Hi John, I enjoyed your analysis of full tiltrotor and partial tiltrotor eVTOLs. We’ve been in the VTOLs with transitions to the horizontal flight business for the past twenty years. For reasons you identified, we never even considered a partial tiltrotor configuration. Early in our development, we identified the transitions as the most challenging phase of flight. We have also discovered that the wing is crucial for achieving smooth transitions. In your video, you are operating in ideal atmospheric elements, which is acceptable for this study. However, all eVTOLs in development will have to operate in less-than-ideal meteorological conditions; we must consider gusts and wind shears. When disturbed during a transition, aircraft with significant mass will experience pitch oscillations that will cause the wing’s AOA to follow the oscillation path, thus adversely affecting the wing’s lift. The stabilization systems will detect this condition and attempt to correct it by adding power/lift to the appropriate set of rotors. Due to the large aircraft mass, it is reasonable to expect overcorrections, resulting in PIO (pilot-induced oscillation) from which the aircraft may not recover. We must understand one crucial fact. Computers are reactive systems responding to inputs from sensors! We must take the AOA gyrations out of the equation to achieve stability governed by physics and aerodynamics. Look me up on LinkedIn, and let’s connect. www.linkedin.com/in/edward-dolejsi-afsi
Hi Edward, Wow! Thank you so much for your detailed and thoughtful reply. I feel humbled and happy that you are reaching out to a beginner like me! I definitely agree with you: from the little prototyping I have done, I have found the transition, especially the back transition, to be the most challenging. The flight dynamics model we built for our prototype was based on ideal atmospheric conditions. We planned to simulate wind gusts until we realised that we were just using this task as an excuse to postpone the inevitable: do the first test flight. Models are never perfect and flying for the first time is always nerve-racking but, at some point, improving the models without test data is just giving diminishing returns. For the pitch-oscillation problem you described, were you talking about a longitudinal static stable aircraft? Did you use a PID controller to trim for altitude or attitude? If it is a PID controller and the feedback control loop is overcorrecting, then I suppose you can play around with the Proportional and the Derivative-gain. I did not quite understand the point you have made on AOA gyrations - I would love to learn more about it! I have reached out to you on Linkedin. Thanks again, John
The transition for both aircraft involves actual downwash on flight surfaces creating 'extra' weight (the rear surfaces and wing tips of the Joby ) and/or the downwash inducing a negative angle of attack on the wing from the front rotors even at a nose up incidence . Indeed the effect of nosing down ,like a helicopter does to accelerate, is to create less or even negative lift in accelerating transition . The rear rotors act to increase the effective wing angle of attack from their downwash partially offsetting the effect of the front rotors which are placed as far ahead of the wing as possible to minimize the 'downlift' they cause other than in cruise configuration - Vertical aerospace VX4 has MUCH shorter pylons than the Archer or Joby and they all compromise the proprotor diameter to reduce these negative downwash effects . The Archer midnight especially has gone to ridiculous lengths (literally) to try to get the wing out of the worst of the front prop downwash in hover and transition -- it is a bad concept all round . The Heaviside and Do29 used only aft tilt props to avoid this issue which is a better deal . Earlier tilt wing vtols like Canadair CL84 and XV 124 etc avoided the downwash penalties that the XV22 has (and suffers the extra 'weight' by using lower disc loading and hence downwash on the wing ) the interaction non linearities must make for complex artificial trim and control made worse by loss of any rotor -the 737 MAX lesson is relevant here with software 'solutions' . The drag of the exposed rear props, stopped, is greater in the front prop slipstreams (and eats power as the cube of local velocity) It is clear from the poor behaviour of these designs AND the wild gyrations of the "0.1, .2, .3, .4 etc 'versions' and even worse patented 'abominations' (look up the Joby patents -unbuilt precedent designs) that they did not arise from carefully considered design procedures but from raw avarice after the projections of immense riches by Morgan Stanley/ Uber elevate et al. Normally such misconceived creations would never leave the drawing board . Take a look at the Autoflight 'prosperity' -- supremely ugly even if it avoids some of the Joby/Archer failings.
What many EVTOL designers tend to do is miss the fact of air turbulence during VTOL lift and do not consider calculating the extra constant balance exceleration of each motor needed to maintain stability of VTOL level hover. This also applies during all levels of control using the motor power. Were as in a helicopter,rotor flight controls are used to keep level flight, however in a EVTOL during VTOL flight power is used to control and maintain hover level. The more turbulance the more power is drained from the batteries thus cutting short any flight paramiters.
I've designed a VTOL (not electric) aircraft that does not have the issues you describe. It is much simpler than these EVTOL's and V22 or similar but it is designed to fly at 26000 metres. Hopefully can build it one day. I'm a dreamer, but I also feel that these electric aircraft are a waste of time presently. With the most dense lithium batteries being highly unstable and self combusting they are possibly more dangerous in the event of collision even light. If a plane runs out of fuel and crashes at least it cant burn upon impact. Lithium batteries can be discharged and still highly flammable. Thanks for the video and your time.
Hi, thank you so much for taking the time to write out a thoughtful reply. Lithium batteries indeed have this problem. Though from my experience, the battery will not be fully discharged during flight and around 10-20% SOC is kept to preserve the battery's health (i.e. the number of charge/discharge cycles). Battery safety is related to battery packaging. If a pouch is used for weight-saving reasons, then the pouch can indeed be punctured easily during a collision. The reactants can then directly mix, potentially triggering an uncontrolled reaction. When comparing the dangers of fuel and batteries, I would perhaps check that the energy content of the fuel/battery is the same during the impact. On that basis, the risk can then be assessed more fairly. I am excited to hear about your ambition and innovation! I support you to follow your dreams, by designing and building your VTOL. The fruits of your labour will not only be the product itself, but the skills and experiences you have developed along the way!
@@zhihenglou Thanks for the encouragement mate. Working on a helicopter at the moment to beat the altitude record of 13960 metres, as I don't have storage for a 20 metre wingspan aircraft. I know that Lithium batteries create their own oxygen which makes them impossible to extinguish. Haven't seen any crash testing of these aircraft, but guarantee it will be a factor for safety.
@@chippyjohn1 Yes, that's right! Batteries carry their own oxidising agent. The battery effectively houses its own "oxygen" (oxidising agent), whereas an air-breathing combustion engine would get the oxygen from the air. I do see what you mean now, in terms of not being able to extinguish the battery fire with conventional means, like suffocating the flame from its oxygen source. I would point out that a fully discharged battery would have, in theory, used up all of its oxidising agent and it would therefore not be possible to react further. If the electric aircraft is discharged to 20% SOC, then approximately 20% of the energy is still stored, which would be the energy source for the flame. Wow, your helicopter project sounds challenging and fun! I wish you every success. If you would like, please keep me updated - I would love to see more of it!
It would be interesting to have a noise profile of these configured aircraft during both transitions --we have 'overflight' figures where the rear props are stopped and some in hover where there is no or little interaction but not in the intermediate transition/conversion where the front props wake and the rear interact (worst case might be in landing -decelerating transition where flaring (rear up to kill forward speed ) might be the worst case (as it is for helicopters ) The loss of power to one or more front rotors in this situation will result in sudden increase of angle of attack on the wing and possible stall --this could be induced from deliberate shutdown of a diagonally opposite rear rotor also,
Nice video! Another concern is failure cases. The more tilting rotors there are, the more ways there are for it to go wrong. Similarly for variable pitch rotors. eVTOLs are much more complex than helicopters in this regard, and all the complexity is in the electronics and software, as opposed to mechanical systems for helicopters. It’s a very different (and arguably much more challenging) safety problem.
Thank you for your feedback, John! I am thrilled to hear that you have enjoyed the video. Lilium's concept is very interesting. It is a very bold design, with significantly more risk and reward. There are good reasons for liking and disliking it, hence there is controversy. Explaining Lilium's design from a propulsion system perspective is on my to-do list! Please come back around January next year to check for the video. In the meantime, I wish you a nice Christmas holiday!
The best design of the type of VTOL aircaft would depend on the intended use by the user. That is what the user operation of the VTOL is going to be, VTOL lift and short, medium or long range straight flight. The shorter the range the bigger the VTOL rotor size and lift design as most of your power and fuel use will be required and used during VTOL flight. Hense the smaller the VTOL lift rotors the more fuel is used during VTOL. So if an operator intends to use such aircraft for short range and more VTOL lifts, it is better to have a helicopter rotor or tilt rotor due to a bigger rotor size, as in the long run less fuel usage. During a straight wing flight less fuel is used due to a fixed wing lift. So the best design for long range VTOL flight would always be a single or a double tilt rotor design such as the V280. For heavy lift and constant Short VTOL flights a helicopter rotor is more suited. One main helicopter rotor or contra rotating rotors will always cover a much bigger lift area thus being more efficient and more powerfull compared to a smaller number of lift fans or rotors grouped together.
Great video. I saw the Joby aircraft for production, is different from the pictures you are showing. It does not have flaps anymore, just ailerons for bank angle control. It see'ms the trainsition from level flight to hover is achieved with thust vectoring of the rotors only, no flaps. DO you know how this can be achieved? With just swash plates I believe might be difficult, there most be another kind of control of the rotors. What do you think?
Kamov stacked rotors like what "Inspector Kido" uses in of film "Man in the High Castle" is best proven configuration in terms of disk loading given how it is skeptical if galvanic batteries even with caustic alkali Groups I to II metals such as Al or Mg could power a VTOL. "Jane's All the World's Aircraft" had an article on a Tesla bladeless turbine for a rotor and of course Coanda should be well known. Still A Tesla fluidic rectifier along with rotorless or shaftless ducted fans are already being used by some designers.
9:48 your vector diagram correctly angles the the aft rotor thrust by 10 degrees. However, the lift vector should also be angled by about 10 degrees. You're in effect modeling the induced drag from the fixed aft rotor, but not from the wing of either craft.
Hi Rally, Thank you for your feedback! I see what you mean and where you are coming from. However, the vector line for Lift is indeed correct like this for the following reason. Lift is by definition the force perpendicular to the incoming flow. In this diagram, an altitude-level transition is modelled, as shown by the vector line for acceleration. Suppose the Lift vector line is indeed angled at 10 degrees, then we would be talking about a climb, with a climb angle of 10 degrees. The induced drag from the wing (and airframe) is captured by the magnitude of the drag component on this diagram. Conventionally, this is called the lift induced drag, which is found on a graph of the drag coefficient versus AOA. I hope I explained this OK. Thanks again and hopefully see you soon! Best, John
Thanks for correcting me on the lift vector definition. A more apt name for what I was thinking of would be the wing force vector, which is going to be roughly parallel to the fixed rotor vector.
@@RallyRat Hi, it’s great to see you again :)! I know what you mean. So the ‘lift vector line that is parallel to the fixed rotor’s thrust vector’ (let’s call this X) has been resolved into two smaller vectors like so: Xcos10 = lift Xsin10 = drag The purpose of resolving X is so we can compare lift and drag forces for all different angles of attack (the example here used 10 degrees). Let me know if this explanation worked. Have a great day :)
Good analysis, but you only hinted to the real elephant in the room in your closing comments - rotor aeroelasticity. Fixed, rigid lifting rotors of any practical scale and blade loading are going to experience ever-increasing ludicrous loads and vibration with any appreciable advance ratio. Ever notice how helicopter tail rotors always have flapping hinges?
I'm not a helicopter expert, so truthfully it is my first time noticing that tail rotors have flapping hinges, too. The general feeling I get from analysing eVTOL concepts is the following: at early aircraft design stages, the rotor design is not given the care and attention it needs, despite it being such a fundamental part. And problems with the rotor design can later become a showstopper for the entire aircraft concept. So I feel that the rotor design should be looked into more deeply early on...
@@zhihenglou You have hit upon the crux of a fundamental issue with the entire eVTOL industry. Many of the players are aerospace (and especially rotary-wing) neophytes who have little grasp on classic rotor problems. Most erroneously subscribe to the idea that the ubiquitous small scale drone rotors (that even the layman SPAC investors are familiar with!) are simply scalable to practical sizes without understanding any of the complicated rotor aeromechanic issues of doing so. Take note of what all the experienced helicopter OEMs are doing with respect to eVTOL - mainly waiting! The showstopper aspect you mentioned has been in full effect - i.e. see the Beta Alia still yet to demonstrate transition and suddenly pivot to a CTOL craft, plus the very suspect video footage of Archer Maker performing their "transition" last November - if you are especially eagle-eyed you may have noticed them stealthily testing with 3 bladed rear lifting rotors as well.
@@ChrisFu7 What is your opinion of JOBY? Seems to me the JOBY is a well thought out EVTOL, but I'm not a aero engineer or a pilot. Improved battery technology and future lower weight batteries or Solid state batteries are coming to the industry as well.
Hi John,
I enjoyed your analysis of full tiltrotor and partial tiltrotor eVTOLs. We’ve been in the VTOLs with transitions to the horizontal flight business for the past twenty years. For reasons you identified, we never even considered a partial tiltrotor configuration.
Early in our development, we identified the transitions as the most challenging phase of flight. We have also discovered that the wing is crucial for achieving smooth transitions. In your video, you are operating in ideal atmospheric elements, which is acceptable for this study.
However, all eVTOLs in development will have to operate in less-than-ideal meteorological conditions; we must consider gusts and wind shears. When disturbed during a transition, aircraft with significant mass will experience pitch oscillations that will cause the wing’s AOA to follow the oscillation path, thus adversely affecting the wing’s lift. The stabilization systems will detect this condition and attempt to correct it by adding power/lift to the appropriate set of rotors. Due to the large aircraft mass, it is reasonable to expect overcorrections, resulting in PIO (pilot-induced oscillation) from which the aircraft may not recover.
We must understand one crucial fact. Computers are reactive systems responding to inputs from sensors! We must take the AOA gyrations out of the equation to achieve stability governed by physics and aerodynamics.
Look me up on LinkedIn, and let’s connect. www.linkedin.com/in/edward-dolejsi-afsi
Hi Edward,
Wow! Thank you so much for your detailed and thoughtful reply. I feel humbled and happy that you are reaching out to a beginner like me!
I definitely agree with you: from the little prototyping I have done, I have found the transition, especially the back transition, to be the most challenging. The flight dynamics model we built for our prototype was based on ideal atmospheric conditions. We planned to simulate wind gusts until we realised that we were just using this task as an excuse to postpone the inevitable: do the first test flight. Models are never perfect and flying for the first time is always nerve-racking but, at some point, improving the models without test data is just giving diminishing returns.
For the pitch-oscillation problem you described, were you talking about a longitudinal static stable aircraft? Did you use a PID controller to trim for altitude or attitude? If it is a PID controller and the feedback control loop is overcorrecting, then I suppose you can play around with the Proportional and the Derivative-gain. I did not quite understand the point you have made on AOA gyrations - I would love to learn more about it!
I have reached out to you on Linkedin.
Thanks again,
John
John your videos are so thorough and interesting. Thank you for the time and care you take in making these!
The transition for both aircraft involves actual downwash on flight surfaces creating 'extra' weight (the rear surfaces and wing tips of the Joby ) and/or the downwash inducing a negative angle of attack on the wing from the front rotors even at a nose up incidence . Indeed the effect of nosing down ,like a helicopter does to accelerate, is to create less or even negative lift in accelerating transition . The rear rotors act to increase the effective wing angle of attack from their downwash partially offsetting the effect of the front rotors which are placed as far ahead of the wing as possible to minimize the 'downlift' they cause other than in cruise configuration - Vertical aerospace VX4 has MUCH shorter pylons than the Archer or Joby and they all compromise the proprotor diameter to reduce these negative downwash effects . The Archer midnight especially has gone to ridiculous lengths (literally) to try to get the wing out of the worst of the front prop downwash in hover and transition -- it is a bad concept all round . The Heaviside and Do29 used only aft tilt props to avoid this issue which is a better deal . Earlier tilt wing vtols like Canadair CL84 and XV 124 etc avoided the downwash penalties that the XV22 has (and suffers the extra 'weight' by using lower disc loading and hence downwash on the wing ) the interaction non linearities must make for complex artificial trim and control made worse by loss of any rotor -the 737 MAX lesson is relevant here with software 'solutions' . The drag of the exposed rear props, stopped, is greater in the front prop slipstreams (and eats power as the cube of local velocity)
It is clear from the poor behaviour of these designs AND the wild gyrations of the "0.1, .2, .3, .4 etc 'versions' and even worse patented 'abominations' (look up the Joby patents -unbuilt precedent designs) that they did not arise from carefully considered design procedures but from raw avarice after the projections of immense riches by Morgan Stanley/ Uber elevate et al. Normally such misconceived creations would never leave the drawing board . Take a look at the Autoflight 'prosperity' -- supremely ugly even if it avoids some of the Joby/Archer failings.
Hi John, this was very interesting and helpful for non-insiders and enthusiasts like me!
Phenomenal video!
i felt like i was watching the engineer who made top gun aircrafts Loved it
Thank you 😂!
This is a fine video, and I can confirm that is describes behavior that I've seen in my Tricopter Tilt-Rotor design.
I checked out your channel - your tricopter tiltrotor looks great!
Excellent subscribed immediately looking forward to your next thoughts. Keep them coming.
Thank you very much for the encouraging words! As you may be able to relate, it means a lot to me at this moment in time.
What many EVTOL designers tend to do is miss the fact of air turbulence during VTOL lift and do not consider calculating the extra constant balance exceleration of each motor needed to maintain stability of VTOL level hover. This also applies during all levels of control using the motor power. Were as in a helicopter,rotor flight controls are used to keep level flight, however in a EVTOL during VTOL flight power is used to control and maintain hover level. The more turbulance the more power is drained from the batteries thus cutting short any flight paramiters.
I've designed a VTOL (not electric) aircraft that does not have the issues you describe. It is much simpler than these EVTOL's and V22 or similar but it is designed to fly at 26000 metres. Hopefully can build it one day. I'm a dreamer, but I also feel that these electric aircraft are a waste of time presently. With the most dense lithium batteries being highly unstable and self combusting they are possibly more dangerous in the event of collision even light. If a plane runs out of fuel and crashes at least it cant burn upon impact. Lithium batteries can be discharged and still highly flammable. Thanks for the video and your time.
Hi, thank you so much for taking the time to write out a thoughtful reply.
Lithium batteries indeed have this problem. Though from my experience, the battery will not be fully discharged during flight and around 10-20% SOC is kept to preserve the battery's health (i.e. the number of charge/discharge cycles). Battery safety is related to battery packaging. If a pouch is used for weight-saving reasons, then the pouch can indeed be punctured easily during a collision. The reactants can then directly mix, potentially triggering an uncontrolled reaction.
When comparing the dangers of fuel and batteries, I would perhaps check that the energy content of the fuel/battery is the same during the impact. On that basis, the risk can then be assessed more fairly.
I am excited to hear about your ambition and innovation! I support you to follow your dreams, by designing and building your VTOL. The fruits of your labour will not only be the product itself, but the skills and experiences you have developed along the way!
@@zhihenglou Thanks for the encouragement mate. Working on a helicopter at the moment to beat the altitude record of 13960 metres, as I don't have storage for a 20 metre wingspan aircraft. I know that Lithium batteries create their own oxygen which makes them impossible to extinguish. Haven't seen any crash testing of these aircraft, but guarantee it will be a factor for safety.
@@chippyjohn1 Yes, that's right! Batteries carry their own oxidising agent. The battery effectively houses its own "oxygen" (oxidising agent), whereas an air-breathing combustion engine would get the oxygen from the air. I do see what you mean now, in terms of not being able to extinguish the battery fire with conventional means, like suffocating the flame from its oxygen source.
I would point out that a fully discharged battery would have, in theory, used up all of its oxidising agent and it would therefore not be possible to react further. If the electric aircraft is discharged to 20% SOC, then approximately 20% of the energy is still stored, which would be the energy source for the flame.
Wow, your helicopter project sounds challenging and fun! I wish you every success. If you would like, please keep me updated - I would love to see more of it!
It would be interesting to have a noise profile of these configured aircraft during both transitions --we have 'overflight' figures where the rear props are stopped and some in hover where there is no or little interaction but not in the intermediate transition/conversion where the front props wake and the rear interact (worst case might be in landing -decelerating transition where flaring (rear up to kill forward speed ) might be the worst case (as it is for helicopters ) The loss of power to one or more front rotors in this situation will result in sudden increase of angle of attack on the wing and possible stall --this could be induced from deliberate shutdown of a diagonally opposite rear rotor also,
Nice video!
Another concern is failure cases. The more tilting rotors there are, the more ways there are for it to go wrong. Similarly for variable pitch rotors.
eVTOLs are much more complex than helicopters in this regard, and all the complexity is in the electronics and software, as opposed to mechanical systems for helicopters. It’s a very different (and arguably much more challenging) safety problem.
JOBY has duplicate motors, batteries and computers in case of plan b.
Enjoyed the explanation... power peak very interesting... would love to see this for Lilium's concept
Thank you for your feedback, John! I am thrilled to hear that you have enjoyed the video.
Lilium's concept is very interesting. It is a very bold design, with significantly more risk and reward. There are good reasons for liking and disliking it, hence there is controversy. Explaining Lilium's design from a propulsion system perspective is on my to-do list!
Please come back around January next year to check for the video. In the meantime, I wish you a nice Christmas holiday!
Yes the lilium !!! I did my own analysis and choose Joby, vertical and lilium basically all configurations. Sold all but lilium
@@livangooday Yes, I am working on the video right now. Thank you for your enthusiasm!
@@zhihenglou lilium would have some cons and pros against Joby, I still believe Joby is less noisy/quieter than lilium
Great video. If possible, I would like to have more information on your mathematical model that would help a lot in our bi-tiltrotor vtol project.
The best design of the type of VTOL aircaft would depend on the intended use by the user. That is what the user operation of the VTOL is going to be, VTOL lift and short, medium or long range straight flight. The shorter the range the bigger the VTOL rotor size and lift design as most of your power and fuel use will be required and used during VTOL flight. Hense the smaller the VTOL lift rotors the more fuel is used during VTOL. So if an operator intends to use such aircraft for short range and more VTOL lifts, it is better to have a helicopter rotor or tilt rotor due to a bigger rotor size, as in the long run less fuel usage. During a straight wing flight less fuel is used due to a fixed wing lift. So the best design for long range VTOL flight would always be a single or a double tilt rotor design such as the V280. For heavy lift and constant Short VTOL flights a helicopter rotor is more suited. One main helicopter rotor or contra rotating rotors will always cover a much bigger lift area thus being more efficient and more powerfull compared to a smaller number of lift fans or rotors grouped together.
Great video. I saw the Joby aircraft for production, is different from the pictures you are showing. It does not have flaps anymore, just ailerons for bank angle control. It see'ms the trainsition from level flight to hover is achieved with thust vectoring of the rotors only, no flaps. DO you know how this can be achieved? With just swash plates I believe might be difficult, there most be another kind of control of the rotors. What do you think?
Kamov stacked rotors like what "Inspector Kido" uses in of film "Man in the High Castle" is best proven configuration in terms of disk loading given how it is skeptical if galvanic batteries even with caustic alkali Groups I to II metals such as Al or Mg could power a VTOL.
"Jane's All the World's Aircraft" had an article on a Tesla bladeless turbine for a rotor and of course Coanda should be well known.
Still A Tesla fluidic rectifier along with rotorless or shaftless ducted fans are already being used by some designers.
9:48 your vector diagram correctly angles the the aft rotor thrust by 10 degrees. However, the lift vector should also be angled by about 10 degrees. You're in effect modeling the induced drag from the fixed aft rotor, but not from the wing of either craft.
Hi Rally,
Thank you for your feedback!
I see what you mean and where you are coming from. However, the vector line for Lift is indeed correct like this for the following reason.
Lift is by definition the force perpendicular to the incoming flow. In this diagram, an altitude-level transition is modelled, as shown by the vector line for acceleration. Suppose the Lift vector line is indeed angled at 10 degrees, then we would be talking about a climb, with a climb angle of 10 degrees.
The induced drag from the wing (and airframe) is captured by the magnitude of the drag component on this diagram. Conventionally, this is called the lift induced drag, which is found on a graph of the drag coefficient versus AOA.
I hope I explained this OK. Thanks again and hopefully see you soon!
Best,
John
Thanks for correcting me on the lift vector definition. A more apt name for what I was thinking of would be the wing force vector, which is going to be roughly parallel to the fixed rotor vector.
@@RallyRat Hi, it’s great to see you again :)! I know what you mean. So the ‘lift vector line that is parallel to the fixed rotor’s thrust vector’ (let’s call this X) has been resolved into two smaller vectors like so:
Xcos10 = lift
Xsin10 = drag
The purpose of resolving X is so we can compare lift and drag forces for all different angles of attack (the example here used 10 degrees).
Let me know if this explanation worked. Have a great day :)
Im also like the #evtol#itsthe fate of our# future
Good analysis, but you only hinted to the real elephant in the room in your closing comments - rotor aeroelasticity. Fixed, rigid lifting rotors of any practical scale and blade loading are going to experience ever-increasing ludicrous loads and vibration with any appreciable advance ratio. Ever notice how helicopter tail rotors always have flapping hinges?
I'm not a helicopter expert, so truthfully it is my first time noticing that tail rotors have flapping hinges, too. The general feeling I get from analysing eVTOL concepts is the following: at early aircraft design stages, the rotor design is not given the care and attention it needs, despite it being such a fundamental part. And problems with the rotor design can later become a showstopper for the entire aircraft concept. So I feel that the rotor design should be looked into more deeply early on...
@@zhihenglou You have hit upon the crux of a fundamental issue with the entire eVTOL industry. Many of the players are aerospace (and especially rotary-wing) neophytes who have little grasp on classic rotor problems. Most erroneously subscribe to the idea that the ubiquitous small scale drone rotors (that even the layman SPAC investors are familiar with!) are simply scalable to practical sizes without understanding any of the complicated rotor aeromechanic issues of doing so. Take note of what all the experienced helicopter OEMs are doing with respect to eVTOL - mainly waiting!
The showstopper aspect you mentioned has been in full effect - i.e. see the Beta Alia still yet to demonstrate transition and suddenly pivot to a CTOL craft, plus the very suspect video footage of Archer Maker performing their "transition" last November - if you are especially eagle-eyed you may have noticed them stealthily testing with 3 bladed rear lifting rotors as well.
@@ChrisFu7 What is your opinion of JOBY?
Seems to me the JOBY is a well thought out EVTOL, but I'm not a aero engineer or a pilot.
Improved battery technology and future lower weight batteries or Solid state batteries are coming to the industry as well.
What if..one puts FI engine in
The #data is very i.portant things to siscuss
More and more nation are now like to intergreat evtol to community
#discusss
@#John lou
Major problem.
Looks like a very inefficient design also.
CO2 is a gas of life, not a pollutant. Neither is nitrogen. If electric cars is not ready for prime time, why are you bothering with electric planes?