I haven't read the proposed regulations, but most likely it is a typo and should be 55 pounds not 0.55 pounds. Because the existing FAA regulations have a lot of things that change at the 55 pound threshold.

0.55 pounds doesn't really make sense, such a light drone can barely fly in modest wind and won't have enough battery life to go very far.

Edit: maybe 0.55 pounds is correct. Because that threshold is also used in other FAA UAV regulations. (e.g. UAV less than 0.55 pounds doesn't need to be registered)

Edit2: maybe not, see https://www.apnews.com/1c50bdd96d6244198df93d84c86bf156

55 flying pounds is enough to kill a person... No way someone could prove that 55 pounds of drone can't hurt someone.

Given that we're talking big business and liability, I would also like to see some sort of bond posted against accidents and injuries, or an insurance requirement.

I doubt Amazon drone deliveries are what the FAA was considering with this proposal. More than likely, DJI Spark type of aircraft is what was considered where the pilots are looking to acquire video footage. Although a quick lookup shows the Spark to be slightly heavier than 0.55 pounds. That thing is tiny, so if it doesn't qualify for this proposed rule, then the crafts that do qualify would be more along the lines of toys. I was under the impression that the Spark was just about the smallest useful drone available. By useful, I meant can generate a decent quality image.

I don't get this either. Almost any existing consumer drone over 0.55 pounds could possibly fall straight down onto someone's head and kill them, in an unlucky scenario.

Maybe the requirement is trying to encourage (or allow) the development of drones that are spatially extended/soft, e.g. drones that contain inflated components.

I wonder if they could deploy something like the airbags they had on the mars rover that bounced down, perhaps with vents allowing air to squeeze out on impact like a crumple zone and cushion a blow if it were to land on someone.

Also... weight is not a useful metric. A 1lb rock has very different ballistic properties than a 1lb feather. A typical 9mm bullet weighs 0.01lbs.

Since this is about objects falling from a certain height, yes, weight is a useful metric for rough safety estimates.

A bullet does damage because it holds a lot more energy from being accelerated - a 9mm bullet will go around a mile up before falling down (source: MythBusters). Two 500g boxes dropped from a likely much lower height will have a similar effect (concussion?) when dropped on a pedestrian regardless of the contents, except for a few outliers. Even for small, heavy objects (like a 1kg camera lens) the load would be spread by its enclosure unless it separates mid-fall.

a 9mm bullet can only go so high because it leaves the barrel at a much greater speed than its terminal velocity in freefall. 9mm in particular has a fairly low terminal velocity; if it falls straight down it is unlikely to seriously hurt an adult.

The bullet, falling from the same height as a crashing drone, is at least as lethal if it strikes a human. There is no "safe weight" for a falling object... but there may be a "safe momentum".

The proposed flying zone for drones like these is between 60-120m height. Seems like a bullet must travel at least 62m/s to penetrate human skin [1], for which you need a height of at least ~200m [2]. So even dropping a bullet from one the delivery drones would not carry a high risk of fatal injuries.

That, and P=MV, momentum/energy increases proportionally to mass. A 'safe weight' can be defined if the altitude is known.

[1] https://slate.com/news-and-politics/2011/03/can-falling-bull...

[2] https://www.grc.nasa.gov/www/k-12/airplane/mofall.html

Right, but a box with a 1lb rock in it, and a box with 1lb of feathers are going to fall from the sky to your head about the same.

I mean, the 1lb or feathers will have a much larger box, and a much larger surface area for wind resistance. In addition, it will spread the impact over a larger area.

The box with the feathers could be very tall but narrow so that the air resistance won't be large.