"Do It Yourself" airborne proximity warning device

On Tuesday, December 10, 2013 1:41:26 PM UTC-8, Sarah wrote:

Well, define "accurate", and "could put in a glider".

Fair enough.

If you were able to put TCAS in a glider that would do it, but trying to get azimuth information off of passive monitoring of radar returns (like PCAS does) has to be a hit-or-miss proposition (pun intended) since you don't have the ability to actively interrogate other transponder-equipped aircraft to string together enough bits of information to get good direction. You are dependent on ground radar or TCAS-equipped aircraft to do the interrogating for you which is no always reliable. Some sort of directional antenna added to a PCAS might help in the way you describe (showing quadrants), but I have to believe it's not the sort of thing you could really count on and would totally suck for glider-glider scenarios.

I'd also add that the research shows that no matter how diligent the scan, see-and-avoid detects not more than half the targets that are collision threats. Non-threats are much easier to pick up because of the angular movement of non-collision targets. So, the fact that you see other aircraft when you are flying to some extent generates a false sense of security - your are much less likely to see the one that's going to actually hit you. There are scenarios in the research where successful detection in time to act is on the order of 10-20%. That gave me some pause.

9B

You don't need directional antennae. Without getting too long winded (I
know, I know...) you monitor the arrival times and frequencies of the
interrogation signals and the replies and combining that with your known
position, you can mathematically determine the positions of all the
emitters. Multiple samples enable the system to determine velocity (a
vector of direction and speed).


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On Tuesday, December 10, 2013 1:41:26 PM UTC-8, Sarah wrote:

Well, define "accurate", and "could put in a glider".

Fair enough.

If you were able to put TCAS in a glider that would do it, but trying to get
azimuth information off of passive monitoring of radar returns (like PCAS
does) has to be a hit-or-miss proposition (pun intended) since you don't
have the ability to actively interrogate other transponder-equipped aircraft
to string together enough bits of information to get good direction. You are
dependent on ground radar or TCAS-equipped aircraft to do the interrogating
for you which is no always reliable. Some sort of directional antenna added
to a PCAS might help in the way you describe (showing quadrants), but I have
to believe it's not the sort of thing you could really count on and would
totally suck for glider-glider scenarios.

I'd also add that the research shows that no matter how diligent the scan,
see-and-avoid detects not more than half the targets that are collision
threats. Non-threats are much easier to pick up because of the angular
movement of non-collision targets. So, the fact that you see other aircraft
when you are flying to some extent generates a false sense of security -
your are much less likely to see the one that's going to actually hit you.
There are scenarios in the research where successful detection in time to
act is on the order of 10-20%. That gave me some pause.

9B

On Wednesday, December 11, 2013 9:12:45 AM UTC-8, Dan Marotta wrote:
You don't need directional antennae. Without getting too long winded (I

know, I know...) you monitor the arrival times and frequencies of the

interrogation signals and the replies and combining that with your known

position, you can mathematically determine the positions of all the

emitters. Multiple samples enable the system to determine velocity (a

vector of direction and speed).

But so what, these ground based multilateration systems have been around for years and are fairly widely used worldwide to supplement SSR radar. The way you get this traffic data to an aircraft today is via TIS-B. The position accuracy is not great (not compared to what GPS/ADS-B data-out can provide). And to receive that TIS-B traffic data your aircraft/glider needs to have ADS-B data-out, which requires an expensive IFR rated GPS, and an ADS-B data-out capable transponder or UAT (but please use a Transponder in a glider for PowerFLARM 1090ES compatibility) and a 337 field approval (for certified aircraft) that is supposed to be based on a previous STC in a similar aircraft (none of which were actually developed for gliders). So while it may be possible, good luck having that conversation with you local FSDO. And to receive that TIS-B signal requires you to be in range of the ground based ADS-B service, YMMV in some popular glider areas. And worrying about this stuff now just seems pointless given that ADS-B data-out carriage will be required in the USA in many aircraft by 2020. So you might as well just read that much higher resolution ADS-B data-out position data straight over the air now and usage will just continue to increase in future.