Primarily for general aviation discussion, but other aviation topics are also welcome.
#1838141
@patowalker
That would be daft, but is not how it works. It receives while stationary, but will only see aircraft which exceed the air/ground threshold speed.


Just for clarification: you are saying the unit will ‘see’ a target once the target has exceeded their user-defined speed (which makes sense), as opposed to the unit will only ‘see’ a target once the receiving aircraft’s threshold has been exceeded.

Not trying to cause trouble but your statement could be read both ways and I just want to make sure :thumleft:
#1838142
I was going to say that I had assumed that the transmit algorithm would take account of the platform type in determining whether or not to transmit at low / zero speed, e.g., light aircraft / helicopter. Thinking about it, it’s going to be pretty rare to encounter a hovering helicopter at typical fixed-wing altitudes.

Iceman 8)
#1838156
patowalker wrote:That would be daft, but is not how it works. It receives while stationary, but will only see aircraft which exceed the air/ground threshold speed.

That is what I would expect. and that threshold speed is configurable (so rotorcraft could put zero).

But that is not what the OP said.
However at around 40kts (activation speed for SE2) I got a traffic warning of an aircraft directly ahead, 100' below. :shock:

His speed reached the threshold, and
The warnings continued around the clock face until it quickly became apparent that whatever was causing the warning was parked on the apron to my right.

The ground target was not using a squat or velocity switch to turn off the ADSB transmission.
#1838160
Don't know how any of this stuff works but on the radar sites I've seen a number of stationery aircraft on the ground at locations clearly not airfields. Last week, for example, there was a Europa showing up at house not far from me for several days and last year two hot air balloons at a house in Caterham on various occasions. I assume the owners are doing work on their aircraft. Would these show up on kit like Sky Echo?
#1838163
If the aircraft on the ground was using a typical fixed installation, e.g., a certified GPS connected to a Garmin 330ES transponder, as per my TB, then as soon as you switch the transponder to Alt at the hold, just prior to takeoff, the transponder will be emitting ADSB-out. I’m not aware that these fixed installations have a velocity filter (although they will be WoW aware).

Iceman 8)
#1838168
BoeingBoy wrote:Thinking about it, one of the active aircraft on the ground was a helicopter. That said, it would have been in my three o'clock at the start of the take off run.


I would suggest that it was the fact that the helicopter had just turned on, rather than your SE2 reaching VSO set in the device.

I haven't seen too many issues with transponders, but FLARM units left on all day, I find annoying.

Edited after it was pointed out that SE2 receives only ADSB and FLARM, and will not see Mode A/C or S transmissions.
Last edited by Ian Melville on Mon Apr 05, 2021 10:34 am, edited 2 times in total.
#1838169
Hooligan wrote:I've seen a number of stationery aircraft

Origami huh?

Hooligan wrote:Would these show up on kit like Sky Echo?

Certainly all the Flarm units in the gliders at my home base show up rather irritatingly as audible warnings when I'm joining the circuit, making my PAw less useful than it could be. All you can do is to try and isolate the ones that aren't at an identical distance below you.

Rob P
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#1838172
Rob P wrote:Certainly all the Flarm units in the gliders at my home base show up rather irritatingly as audible warnings when I'm joining the circuit, making my PAw less useful than it could be. All you can do is to try and isolate the ones that aren't at an identical distance below you.
Rob P


Yes this is annoying, we considered filtering on ground speed, but that is not useful for helicopters

(Copy)@Tim Dawson

Tim in SD you have a model of the terrain, as you can report above ground height.
Could you not combine the data from traffic speed and height above ground of these aircraft in order to filter (under user control) ?

You can certainly do this with the pilotaware/flarm data as the vertical component is relative
Not sure you can do this with GDL90 traffic, as it is reporting altitude not height, unless there is a message reporting both height and altitude to get the conversion correct

Thx
Lee
#1838174
Rob P wrote:
Hooligan wrote:I've seen a number of stationery aircraft

Origami huh?

Rob P


:lol: Doesn't the Europa have folding wings? Balloons certainly have envelopes...

Thanks, always wondered if they might show up - you occasionally see gliders showing up late at night at gliding sites - assume someone has forgotten to turn things off...
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#1838175
I would suggest that it was the fact that the helicopter had just turned on, or not previously been pinged by a radar head, rather than your SE2 reaching VSO set in the device.


Why would the helicopter getting pinged by a radar head allow it to be shown up on the SE2? As I understand it, SE2 does not receive transponder traffic. Obviously a transponder has to be pinged in order for it to reply and make its position known but, if the helicopter was only transponder equipped, it would make no difference if he was pinged or not to be shown on BB's display.

Maybe the helicopter has managed to configure his ADSB Out such that it operates when off the ground, regardless of speed. I wish some of the aircraft at Sandown, yesterday, had done the same. One of the aircraft was still showing red on my PAW Traffic screen about 5 minutes after him landing :roll:
#1838179
Gliders hill or wave soaring often have very low (or even zero/negative) groundspeeds, and they often fly in large concentrations on many hill and wave soaring areas.

Most glider flarm installations are "on" when the A/C power is on, and many pilots switch the power on in the morning and leave it on all day. It does not normally cause a problem to other gliders, as the flarm warnings for collision avoidance use the relative motion as a trigger, not proximity. Very few gliders have a flarm on/off switch.

Gliders hill and/or wave soaring often fly large distances away from their launch site, so please do not assume you will only meet them near the club airfields.

As always, it is wise to be aware of how others operate!

You will of course be welcome to come and see how we do it!

Terry
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#1838180
leemoore1966 wrote:Yes this is annoying, we considered filtering on ground speed, but that is not useful for helicopters


I can't offhand recall any mid-air collisions involving a hovering helicopter :lol:

Rob P