 300 comprises a first fuel cell 321 , a second fuel cell 322 and a third fuel cell 323. The ESS 324 may be a battery, capacitor and/or super-capacitor or the like as discussed above.

The arrangement 300 also comprises a controller arrangement 330. The controller arrangement 330 includes a main controller 331 , an ESS controller 332 and an aircraft power controller 333.

In more detail, the main controller 331 may be referred to as an intelligent electrical system controller 331. The ESS controller 332 is an intelligent ESS controller 332. The aircraft power controller 333 is an aircraft electrical power controller 333. Together the controller arrangement 330 provides analysis of the safety event, the power capability of the aircraft and devises an approach for responding to the safety event.

In particular, the roles of the elements of the controller arrangement may be as follows. The intelligent electrical system controller 331 may understand the state of the aircraft and calculate the optimal discharge priority of the ESS 324. The intelligent ESS controller 332 may manage the battery operation.

In a specific use example, we can consider the loss of both propulsors 314, 314 (from the arrangement of Figure 3). The intelligent electrical system controller 331 establishes the state of charge of the ESS 324, the projected glide time (based on e.g. present altitude and velocity measurements from a sensor arrangement) and aircraft power required to support gliding. These data points may be continually updated during the glide period for improved responsiveness. The intelligent electrical system controller 331 estimates the optimum approach and minimum and maximum period of time in which to safely purge the fuel from at least one of the fuel cells 321 , 322, 323. The intelligent ESS controller 332 calculates the energy extraction involved in deeply discharging the ESS 324. The intelligent electrical system controller 331 may operate a fuel cell (or number of fuel cells 321 , 322, 323) to provide aircraft power during the glide phase alongside dumping of fuel. This provides a “best condition state” of the aircraft and the components of the propulsion arrangement at the point of contact with the ground.

In a further specific use example, we can consider the loss of both propulsors 312, 314 close to the ground. This may occur from safety events such as a multiple bird strike. During such a safety event, the controller arrangement 330 will operate to shut down the fuel cells 321 , 322, 323. In use this may include over-driving an electro-turbo-compressor to accelerate purging the fuel cells 321 , 322, 323. This may also include discharging the ESS 324 as described above. Discharging the stored electrical energy requires energy users (i.e. components that use electrical energy). When low to the ground, there may be insufficient secondary aircraft loads requiring electrical energy to completely deep discharge the ESS 324. In such an example, the intelligent electrical controller 332 will communicate to the aircraft electrical power controller 333 to turn on optional dump loads. These optional dump loads are electrical components that can optionally use the excess electrical energy from the ESS 324. This may include the de-icing system, the galley ovens, electro-turbo-compressor systems, and the like.

During gliding phases, the fuel cell arrangement may continue to provide electrical energy or use in the aircraft. The controller arrangement can detect an amount of time in gliding based on velocity and altitude of the aircraft. This time is used to provide a limit by when the fuel cells must be shut down and purged and energy provision is to switch to the ESS rather than the fuel cells. Power from the ESS is used for glide capability primarily. Once the glide capability is fully provisioned with energy from the ESS, electrical energy from the ESS may be provided to secondary systems and/or used to dump fuel or the like. As a later step, the batteries may be deeply discharged shortly prior to landing. This is controlled by the intelligent ESS controller 332 alongside the intelligent electrical system controller 331. During deep discharge, components such as the de-icing system, the galley ovens, electro-turbo-compressor systems may be operated as suitable energy sinks.

In a further specific use example of a different safety event, we can consider a safety event of the loss of fuel in the arrangement. As noted above, the system may include a series of containers or the like for holding fuel. The fuel may be in a cryogenic form (likely liquid) and then provided for use in the fuel cells as gaseous form. The fuel may be used in heat exchanger functions prior to use in the fuel cells to maximise the efficiency of the cryogenic fuel. On loss of fuel, the system will be unable to continue providing fuel to and providing from the fuel cells. As such, initially, the intelligent electrical system controller 331 continues to monitor the state of charge of the ESS 324, the projected glide time, aircraft speed, aircraft power, stability etc. The intelligent ESS controller 332 may inform the intelligent electrical system controller 331 to calculate the energy involved in deep discharge of the ESS 324. The intelligent ESS controller 332 may calculate how much spare capacity the ESS 324 has as the aircraft approaches the ground. The controller arrangement 330 may inform the pilot of the propulsion power available to provide a more controlled landing. The provision of this additional propulsive power is intended to provide an increased safety of landing than is possible on modern aircraft.

It is noted that if the aircraft can be landed intact with this arrangement it may be beneficial that the ESS 324 is replaced if the ESS has been operated beyond its normal limits of discharge. This maintains the high levels of safety of the arrangement disclosed herein.

The arrangement 300 shows the relative positions of controllers. The intelligent electrical system controller 331 sits above and provides control over all the other elements within the control arrangement 330. This allows the intelligent electrical system controller 331 to be the master control over controllers in the aircraft. This is particularly salient as this present arrangement allows the aircraft’s needs to be prioritised over the battery lifetime. Typically, battery controllers do not allow actions that would damage the battery (capacitor, supercapacitor, etc) long term. Battery controllers may be referred to as the battery management system (BMS). In the above, use has been made of deep discharge of the battery. This is a damaging process to the battery. As such, in ordinary schemes, this cannot be provided. In modern aircraft this is not recognised as an issue as modern aircraft systems operate on kerosene engines. This issue is considered by the present arrangement due to the use of environmentally friendly fuel types.

T o overcome this issue (and to allow in part aircraft transportation with environmentally friendly fuels), the controller arrangement is such that the intelligent electrical system controller 331 sits above and provides control over all the other elements within the control arrangement 330. In particular, the intelligent electrical system controller 331 controls the battery usage and can force actions that otherwise would be prevented by the intelligent ESS controller 332.

In the above, the term “safety event” is used. This may refer to any event that requires or may require action to resolve. This may include for example temporary or permanent events. These may include power loss, loss of fuel cell functionality, loss of propulsor functionality, bird strikes, fuel loss, total power failure or the like.

In the example of Figure 3, the arrangement 300 comprises a series of links linking components to one another. There is shown a link 302 which may represent a busbar or the like. Busbars may conduct large electrical energy from e.g. fuel cells and the ESS to motors or the like. Such an electrical conduit may be cooled by the cryogenic fuel in the arrangement to improve the electrical conduction along the busbar. Any suitable link between components may be a busbar in the arrangements disclosed herein. For example, the motor 311 to propulsor 312 link is not a suitable link as the motor 311 to propulsor 312 link is a mechanical link and not an electrical link.

In examples, the controller or controller arrangement is arranged to ascertain the circumstance of the safety event, the severity of the event, the currently available resources and the theoretically available resource, the risk associated with producing the theoretically available resource and design a response that optimises use of the resources alongside minimising the risk to the aircraft. This may involve damaging (over the long term) the equipment within the aircraft. This is advantageously allowed where modern equipment does not allow this. The approach herein is a clear direction change in thinking from modern systems.

In examples, the controller is arranged to, in response to detecting a safety event, at least one of: calculate a likelihood of return to normal flight conditions; calculate a requirement to jettison a fuel source for the at least one source of electrical energy; calculate a requirement of a deep discharge event of at least one source of electrical energy; calculate a failure state of the aircraft; and, calculate an energy need for a failure state of the aircraft

Calculating a likelihood of return to normal flight conditions is advantageous as this allows the system to design responses when such a response is required. If the event is minor, common and always or very often overcome with a return to normal flight conditions (e.g. experiencing a minor amount of turbulence) the controller need not perform calculations and design a response. As such, this aspect allows a response to be designed when it is needed and not when it is not.

Calculating a requirement to jettison a fuel source for the at least one source of electrical energy is advantageous as this improves the safety of the designed response to the safety event. For example, where the aircraft is in an unintended descent, jettisoning of e.g. hydrogen fuel is advantageous to improve the safety of landing. Similarly, where there is no requirement to jettison components, this is ascertained by the controller and fuel is not jettisoned. This of course provides savings in fuel and therefore cost. A more detailed, more appropriate and more bespoke response to any particular safety event is provided by taking into account whether or not it is advantageous to jettison fuel.

Similarly to jettisoning of fuel, it is advantageous to ascertain whether a deep discharge of the batteries (or the like) is required or not. As noted above, the deep discharge can damage the batteries (or the like) in the long term. This is deemed acceptable in the present arrangement. However, it is not desirable to damage the equipment if there is no need to do so. As such, when ascertaining the total energy resources available the controller arrangement may calculate whether a deep discharge is required. If it is, then this will be factored into the safety event response designed by the controller. If it is not required, then the controller arrangement will not look to signal for a deep discharge. In this way, the response is again more detailed, more appropriate and bespoke for the safety event in question. Damage will only be done if the safety event requires it and in this way there is savings in hardware lifetime and therefore cost. As noted above, dump loads for the electrical energy may include de-icing gear, galley ovens and electro-turbo compressor systems and other similar systems.

Calculating a failure state of the aircraft may include noting that the aircraft state is rapidly changing (e.g. altitude is rapidly decreasing). This may be indicative of a plummeting aircraft state. Similarly, if the aircraft state has changed to a lack of propulsor power but altitude is being mostly maintained, this may be indicative of a gliding aircraft state. Other failure states may include e.g. uncontrolled flight or uncontrolled landing. Each of these aircraft states may require a different safety event response. For example, noting the aircraft has switched to gliding state may provide the controller is a greater amount of time to devise and enact a response. In contrast, a plummeting state will require an almost immediate and very strong response (which may include deep discharging of batteries and total jettisoning of fuel).

For example, noting the aircraft state may inform the controller as to the estimated glide time of the aircraft. This time impacts how long the controller has to arrange purging of the fuel cells and how long power will be needed for prior to preparations for the next stage of the safety event and/or safety event response. The power needed may include the power required to maintain glide for a period of time, this may also include power required for aileron activations, landing gear activations, actuation of rudders etc. The controller arrangement operates on data received from a sensor arrangement. The sensors arrangement may comprise at least one of: a status sensor configured to detect a status condition of the at least one source of electrical energy, wherein at least one status condition is one of voltage, current, temperature, coolant input temperature, coolant input flow rate, coolant output temperature and coolant output flow rate; and, a state of health sensor configured to detect a state of health of components within the electrical aircraft propulsion arrangement. These data are used by the controller arrangement to design a more suitable response for the safety event.

In particular, relevant data may include all the details of the electrical energy store and/or electrical energy source. This can be used to provide energy calculations and state of health of these elements. As the controller may use the electrical energy store/source in a safety event response, it is advantageous to have an understanding as to the work that can be demanded from these elements.

The sensors in the sensor arrangement may be located close to the elements on which the data is being provided. For example, the sensors on the batteries (or capacitors/super- capacitors) may be located proximal to the battery system. States of charge can be ascertained by the data taken by the sensor arrangement. On a wider scale, system voltage and current measurements may be taken to provide data on the transmission of electrical energy through the arrangement. If a conduit is damaged this can be noted by the sensor arrangement and provided to the controller for consideration. This may therefore be used in calculating repair schedules as well as in response to safety events. Where unexpected readings are found, e.g. much less current than expected, this may be used to indicate a “state of health” error or concern for review.

Supporting systems may also include measurements such as flow and temperature measurements on the fuel system alongside fuel tank level meters. Again, somewhat local sensors to these systems will provide data on the state and send this to the controller arrangement. Data may be received by the controller and a conclusion of any of healthy, no fuel left or fuel starvation may be made for relevant elements.

The sensor arrangement may therefore be located in the aircraft in a distributed manner. In this way, the relevant sensor may be located proximal to that on which data is being taken. Proximal may not been adjacent, but close enough that relevant data may be taken while providing a space conscious arrangement. Data may also be taken on the aircraft itself such as altitude, aircraft speed and general orientation. Other relevant data may include projected landing profile (range from landing), proposed rate of descent, estimated projected time of glide, estimated projected time to landing, estimated projected speed etc. Further relevant data may include data on actual and projected aircraft load usage. For example when and how much power required to deploy the landing gear.

As such, it is clear that while the electrical aircraft propulsion arrangement may standalone, it may be used best within an aircraft.

Referring now to Figure 4, there is shown a pair 400 of related graphs 410, 420. The upper graph 410 shows a plot of time on the X-axis 411 against altitude 412 of an aircraft. The upper graph 410 has time points of interest with dashed lines that correspond to time points of interest on the lower graph 420. The lower graph 420 shows a plot of time on the X-axis 421 against ESS energy 422 (equally “state of charge”).

Referring to the upper graph 410, the aircraft altitude drops after a safety event as shown by line portion 413. The portion 413 may be referred to as the maximum glide path. The glide of the aircraft is shown as the aircraft continues to glide while losing altitude. At point 414, there may be a successful restart of the propulsion system after the safety event. In the event of a successful restart at point 414, the aircraft may regain altitude as per the line 415. If there is no successful restart the aircraft continues to lose altitude and follows the line 413 to an ever decreasing altitude.

Referring now to the lower graph 420, during the glide portion of flight (prior to the restart marker), the energy in the batteries is shown by constant line 423 (at 100%). The battery may not be being used during this phase and the aircraft is gliding without power from the battery. If the restart is successful, the aircraft continues to be powered by the fuel cells. The battery may be being used only slightly, for example the battery may be supplying only a minimal load which may include flight control surfaces and navigation computers.

In contrast, if there is no successful restart the controller arrangement devises a solution using power from the battery and planning for a safe landing. During descent, the fuel cells are shutdown and may be purged of fuel in them. This is shown in portion 424. In portion 425 the ESS provides energy to the aircraft to maximise the glide capability and provide the aircraft with further to glide and prepare for landing. In portion 426 the ESS is deeply discharged as per the above description. This means a maximal energy can be provided to the aircraft to increase glide capability prior to landing. Discharge may include providing energy to dump loads (as per the above).

The fuel cells have been purged and the batteries have been deeply discharged. The aircraft is therefore provided with a maximum energy to use in the landing and as little energy onboard to decrease the danger of landing. This in combination makes the landing as safe as possible. Furthermore, there is an extended period of time in which a possible restart can occur. A preferred outcome of each safety event is a successful restart and the present system maximises the time for this to be arranged by the controller arrangement.

Referring now to Figure 5, there is shown a pair 500 of related graphs 510, 520. The upper graph 510 shows a plot of time on the X-axis 511 against altitude 512 of an aircraft. The upper graph 510 has time points of interest with dashed lines that correspond to time points of interest on the lower graph 520. The lower graph 520 shows a plot of time on the X-axis 521 against ESS energy 522 (equally “state of charge”).

Referring to the upper graph 510, the aircraft altitude drops after a safety event as shown by line portion 513. The portion 513 may be referred to as the maximum glide path. The glide of the aircraft is shown as the aircraft continues to glide while losing altitude. At point 514, there may be a successful restart of the propulsion system after the safety event. In the event of a successful restart at point 514, the aircraft may regain altitude as per the line 515. If there is no successful restart the aircraft continues to lose altitude and follows the line 513 to an ever decreasing altitude. In this example (unlike the example of Figure 4), the line 513 continues to a point 516 where the line may continue as per line 513 or may branch off as per “reduced propulsion” arrangement shown by line 517.

The vertical dashed lines relate to points 514, 516 and the end of line 517. These represent the potential moment of successful restart (or the cessation of attempts to generate a restart) 514, the point of split 516 between line 513 and line 517 and the end of line 517.

Referring now to the lower graph 520, during the glide portion of flight (prior to the restart marker), the energy in the batteries is shown by the slightly decreasing line 523 (from 100%). The battery may not be being used during this phase and the aircraft is gliding without power from the battery. If the restart is successful, the aircraft continues to be powered by the fuel cells. The battery may be being used only slightly, for example the battery may be supplying only a minimal load which may include flight control surfaces and navigation computers.

In the event of total loss of primary power source (e.g. the fuel cells), the battery (or batteries etc) supplies electrical power for all flight-critical systems (including flight control surfaces, navigation, control systems). The ability to supply propulsive power in this event is a significant advantage of the present system. The energy to supply flight critical systems is lower than the propulsive power (energy requirement) but is notable especially as it is flight critical. As such, in emergency events the present system provides a strong response maximising the opportunity for restarts where this is achievable.

In contrast, if there is no successful restart the controller arrangement devises a solution using power from the battery and planning for a safe landing. During descent, in portion 524 the ESS provides energy to the aircraft to maximise the glide capability and provide the aircraft with further to glide and prepare for landing (different from Figure 4 example).

In portion 525 the ESS provides energy to the aircraft for propulsion (providing a reduced level of propulsion shown in line 517). This extends the glide time slightly as can be seen in the upper graph 510. In portion 526, the ESS is deeply discharged as per the above description. This means a maximal energy can be provided to the aircraft to increase glide capability prior to landing. Discharge may include providing energy to dump loads (as per the above).

As shown in the graphs 500, the aircraft may be landed after a battery-enhanced glide period (line 517). The safety of landing can be improved by using the power from the batteries (also referred to herein as ESS and this may also as noted above include capacitors and supercapacitors) to increase the glide time to increase the response time for the controller arrangement and to allow for a shallower and therefore gentler decrease in altitude during descent.

Referring now to Figure 6, a method 600 according to an example of the present disclosure is shown as a flow diagram. The method 600 has four steps 605, 610, 615, 620.

In a first step 605, data is received at the controller from a sensing unit relating to at least one of flight condition; aircraft condition; and, electrical energy store condition. In examples, the controller may receive data from the sensing unit relating to all those aspects. In any case, the controller is able to, with data from the sensing unit, obtain an understanding of the flight condition of an aircraft related to the controller and sensing unit.

In a second step 610, the controller calculates the presence or not of safety events based on the data. This will lead to two scenarios. One is that the controller detects no safety event occurring. In this instance, the method returns (following arrow 612). The other is that a safety even is detected and this engages method step 615.

In a third step 615, in response to detecting a safety event the controller calculates one of the following: a likelihood of return to normal flight conditions; a requirement to jettison a fuel source for at least one source of electrical energy; a requirement of a deep discharge event of at least one source of electrical energy; a failure state of the aircraft; and, an energy need for a failure state of the aircraft. Each of these are highly relevant for the controller to devise a response strategy to the safety event. As noted, if there can be a safe restart of equipment that leads to a return to normal flight, this may be the most preferred outcome. Therefore the controller may look to ascertain this calculation first. Each of the remaining details are relevant for the strategy devised by the controller in response to the detected safety event.

In a fourth step 620, the controller controls production, storage and provision of electrical energy from at least one source of electrical energy according to the calculations in response to detecting a safety event. In this way a response to the safety event is devised and executed which can be optimised in light of e.g. aircraft altitude, speed and remaining useable energy alongside minimising the danger during landing.

In this method therefore there is high responsiveness to a safety event or the like where both a return to normal functioning and emergency response of varying severity can be executed. The variance in severity is related to the seriousness of the safety event. Where the safety event requires an immediate and strong response, the controller is able to detect this and design a suitably strong response. The method is therefore highly responsive alongside being able to provide bespoke solutions for particular safety events occurring at particular times on flight for different aircraft with varying structures and varying equipment. The method provides an optimised response for different aircraft while maximising the safety of landing (or otherwise recovery) from the safety event.

The method and arrangement discussed herein may be operated in a stand-alone arrangement. The method and arrangement discussed herein may be operated within an aircraft. The arrangement disclosed herein may be operated in a distributed manner, for example wherein the controller is located remotely from the aircraft while the remaining elements of the arrangement (prime movers, source of electrical energy and sensors) are arranged on the aircraft. It is advantageous to have the sensors on the aircraft as noted above, proximity is preferable and provides improved readings. The controller may be held remotely and communicate to the remaining elements via wireless signalling.

In the above, there is discussion of a controller arrangement that is able to control production and release of electrical energy in response to detected safety events. The controller arrangement may be seen as including a battery management system (BMS). The controller arrangement does not permit over charge or over discharge during normal operation of the aircraft.

Where the propulsors are powered by hydrogen fuel in normal operation, in response to a safety event the controller arrangement may simultaneously: jettison hydrogen fuel; attempt restarts of the propulsors; calculate glide time; calculate optimum discharge profile to ensure the ESS is deeply-over discharged at the point of landing; and/or override normal battery management operation to permit deep discharge. As noted above this is highly advantageous in developing a flexible and suitable safety event response.

In example, the propulsors may be cryogenically cooled and/or superconductive. The controller arrangement may factor in reduced cryogen availability since the cryogenic fuel may have been deliberately jettisoned or lost due to failure. The controller arrangement may optimise the timing of release of the available electrical energy store electrical power to the propulsors to improve safety of landing. This may be e.g. waiting until the final approach before providing power. This may assist in preventing the propulsor being of reduced functionality at critical moments (e.g. landing).

Prior to landing the electrical energy store may be reduced substantially to 0% charge and the fuel in the electrical energy source may be purged. Reducing the energy in the batteries to around 0% may reduce the likelihood of thermal runaway and prevent further emergency events on landing.

Together these synergistically reduce the total potential energy on the aircraft almost to zero ahead of landing. This may be useful in optimising the safety of the landing and therefore increase the chance of a safe landing. The above integrated controller arrangement provides an adaptive response to safety events and maximises the safety of landing.

Claims

1. An electrical aircraft propulsion arrangement comprising: at least one electrically operated prime mover for providing thrust for the aircraft; at least one source of electrical energy arranged to provide electrical energy to at least one electrically operated prime mover; a controller arranged to control production, storage and provision of electrical energy from the at least one source of electrical energy; a sensor arrangement arranged to provide data to the controller, the data relating to flight condition, aircraft condition, and electrical energy source condition.

2. An electrical aircraft propulsion arrangement according to claim 1 , wherein the at least one source of electrical energy comprises at least one of an electrical energy source and an electrical energy store.

3. An electrical aircraft propulsion arrangement according to claim 1 or 2, wherein the at least one source of electrical energy is at least partially cryogenically operated.

4. An electrical aircraft propulsion arrangement according to any of claims 1 to 3, wherein flight condition comprises: stage of flight; and, details of flight; aircraft condition comprises: prime mover condition; and, aircraft integrity; electrical energy source condition comprises: charge status; fuel status; operational status; and electrical status.

5. An electrical aircraft propulsion arrangement according to any preceding claim, wherein the controller is an intelligent electrical system controller.

6. An electrical aircraft propulsion arrangement according to any preceding claim, wherein the controller is arranged to detect safety events from the data provided by the sensor arrangement.

7. An electrical aircraft propulsion arrangement according to any preceding claim, wherein the controller is arranged to, in response to detecting a safety event, at least one of: calculate a likelihood of return to normal flight conditions; calculate a requirement to jettison a fuel source for the at least one source of electrical energy; calculate a requirement of a deep discharge event of at least one source of electrical energy; calculate a failure state of the aircraft; and, calculate an energy need for a failure state of the aircraft.

8. An electrical aircraft propulsion arrangement according to any preceding claim, wherein at least one electrically operated prime mover is an electrically operated propulsor.

9. An electrical aircraft propulsion arrangement according to any preceding claim, wherein at least one electrically operated prime mover is at least partially cryogenically operated.

10. An electrical aircraft propulsion arrangement according to any preceding claim, wherein the sensor arrangement comprises at least one of: a status sensor configured to detect a status condition of the at least one source of electrical energy, wherein at least one status condition is one of voltage, current, temperature, coolant input temperature, coolant input flow rate, coolant output temperature and coolant output flow rate; and, a state of health sensor configured to detect a state of health of components within the electrical aircraft propulsion arrangement.

11. An aircraft comprising the electrical aircraft propulsion arrangement of any of claims 1- 10.

12. An aircraft according to claim 10, wherein the sensor arrangement comprises at least one of: a status sensor configured to detect a status condition of the at least one source of electrical energy, wherein at least one status condition is one of voltage, current, temperature, coolant input temperature, coolant input flow rate, coolant output temperature and coolant output flow rate; a state of health sensor configured to detect a state of health of components within the electrical aircraft propulsion arrangement; a fuel sensor configured to detect a condition of a fuel source for use in the aircraft; and, an aircraft condition sensor configured to detect an aircraft condition wherein an aircraft condition is one of altitude, aircraft speed, orientation, projected landing profile, stage of flight, estimated remaining flight time, elapsed flight time, and landing gear deployment status, and wherein a portion of the sensor arrangement is arranged proximal to the at least one source of electrical energy.

13. Method of operating an electrically operated aircraft comprising: receiving at a controller data from a sensing unit relating to: flight condition; aircraft condition; and, electrical energy store condition; calculating, by the controller, the presence or not of safety events based on the data; in response to detecting a safety event, calculating at least one of: a likelihood of return to normal flight conditions; a requirement to jettison a fuel source for at least one source of electrical energy; a requirement of a deep discharge event of at least one source of electrical energy; a failure state of the aircraft; and, an energy need for a failure state of the aircraft, and, controlling, by the controller, production, storage and provision of electrical energy from at least one source of electrical energy according to the calculations in response to detecting a safety event.

14. A method according to claim 13, wherein controlling, by the controller, production, storage and provision of electrical energy from at least one source of electrical energy according to the calculations in response to detecting a safety event comprises at least one of: jettisoning a fuel source; purging an electrical energy generation system of fuel; activating a deep discharging event of at least one source of electrical energy; providing electrical energy to essential glide systems; and, activating electrical energy dumping.