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

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.

Excellent subscribed immediately looking forward to your next thoughts. Keep them coming.

Phenomenal video!

This is a fine video, and I can confirm that is describes behavior that I've seen in my Tricopter Tilt-Rotor design.

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 felt like i was watching the engineer who made top gun aircrafts Loved it

Enjoyed the explanation... power peak very interesting... would love to see this for Lilium's concept

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,

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.

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.

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?

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.

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.

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.

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.

Im also like the #evtol#itsthe fate of our# future

The #data is very i.portant things to siscuss

#discusss

@#John lou

What if..one puts FI engine in

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?

More and more nation are now like to intergreat evtol to community

Major problem.

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?