Technical Challenges Facing eVTOL Aircraft Development

welcome everyone for joining us today for this iet midlands power group event today's event is on the technical challenges uh to electric

electric takeoff aircraft including a focus on the battery electrical machine design as well as covering some generic topics around the aircraft configuration

and certification the electrification of air travel is one of the rapidly developing areas of industry and is currently helping to drive innovation in high power density energy storage

power electronics and electrical machine design for aerospace applications the bristol-based vertical aerospace is one of the companies leading the way in the development of all-electric

e-vitol technology and has had their first flight of their second evil evil evital aircraft in 2019

i'm very pleased to welcome lawrence blakely who is a head of powertrain at vertical aerospace he will be presenting on the technical challenges to ev told development lawrence has 16 years

of experience in aerospace electrical systems including 12 years in the airbus group leading the development of

a400m and the a350 electrical system architecture just before i hand over to lawrence i'd like to remind everyone that there is a q a button at the bottom of your screen and so

please use that for any questions that you might want to ask during or after the presentation i'll now welcome lawrence and hand over to him thank you lance thank you very much

andrew and uh thank you everyone for logging on to listen to me talk about the technical challenges that we face in evital um now in an hour i don't expect to

cover all the technical challenges i hope to give you a flavor of what we face um and some of the high-level topics as andrew mentioned please feel free to

ask any questions i'll do what i can to answer after if there are subjects that i'm i'm not expert enough to answer then i can take them away

and uh i'll follow up no problem until uh just to expand briefly on my on my career history um as a bit of an introduction i actually started as an

aircraft electrician um doing an apprenticeship at marshall's aerospace in cambridge um it gave me a flavor of the hands-on elements

of aircraft installation but also what is good design and what is not so good design and that kind of set me up in a in a career in aerospace

um and airbus gave me a lot of opportunity to move around and really understand um how things are designed

and really quite importantly how you design things to meet the regulations so we talk about the intent of regulations a lot so i'll probably just touch on that

towards the end of of this presentation um i've now been with vertical aerospace three years um i was number nine um in the company we're now

about 110 growing slightly over the next six months as we move forward in our development again i will touch on those timelines as

i go through um so i'm hoping now my presentation works there we go so vertical aerospace uh we

were founded by um the owner of ovo energy stephen fitzpatrick and the the real basic premise of vertical is to enable electric flight for

everyone um and we need to break that down into things that are slightly more meaningful and from an engineering perspective and

the three areas that we've kind of focused on um is making air travel personal um on demand and emissions free emissions free really at the moment that leads to

electric um propulsion battery propulsion quite specifically um making it on demand so that is really driving towards much

smaller um vehicles that you you almost hail like a taxi i don't think the model will be exactly like a taxi but

um that's the kind of ethos and personal being it should meet the needs of the public and and one of the big

needs here is going to be around noise and environmental impact that aviation is happening not just um is is it meeting your

flight mission needs uh so that's really our guiding light for for our development now when steven set up

our company he was really keen not to just draw from aviation if you take um an already tried and tested system

and apply it to a new design you're going to get probably something that is very similar to what's already out there and stephen wants something

different um so he's purposely drawn from across the various industries um he himself is from energy over energy is one of the

leading um suppliers of renewable energies um uh he's also an avid formula one fan

and um a formula one team for a while mana racing um and uh he's very keen that we integrate that

fast-paced um and very critical design criteria into our into our aircraft um if you saw the uh

the formula one at the weekend and a pretty high impact crash and the driver steps out and walks away um that's that's some pretty impressive engineering

um a pretty impressive design capability um and the drivers obviously very pleased that the f1 engineers are able to design a very lightweight but

strong and resilient structure and and we want that in our in our aircraft quite clearly um so far so i joined

at the end of 2017 um actually just after the initial um what we call the park proof of concept has been built

um i i did a small amount of rework on the electrical systems but not so much really the credit goes to the six engineers that started the company to pull that

um that prototype together it flew it flew really well actually um it's now parked at our facility it's not a product we want to take forward

it was about developing a capability um and really the challenge there was integration it was off-the-shelf components and um

pulling pulling those together into a vehicle and integrating i'm going to talk about integration quite a lot as i move through my slides and

integrating those systems uh into uh into a vehicle we then decided that the technology was essentially ready to take some steps

into creating more robust vehicles um so a bit of a recruitment drive we're now at 30 plus engineers and we are designing serif during 2018

um serif really focused on uh on taking a step forward there's now some bespoke areas of this of this design

um i will touch on serif uh in a bit more detail in just a second um we then flew serif in 2019

now we're really gaining momentum we were 70 plus engineers and by the end of 2019 we've uh acquired uh what was

called mgi technology so mike gascoigne is a veteran of formula one he had a consultancy company that really specialized in composite design

um and we've rebranded uh his company vertical advanced engineering they're very focused on developing our composite structures um and really

taking that technology from formula one that i briefly touched on a moment ago and and looking to integrate that into aerospace um so the park uh if anyone has seen our

website you will have probably seen uh a couple of the slides that i'm going to show um it's a proof of concept vehicle

it completed its flights um and really it was just demonstrating that the the company those that original six people and a few extras as they came on board

could integrate off the shelf equipment um and uh complete a flight test program

um it weighed in at uh somewhere near 750 kilos maybe just over 750 kilos

and i think the battery weight for this and this is an important topic which uh drives all of aviation uh weight and the battery weight of this vehicle i

think was about 350 kilos from a product perspective if this was to be taken forwards um it would be a single um

a single passenger vehicle um potentially some uh some payload some additional payload that could be utilized but um

not really the uh the groundbreaking uh disruptive uh aerospace approach that stephen had in mind

so we moved to serif now there's a lot of obvious differences between this vehicle and the previous and one of them is we've moved from four from a quadcopter essentially four

rotors in shrouds to a multicopter this has six arms each arm has two props

um and no longer um there's there's a few other uh differences internally on the previous

vehicle on the pop there is no um no redundancy in any of the systems here we're really looking at how do we ensure that

after a failure we can continue safe flight and landing so this is one of the the cornerstones of aviation and the phrase is no catastrophic

failure can and so no no single failure can cause a catastrophic event so we we keep that as a bit of a mantra um throughout all of our design activities

so this vehicle um as i've mentioned we're looking at redundancy testing and we also designed the rotors

ourselves a you can't buy rotors off the shelf for a a

two ton um not two ton sorry 1.2 ton vehicle um with 12 rotors they don't exist so we had to design our own rotors and that took a lot of simulation work

before we actually built them and then during the flight test um we then looked to validate our testing

our simulation sorry and all the way through this we are really focused on developing our internal company capabilities as

well as looking at improving the vehicle and so company design tools and techniques uh here we've got uh aerodynamic analysis there's also

a lot of uh electrical load understanding um so when when one prop is spinning what are the other props going to do so what's the

interaction of the flight controller with the different propellers and the the interaction onto the the powertrain so i'll focus a bit more on the powertrain in just a moment

um we wanted to create a vehicle that could take two passengers and some luggage so we equated that to about 250 kilos

and actually this this vehicle it's pretty crude if you take the outsider away and but it met all those objectives

so it's it could carry the payload um it flew uh i think 80 kilometers an hour was the maximum speed

um and quite critically we had we failed a motor and we were able to continue safe flight and landing so

from a redundancy test perspective it was an extremely robust vehicle um i'm just going to touch on the power chain now

as this is one of the focuses of the presentation and what i really want you to take away from this this section of the presentation is um integration is

absolutely key there's nothing on the on the vehicle that is standalone that you can design in a in a closed room um and it it will just

fit onto the vehicle and and perform um really in integration is key so if we just have a look at the what we have in this in this photo in this cfd analysis in

the bottom left um we have two propellers we're going to focus on just one propeller connected to a motor

the motor is then connected uh through their ac cables so you see the three phase um in the red and the blue

and i think it's probably black in there in the color behind um and you the blue pipes are the cooling systems

now to design this system we need to break it down into what are we actually trying to do um and then how do these things

connect together so we have the rota rotors and they are producing lifts you've got a motor and the motor is driving the rotor i know some of this sounds obvious

the inverter is converting the hv from the batteries into an ac that is driving the motor the motor and inverter need cooling the battery needs cooling the battery also

needs venting but you can't sit down and design this at this point in time you need some more information so the main information this is clearly not

all the information but some of the really high level pieces of information are what is the mission profile that we want to to fly what is the the vertical acceleration in that mission profile so

we want to climb to 50 meters how fast do we want to climb to 50 meters um if we want to avoid um another vehicle in the air

maybe someone is flying a drone how fast do we need to do that evasive maneuver um what's our horizontal acceleration i

talked about 80 kilometers an hour um which we achieved with the vehicle as you're flying 80 kilometers an hour how quickly do you need to maneuver what maneuvers

need to be need to be made during during that mission profile all of that feeds into this system

and it feeds into this system by understanding the airflow from the rotor the airflow we are using also is our cooling so there's a really

really good link there between the airflow and our cooling capability the motor is sized and these uh

bespoke motors um for us they got bespoke windings to ensure that the uh the rpm is at the right is the right speed to

the right value rpm for the rotors that we've designed um and we are able to control the temperature of those uh those motors with this cooling system

the cooling system is also linked to the inverters not shown in this picture that are installed in the main body of the vehicle so jumping through what do we get out

of this uh of this system we get a a powertrain weight weight is critical so we get structural weight from the powertrain weight so what

structure how how large is that arm how much load what loads are we taking from the rotor through the housing um through the arm

uh the housing that is holding the motor is metallic we've then got a composite arm so we have an adhesive bond and what's the strength of that adhesive bond

so from the output of this exercise we call the sizing exercise we're getting um essentially the aircraft's size um we then want to have an available

payload um in the case of serif it's two people and and uh and a pilot so there's 250 kilos um

and then we need to actually understand how the vehicle is going to fly so what are the flight control laws that are needed to um to control this so

uh this from a flight control laws perspective um we're touching back onto the acceleration topic when uh when you want to change direction which

motors are going to be engaged how fast do they spin when you want to yaw so your is twisting around the z-axis um [Music]

sorry the y-axis which uh which rotors are you speeding up which rotors are you slowing down and then when you've gone through that exercise

you need to feed back into the beginning because you don't know unless you put the numbers back into the start if you have closed the loop so if

the weight that you end up with actually enables the mission profile that you wanted in the first instance so that closed loop is is really important what you end up doing from a

design perspective is you iterate around around this loop a number of times hopefully coming closer and closer making smaller and smaller changes

sorry so i've got a little video hopefully this will play as i want to ensure there is proof that we

actually were able to design and fly this vehicle

all right sorry i don't know so [Music] [Music]

[Music] so where do we go next um i think something that's quite evident

is we've built two full-size vehicles learning from full-size vehicles is so much more extensive than it is from from part vehicle part size vehicles subscale

testing so we're going to follow that trend and we're going to build uh a another prototype another full-size prototype

um the previous two really were were essentially a warm-up um we always intended to develop a winged concept

and now wings already exist which is why winged concepts weren't or weren't focused previously and we were focusing

on understanding the the powertrain and the uh the the rotor um elements but now we have uh defined the vehicle that we are going to

take through to eventually to certification but take through to a full-size prototype um

at the end of 2021 so about a year from now hopefully less than a year from now and just to to touch on some of the

criteria for for this vehicle so 100 miles at 150 miles an hour

um now that size is the battery straight away that says we need to have uh uh 45 minutes of flight maybe slightly longer because you

don't start at 150 miles an hour and we also need to have a diversion so already first requirement um we're defining a a

an element of the aircraft one pilot for passengers there's our payload again that defines the weight that we need to carry

um for that period we also now have a size for the fuselage all electric so we will use batteries we're not quite there with hydrogen yet

i don't think so we're on batteries uh low noise to blend into the city life now if anyone's heard a single rotor

aircraft fly over their house or an a a helicopter these things are not quiet um noise is a real big factor when it comes

to aircraft operations the example i i often draw is in london there is a uh a helicopter pad in the center of

london um at battersea and that's limited to six flights an hour and the limitation is noise and it's about disturbance um

so if we can reduce the noise of the vehicle uh that six flights an hour straight away goes up

um so there's there's a clear benefit uh in focusing on that canary wolf to heathrow airport in under 20 minutes so this is

um a actually drawing on a different requirement um so in the top left we have a one

solid mission of flying 100 miles now under 20 minutes we're talking about shuttle uh a shuttle mission so that gives an a different

mission for us to work to so in my previous slides i was looking at this mission and the accelerations etc um we've got two extremes of

uh of mission that we're going to focus on with this vehicle and significantly more affordable um there's no point in creating this this lovely new vehicle if it's going to cost

you twice as much to fly on it nobody will use it so it needs to be cheaper we're actually targeting about five

to six dollars a a mile um which is extremely cheap so that means your flight from canary wharf to heathrow is um in the

in the 50 uh 50 pounds bracket um not the 2000 plus probably that it would be for a helicopter

um so a real step change in the cost and a lot of that is down to the electrical powertrain i'd like to just draw attention to the same system

but the additional complexity that we now have in our new vehicle so i i don't know if uh if anyone noticed i'm sure i'm sure it was picked up

uh in our layout now we have eight rotors not 12. um

and the forwards four are tilting so you take off and they're all in the vertical position and then to go to forward flight those

front four transition now we've settled on eight uh this is really down to um understanding failures so that phrase i

mentioned at the beginning no single failure can cause a catastrophic event and if we were to lose any motor any rotor

um we are able to still continue safe flight and landing with the remaining seven it doesn't matter which um which failure it is

um any failure we can continue and that's that's a really critical point um if any anyone wants to certify a vehicle um that's that needs to be

demonstrated um and eight we believe is the minimum number um so if you were to go down to seven or six or five

rotors um it starts to get harder to demonstrate that one failure is is a survivable event so with this addition we now have a tilt

mechanism so the addition of the the this moving prop the moving rotor we now have a tilt mechanism so the rotors are no longer just lift

but they're also crews so that cooling system that we looked at in serif needs to accommodate two different phases of flight

two different orientations of airflow um the epu so this is the electrical propulsion

unit that is comprising the motor um and the associated cooling system one day it might also include the inverter but at the moment i

was still separate um the the road the the propellers and the rotors and this this tilt mech it all makes up this one system that we've

that we've defined uh it and i think it's quite obvious but just to highlight um this is this is what's happening we have an actuation between the forward thrust and the

and the lift thrust but this is putting huge loads through um through this section of structure so from an integration perspective

um and talking about you can't design in isolation we now have huge um gyroscopic loads that are being transferred from the rotors through a tilting

mechanism along the structure and into the wing which creates a huge uh issue for for us to manage a huge engineering

challenge for us for us to deal with um and just to highlight the the addition of this in in that the fairly basic uh

system design i i put forward earlier we have the lift rotors mounted on this the motor the motor the inverter the cooling systems all need to be

integrated with this tilt mechanism so the tilt mechanism needs to have dynamic hv cables ac cables cooling systems whatever the final design is it needs to

enable this dynamic movement and it needs to react to the the structural load so from a weight perspective closing this loop um uh

is is an additional challenge for us to for us to solve but as with uh electric cars really electric cars are just batteries packaged in a car

in a they just happen to be in a car shape really here we are a battery just packaged in an aircraft shape um because the battery is uh

is the largest system the heaviest system on the vehicle um it's probably going to be about a third of the vehicle weight

um in its in its entirety um and it also presents one of the not the only but one of the biggest challenges that we that we have to solve

integrating a battery system into the vehicle and all the complexities that go with it and one of the questions that i often get asked is

why can't we take a tesla and strap it on the bottom of our vehicle and and away we go well as good as the

tesla battery is um it's not designed for aerospace uh firstly there's no redundancy so imagine

a cell failure at any point and in your in your downtime feel free to google uh ev car um fires you you'll see plenty of uh

of examples unfortunately um interestingly more around charging than in discharging but they they exist um so what happens when we have a

failure so a cell goes into thermal runaway so it could be an internal failure to the cell there could be some some debris inside the battery for

whatever reason and uh or it's taking a bump and there's there's some damage

and it creates a short circuit and uh that leads to thermal runaway uh a cell sets on fire the

it burns maybe for a couple of minutes um at about 600 700 degrees c possibly higher as well um it becomes difficult to measure

and invariably it will set the next cell on fire and then the next cell on fire and you have a cascade effect um and

the beauty of a car is you stop and you get out and and it it actually doesn't happen quickly it's not an instantaneous explosion

as you would have with uh with a jet fuel or um or petrol um but it's it it happens quick enough that

you want to stop and get out we can't have that in an aircraft stopping and getting out is not so simple and if this event starts to happen on the vehicle

we need to be able to still draw enough power to be able to land the vehicle in a safe manner and sticking to that phrase no single failure can cause a

catastrophic event i should qualify catastrophic is uh is is not good you're looking at losing the vehicle and losing passengers so this really is uh a a a focus for

aviation now tesla the the pack is an extremely powerful pack for automotive um it's 168 i think give or take kilowatts per

kilogram um that's not enough for us um we need a higher power dense pack um now interestingly cars it's much more

about range the focus is on energy density um so the cells that are going to be produced more and more for automotive and not necessarily going to be the

cells that will suit aviation um as we need power that the the vertical takeoff period of the vehicle um really draws huge amounts of power

and we can see see that in a couple of slides i think um so the automotive power density is not enough for us

cooling um actually i'd like to refer to it as heat extraction um when you're in a energy draw situation not a

power draw situation um you can maintain the uh the temperature of the pack fairly fairly well um it's

drawing the power that creates the heat um and what we're finding is we're drawing so much power and so quickly and [Music]

being able to extract the heat is very difficult um so we're we are having to design the pack really to cope with um

that raising temperature and not expecting a very fast extraction of heat structural integrity is uh is an is another challenge and

and actually this is around trying to achieve a higher power to weight ratio so this kilowatts per kilogram um so

this tesla pack it's designed to be the underside of a vehicle so any debris from the road can come up and strike the pack um we don't need that on an aircraft so

we can actually have a much less robust um structure than uh than the tesla so straight away without changing the cells

um but changing the casing we could improve the power to weight ratio um and also the parallel and series layout and so here you're looking at modules that

are arranged um to to give a specific voltage and a specific current um now we're looking in

the aviation uh arena to move the voltages from around the 400 volts which most automotives are at to around the 800 volts

and quite interestingly porsche are pushing or have um an 800 volts um vehicle um and really

you get benefits from weight with going up in voltage um there is always a trade-off and so creepage and clearance so the distance that um electronic

components can be has to increase um and that makes things larger and larger means heavier so there is always a balance but also

i i didn't want to list everything um but i i really wanted to draw attention to the fact that this is this tesla pack is designed to automotive requirements

um not aerospace requirements and when we look at the aerospace requirements for these vehicles um ev tell vehicles electrical vertical takeoff and landing

vehicles and for us to run commercial operations we need to meet a failure rate of uh one failure every 10 to the minus nine

flight hours and that that that's really very high uh that's a really very difficult failure rate to meet it's equivalent to

um standard large aircraft aviation so your a320s a350s sorry i'm airbus um boeing 787s etc they they meet this

this very stringent requirement and you can't you can't meet that through testing at the end through um just a solid design process you need to implement

um processes and procedures to integrate what's called design assurance so you know that when you follow this process

you get a safe design at the end and actually the the the aviation requirements they are all about defining process um

if the vehicle is not flyable at the end it's too heavy that's actually not a yes's issue it's not the faas issue their issue is ensuring that you can

produce safe aircraft so we'll keep in mind those aviation requirements this is an example of a pack that we've

we've designed um we've actually not taken this through and i'm sorry i can't give too many details around around this pack the the battery design

as in the automotive world um is going to drive um performance of the vehicle and therefore is it does bring a a pretty good

competitive exhaust advantage if we can if we can uh outperform our emerging competitors but uh really i'd like to draw on on a couple of things firstly

we're looking at having multiples of these packs so this is one of um a number of packs that are all going to work together and inside the packs

we have modules now that's actually not so dissimilar to the tesla if i jump back here you can see in this pack

a number of modules um what we've done is we've got modules inside packs and then we've got a number of packs um so if you have a failure a fire

um it will only take away one pack not all of the um not all of the packs and we have a number of requirements

that you can that i've summarized here into having a minimum weight maximum power so this is again this uh power to weight ratio 168

it's good for automotive we are pushing uh over the 200 kilowatts per kilogram uh one of our competitors um joby in the states i think they are

talking around the 235 238 kilowatts per kilogram uh region um we'd be happy if we achieved that as well that's a good target

to uh to set so how do you go about designing this pack so i talked about heat extraction and it really is all about heat extraction i would just

like to make a note these values are hypothetical they are not um a direct extraction from the vehicle we're

designing um but let's say we uh need to draw 14 uh so 1.4

megawatts of power for our v e vetol phase the thing that cuts us off is this temperature line the temperature line that is

consistent across the three graphs so we are fully designing around temperature so how we control that temperature how we're drawing the power um where the

temperature is coming from and the cells are an obvious um source but then the uh the the distribution of electrics inside the

pack is also a source of um sorts of heat and the maneuvers you can see the maneuvers that we are now coupling to this

this uh temperature increase so take off vertical takeoff climb hover your these are all in the vertical

um phase as soon as we move to conventional flight the power draw on the vehicle drops off really quite a lot and

so it's not it's not been so much of a focus from a sizing perspective we need to be able to complete a vertical phase of flight and we also need to be able to complete

a vertical phase of flight when we lose a rotor and lose a uh a subpac failure so this is one of the battery packs

so if we use a uh i use the example on the right in this simulation that we were running if we lost one of the battery packs the

power draw is uh is such that it is going to during that second yaw or that in this case sorry the first

your um maneuver the temperature is going over the uh 65 degree cut off um

and it's actually i think around 85 degrees that um thermal runaway is is a potential

um so we have a safety margin in there but clearly this is not a good situation in that right hand graph um so we need to

maybe increase some uh some additional cells and add some additional cells in there to distribute the power more more across the uh the batteries

um or look at ways we can extract heat um more efficiently and more effectively so this just gives a flavor of

that cycle that i talked about before which is um understand what you want to achieve with the vehicle design your powertrain system understand what you have

after that so what is what is what have you designed and then feed that back into the start of this this design loop um and to touch on the regulations because aerospace is heavily driven by

regulations if anyone has ever worked in the industry um we'll know um we are we're doing everything we can to uh draw from other industries i touched on

the formula one uh quite specifically earlier but we have a lot of experience from dyson from jaguar land rover from

um other land-based uh kind of system designers as well um to look at essentially streamlining how

we can achieve um the aerospace requirements but you've got three kind of levels the first one

is called part 21. um

this is how do you define an organization that can design aircraft um in a in a safe and robust way

so that's the there's the organizational requirements so what roles and responsibilities are within the within the company who does the design work and then who checks

that design work and then whoever signs that um who's taking ultimate responsibility and accountability it's all defined

in this document the middle document is the special condition that has been created for vertical takeoff and landing aircraft this is because

it's a novel vehicle it does not fit into the standard requirements that um essa has already defined uh and it's exactly the same situation for

the faa um yeah being european the faa being the american and generally driving the the global um aerospace requirements and these

aircraft design requirements they define essentially everything around the vehicle but they don't tell you how to do it they say um we need the vehicle to be safe in this condition

we need to ensure that the vehicle can um have sufficient flight um after a failure to get to a diverted

landing point for example um really the how you do it is then defined in uh acceptable means of compliance so

um i've drawn out the battery one here um but really this is a suite of documents that if you follow um then you will be in line with

the uh with the special condition um one of the unfortunate things with ev tools is actually the requirements are not

fully defined therefore the applicable means of compliance the typical means of compliance and not um and are also not fully defined so in a lot of these instances when we're

passing through this design loop and trying to understand how we want the the the systems to behave in certain scenarios we are also having to work with the

authorities to define what those requirements are and our internal battery specialist is actually leading

um the rewriting of this this battery document do 311a and that's defining things like if you were to drop the pack what do you expect

to happen um if the pack overheats what do you expect to happen what are the charge rates what are the different conditions for charge etc

and so it's a very all-encompassing document um so they're they're kind of the main focuses

that uh that we're working on just to kind of look forwards over the next few years um uh for vertical aerospace and i i

i guess actually all the other um evito aircraft designers um we're looking at designing and developing

our full-scale prototype we will also design and develop a number of test rigs and this is about validating uh and there and verifying

our assumptions um so we believe that a system will get to a certain temperature based on our simulation modeling

we then create a test rig and we prove that it does get to that temperature um so that will happen the vehicle will be built throughout the second half of next year

and hopefully flying before the weather comes in so around the september october time we'll start test flying that vehicle and the flight test program

will run for about 18 months um in that time we will uh uh achieve uh what's called doa

and poa so just referring back to the part 21 document that i mentioned on the previous slide um we have the design organization authority and the

production organization authority so this is um the caa and esa agreeing that we have all the processes

and procedures in place to design and build aircrafts um in a safe manner and so that's really critical if we want to be an aircraft manufacturer and an

aircraft uh supplier then um we need to have that uh have that legislation

uh in place um the prototype it's not going to be uh quite good enough for certification it's a stepping stone a technology stepping stone so we will start

the design actually probably by summer next year um of the certification vehicle um and that will be taking everything that we're learning from

designing this latest prototype um improving it improving the safety improving the integration saving weight critically in every area and

um and then starting the certification activities so we will have these the first certification standard

built by the beginning of 2023 and then we have approximately a two year window of flight testing

um and this is uh is a really uh time-consuming um uh but clearly critical area where every

every eventuality of of a flight condition needs to be explored to prove that the vehicle is safe to enter service

and then at the beginning of 2025 everything's perfect we have a vehicle and it's ready to sell but unfortunately the problems don't stop there

the vehicles i apologize i've only used serif in this in this slide i pinched it from somewhere else but the vehicles need an infrastructure to integrate within as well it's not just

about creating an aircraft and we need to enable and we're not going to do with this all we need to enable other industries to

to develop um the whole infrastructure of this emerging aerospace um so if we just work uh from left to right on this uh on this

slide um we have what we call inverter ports um now we need charges how many vehicles are going to be charging at once

um what kind of maintenance activities needs to happen clearly a very different operation than um than a helicopter operation um we want to take credit of

the latest standards of uh of of technology and 4g 5g is just an example of that how uh how are

the vehicles integrating into the emerging um networks that are being investigated and invested in at the moment

how do the vehicles uh communicate to the air traffic control service atc service um how do the vehicles communicate with other vehicles

in the air so tcas is an example of that um but how are we going to draw on that on that technology and then

hopefully take it to the next step um how is it into how is it integrating with what's already on the ground so the ground base

uh systems and sensors so if we fly over a a a radar of a of an aerodrome do we uh disturb that signal does that signal disturb our vehicle

those things need to be integrated so moving to the right integration to airport security um in theory we should have a lot more people being able to

travel via via air transport now how would the airport security systems going to enable that and anyone passing through an airport knows it's not a very fast

activity so we need to enable something to enable this additional throughput in in vehicles in passengers sorry

and um we've also got the enable the integration with already established aviation so

how does the latest technology evital vehicle talk to the old uh the the old aviation um uh vehicles that are flying so

a cessna 182 for example that might not have all the bells and whistles and might not be able to communicate in in the way that um the latest technology is driving

and uh just a a another note which is actually an increasing issue i'm sure people have seen in the news um is the interaction of

drones um within our airspace so how how's that managed um and drone services are going to come online companies like amazon

are going to use drones to for cargo delivery um how is that integrated into the into this overall i guess system of systems

um so i just my finishing words really are the vehicle is a very complex um problem to solve um but it's not the only problem to solve

if we want to fully enable the ev till market to to be established and to be profitable come 2025. so thank you very much for

2025. so thank you very much for listening and i think i'm handing back over to uh to andrew so thank you thank you for that lawrence that was a

really interesting presentation i think um it has generated quite a lot of questions and it's it's clearly an area where we're making some great developments um but there's

still unanswered questions in how that's going to apply um in real life into a commercial system so thank you for that um if i can just start off with a

question of my own could you give us a sense of um i know you might not be able to give an exact figure but the power requirements for vertical takeoff for example for

your vehicle yeah sure um if if anyone with a sufficient uh mine were to sit down it's not difficult to to equate the

weight of the vehicle to a power demand so it's not necessarily that that's that much of a problem to share so the

legislation allows us to go to a 3.15 ton vehicle um and for vertical takeoff for that vehicle you're looking in the region of about a

megawatt up to about maybe 1.2 megawatts okay thank you for that so we've got 23 questions i won't be able to go through them all in this session but what we will do

is um send out um a written response to some of these questions that we we don't get a chance to answer um and we've got the distribution list for everyone who's attended

so the first question this was from uh paul ellis have you considered removing the pilot which allows additional passengers absolutely and

uh a really good question um and there's a company called wisc um that are actually linked to boeing that are focusing on on this they believe it's a really good

route to market um the the vertical aerospace position um is that we don't think that the legislation

is going to enable um pilot luss flying in in the short term um so if we if we go to

uh driverless cars um there is that there are a lot of vehicles out there that um that you would say now has the have the ability to

be driverless and yet still the legislation says that the driver needs to be able to take control um it's going to be a similar

uh kind of slow approach um we think of vertical for the pilot less to come into the loop there are there are elements so i'm specifically saying pilotless

you could move the pilot onto the ground so the pilot is no longer in the air um so you have a pilot sat in a seat essentially flying a simulator but that simulator is an actual vehicle

um you could have that situation through to fully autonomous so it's not necessarily autonomous flying that will come first um but the technology is

maturing um we're actually part of a consortium um through for a a uk competition called cesar that is looking at some

elements of autonomy um i think it's looking at doing an autonomous takeoff and then an autonomous land but not a full autonomous route so it it will be explored and it certainly

will be the future in 20 years i'm sure there will all be autonomous thank you lauren i suppose perhaps we'll see autonomous in small cargo evita applications before

you see in passenger aircraft yeah completely and and really it's the the regulations are driven around safety if you have uh

a route that doesn't fly over people no one's on the vehicle and then you can imagine autonomy is a lot easier to integrate than if you're flying

passengers over schools for example um there was the next question's about the helicopter helicopter controls and there's actually another question or a similar vein to that so um are the controls similar to those in

a helicopter and just adding in the other question um about training so so pilot training for controlling this as well so pilot training i i will touch on that

first um it's an extremely difficult topic um and it's a real chicken and egg topic

so these these vehicles don't exist so we can't train the pilots and they will exist in a relatively short amount of time and at that point we need probably

hundreds of pilots to be starting to train so where is this influx of pilots going to come from are we going to be able to enable that it's it's a really difficult topic to answer

and and actually i was on the on a call with nasa yesterday afternoon talking about this very topic and they're looking at writing a white paper that will focus around this um or that's

an element that they'll focus on now with respect to helicopter controls um yes and no um so if

if i draw to the what the pilot sees um when you're in a helicopter you have a a collective so you're you've got a lever that is

lift that is doing your vertical movement you then have a joystick that's doing um your your attitude and and you have pedals as well that's

doing your that that are doing controlling your yaw um now as you move into conventional flight you're you're no longer controlling

through the rotors you're controlling through your the the um the wing surface control so the ailerons um and uh and the flaps and things like

that um so your the the connection changes so yes it is similar the way the control is done is different

though so if you're looking at your ring in a helicopter you use the tail plane and the tail plane is is is yawing the vehicle um in

a multi-copter generally you're using uh diff changes in the rotor speed um so you're using the inertia of the rotors to create a yawing moment

you can also angle the the propeller slightly to also drive some some your control so the pilot will have the same controls

in the vertical flight as a helicopter he'll have the same controls in the conventional flight as an aircraft so here's a pretty big challenge for us to solve but in the vertical flights how the

vehicle is actually controlled is different to a helicopter i hope that answers the question or maybe uh raises more questions i don't know it possibly raises more questions but no i think that was a good

answer thank you very much um i had a few people actually ask about uh removing the shrouds on the on the rotors so um going from the ducted fan

to to an open design a really good question and uh they were actually some of the slides i cut out um because it's a really obvious difference between uh the park and serif

um and you get some some benefits of the shroud so just to touch on the benefits um from a noise perspective they're really good at containing the

noise of the rotors um you also generate lift from a shroud and so the shroud is essentially a wing so as the air is being sucked in by the propeller

you're creating lift um and if you have a rotor failure you could imagine that the shroud can contain that rotor failure just like in a jet engine

and um some of the blades not all but some of the blade stages can be contained by the by the engine by the shroud but they're heavy so we we have a weight

penalty um and they also act like a like like a wind break as soon as you start forward um a transition

so any forward motion and when we flew the puck we i i think we were about 15 degrees um to actually get any forwards um

forward speed and any decent forward speed and from a passenger experience this is quite a change in um in the attitude of the aircraft

and i i think it's about five degrees maybe even slightly less when you remove the shroud so it's making a really big difference

um for that initial transition phase and going back to the powertrain you need a huge amount of power to overcome

that that drag that has been created so it's additional burden on the battery and the hv powertrain etc and the motors so that's really

primarily why we remove them thank you um you also mentioned about the the

single event failure for one rotor and there's a few questions on on that kind of topic so um sorry let me just find one

so how is a single type failure avoided different equipment diversity etcetera so i think this is more long lines how do you um ensure that multiple voters don't have a

similar failure mechanism at the same time really good question so uh the title for that topic is common mode failure

um and just some examples of what a common mode failure could be um so it could be at a temperature

uh a bearing fails or a or a seal fails or something so if you're taking off at minus 20 degrees in in canada um the bearings are always

going to fail because they're they're too cold so so that could be an example of a common mode failure um another example of a common mode failure and it's one that we're in

quite heavy discussions with the authorities on is what happens if you lose a blade so a blade fails and it hits an adjacent blade which hits an adjacent blade

so you have a cascade effect so it's not they don't all fail at the same time but it's a cascade effect of failures so we need to treat both of these topics the common made failures

and the cascade effect so from a common mode the approach is generally it's not perfect uh and there's a lot of techniques it's a huge topic

which i i i'm not going to be able to fully answer just in this in this call but um we we need to basically design away the common modes

so we imagine though what are the common uh modes between so in in the motor it's the bearings it's the magnets it's the windings um and then we look at what are the

external influences that could cause a failure now if there are if we can ensure there are no external influences that can cause that failure and now we're just looking at it they

might fail after 10 to the five flight hours they won't all fail at the same time at that point so you'll have one failure and at the

end of a bearing life and but that's not going to be at the same minute after you've been flying for a hundred hours um as as the other failures but you

could then start introducing things like maintenance rotations so you're replacing things more systematically and maybe out of sequence and to ensure that things aren't coming

to the end of life at the same time and the cascade effects really is it's around analysis and there's a lot of aerospace processes and procedures around

following failure hazard analysis system safety analysis failure mode and effect analysis and so these things they help in identifying the common modes the cascade

failures um uh as well as uh it's just some just generic failures and but the the cascade effects the propellers are an easy one to see but

you could have a short circuit that short circuit could draw a lot of power from the battery that in turn could cause uh battery failure that means the other batteries are now more overloaded so

now we need to understand if another battery pack is going to fail as well so it's really sequentially thinking about what are all the failures that could occur and in each failure instance

how how could that impact the surrounding systems and how are we going to treat that so it's extremely uh i don't want to say laborious because it sounds like we don't want to do it

it's critical and it's one of the main parts of aviation is actually analyzing each potential failure analyzing each part of the system how could it fail what could cause that

and what are the repercussions of that happening yeah really clear it's a really complex issue and i guess the processes are currently available within aerospace for

helicopters and um even for your commercial airliners are applicable here in terms of failure propagation and actually um one of the the main benefits of moving to electrical

propulsion is is to make vertical flight safer helicopters um actually have a failure rate of about 10

to their 5 and that's really around the gearbox uh very complex gearboxes very complex gas turbines i i should caveat that the

more complex and the larger helicopters actually are better than 10 to the five i'm talking more the small the small helicopters um and when you introduce electrical

systems you're able to remove a lot of the complexity and with compre complexity often comes failures so once you remove the complexity you have a much more simple system on our

vehicle the only moving part is is the motor that's it there's no other moving parts so you can probably imagine that's extremely simple compared to a helicopter

exactly and i think that drives the the desire for electric proportion throughout the entire aviation industry and even in automotive to yeah for servicing um you mentioned some standards there

for uh certification and one of them was the do-311a um lithium-ion uh battery standard um there's a comment that that's not

going into revision can you clarify what works being done around the standards that were mentioned yeah of course so uh the official release of do311a is called amendment b there's actually an

amendment c which is not an official release that's um uh clarifies some of the testing and but it's currently in revision

it's in euro cae um and it's working group 112 and i think it's 112 and that's looking

at rewriting uh it's not completely from scratch um but some of the elements of there to look to make the test more representative of the batteries that are

going to be going to be used so it was originally written to to facilitate batteries in um general aircraft where the battery is a

source of backup power essentially um rather than the main source of power which is uh which is an engine um so there are some differences

in when when it comes to the failures associated with those packs so if if they want more information you're a cae working group

112 is where to go looking thank you for that um there's another question on the battery development about fuel cells and would you consider

fuel cells as an alternative to the lithium battery yeah for sure um i think what i will state is we're very unlikely to develop our own fuel cell um

but there is clearly a lot of interest and increasing traction around fuel cell and so in the uk um at least i know uh there's a company called zero avia that are investigating

fuel cells um in my time previously at airbus um there was a a number of projects looking at fuel cells so i expect that's continuing

um there's a lot of automotive interest in fuel cells as well um but with fuel cells comes additional complexity

uh a battery it sits there it produces it you can draw power from it um or not that's that's it there's there's nothing else happening really

um with a with a fuel cell you have um quite an additional added complexity of containing your fuel in a

in a safe manner um which is not so easy to achieve and then you need additional systems on how do you purge stacks and how do you keep pressures at the right level etcetera so

um it i expect it will come it's not a simple solution and and really we're looking at how do we get any veto to the market as quick as possible

i'm expecting the first fuel cell solutions to be coming out for aviation in around 2025 and now we want a vehicle certified and going into operation then so um the

battery is the way to get there in the in the first instance yep yes that's uh they're on the horizon but they're not quite ready yet yeah we're certainly keeping a watching brief

yeah and with batteries obviously you have to cope with the discharge range of the battery as well which makes optimization of the inverter for your motor drive a little

bit more complex um because you have to consider the voltage range are you going is it currently an unregulated dc distribution

or is it regulated at the 800 volts so uh it's i guess regulated um so we are

actually just under the 800 volts so as we say 800 volts but it's actually just under and um depending on the chemistry of cell that you select

you you have your your discharge profile and then you need to design the inverter to match that discharge profile so if if you're starting at 800 volts and you're using

um let's say lfp as a as a chemistry uh i think lfp is a pretty flat discharge so maybe it's actually only 700 volts

before the the you drop off the cliff um so you only need to design for for that hundred volt range window in the inverter

whereas if you're if you're looking at uh um a different chemistry sorry it's not my area of expertise but a different chemistry

you could see a lot a lot quicker a drop in that voltage but when you look when we're looking at that flight duration it's trying to predict particularly

if there's a flat voltage discharge or a flat voltage during the discharge it's trying to predict when the voltage is going to drop off the cliff and and diminish to to an unusable value

that is the key in in in in trying to understand and trying to define to the pilot how much time he's got left

so the difference between 710 volts and 700 volts might be uh half a second or it could be five minutes

um and where are you in that range it's it's not so easy to develop i think i think we'll take just one final question and and they still they're still coming in

lauren so um i'll send you the list over after this and we'll reply to that they're not all coming from vertical aerospace know the answers um so given the high voltage and current

being controlled has emc been an issue uh yes absolutely um so emc and and i guess i'll also just

mention static as well so um emc by the point by virtue of we need to turn ac to dc uh sorry dc to ac um

so that section from the inverter to the motor is very electrically noisy environment um so we need to reduce that as as much as possible but the motives themselves are

obviously going to generate a lot of um uh emi to to try and manage so we we can't stop that being produced

so we then look to um screening we look to um filters on on systems we look to getting communication

uh uh signals out of the same frequency as as as that's emi um so it it's that

there is a lot of uh interference being produced but it it's not unmanageable there are there are tried and tested ways to manage this um

but from a static perspective as well we now have eight rotors not just a single rotor all of them producing static so as soon as something's moving in air you're going to um electrically charge

the the vehicles so we now need to manage the the ground plane of the vehicle um and how we couple things to that ground plane or don't couple them to the ground plane

is quite important yeah clearly quite a challenge i guess that's why it's really important that we do these kind of demonstration vehicles and

develop that learning yeah fantastic i will just add when you have a composite vehicle it becomes harder to manage these things um metallic vehicles

are a lot easier um so having metal mass is a is a real benefit um that we just don't have um in a composite vehicle so that's that is an added challenge sorry

thank you and with that so the rest of the questions that we haven't been able to answer today um we'll follow up with with an email to the attendees just to um to try and answer those as best as as we can

and with that i'll hand over to martin thank you i uh thank you uh thank you andrew um well martin wood vice chair of the midlands power group

um right well uh it's it's amazing um to me anyway uh just what the vertical um aerospace um have achieved

since since 2017. especially as you've progressed progressed the design build and testing of uh not one but two prototypes in that time

in an integrated systems approach uh and also fascinating fascinating to see um what you're what you're planning for the future uh so behalf i'm sorry so on behalf of the

midlands power group uh and everyone on the call um it just remains for me to thank you laurence for a thoroughly interesting

and an enlightening presentation um there are a couple of closing points um so firstly cpd certificates will be mailed out for everyone

attending uh within the next week uh apologies for anyone that attended the our last event and hasn't yet received a cbd certificate that there is

there is a slight back backlog there that we're going to get addressed um and lastly uh

the midlands power group our next event is titled dsear achieving electrical safety in hazardous environments and that's

provisionally scheduled for the 26th of january 2021 uh that that may change but but please keep an eye on the iut events page

for anyone interested in dangerous substances uh and explosive atmospheric regulations okay um right so uh we'll we'll bring this

call to a to a close and uh thank you everyone for

attending

thank you very much you