By the Shahed-Load

I got to wondering what the most successful aircraft has been, and setting aside the Airbus 320 and Boeing 737 ~ each of which I flew at the time they achieved a rank of best-selling airliner ~ the answer if apparently the Cessna 172 above. Since its appearance in 1955 it has sold 44,000.

Now however it will have been supplanted by Iran's Shahed drone, of which they've 80,000 in stock and licensed versions of which are produced at rates of upto 500 per day by Russia, which launches as many as 5,000 monthly.

Costing $50,000 to make but selling for $200,000, then compared to the $400,000 required for a Cessna you do get more bangs for your buck*. Nonetheless if it's purely a numbers game the drone does have the advantage it is not intended to survive a single flight, whereas you'd like to think that your Cessna would do a little better.

Confusing the issue tho' as it will for you as it did for me, there is not just one type of Shahed drone but any number, the company itself bearing the name. This one tho' is the one I suspect the stats relate to, and does if nothing else demonstrate that if it is sheer volume you're set upon then foam and plywood go a long way to meet that goal.

But we knew that already, didn't we?

* Ed. with apologies to anyone on the wrong end of a guided missile. The phrase originated with the US military around the time the 172 was being developed, since entering common parlance as meaning 'value for money'.

Back to the Future #23

Much of what we see here has been influenced by my carting sub-scale personal air vehicles the length and breadth of the country, and what that means for practicality.

Among my first concerns was the exposure of the propeller blades, not so much as regards the limbs they might separate as to how they might be damaged or blood-stained.

Bear in mind that aircraft ~ and increasingly personal air vehicles ~ make no effort whatsoever to shield bystanders in this regard, which is why any number of people have died walking into propeller and rotor blades.

I think we can improve on that in the fulness of time, and principally I feel by using an array of sensors (as cars are festooned with nowadays) to shut motors down when anything with a pulse appears within the circle of operation.

Failing that, or as well as, it is about perspicuity and propellers once spinning have never been awfully good at this. Accordingly I shall set the power-units on a bar in order to 'outboard' them, viz. make them removable on demand in just a moment.

This has any number of benefits, not least the fact that the extent of the assembly (which I shall call the 'sound bar' or 'power bank' as it's my party) is obvious to a bystander. Besides that (a) it allows for rapid replacement or practical repairs in the field (b) it allows for removal for transport and storage and (c) it allows the craft to be stood on end for maintenance or storage without damaging its 'Achilles heels'.

It hurts that the axes of the motors are not aligned with the booms, but does mean the rig can be dropped into place on half-cent brackets. These being pusher-props too, under power the motors are trying to stay fixed rather than tear themselves from their mounts as would tractors.

Accordingly, as was the case of any number of the scale personal air vehicles which we flew, the motors will be mounted on the spar by just two bolts instead of four.

N.B. Blades swing outboard and downwards, CCW and CW viewed from rear. Power to the left motor applies differential thrust for a turn to the right, and shifts weight onto the right ski by torque reaction to supplement the effect.

One Shade of Grey

... and the only shade I'm getting nowadays. Tho' it is time to decide what colour to go with for prototype #001, and I have selected light grey because (a) it is standard for experimental aircraft (b) it is standard for naval craft and (c) I've an emulsion in the garage left over from decorating the hallway.

It's a shame in a way, because the laminated foam backer-board used for the shell comes in black, and despite me contacting the factory and requesting they switch to light grey during this time of national emergency, they suggested I do something to myself that frankly I'd rather not.

Black is the go-to colour for drones ~ as you've probably noticed ~ but usually this is because carbon-fibre and 3-D print cartridges come in the colour. Also, as drones generally struggle with weight, adding paint is considered surplus to requirements.

(It also looks cool and sexy, although that is beginning to change: the world's most successful personal electric air vehicle is sold by Pivotal, which used to be known as Blackfly because (a) it was black and (b) it flew. Now however it comes in a range of colours featuring a lot of white, for as boaters know white best protects against the debilitating effects of solar radiation.)

For the exercise you'll need a dust-sheet and step, because this is ideally done with the craft on its end. We're in good company here, because this is how Lockheed's famous skunk-works assembled the prototype F-117 as I recall. Although according to Wikipedia, it was not finished in washable vinyl matt.

Leonardo di Carpio

Problem with conventional design is the hammer viewing everything in life as a nail, and two European programs struggling with reality at present are Future Combat Air System ~ that bizarrely proposes a piloted jet fighter at a modest cost of some 100 billion dollars to take us to 2040 and beyond ~ and the New Medium Helicopter in the UK, for which there is only a single bidder in the shape of Leonardo in Yeovil.

They've been going for eighty years, which may not be much of an advantage the way eighty years of whale-bone corsets may not be the ideal way of inventing the Wonderbra.

If you take their autonomous helicopter Proteus, for example, it looks like any other they might have built but with the windows blanked off. Whereas the defence giant Anduril in the US ~ who've been going less than ten ~ produce one called the Ghost that looks altogether more like one should look.

For instance it replaces the gearbox and drive-shaft connecting a tail-rotor with a (Chinese) electric motor from hobby stores that meets the same end... it's what I was told at the outset of inventing was the 'not invented here' barrier to progress.

Is suspect the government ~ on whom Proteus, the NMH and the whole company appears to be relying on ~ has looked at what's happening in Ukraine and begun to get cold feet.

Proteus is advertised as something to go looking for submarines, without needing the crew. But it can only cover so much ground albeit less expensively; something that can do this less expensively again however is any number of drones operating over a network covering a greater expanse altogether.

Which may be why Anduril is heading up, and Leonardo down.

Or at least in the UK: successive governments policy of flogging off UK manufacture to foreign buyers for a short-term fix to save jobs reveals who has the swim-trunks when the tide is out.

Back to the Future #22

One of the things that has positively been hurting inside is that the efflux from each lift propeller is inhibited to some extent by its encounter with the topside of the ski.

I devised all sorts of workarounds for the skis themselves before realising that the most elegant solution was simply a deflector to direct the efflux largely clear of that surface. Whilst you can get 3-D modelling apps to visualise the airflow, I've always found it easier and healthier to walk around to the timber yard for a look-see.

This is a length of uPVC extrusion used for I don't know what, but will work here as required once a second length is fitted to the other side too.

P.S. I bottled out of reducing the struts from 16" to 12" because as no rabbi will ever admit, you can take it off but you can't put it back on; now they're 350mm (or 14") and set to remain so. 

Back to the Future #21

Time to flesh out where the lift motors are going, and as these are 22" props I pitch the axis 12" forward of the bulkhead and mark the tips forward and rear.

Looking from above and working clockwise from the foremost left prong, quad props rotate CW, CCW, CW and CCW. This means that the outboard blades will be creating most lift under forward motion (and the inboard at the rear).

Which is nice because credible three-wheelers all locate two wheels at the front for the widest stance and the best handling... what we are achieving virtually here too.

Pure serendipity I'll admit, but you only get to benefit from her ample gifts if you put yourself out there in the first place.

Chinese Whispers

Staggering to see the extent to which China ~ and to a similar extent the US ~ are powering ahead of Europe in the 'low altitude' economy.

In the Bay Area of the former, hundreds of such drones  ~ tho' we know about LIFT + CRUISE configurations too ~ shuttle parcels between cities at twice the speed it took in a van. Here in the UK in contrast the CAA has a wet dream whenever a drone makes it to the Isle of Wight with a box of pills.

Crucial to the venture according to the manufacturers are reliable navigation to fly from A to B, along with equally reliable flight-controllers and AI systems to optimise the network.

And it's not just cargo drones they're turning out in the hundreds and thousands but agricultural and fire-fighting drones that are up to fifty times more efficient than the manual labour that would otherwise be required.

And the principal export market for such products? Three quarters go to the Far and Middle East, where manufacture is not something parents steer kids away from because money lies in the talk-talk occupations from which our politicians emerged.