Author Topic: Toggle switch for small aircraft charging system in case of failure  (Read 7790 times)

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Offline floobydust

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #25 on: April 17, 2020, 06:38:38 pm »
I think it's important to look at the root cause of the regulator SCR's failing. For what you are trying to do, the added wires, switch and complexity I think would lower reliability maybe worse than the voltage regulator's alone. I see a main output circuit breaker anyway on airplanes to fuse/disconnect the output winding which seems best.

Having a TVS diode or snubber or diode-clamp at the winding will prevent large voltage spikes from stressing the regulator. Some older designs had almost nothing for surge protection. Not sure of your part number. I looked at a Rotax/Ducati RV12 and was not impressed, they are terrible bad solder joints and connections, nothing for surge protection.  Also I've seen a huge capacitor 22,000uF 40V added to Rotax 912/914 engines, so it's possible ignition noise and spikes are high. Heat is also the other enemy, so located away from the engine in a place of cool airflow. Vibration is not good for them either.

Never short the output of a PM generator (dynamo). It will just load the engine and burn up the stator winding. Whoever said the short-circuit current is small is out to lunch. I have seen Kawasaki voltage regulators fail shorted and the engine was loaded and the stator (oil immersed in the crankcase) burned up as a black tar covered piece of carbon.

Example schematics of PM generator voltage regulator- Kubota, Yanmar Tractor RS1105
https://www.eevblog.com/forum/projects/ac-generatoralternator-charger-rs1105-replacement/msg1256470/#msg1256470

Just a note, a vehicle has a few grounds- the battery (-ve) connects to the engine block but also it's important to have a thick wire braid from engine block to chassis, where the regulator, nav, radio stuff is. If you instead ground the chassis at the battery, there is a surge (at the engine block) during cranking that can raise havoc - like your USB troubles it can damage some electronics connected to the block.
 

Offline SkyMaster

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #26 on: April 17, 2020, 07:15:32 pm »
It should do no harm to test it, from the stator's perspective it's the same as normal regulation, and the rectifiers will see only a modest current.

You're doing the project I've wanted to do for a long time, but the rules here are very different which makes it much more difficult, plus there's the question of space. Got any photos?

Sure do!  Keep in mind its a little rough still because I inherited the built from someone else and am going over it.  The fabric will be coming off next week and replaced and repainted with new stuff.  Also, these photos are in no particular chronological order, covering the span of 2 years. Hence the different looking engine, different instrument panel, windshield, no windshield.. etc.  The First picture is the most current.

When looking at your instrument panel, a Glass Cockpit no less, it is not possible to imagine that this is for a Minimax.

FBW CTRLS... Fly-by-wire  ;)

Electric trims, on all three axis; wow.

Your project looks like a lot of fun.


What is the EFIS you are using? It this your own creation?


 :)
« Last Edit: April 18, 2020, 12:17:12 am by SkyMaster »
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #27 on: April 17, 2020, 07:22:53 pm »
If his regulator is of the type he described then it is a current source, designed to be shorted. That's what the SCRs do in normal operation, and the stator has deliberately high leakage inductance so to make everything behave. This was the normal design on engines of this era (I read 80s on wiki). In fact this type predates regulation at all and battery overcharging at sustained high revs was normal.

There are designs meant for use with modern regulators that have low inductance and act like voltage sources, the regulator for one of those is essentially a buck converter. This type shouldn't be shorted but you're unlikely to find that type of stator on an 80s engine.

If there's any doubt the two types can be distinguished by measurement.
 

Offline floobydust

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #28 on: April 17, 2020, 07:55:09 pm »
I've never seen or encountered a constant-current dynamo. I guess they would be on a moped or small engine, where do you see them used?
I see the regulator uses SCR's as a switchable rectifier diodes, doing cycle-by-cycle control, not shunt regulation.
KZ440A service manual gives 75VAC at 4,000RPM with no load on the dynamo - but this is a 4-stroke bike and OP said he has a 2-stroke engine. Anyhow, some idea of the open-circuit voltage.
 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #29 on: April 17, 2020, 08:14:38 pm »
@richard.cs and @floobydust

At this point I'm leaning towards it being the shortable coil style, but I could be wrong!  The points you brought up about crummy regulators is also an interesting point.   
The solder looks okay at least, but I can not check any further as it is epoxy potted and I can not get it out without likely destroying it.

Identifying marks are sparse, but I can see:  "2" "TYMPANIUM CORP"  "620403" "4990"

Googling reveals this similar product with some semblance of spec sheet.  What do you think?  https://www.classicbritishspares.com/products/tympanium-regulators

Also, what measurements can I do to test as you suggested, richard?

@skymaster

Hahahaha yeah, right?  I love it.

The fly by wire controls are a backup system I decided on to raise the travel limits of the trim motors and raise the speed so god forbid something happens to the teleflex control cables, I can fly the plane home via the trim motors.

It is tremendous fun!!

The EFIS is my own creation, running on a pi 3b+ (well a 3b, i got a b+ to swap in though for more performance) running on processing 3.  Which is why it looks like garbage.  The screen is a 10.1" 1200nit brightness non touch with a glass multitouch overlay stuck on top.


Still tidying the wiring on the switches on the right!  I had connectors on it to remove them (glad I did since I had to twice to shuffle things around)


Here is a custom board I made to run power for everything.  On it is an arduino to listen to the rotary encoder and backup mfd hardware buttons, and to run the power supplies.  On startup it listens to the power switch, turns 12v and 5v on (for the pi and 12v lcd) and the pi raises a gpio high while the software is running.  Then when I flip the power switch on the panel down, it lowers a gpio to the pi and the pi sees that and shuts itself down, eventually powering down and the gpio its holding high drops, which signals to the arduino its safe to cut power.
KD2CHS
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #30 on: April 17, 2020, 08:16:42 pm »
@Floobydust, the schematic you just posted is simplified (missing the SCR gate drive) but shows the SCRs as shunt regulators. With the SCRs off you just have a rectifier bridge. With them on one SCR and one bottom diode will conduct at any time, shorting the stator. The top diodes prevent any current flowing backwards from the battery into the short under this condition. The SCRs are not in series with the output so are not acting as switchable rectifiers.

The 3phase version in the second post is similar only with the SCRs inverted so it's the top diodes that conduct when shunting the winding.

Knowing the specified open circuit voltage is useful, not only in itself but the shear fact they specify it means that it is measurable without damaging the stator insulation. Transients from opening disconnecting the battery whilst running could still be many kV and trash the insulation though.

The other common constant-current dynamo is the bog standard 3W pedal bike dymano. It's roughly a 0.5A current source which is how it (usually) avoids blowing tungsten lamps at high speeds. Modern ones with rare earth magnets are better, giving higher open-circuit volts per rpm so both lighting at lower speeds and being closer to constant current (because Voc>>Vload).
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #31 on: April 17, 2020, 08:33:21 pm »
@ITman496, the simplest measurement is short circuit current (without rectifier or regulator), measure it at idle and then even if it's not a shuntable type you shouldn't break anything with a brief test. A shuntable one will have Isc perhaps 1.1*Inominal, whereas for a low impedance one it might be 5-10*Inominal and may well stall the engine. Don't remove it under power unless you have a TVS fitted because you'll get a huge voltage spike - stop the engine instead to stop the test (actually I'm not sure I'd switch a short *in* with the engine running and no TVs either because switch bounce will make spikes).

If you don't fancy that then measure the resistance and inductance of the winding (one of the cheap component testers will do), and then measure the frequency and open circuit voltage at tickover. You can then calculate how it behaves at any speed or even put it into SPICE. I have done this to fully (well, mostly) model one when designing regulators. That then allows you to see what the current will be shorted or with any given load (resistor, battery, etc.), at any rpm, which it kind of cool.
 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #32 on: April 17, 2020, 10:28:36 pm »
This is a picture of the unit that I found online.



I will take those measurements when I can!  And good point about the test. I'm not gonna do it until I have the TVS diodes in place anyway.

I've never done a spice model before but I'd certainly love to try.  When I get those measurements I'll do my best!
KD2CHS
 

Offline floobydust

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #33 on: April 17, 2020, 11:22:51 pm »
The Tymphanium is series, and old Kawasaki is shunt-type. I find there are many types of dynamo regulators, series and shunt, SCR or MOSFET i.e. https://www.shindengen.com/products/electro/motorcycle/reg
The series-type is only two diodes, not four. I just can't get over the waste in a shunt reg or why use more parts.
 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #34 on: April 17, 2020, 11:32:23 pm »
The Tymphanium is series, and old Kawasaki is shunt-type. I find there are many types of dynamo regulators, series and shunt, SCR or MOSFET i.e. https://www.shindengen.com/products/electro/motorcycle/reg
The series-type is only two diodes, not four. I just can't get over the waste in a shunt reg or why use more parts.

That page was extremely helpful to explain how my system works.  Thank you!
KD2CHS
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #35 on: April 17, 2020, 11:39:00 pm »
I've never done a spice model before but I'd certainly love to try.  When I get those measurements I'll do my best!

Attached is a spice model I made a while back for a small bicycle hub dynamo, based on published measurements. It has the constant-current characteristic discussed, but at much lower output power. In this model I got fancy and used a modulator block to simulate the voltage and frequency change with road speed, but you can also put it in as an equation and have something like voltage=rpm*const1*sin(const2*rpm*time), from memory I started using the modulator because the simulation ran faster.

In this model there are some sources on the left performing simple calculations with V1 as a speed input, and then A1 turns it into a speed dependent voltage and frequency which represents the open circuit voltage. E3 just allows this to float and not be 0V referenced which is useful when it's used in a more complex simulation. L1 represents the inductance of the stator, and R2 the resistance. R1 represents the iron loss in the dynamo but doesn't affect the result very much. That's it for the stuff in the dotted box modelling the dynamo.

Outside the box is a resistor which is switched between 0.1 Ohms, 1 Ohms and 10 Ohms. The waveform plot shows the current in that resistor. Between 0 and 1 second the model has the bike moving at 5 mph, then at 10, then at 20 mph. The cyan line is current into 10 Ohms, red into 1 ohm and blue into 0.1 ohms. Of particular note is that 1) as the bike speed and therefore dynamo rpm varies 4:1 the current only varies 1.3:1, and 2) as the load varies 100:1, the current varies only 1.6:1 at low speed and 1.2:1 at high speed (where L1 dominates much more over R2).

Obviously this is not what you've got, but this type of model can be modified to suit your particular dynamo. There are two constants to tweak that set frequency(rpm) and voltage(rpm), and then put your measured resistance and inductance into R2 and L1. You then have a model that's a reasonable approximation and you can then connect things to the outputs like rectifiers, batteries, short circuits and see what kind of behaviour to expect.



 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #36 on: April 17, 2020, 11:54:08 pm »
Wow, that is fancy.  Is spice free?  I've never actually used it before.  I have an LCR meter, a decent handheld one, and a scope, so I'll be able to get the measurements pretty easily when I do get the engine running (Hopefully in a few days)

When you were looking into aircraft, did you have any particular model in mind?  I've seen a few minimaxes flying around in england, though I believe they are called the 88 instead of 1100.  I saw a picture of an english spec one on another forum that looked pretty sweet!

KD2CHS
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #37 on: April 18, 2020, 11:40:04 am »
There are lots of implementations of SPICE, some free, some not. That one is LTspice which is free to use and very powerful, but has a slightly odd user interface.

Aircraft-wise it's been years since I looked at it properly, but at the time I thought it would be cool to make a modern version of one of the early aircraft, which after all were very much man-in-a-shed technology. Something like a Blériot XI or Fokker Eindecker perhaps. Not in any way a historically accurate replica, but more using it as an inspiration for the basic airframe and then tweaking it to use a more modern construction and engine.

Did you ever see the scrapheap challenge / junkyard wars "flight of the century" special? There's a very poor quality rip on youtube:

When I looked into it it basically seemed that for the UK there are not really any simplified rules for small aircraft, either for construction or flying them,* and it looked to be a massive regulatory pain-in-the-arse (I do remember finding French rules interesting, under 250 kg is/was basically a free-for-all). Combined with leaving university and switching from "lots of time, no money" to "money for project, no time" it just got dropped. Ten years ago or so there was almost no-one building them in the UK, or at least not people who put stuff online. Perhaps that's changed now and I should revisit it, find some forums and see how other people are doing it and especially how they're dealing with the regulatory side.

Of course then there's the problem of finding space in a suburban house...

*It was a long time ago so memory is a bit fuzzy here. I would be pleased to be proved wrong.

edit: the forum seems to insist on embedding a youtube preview when I put a link in, and I can't seem to get rid of it even if I remove the URL tags. It doesn't appear in the preview of my post though. Unless that's my browser doing it?
« Last Edit: April 18, 2020, 11:44:18 am by richard.cs »
 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #38 on: April 18, 2020, 06:32:31 pm »
I have no idea how it works in the UK, but I would certainly check into it!  There are certainly small aircraft flying around, people seemed to have found a way.

I know mine was designed to be built in about a 1 bay garage.  2 would be better, but you can make the dream work in a single bay.

I used to be ADDICTED to junkyard wars.  That show inspired a lot of what I learned and became today!

The usa ultralight class of aircraft (less then 255lbs) is also a free-for-all, including no license or anything needed.  I wish it was 250kg!!!  I'd have about twice the horsepower and twice the engine strokes.  But alas.

KD2CHS
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #39 on: April 18, 2020, 10:30:30 pm »
I know mine was designed to be built in about a 1 bay garage.  2 would be better, but you can make the dream work in a single bay.

It surely doesn't fit in a single garage once complete? Unless the wings are removable?

Quote

The usa ultralight class of aircraft (less then 255lbs) is also a free-for-all, including no license or anything needed.  I wish it was 250kg!!!  I'd have about twice the horsepower and twice the engine strokes.  But alas.

It looks like I would need a private pilots license to fly something like what you've built in the UK, unless it can be made <70kg in which case it falls into a catagory meant for self propelled hang gliders. This wasn't possible until 2017 when this catagory had to take off on foot but now they seem to be allowing slightly more conventional aircraft within the mass and stall speed limits.

Construction wise it looks like it's a submit plans before beginning kind of job with multiple inspections throughout the build.
 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #40 on: April 18, 2020, 11:55:47 pm »
The wings come right off with just 3 pins!  Big pins, but.. still actually quite fast!

Some quick googling seems to suggest your microlight license is still significantly cheaper, at 4000 pounds, vs 15k for a normal ppl?

One thing I know I saw on the forums was that the blueprints for the plane had to be approved in the UK.  Luckily, the minimax has been already approved so I think you can just say hey I'm making one of these and they go oh ok we've seen those before and approved them already.  I'm sure there are other models just like that.
KD2CHS
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #41 on: April 19, 2020, 12:29:08 am »
It looks like a pre approved design helps but there's still a lot of faff, lodging plans beforehand, logging the whole build, every item that goes into it and where it came from, inspection at the end, a series of formal test flights, etc. It also looks like they want a full assessment for even minor deviations from an approved design.

It's clearly possible and I'm sure people do it, but it's nothing like the US ultralight class. For me it pushes it from "fun, cool project" to "pain in the arse" which is quite sad really.

If you're interested the whole UK process is in a document called CAP 659.

Maybe I should learn French.
 

Offline SkyMaster

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #42 on: April 19, 2020, 12:41:24 am »

It's clearly possible and I'm sure people do it, but it's nothing like the US ultralight class. For me it pushes it from "fun, cool project" to "pain in the arse" which is quite sad really.


The United States ultralight category (Part 103) is for very small ultralight with an empty weight of less than 254 lbs, max speed of 55 kts, etc.

But, you could buy an already flying aircraft ;)

On the other hands, all those regulations are there for a good reason; safety.

 :)
 

Offline SkyMaster

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #43 on: April 19, 2020, 01:10:18 am »

The fly by wire controls are a backup system I decided on to raise the travel limits of the trim motors and raise the speed so god forbid something happens to the teleflex control cables, I can fly the plane home via the trim motors.

It is tremendous fun!!

The EFIS is my own creation, running on a pi 3b+ (well a 3b, i got a b+ to swap in though for more performance) running on processing 3.  Which is why it looks like garbage.  The screen is a 10.1" 1200nit brightness non touch with a glass multitouch overlay stuck on top.

Here is a custom board I made to run power for everything.  On it is an arduino to listen to the rotary encoder and backup mfd hardware buttons, and to run the power supplies.  On startup it listens to the power switch, turns 12v and 5v on (for the pi and 12v lcd) and the pi raises a gpio high while the software is running.  Then when I flip the power switch on the panel down, it lowers a gpio to the pi and the pi sees that and shuts itself down, eventually powering down and the gpio its holding high drops, which signals to the arduino its safe to cut power.

Very impressive.

Your Instrument Panel would fit right in a BD-5, or even a BD-5J.

 :)
« Last Edit: April 19, 2020, 02:32:46 am by SkyMaster »
 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #44 on: April 19, 2020, 01:26:50 am »
It looks like a pre approved design helps but there's still a lot of faff, lodging plans beforehand, logging the whole build, every item that goes into it and where it came from, inspection at the end, a series of formal test flights, etc. It also looks like they want a full assessment for even minor deviations from an approved design.

It's clearly possible and I'm sure people do it, but it's nothing like the US ultralight class. For me it pushes it from "fun, cool project" to "pain in the arse" which is quite sad really.

If you're interested the whole UK process is in a document called CAP 659.

Maybe I should learn French.

Yeah, that is quite depressing.  Reasonable, but depressing. I'm honestly shocked that the FAA of all groups in the usa allows ultralights to exist still.


Very impressive.

Your Instrument Panel would right in a BD-5, or even a BD-5J.

 :)

Oh thank you very much!  I know the bd-5 and bd-10 were two things that super inspired me to want to make my own airplane.  Too bad the bd-10 was a failure.

I'll be sure to start a thread on the electronics of the aircraft once I get more progress!  It's going to be quite the system, with a bunch of modules talking over CAN bus!
KD2CHS
 

Offline SkyMaster

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #45 on: April 19, 2020, 02:54:07 am »
  Too bad the bd-10 was a failure.


John Bede was a genius. Among other things he designed the BD-1, which became the Grumman American AA-1. Instead of using rivets, the skin is glued to the inner structure. I never flew the AA-1, but flew the GA-7 were Grumman American took the same approach; smooth skin everywhere, no rivets.

Unfortunately, except for the BD-4 none of Bede design were commercial success.

I saw a BD-10 in a museum in Toronto, I was surprise how relatively small it was.

 :)
 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #46 on: April 19, 2020, 04:12:30 am »
That is fascinating!!  I know another plane I wanted to make which would have a similar appearance was the Velocity, specifically the v-twin.  Because fiberglass.

I didn't know there was a museum with a BD-10 in it in toronto. That's only 8 hours from me, maybe when this whole covid thing blows over I'll go over and find it!
KD2CHS
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #47 on: April 19, 2020, 04:54:10 pm »
Yeah, that is quite depressing.  Reasonable, but depressing. I'm honestly shocked that the FAA of all groups in the usa allows ultralights to exist still.

What I did find looking at things (far too late last night/this morning tbh) is that as a result of a change in 2017 the UK almost has an unregulated category again, but a very restrictive one. Under 70 kg and under 20 kt stall speed is now in the same category as paramotors, with no requirements other than insurance. I'm currently mulling over whether modern materials allow any kind of conventional design in a 70 kg mass budget. I suspect you need so much wing area to meet the 20 kt stall speed requirement that it eats up most of the budget straight away.
 

Offline ITman496Topic starter

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #48 on: April 19, 2020, 09:50:40 pm »
Oof, that is not a lot of weight!  I suspect you're squarely in the territory of those paramotors but instead of a backpack its a gokart kind of thing.

Do they actually check?  I know with the FAA they have their limits but nobody actually comes and weighs the airplane.
KD2CHS
 

Offline richard.cs

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Re: Toggle switch for small aircraft charging system in case of failure
« Reply #49 on: April 20, 2020, 08:24:01 am »
Oof, that is not a lot of weight!  I suspect you're squarely in the territory of those paramotors but instead of a backpack its a gokart kind of thing.

Do they actually check?  I know with the FAA they have their limits but nobody actually comes and weighs the airplane.

It's intended for paramotors with gokarts (people here call them trikes).  It came about in response to various disabled people wanting an exemption to use a trike because they were unable to footlaunch. You may well be right that it's all that can be done in 70 kg but when I get some time maybe I'll run through some design calculations.

The question of enforcement is an interesting one. I mean if I were to build anything and fly it at low altitude over private land it seems highly unlikely anyone would either notice or care however big it were. Not that I or anyone I know owns a plot that big. However if I made something that looked like a microlight but didn't have paperwork, registration numbers, etc. and took it anywhere where I might encounter someone who knows the rules then it is likely to at least get questions, and if the response is "it's under 70kg" then that's going to raise interest if it's not a paramotor simply because that's hard to do (if it's even possible).

 


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