Re: [Drip] ADSB

[Stu Card <[e-mail]>]

Very short answers (all for which I have time):

The rules for RID are based not primarily on RF considerations, but on aviation considerations.

Crewed aircraft _mostly_ fly above 500 feet, except during takeoff and landing. Small uncrewed aircraft _mostly_ fly at much lower altitudes, as they are flown largely not to get from one place to another, but for photographing or otherwise sensing things on the ground (or for recreation). The FAA has established an upper limit of 400 feet AGL for small uncrewed aircraft flying under their rule appropriate for most such, to provide 100 feet of vertical separation from these small UAS and where the crewed aircraft _mostly_ fly.

WRT units: yes it is a mess; no the EU does not use precisely the metric equivalents of feet etc. in their rules; note my original message said "EU rules are similar" not "EU rules are the same except for translation of metric units".

IETF does not get to write rules for aviation, therefore neither does IETF get to write rules for aviation communications; we can only provide technical standards for interoperable network protocols that _enhance_ those communications.

-----Original Message-----
From: Alexandre Petrescu <[e-mail]> 
Sent: Wednesday, July 12, 2023 9:45 AM
To: Robert Moskowitz <[e-mail]>; Carsten Bormann <[e-mail]>
Cc: Stu Card <[e-mail]>; [e-mail]
Subject: Re: [Drip] ADSB



Le 12/07/2023 à 13:56, Robert Moskowitz a écrit :
> 
> 
> On 7/12/23 06:45, Carsten Bormann wrote:
>> On 2023-07-12, at 11:52, Alexandre Petrescu 
>> <[e-mail]> wrote:
>>> why not 400m
>> This is not a domain where we get to invent boundaries.
>>
>> (Also, generally speaking, of course we should have a strong bias to 
>> using SI units, but in a domain where regulation is widely based on 
>> furlongs per fortnight, we’ll have to adapt.)
> 
> And anyway it would be 125M to be a bit more than the Imperial 400'.

True.

And it obviously begs the question whether in Europe they also have the same limit of 400' equivalent in meters.  I strongly doubt that an EU document would talk about a limit of precisely 121.92 meters just because of being converted to the easy to grasp 400 feet.

At that point we talk about devices that might be different in an EU market than in an US market.

What is the EU altitude limit for numerous drone aircraft to be considered flying very low, so numerous and so low such as to be forbidden to carry ADS-B equipment (or turn it off at lower than that altitude if it carries one)?

> Why 400'?
> 
> I think it was to keep general aviation some reasonable distance above 
> people on the ground.  As the ceiling for UA that is a consequence.

You see, I think there is an error.

400 feet might be a good limit in terms of separation of people and objects above their heads, but it is certainly not any limit in terms of radio communication.

If there is to be a radio communication limit (use or not use ADS-B) it should be based on the power levels it uses and the guarantees of range. 
  In WiFi, bluetooth and 2G..5G that's how they separate.

For example, an 5G-carrying UAS would be limited to 450meter altitude because that is how high the ground 5G oriented towards ground reaches high.

A bluetooth-carrying UAS (and not carrying ADS-B) would be limited to
100 meter altitude because that is how high a bluetooth device is allowed to emit, by bluetooth regulation.

> "They can't go any lower, you can't go any higher."

Strange.  Many devices, especially those who plane or glide like these UAS drones, and helicopters too, will stay stable at very many low altitudes.  Their power systems - more and more performing, allows for that.

I very well see a helicopter stable 100meter above the ground, and surely it carries an ADS-B device, if not several of them.

> 
> It is called boundaries to keep unequal players apart.
> 
> One of the interesting debates in this is that the 400' floor is to 
> ground obstacles like radio towers.  Thus since big birds have to stay 
> 400' from that 700' radio tower down the block, you can take your UA 
> up to 1100' right next to it...  Or so some claim.

Right!

RAdio towers, or radio towers with even higher anti-flash ('paratonnerre', fr.) on them?  That adds some 10 meter to the picture, to which an UAS drone would need to pay attention, just like helicopters need to care about power lines above ground too.

> 
> And speaking of Imperial vs Metric...
> 
> Civil aviation separation is 1000'.
> 
> This has already caused incidents where a lesser  Metric distance was 
> used by one aircraft against one using the greater separation of Imperial.
> 
> Fun!
> 
> Not.

I agree.

Alex

> 
> Bob
>