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Creating rules with one dimensional thinking

vindibona1

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I've been sort of house bound recently due to an illness ( and a little grumpier than normal- hence the post) and so have been playing with my Mini 2 indoors, practicing flying in atti mode (lots too write about there too). Indoors in atti, for most of us, would pretty much require prop guards. So obviously I put some on while keeping the leg extensions on as well. I had to wonder "How much does this setup weigh?" and put the contraption on a jewelry scale. 297 grams.... 47 grams over the generally recognized "weight limit" for a bunch of restrictions. So, 1.6 ounces over the limit. What's that equivalent to?

Anyway, the geniuses that did the computations to come up with the magical 250 gram threshold, I believe, forgot one thing: Distribution of mass. I suppose it came to my attention as I'm reading the new rules for flying over people; "250 grams max, with no rotating parts that can cause lacerations". It reminds me of the old joke; "Which weighs more, 50 pounds of feathers or 50 pounds of lead?" One would think that the measly weight addition of prop guards would be more than offset by the mass distribution in the event of a catastrophic failure over people.

If you look at the configuration below, imagine something like that falling on your or flying into you. Anyone with any kinesthetic awareness can see that the impact of any contact would create little if no harm to the person unlucky enough to be struck. In my mind, the question begs to be asked: Why has mass distribution been ignored in the calculation? You would think that the addition of prop guards, with the minimal addition of weight would make them safer than exposed props but a couple ounces less weight? To me it seems like one-dimensional thinking overlooking at least one aspect that could make drones safer, though exceeding their made up "magic weight number".

While flying over people is a concern, there is no physics rules that says your drone will crash straight down. You might be flying high, away from people, but if one prop fails there's nothing that says you still won't crash into people or property. You'd think some physicist working on the project would create at least one rule exception when it comes to weight AND distribution. In the new rule about flying over people, they were adamant about adding "no rotating parts that could cause lacerations" but failed to accommodate the one simple thing that would have added TWO LAYERS OF SAFETY; PROP GUARDS in spite of having to make a small weight exception.

Dismounting soap box

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In the US the whole flying over people rule is built around kinetic energy transfer. 250 grams is just the number where kinetic energy is so low no matter the material or configuration the kinetic energy transferred is below the threshold of causing serious injury for a fall from 400 ft.

For drones over 250 grams they would fall into one of two categories depending on the kinetic energy transferred in case of a crash either under 11 foot-pounds of kinetic energy upon impact from a rigid object or 25 foot lbs of kinetic energy. To fly over people you must always use prop guards that prevent lacerations in case of a crash no matter the weight of the aircraft.

That was all part 107 stuff btw. At this time there is no rules explicitly against for or against recreational pilots flying over people, though this is going to change any day now…

For recreational pilots all having a drone under 250 grams does for you is saves you the $5 registration fee. For recreational pilots the 250 grams thing was more intended to not make criminals out of grandparents who bought toy drones for their grandkids and don’t understand you have to register them. Part 107 pilots have to register all drones regardless of weight.
 
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In the US the whole flying over people rule is built around kinetic energy transfer. 250 grams is just the number where kinetic energy is so low no matter the material or configuration the kinetic energy transferred is below the threshold of causing serious injury for a fall from 400 ft.

For drones over 250 grams they would fall into one of two categories depending on the kinetic energy transferred in case of a crash either under 11 foot-pounds of kinetic energy upon impact from a rigid object or 25 foot lbs of kinetic energy. To fly over people you must always use prop guards that prevent lacerations in case of a crash no matter the weight of the aircraft.

That was all part 107 stuff btw. At this time there is no rules explicitly against for or against recreational pilots flying over people, though this is going to change any day now…

For recreational pilots all having a drone under 250 grams does for you is saves you the $5 registration fee. For recreational pilots the 250 grams thing was more intended to not make criminals out of grandparents who bought toy drones for their grandkids and don’t understand you have to register them. Part 107 pilots have to register all drones regardless of weight.
While I understand, it doesn’t address the point. They created a rule for flying over people but added a stipulation about “rotating parts that could cause lacerations” , failing to understand, acknowledge or modify the weight cut-off even slightly to accommodate prop guards, which would not only protect from lacerations but spread the impact over a much larger area, thus trading under 50 grams for exponentially more protection. A simple exception to the rule could have been “250 grams OR 300 grams with propeller guards”. But no… One dimensional thinking, just like typical bureaucratic wonks that limit freedoms when alternatives are staring them in the face.
 
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I don't see the numbers as being arbitrary. There has to be some sort of fixed limits. If you make it 270g, someone will just say why not 280g? And so on...before you know it...be 5000g.
 
@spsphotos hit the nail on the head. No matter what seemingly random weight was selected, someone would always want to question it and suggest it's faulty.
 
In the US the whole flying over people rule is built around kinetic energy transfer. 250 grams is just the number where kinetic energy is so low no matter the material or configuration the kinetic energy transferred is below the threshold of causing serious injury for a fall from 400 ft.
Actually, the 250 gram limit came from a kinetic energy calculation of an object dropped from 500 ft.
It's all in this final report of the FAA's Aviation Rulemaking Committee of November 2015.
Read it here: www.hsdl.org/?view&did=788722

I don't see the numbers as being arbitrary. There has to be some sort of fixed limits. If you make it 270g, someone will just say why not 280g? And so on...before you know it...be 5000g.
The 250 gram number is totally arbitrary and not based on any actual risk analysis or supported by any physical or statistical data. The number was arrived at by calculation based upon many questionable input assumptions. An object shaped like a brick, with coefficient of drag equivalent to a baseball, dropped from 500 feet, at sea level atmospheric pressure, reaching a terminal velocity of 57 mph, would deliver 59 ft-lbs of kinetic energy, if that object weighed 250 grams.

From the report: "an object with a kinetic energy level of 80 Joules (or approximately 59 foot-pounds) has a 30% probability of being lethal when striking a person in the head."
 
It reminds me of the old joke; "Which weighs more, 50 pounds of feathers or 50 pounds of lead?"
Exactly. The shape of the object will certainly influence its potential for injury.

An opened umbrella weighs exactly the same as a folded umbrella but, unless dropped in a vacuum, they will fall at significantly different speeds and pose different levels of risk to anyone below.

A Mini with prop guards installed will certainly have a much greater coefficient of drag than a baseball, and is not shaped like a brick, unless you first remove the prop guards, remove the propellers too, and fold the arms. But in this configuration you're very unlikely to ever see a Mini flying at 500ft, unless tossed out of an aircraft window.

The 250 gram limit is very much an arbitrary number.
 
vindibona1 - this discussion can apply to a lot of different areas. I'll pick speed limits. The agency controlling roads set a speed limit...say 40 mph. One could argue 40 is a wrong speed because a lot of cars shift into the highest gear about 45 so driving slower is a waste of fuel. However, the area could be densely populated so 40 was set to allow for shorter stopping distances as a safety factor, should the need arise. Speaking of speed limits, when have you seen EVERYONE obey the posted limit? Hell, I don't even obey it all the time.

People have always wanted more. Romans had chariot races, there are horse races, people started figuring out how to add horsepower to cars soon after they were built, faster airplanes, higher flying airplanes...and the list goes on.

As pointed out in several posts the weight helps "minimize injury" vs a drone weighing 2-3 times more. Distribution of mass would only come into play if a drone hit someone flat to spread out the impact. Something there NO guarantee of happening every time. Example: if the drone fell flat on someone's face when they were looking up, it would likely cause less injury than if the drone came down on a corner (Prop guard installed) and hit them in the eye.

Just my opinion., of course - Do with it what you want.
 
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vindibona1 - this discussion can apply to a lot of different areas. I'll pick speed limits. The agency controlling roads set a speed limit...say 40 mph. One could argue 40 is a wrong speed because a lot of cars shift into the highest gear about 45 so driving slower is a waste of fuel. However, the area could be densely populated so 40 was set to allow for shorter stopping distances as a safety factor, should the need arise. Speaking of speed limits, when have you seen EVERYONE obey the posted limit? Hell, I don't even obey it all the time.

People have always wanted more. Romans had chariot races, there are horse races, people started figuring out how to add horsepower to cars soon after they were built, faster airplanes, higher flying airplanes...and the list goes on.

As pointed out in several posts the weight helps "minimize injury" vs a drone weighing 2-3 times more. Distribution of mass would only come into play if a drone hit someone flat to spread out the impact. Something there NO guarantee of happening every time. Example: if the drone fell flat on someone's face when they were looking up, it would likely cause less injury than if the drone came down on a corner (Prop guard installed) and hit them in the eye.

Just my opinion., of course - Do with it what you want.
I'm glad you mentioned speed limits. It is a fact that people (in general) drive what feels like a safe speed, regardless of the posted speed, do so safely- unless there is a speed camera or guy with a radar gun. In many, if not most situations, speed control is related more toward revenue than safety. Additionally, if we want to draw a direct parallel, many highway speed limits were set at the onset of the Arab Oil Embargo, (in 1973) with the intent of fuel savings. Once the embargo was lifted, most of those speed limits remained in place in spite of the fact that much of the widespread deployment of safety equipment (disc brakes, steel belted radial tires, sensors, etc) and greatly increased fleet fuel economy.

My point being that the same mentality of one-dimensional thinking and approach to problems prevents the very thing your're after- more safety. Case in point: The highway near my suburban home is marked at 55mph. This same stretch of road prior to 1973 was 65mph. If you dare drive the speed limit you are far less safe than if you travel with traffic between 70mph and 75mph. And while I cannot pull up the stats, believe me when I tell you the accident rate is far lower than in the 1970's.
 
My point being that the same mentality of one-dimensional thinking and approach to problems prevents the very thing you're after- more safety.
Inattentive or incompetent driving is far more dangerous than simple speed. But enforcing rules about texting-while-driving, or driving under the influence, or just plain stupidity, are far more difficult to apply than simply pointing a radar gun or speed camera.

Our highways are generally posted at 100 km/h, but traffic normally flows at 110-120km/h. Sure, the police have free rein to pick anybody out of that stream of cars for ticketing, but unless they're bored they generally won't stop you unless you're doing more than 130km/h.

The one that really gets me going is that heavy trucks are required to have speed governors limiting their speed to no more than 105km/h. At first glance this seems like a perfectly reasonable rule. Some politician decided that heavy trucks are "safer" that way.

But it's nuts.

Now all the trucks run at near exactly the same speed of 105km/h. Except every now and then one truck will feel the need to pass another truck. One will be going 104.9km/h, the other exactly 105km/h. With a length of 72ft (22m), it takes nearly 15 minutes for the faster truck to pass the slower truck.

Meanwhile, the rest of the traffic that had been happily cruising at 110-120km/h is now stacking up behind this bottleneck. The less patient idiots will push and shove, pass on the right, jam themselves back into the line somewhere further upstream, and generally cause mayhem and road rage.

So maybe the trucks are somehow "safer" when they're all governed to the same speed, but overall highway safety suffers as a result.
 
Inattentive or incompetent driving is far more dangerous than simple speed. But enforcing rules about texting-while-driving, or driving under the influence, or just plain stupidity, are far more difficult to apply than simply pointing a radar gun or speed camera.

Our highways are generally posted at 100 km/h, but traffic normally flows at 110-120km/h. Sure, the police have free rein to pick anybody out of that stream of cars for ticketing, but unless they're bored they generally won't stop you unless you're doing more than 130km/h.

The one that really gets me going is that heavy trucks are required to have speed governors limiting their speed to no more than 105km/h. At first glance this seems like a perfectly reasonable rule. Some politician decided that heavy trucks are "safer" that way.

But it's nuts.

Now all the trucks run at near exactly the same speed of 105km/h. Except every now and then one truck will feel the need to pass another truck. One will be going 104.9km/h, the other exactly 105km/h. With a length of 72ft (22m), it takes nearly 15 minutes for the faster truck to pass the slower truck.

Meanwhile, the rest of the traffic that had been happily cruising at 110-120km/h is now stacking up behind this bottleneck. The less patient idiots will push and shove, pass on the right, jam themselves back into the line somewhere further upstream, and generally cause mayhem and road rage.

So maybe the trucks are somehow "safer" when they're all governed to the same speed, but overall highway safety suffers as a result.
I agree. I get really annoyed when I see people texting or doing other things with their phones while driving. As far as general driving goes traffic will generally flow on its own at a safe speed for the conditions at hands. What aggrevates me beyond words is the speed cameras in the City of Chicago that do nothing to add one ounce of safety but takes in billions in revenue (that gets wasted by a one-party political system). In fact, it was found out, not too long ago, that the cameras weren't calibrated, but rigged to send tickets out to people driving at legal speed and garnered over $75 million in illegal proceeds, 50% going to the city and 50% going to the speed cam company.

So perhaps I'm a skeptic when it comes to governmental bullspit that sells you one thing and delivers another... and even more so when it comes to private companies that have a lot of control over our lives and freedoms.
 
I'm reading the new rules for flying over people; "250 grams max, with no rotating parts that can cause lacerations".

If that's the new rule / proposal for hobbyists and / or even commercial pilots, FAA has probably all but ruled it out by default for consumer drone hobbyists, and maybe made it a very hard process for professional pilots.

Our drone prop blades are the rotating parts that can cause lacerations, and those will be with us for a while yet of course.

Unfortunately, the prop guards made for pretty much all DJI drones are not what the FAA, CAA (Canada, UK, NZ), or CASA here would consider sufficient for human impact requirements.

Guards (as we mostly have) are great to deflect side movement . . . wall impacts, and other such like tree trunks, a car body, etc.
Don't expect easy approvals (if at all) for flying near people with plain guards, even if you can get one without cages and still be under 250g total.

Almost anything else is going to be over 250g with a decent camera for video / photos, at least I can't think of one on the market that meets those weight / quality requirements.

For flying near people, propeller CAGES do protect very well from impact and cutting flesh, full enclosed ones like were available for the M1P (photo below), and I think that's the only DJI consumer drone that actually had them made like this.

content_Mavic_Pro_with_Propeller_Cage.jpg

Other setups like the Elios 2 with totally enclosed drone, or (general distance rules aside) small FPV drones with enclosed prop ducting can also be used around people with reasonable safety.

There is (was ?) also the Snap drone, some news agencies took them on for flying over crowds, with apparently FAA approval.
Not quite totally enclosed cages, but pretty good protection, and that drone literally broke up on impact to reduce risk of kinetic injury.
Vantage Robotics no longer shows this in their product line up.

If it was needed at the cheapest price point, then I'd be looking at micro FPV that can take a gopro for vision.
A lot harder to master flight, especially smooth flight.

If $ were no consideration, the Snap looks great, if it was still available.
 
My Mini2 is Category 1 compliant. I have Japanese batteries and I shaved 5 grams off of the prop guards.

Ready to fly over people. Legally. ?
 
My Mini2 is Category 1 compliant. I have Japanese batteries and I shaved 5 grams off of the prop guards.

Ready to fly over people. Legally. ?

Forgot about the 50g saving on the jap batteries.
That is an easy way to fall into the regs no worries.

I remember way back when the mini was released and some of the Japanese users got these, they get aircraft to 199g, so the props are easy enough to tweak into under 250g.
Good to confirm.
 
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