[Cryptography] improved identification of non-targets

[Michael Kjörling]

On 12 Jan 2020 23:35 -0700, from cryptography at metzdowd.com (John Denker via cryptography):
> On 1/12/20 6:37 AM, Michael Kjörling wrote:
>> A simple NOTAM (Notice to Airmen) closing the relevant airspace to 
>> traffic could potentially have prevented the PS752 disaster.
> 
> Iran is not going to do that, because it would cause economic
> harm to themselves.

I never said that they would need to close _all_ of the airspace,
though of course they could do that if they really wanted to (and as
you say take the effects). They could easily leave a narrow corridor
open for arriving and departing flights, while closing the surrounding
airspace. The corridors could be made however long and at whichever
altitudes the authorities consider appropriate at the time, and could
be changed quickly if necessary. Airspace closures of various shapes
and sizes is nothing unusual.

Or, just tell ATC not to clear flights for certain instrument arrival
or departure routes. You don't even need to tell the ATC controllers
why you're doing that, let alone the pilots, though telling the ATC
controllers will allow them to give better assistance should an
aircraft develop an emergency. A separate NOTAM could simply inform
pilots that into and out of a given airport, normally available routes
A, B, C and D are unavailable, leaving E and F. They could even do
this on a per-carrier basis if they really wanted, especially if they
do it through ATC. Again, standard procedure, nothing unusual, pilots
already deal with variations of this every day.

A strong limiting factor in actual airport capacity is going to be
wake turbulence anyway, so if done right, neither of this needs to
affect actual throughput capacity much.


> There should be a mechanism, and a procedural requirement, so that
> an aircraft can verify that its IFF is working *before* it becomes
> a critical issue.

IFR traffic is procedurally required to have a filed and approved
flightplan; ATC won't let IFR traffic onto the runway without a
flightplan. At some point prior to departure, the flight will be
assigned a transponder code. I don't know what ATC will do if the
flight does not squawk its assigned code, but due to simply the risk
of conflicting code use, they will have to do _something_ in such a
situation. And in case of doubt, ATC can always request that pilots
IDENT (which sends a specific signal back to the ground station) to
highlight the flight on their displays, helping provide positive
identification of a radar return. That's sometimes used in cases of
radio failure, too, to establish whether an aircraft can _receive_ but
not _transmit_ on voice radio, or if they also cannot receive others'
transmissions.

>  -- This includes a pre-takeoff check at the departure airport,
>   pertaining to the local jurisdiction.
>  -- This includes an airborne check for each new jurisdiction
>   along the way, so that the aircraft knows they have been
>   positively and favorably identified *before* entering the
>   new airspace.

That's already done all the time. Aircraft crossing airspace
boundaries will typically identify with ATC giving their flight number
and current altitude, as well as their target altitude if they are
climbing or descending. This allows ATC to identify the flight; again,
they can always request an IDENT in case of doubt.

-- 
Michael Kjörling • https://michael.kjorling.se • michael at kjorling.se
 “Remember when, on the Internet, nobody cared that you were a dog?”