Chickens, home, roosting.

The conventional helicopter and especially its turbine versions has long been viewed as beyond reproach, though here is one issue that eVTOL will never be susceptible to.

Whilst still an Airbus pilot I went to a conference at Cranfield attended by any number of sufferers from, and experts on... contaminated cabin air. Some of the best-known names associated with the campaign no longer appear in Google search for the simple reason that they've died prematurely.

At the time, those organising or airing the issue were made to feel about as welcome in the airline industry as the witches were in Salem.

The issue though was simply this. All airliners are pressurised, and the pressurised air is drawn from the compressor section of the jet engines. Should their oil seals leak then super-heated oil vapours containing neurotoxic chemicals are released into the air that we've all to breathe for a half-dozen hours or more.

Naturally pilots and crew were most exposed to the effects, but there were workers at the conference from oil-rigs, where turbine-powered systems did the air-conditioning.

As jet-aircraft are often in service for decades and involve budgets of billions, this was a lot easier to cover up than to fix, as we've come to learn with tobacco, lead in fuel and most recently global warming.

Now though even military helicopter pilots are suing the UK Ministry of Defence over the illegal effects of prolonged exposure to the emissions from turbine engines.

I've spent half a lifetime in aviation, and regardless of how shiny it appears from the outside, it's as corrupt as any other human endeavour.

Among our organisations and industries, crime syndicates are at least honest about what they do.

https://www.theguardian.com/uk-news/article/2024/may/29/mod-sued-over-allegedly-carcinogenic-fumes-from-military-helicopters

Re: view

It's been a worthwhile exercise, if only because in future I'll revert to square-section cantilevers which form an independent four-pronged drone.

With an outline that encapsulates the top end of the space-frame, it could therefore be dropped directly on top of it to secure.

This means too that the brackets can be dispensed with, along with the paraphernalia used to clip them to the topside of the passenger booth.

I'd like to get a handle on just how much more efficient co-rotating propellers of this kind are, as compared to contra-rotating.

Nonetheless the benefit of continuing with the current design ~ and I'm too far along to revert to any other ~ is firstly that the underslung propeller is well clear of the pilot and secondly that the leverage of the combined pair is greater than a co-located type.

Moving along from this 3/4 scale mockup, my preference is to try a full-scale version that can at least be sat in even if it has only the power to fly unladen.

It would look more like a step in the right direction, although it would involve a switch to carbon-fibre tubing.

The one benefit of it being populated by a pilot cabin, though, is that drone and cabin can be built separately.

Tho' as it won't happen any time soon, I'll post it to the VFS database for the record.

Homebuilt Helo #52

I make the decision to render this airframe as a non-flying mock-up, or visualisation.

More on that later, but for now I start by clipping a dog-bone bracket to each arm of the drone, and fixing a tin of tuna and a (floor-laminate) pretend propeller to that.

Readers are advised not to launch aircraft from a cliff powered only by tuna tins.

Digital Commoner

Of those papers I've posted on the digital commons, the one attracting the most views is https://www.tdcommons.org/cgi/viewcontent.cgi?article=7886&context=dpubs_series

The commercial concerns downloading this include major helicopter manufacturers as well as a company that builds access platforms, or 'cherry-pickers' to you and I.

What this demonstrates I believe is that irrespective of the arrangement of drone that provides the lift, there is a future for eVTOLs that suspend a standing human operator.

And I say suspend, because there are any number of prototypes out there which have flown human operators and feature the airframe beneath a standing operator.

For those of us who've spent a lifetime flying, though, the principal problem with this is the fact that if all else fails it ends up falling from the sky with its operator beneath it... which is not the ideal way to hit the ground.

Most helicopter designs include two principal features viz. (a) power-plants up top and (b) a rotor up top, because it provides (a) more room for payload and (b) a safer means of unpowered descent in view of failure i.e. right way up.

I'd add a third to these desiderata, which is that the arrangement shown in the paper linked above promises as compact and portable a helicopter as you could hope for.

And that's why ~ if you're to be a fellow traveller on our journey ~ it is worth persisting with the passenger frame with a seat because (a) it suits the recreational market that it might address and (b) it is easily adapted to the outline appearing in the paper.

Furthermore when goods were first containerised in the 1960s it was never certain the idea would take off, yet now everything comes containerised. With eVTOLs therefore, for the first time ever it's possible that people-carrying drones be adaptable to space-frames of various sizes and including either a standing or a seated passenger.

Take a look and leave a comment ~ I for one won't be reading them.

Homebuilt Helo #51

It all began with a spare chair knocking around the workshop and as we contemplate a way forward one option with the three-quarter scaler is to build entirely from scrap as we've done to date and to use it solely for a promo pic for the website.

What it principally functions as is a means of figuring out how it all hangs together and whether it looks viable to scale up. Nonetheless we cannot risk trying to fly an overly flexible drone and failing, because that costs money and time and effort.

Better I think to bite the bullet once back from the studio with the current build, and commence a full-scale version with more exotic materials that provide the required rigidity.

If nothing else I'll be left with a very high-tech chair to sit on, and between you and me I think it's the most imaginative part of the whole exercise. I've posted papers to the digital commons and actually the bulk of commercial interest judging from the data is actually in the stand-up version of the suspended space-frame.

Again tho' we shall persevere with seated versions because, to paraphrase JFK I do it not because it is hard, but because it is easy.

Note from the pic that the 15-inch footprint used for the child-sized flyer has only to be enlarged to around 18- or 20-inches in order that I can sit in it myself.

Prior to that decision we shall need to see what size of space-frame I can squeeze into, as we're flying on the edge here. As ever there are precedents... Nigel Mansell's F1 cockpit was so tight a fit that he'd to cut the toes off his footwear in order to race.

Homebuilt Helo #50

Here's an overview of how we're fitting that bracket on the cantilever so as to mount the motors... note the overhang at the far end which will allow the outermost motor to be mounted inverted.

I've also managed to locate 20mm conduit clips with which to secure and we'll double down on them with a rivet fired into either side.

The world of furniture and buildings (what the French call movables and immovables) is essentially a square one and eminently suit the square sections we used to build the suspended space-frame. When it comes to the machinery of life, however, tubular sections of a round profile generally dominate and for good reasons.

In Europe they focus at this scale on 20mm and 22mm fittings designed for electrical and plumbing installations respectively. Carbon fibre tubing, which we'll use when the time is right, is happily provided at 20mm gauge too.

Am still agonising over whether the drone itself should be complete and independent of the passenger frame if only for transportation purposes, but I shall persevere with the current solution where the space-frame includes the flight controller and the four cantilevers are removable.

If nothing else this provides for separate transportation of the space-frame and the cantilevers prior to final assembly... which is not unlike the way the the wings of the giant Airbus 380 arrive in Toulouse from the UK under separate cover, to be married permanently to the fuselage.

Homebuilt Helo #49

While we wait for those M3 bolts to arrive, let us consider another aspect of the proof of concept craft relating to battery stowage. Currently we've a pack addressing each of the motors, although we are likely to revert to past practise and use a single pack via a PDB or Power Distribution Board.

The reason for so doing is that I'd like to stow the substantial battery mass behind the head of the occupant on a perforated sheet upon which both this and a head-rest can be mounted.

A further reason is that there is a limited amount of room up top and from operational points of view a pack that can be swapped out conveniently from the rear works best.

The principal benefit of hanging battery packs here however is that it re-balances the vehicle given that the lower limbs of the occupant overhang the outline of its frame.

Building prototypes does take you down rabbit-holes and wondering what our lower limbs weigh is one such. There's a secure unit down the road here and one option was to have interviewed any number of chain-saw murderers to see if they could cast any light on the subject?

Alternatively you can scour the net at cost of being suspected of planning for body-part disposal yourself... though I've taken that bullet for you.

Using the table above we're looking at around 7.5% of body mass for the lower leg and foot (plural) and some 8.5% for a pair of thighs. I'm taking some of that seeing as how they overhang the edge of the seat, and so let's call it 12% all in. Give me a break here, because you're wearing a pair of boots unless you're levitating for enlightenment?

Apparently mens' perceived ideal weight in the UK is 77kg, which is me with clothes on... and no surprise that I'm perfect in that way too. That means we can hang 10kg of battery out back there on a full-scale prototype, which is a very respectable payload. In fact it is just about four of the largest six-cell LiPo battery-packs each providing for 22,000 milliamp hours.

A target application for a machine of this type is shuttling you upwards for a birds-eye view of the world ~ for which tourists will always part with money ~ or else launching parachutists or powder-skiers by a more cost-effective means. For most such uses a means of swapping out battery-packs quickly and efficiently would be required.