INTERVIEW: Jurgen Greil of FlyNow Aviation gives a technical overview of company’s eVTOL family

The Advanced Air Mobil­i­ty mar­ket is get­ting crowd­ed, with the lat­est num­ber from the Ver­ti­cal Flight Soci­ety’s World Air­craft Direc­to­ry now stand­ing at more than 700 eVTOL con­cepts.

The data­base fea­tures many dif­fer­ent designs which are at var­i­ous stages of their devel­op­ment, and we were giv­en the oppor­tu­ni­ty to speak with Aus­tri­an start­up Fly­Now Avi­a­tion CEO Jur­gen Greil in detail.

His com­pa­ny is devel­op­ing what it describes as an effi­cient, auto­mat­i­cal­ly fly­ing, elec­tric mod­u­lar eVTOL fam­i­ly con­sist­ing of car­go and per­son­al air vehi­cles. Our con­tent writer, Boris Sedac­ca, asks the ques­tions.

eVTOL Insights: Can you tell us about your expe­ri­ence and back­ground at Opel, Porsche, BMW Group and Great Wall Motors?

Jur­gen Greil: “I grad­u­at­ed from the Tech­ni­cal Uni­ver­si­ty of Vien­na in Aus­tria with a degree in Mechan­i­cal Engi­neer­ing. Beside skills in var­i­ous vehi­cle propul­sion tech­nolo­gies and archi­tec­tures, I gained insight into gen­er­al mobil­i­ty con­cepts and set the basis for a gen­er­al under­stand­ing of many aspects of traf­fic as such.

“After five years as a design­er in aero­space, I changed to the auto­mo­tive indus­try where I was active for more than 20 years in var­i­ous design and man­age­ment roles at Opel, Porsche and BMW. I was respon­si­ble for inno­v­a­tive vehi­cle con­cepts with alter­na­tive dri­ve trains. With­in BMW’s ‘Project i’, I con­ceived and led the elec­tric dri­ve mod­els i3 and i8. Lat­er to evolve the Hydro­gen Fuel Cell Vehi­cle Project where I start­ed to work on inno­v­a­tive Hydro­gen stor­age inte­gra­tion solu­tions.

“Dur­ing this time, it became clear­er and more vis­i­ble to me the futur­is­tic lim­i­ta­tions and bot­tle­necks of urban mobil­i­ty espe­cial­ly in megac­i­ties. At the same time, I held com­mer­cial licens­es for air­planes and heli­copters with instru­ment- and mul­ti-engine rat­ings, which forced me to think about the lim­it­ed pos­si­bil­i­ties of ground-based solu­tions.

“Giv­en my pas­sion and exper­tise, both in ground and air mobil­i­ty, it moti­vat­ed me to put togeth­er my idea into real­i­ty of facil­i­tat­ing 3D-mobil­i­ty for every­one. Today I am glad to see that what was a dream to me, became more and more a valid option for mobil­i­ty rather than an absurd idea.

“After hav­ing left BMW in 2016 I became Head of Vehi­cle Archi­tec­ture at Great Wall Motor (GWM) in Chi­na in the Fuel Cell Elec­tric Vehi­cle project. How­ev­er, after two years I decid­ed to leave the big auto­mo­tive com­pa­nies behind to give wings to my idea and found­ed Fly­Now Avi­a­tion in 2019.”

Q: What were the main rea­sons for set­ting up Fly­Now Avi­a­tion? 

JG: “Besides hav­ing the dri­ve and pas­sion for 3D air vehi­cles, we became more aware of the exist­ing air vehi­cle mar­ket dynam­ics, where near­ly all the competitors/ exist­ing play­ers offer air vehi­cles for a pre­mi­um mar­ket seg­ment. We found the gap in the mar­ket and realised that large major­i­ty of the pop­u­la­tion is deprived/ exclud­ed from the attain­ing the ben­e­fits of 3D Mobil­i­ty.

“This in return, also leads to prob­lems in accep­tance and miss­ing polit­i­cal sup­port. We saw this as his­to­ry repeat­ing itself, as this was the same mis­take the auto­mo­tive indus­try did with elec­tric cars.

“So the main rea­son why we found­ed Fly­Now Avi­a­tion was to devel­op a mod­u­lar eVTOL fam­i­ly con­sist­ing of a car­go and a sin­gle- and twin seater pas­sen­ger ver­sion using less resources and ener­gy to pro­duce and oper­ate than any of  the exist­ing com­peti­tors, in the mar­ket, today.

“We want to suc­cess­ful­ly imple­ment a new means of trans­port that is safer, more com­fort­able, faster and above all cheap­er than exist­ing solu­tions and is avail­able and afford­able for every­one — is our mantra.”

Q: How will it work once it is oper­a­tional? Will peo­ple be able to buy and own one them­selves, or will it be used as part of a UAM ser­vice?

JG: “Flights are booked via an app and car­ried out by apply­ing a specif­i­cal­ly cre­at­ed flight plan, which is auto­mat­i­cal­ly flown from the take-off to the land­ing site via pre­de­fined way­points. 

“The car­go ver­sion will be oper­a­tional first. An eVTOL with a pay­load of 200 kg, it can be applied in real life in sev­er­al ways; start­ing with the trans­port of food and oth­er essen­tial goods for dai­ly needs to more remote areas, through time-crit­i­cal med­i­cines or tech­ni­cal equip­ment, to civ­il pro­tec­tion and res­cue ser­vice tasks. 

“In the sec­ond phase, the pas­sen­ger vari­ants will be intro­duced, which can be used in cities and munic­i­pal­i­ties as pub­lic trans­port, taxi and air car­ri­ers, by hotels or man­u­fac­tur­ing units with sev­er­al loca­tions for inter­nal fac­to­ry trans­port and logis­tic com­pa­nies.”

Q: What are the elec­tric motor and dri­ve-train com­po­nents?

JG: “The lift is gen­er­at­ed by two counter-rotat­ing two-blad­ed rotor pro­pellers, which are each dri­ven by a quadru­ple redun­dant, per­ma­nent­ly excit­ed syn­chro­nous e‑motor. Each e‑motor dri­ves one rotor pro­peller via coax­i­al­ly arranged shafts. The entire unit is con­nect­ed to the cab­in via a uni­ver­sal joint and forms a so-called tilt­ing head mech­a­nism.

“Counter rota­tion coax­i­al rotors are known to be the most effi­cient arrange­ment. Down­siz­ing of this effi­cient con­cept by sub­sti­tu­tion of ful­ly artic­u­lat­ed coax­i­al rotors by fixed pitch rotors and rpm con­trol instead of com­plex coax­i­al swash plate assem­bly results in afford­abil­i­ty and elec­tri­fi­ca­tion of the dri­ve­train lead­ing to sim­pli­fy­ing and poten­tial to cut down the cost fur­ther, man­i­fold.”

Q: What about the actu­a­tors: where and how are they pow­ered?

JG: “In order to roll and pitch the air­craft, there are two elec­tri­cal­ly pow­ered actu­a­tors posi­tioned between the e‑motor hous­ing and the cab­in manip­u­lat­ing the tilt­ing head mech­a­nism. Yaw is con­trolled by the torque dif­fer­ence of the two elec­tric motors where climb and descend is achieved by increas­ing and decreas­ing the rotor rpm. This is the sim­plest means of con­trol­ling six degrees-of-free­dom in 3D space.”

Q: How do you achieve sta­ble flight char­ac­ter­is­tics due to low cen­tre of grav­i­ty?

JG: “If you have a mul­ti­copter sys­tem and one of the pro­pellers fails, you also must shut down the oppo­site side pro­peller to avoid insta­bil­i­ty. In our case, the cab­in cen­tre of grav­i­ty is way below the gim­bal joint. So, the air­craft sta­bil­i­ty behaves like a pen­du­lum in the sta­ble posi­tion. 

“The motors are large in diam­e­ter because we need high torque at low RPM to have a low rotor tip speed and there­fore reduce noise emis­sions. The air mass accel­er­at­ed by the two rotors is high and com­bined with a low down­wash veloc­i­ty and a low disc load­ing helps to fur­ther low­er the noise par­tic­u­lar­ly over urban areas. 

“We expect that flights will be at 500–1,000 feet in most cities and coun­tries to avoid oth­er air traf­fic above 1,000 feet, while below 500 feet there may be fire­works and small drones. With low noise emis­sion, we are talk­ing about 55 dB(A) at 500 feet, this is 5–10 dB(A) low­er than you have from back­ground noise in cities at around 60 to 65 dB(A). 

“Noise emis­sion is on a log­a­rith­mic scale, so every 3dB equates to a dou­bling of sound pres­sure lev­el (SPL), but it is not only about SPL — the audio fre­quen­cies also need to be kept low, and since we have low speed of 650–750 RPM, this leads min­imis­ing the annoy­ing high fre­quen­cy whine dras­ti­cal­ly, even of high­er speed rotors.

“To the con­trary are mul­ti­copters, which have small­er rotor diam­e­ters and there­fore need to increase their rotor speeds to some 2,500–3,500 RPM. Even if SPL would be  the same – which they are not — the high­er fre­quen­cies are more annoy­ing. 

“The auto­mo­tive indus­try works on mod­u­lar vehi­cle con­cepts to be able to pro­duce dif­fer­ent prof­itable vari­ants accord­ing to dif­fer­ent cus­tomer require­ments. This is why we devel­op a mod­u­lar fam­i­ly of a sin­gle-seat, twin-seat and car­go air­craft using the same dri­ve-train with the bat­ter­ies at the bot­tom of the cab­in, because they make up almost half the weight of the air­craft.

“Apart from bat­tery pow­er, we also have incor­po­rat­ed the abil­i­ty to swap to hydro­gen fuel cell pow­er because we believe that by the year 2030 there will be demand for such appli­ca­tions, giv­en the infra­struc­ture has been built. Fly­Now has now built three pro­to­types. 

“The car­go ver­sion, which uses a roll-on, roll-off con­cept with an 800 x 1,200 mm Euro pal­let with one cubic metre vol­ume. It uses a matrix con­duc­tive charg­ing sys­tem which con­sists of a sta­tion­ary pad and matrix con­nec­tor on the vehi­cle. 

“The upper part is in the vehi­cle and the low­er part is sta­tion­ary, which can charge up to 30 kW, so you do not have to plug in and out man­u­al­ly. Since the ener­gy con­sump­tion is around 500 — 800 W per minute, we have eval­u­at­ed based on cus­tomer feed­back, that most flights will be between 10 — 25 km and will take between eight and 15 min­utes. This entails an aver­age ener­gy con­sump­tion of 6 — 8 kWh per flight. By charg­ing at 30 kW, the turn­around time is about 12 — 15 min­utes. 

“We do not use hydraulic pow­er and as the elec­tric motor is air-cooled, it does not use any flu­ids. At the same time, at Fly­Now, we have designed the air vehi­cles with­out the need of a gear­box, as toothed wheels are known to cre­ate prob­lems.  The elec­tric motor is direct­ly dri­ving the shaft of the rotor blades.”

Q: How are the sig­nals inter­con­nect­ed for feed­back loop & PID con­trol?

JG: “Fly­Now air vehi­cles use mod­el-based con­trol sys­tem which has a PID loop that pre-defines the actu­a­tor posi­tions, so that the actu­a­tors have to make minor changes only. It has sen­sors for the air­craft posi­tion in space, so the con­trol is achieved by using two feed­back loops, big and small. 

“The big loop is a macro type to keep actu­a­tors and rotor RPM with­in range, while the small micro loop is mak­ing the small adjust­ments when­ev­er required to react in the event of gusts and changes in wind direc­tion, to pro­vide a smoother ride.”

Q: Why do you use over­head-posi­tioned coax­i­al rotors?

JG: “The rotors should be locat­ed out­side the reach and move­ment of the users to avoid both injuries and dam­ages. This arrange­ment of the rotors includ­ing the dri­ve train above the cab­in also enables a very space-sav­ing foot­print.

“We are in talk with sev­er­al logis­tic com­pa­nies about the car­go ver­sion. Most play­ers have a wingspan of around 10 m so they use up to 100 sq. m on the ground, while we can have 14 of FlyNow’s eVTOL con­cept with­in the same space. 

“Fly­Now air vehi­cles can be trans­port­ed in a con­ven­tion­al 20- or 40-feet con­tain­er by tak­ing the rotor blades off, but how do you get an air­craft with a 10 m wingspan to your cus­tomer if you can­not fly it? The air­craft must be dis­as­sem­bled and trans­port­ed to the cus­tomers, who then have to reassem­ble the air­craft on site.”

Q: What is sim­ple-tilt­ing head thrust vec­tor­ing?

JG: “With the gim­bal mech­a­nism, the whole dri­ve-train can be rolled and pitched in the X and Y axes using two actu­a­tors. By push­ing them up or down, you can roll, pitch or both and there­fore vec­tor the thrust.”

Q: Can you talk about bat­tery pow­er den­si­ty and the size, weight and pow­er (SWaP) trade-offs? 

JG: “The pow­er den­si­ty of the total bat­tery sys­tem includ­ing every­thing is around 200 Wh/kg for the bat­tery which con­sists of four inde­pen­dent units that sup­ply pow­er via four cables to the two elec­tric motors. Since it is a sim­ple dri­ve-train, the wiring har­ness is also sim­ple. 

“The charg­ing is at the front side and the ener­gy sup­ply to the motors is at the rear. The invert­ers are ful­ly inte­grat­ed into the elec­tric motors, so there are no cables — only bus­bars of cou­ple of cen­time­tres from the invert­er to the motor sta­tor. 

Q: Do you have an esti­mat­ed time­line of when you expect the air­craft to be cer­ti­fied?

JG: “We are fol­low­ing a three-step approach with the Aus­tri­an Avi­a­tion Author­i­ty as part of the EASA (Euro­pean Union Avi­a­tion Safe­ty Agency). Recent­ly, just before the onset of the new year we got our Proof of Con­cept cer­ti­fied in the so-called ‘spe­cif­ic cat­e­go­ry SAIL 2’.

“In the sec­ond step we will cer­ti­fy the car­go ver­sion with a high­er SAIL between 4 and 6 depend­ing on the use case, to final­ly enable the com­mer­cial oper­a­tion by the end of 2024. After suf­fi­cient expe­ri­ence with the oper­a­tion of the car­go ver­sion by all stake­hold­ers, we are putting step in the right direc­tion to seek nec­es­sary cer­ti­fi­ca­tion of the pas­sen­ger vari­ants in the cer­ti­fied cat­e­go­ry by ear­ly 2026.”

Avatar photo

Jason Pritchard

Jason Pritchard is the Editor of eVTOL Insights. He holds a BA from Leicester's De Montfort University and has worked in Journalism and Public Relations for more than a decade. Outside of work, Jason enjoys playing and watching football and golf. He also has a keen interest in Ancient Egypt.

eVTOL Insights is part of the Industry Insights Group. Registered in the UK. Company No: 14395769