Wednesday, March 31, 2021

Movie Trailer

After some Springtime spit-and-polish I return to the former RNAS Ringtail for a few PR shots to take the campaign forward. People who build VTOLs are very aware of the challenge of logistics when it comes to transporting air vehicles and in fact the outline of the drone here is adapted somewhat to the one by two metre flatbed trailer itself.

Electrical flight is the first technology to permit the deployment of aircraft practically single-handedly, so long as you discount powered parachutes or individual jet-packs. Only recently the US Army issued a tender for just that ~ a means of air mobility which can be deployed by a single soldier for transient operations.

Monday, March 29, 2021

Skid Row

Without a doubt the undercarriage has always been ~ quite literally ~ the Achilles heel when it comes to the design, but the one thing we learned from the test-flights back in December at Llanbedr was that cross-bars (or lateral stabilisers) proved to be quite unnecessary. In fact it was they that broke free during one heavy landing and took out all four of the lower props... precisely what they were supposed to be there to prevent.

Short story long however I've gone for a relatively conventional pair of skids and left them aligned with the arms of the drone. There are operational reasons for doing so in so far as it makes carrying the vehicle altogether easier, and looking ahead to a scaled up version, altogether easier to get in and out of whilst providing for the best possible view. At the same time, raising the lower quad has improved the propeller clearance over the previous prototype, which again removes the need for lateral stabilisers.

For the techies out there the diagonal measure between the motor axes is 1.40 metres and the weight including the lower battery set is around 35 kilos or 78 pounds without the dummy onboard ~ he weighing a further four kilos. The accommodation is two feet tall, such that the model is the best part of two-thirds scale.

The lower quad will provide the greater portion of the lift ~ for which Phil already has an Arduino program to suit ~ and the motors are addressed directly by an associated battery-pack. The upper quad will be conventionally wired and you see from the wing-nuts that it is removable such that it can be tested independently as a regular drone that falls within the regulatory weight-limit.

Remains to be seen whether it all works to spec... but it's the taking part that counts.

Friday, March 19, 2021

Please Be Seated

For a variety of reasons that you'd only appreciate if you'd spent two years of your life designing and building eVTOL variants, I have elected to go for a half-scale model in the most compact format possible. As such I have reverted to flying perpendicular to that direction you'd expect from an 'H' quad, as it allows for a reduction in the vertical extent of the accommodation. I've also reverted to seating in lieu of standing for the same reason.

I'm also avoiding the complexity of multiple levels of redundancy because at this stage of the game ~ and the project is not alone in this regard ~ it's a case of walking before you can run. As a consequence the lower quad supplies lift alone at a constant RPM across all motors, and these are individually addressed by a battery-pack each to keep life simple from the electrical point of view.

A by-product of this is that even at full-scale the height reduction brings the vehicle back within the remit of the GoFly challenge in terms of size, although larger motors, propellers and batteries would nonetheless be required.

Weight-wise what you see here (without speed controllers, avionics and skids) tips the scales at 35 kgs (77 lbs) with dummy and 31 kgs (68 lbs) without. Having put several such airframes together I can say with confidence that in order to bring the vehicle in below the CAA's official drone classification of under 25 kgs (55 lbs), smaller motors and batteries would certainly be required.

This one will be registered here for testing as a large radio-controlled model, on which basis it will also be devoted to the display circuit in perpetuity, which should do no harm to the prospect of scaling it for human flight. Also you'll notice the upper quad is removable so that it can be tested independently AS a regular drone, prior to fitting to the remainder in order to provide the steering beside a portion of the lift.

This division of 'brains and brawn' will simplify testing altogether, which is ultimately the key to success in such endeavours.

Saturday, March 6, 2021

Cage F(l)ight

There's always a compromise in structural design between access and integrity, and few people realise that decades ago airframe designers seriously suggested airliners be built without windows... although it has taken until now for the ubiquity of screens to allow idea that is being revived for the next generation of supersonic passenger jets.

Accordingly I am likely to include windows in the above not so much for the comfort it provides as for the fact it bolsters the construction by multiplying the distribution of shear webs to prevent distortion. There's no shame in flexure in aviation and indeed wings flex considerably, whilst fuselages both bend along their length like a sausage dog and twist considerable too. At the outset though it's best to pursue a rigid outline from which you can work backwards with operational experience.

Ingress will eventually be required once this prototype is doubled up, however, and so I have designed it so that the 'bin' that you stand in is separate from the upper half of the accommodation, which effectively forms a cage around the upper torso. It's not as convenient to access as might be hoped for, though with prototypes it's an issue of 'horses for courses'.

In lots of great vehicles like Apollo moon-rockets or Avro Vulcans, access is difficult and the cockpit rarely commodious... which is as it should be.

A child of the Sixties, I don't design for the snowflake phenotype.

Wednesday, March 3, 2021

First Person View... point

Revealed yesterday, DJI's clue as to where it is headed... your head, specifically.

It'll take likely longer than you'd like to think, but there is no reason why this could not be developed over the internet, such that you might fly from your armchair around any place in the world that you might choose.

For anyone developing eVTOLs the question then has to be, why bother? Are we those dinosaurs trying to put people in the sky when we might merely go there virtually, the way we watch wildlife on TV instead of being there to see it ourselves?

Granted it was the likes of Warhol who said there was no substitute for 'being there' in person, but DJI's current offering is at least fifty times cheaper than say Jetson's personal air vehicle.

Accordingly, besides those few of us wedded to bodily flight ~ or refusing electrical cars  ~ it looks like the future of recreational aviation lies with the likes of DJI.

Which means that eVTOLs more than ever will need to be focussed on the corporeal task of moving you or I between one location and another. Which is why no doubt the best-funded efforts take the form of flying taxis for two or above.

There will however always be a market for solo air vehicles so long as BOTH the price and practicality are right.

And if other developers disagree, then there's more room for us in the sandpit.