First flight - questions

[tj80]

Hi,

I finally took my PAW out for a flight yesterday evening and I have to say it performed well.  It was a quiet evening so mostly commercial traffic about, but I think it may have spotted two very relevant aircraft (one presumably ADS-B, the other Mode-S) and would like to verify a couple of things.  Can I do this from the track log?

First, ATC warned me of a nearby Kingair.  I spotted it visually some distance away and could also see an aircraft on Skydemon in the same direction - but it looked further than the one I could see.  I don't know the registration of the one I saw, is there any way of checking if the contact PAW picked up was indeed the same aircraft?  If I could find the contact in the log by time or approximate location it would be easy enough to check if it's the right aircraft!

Second, a helicopter overtook me fairly close by (we were in contact with each other on the appropriate frequency so we both knew each other were there and each other's intentions).  I was entering the circuit so not looking at Skydemon, and unfortunately have no audio set up yet - however I checked and there was no traffic identified before I entered the circuit when I know he would have been quite close behind (and said he was visual with me).  I did notice a red "danger" Mode-S ring when I glanced at the iPad a little later but by that time the helicopter was very close to and directly in front of me.  I'd like to know when PAW first picked up the contact - perhaps I need to change from "Medium" to "Long" range to get earlier warnings, or perhaps it didn't detect it at all until it was in front of me.

I did run the log through the post-processor, but I couldn't find the Kingair or any Mode-S contacts.

Finally, am I right in thinking this is another PAW?
$PAWRT,EA8935,0,0,0,0,1,0,*42

If so, how can I tell where and when this was?

Thanks,
Tim

[AlanG]

Hi Tim

I'm sure Lee will be along to answer your questions more fully shortly but in the meantime here's my two-penneth.  Firstly, the setting for Mode S range will very much depend on the positioning of your antenna.  Having done a lot of the testing that led to these settings being adopted I can say with some authority that the described ranges are with as good a view of the sky as possible.  Put something like an engine a huge bag of water(you or your passengers) between the antenna and the target and some serious attenuation can occur.  On my flexwing, the antennas are mounted on the top of the pod behind the windscreen so most of my attenuation is rearwards and this did become apparent with signal strength readings during testing.  I do however feel this is the best situation as anything coming toward me is going to hit me quicker than something coming up behind.  It is likely that the helicopter was the Mode S warning you received when it was positioned ahead of you.  I personally use the short range setting for Mode S and find this adequate for GA transponders at around 4/5 miles for an amber alert.  Commercial traffic Xponders are more powerful and therefore activate warnings from further out but they're usually bigger and visible from greater distances too.
Depending on your set-up you will need to adjust the settings until you find the one that you are happy with.  Alternatively you may be able to move your antennas to more suitable positions and try again.
Sorry if i'm preaching the obvious but installation is a fairly critical part of getting the PAW to perform at its best.

Regards
Alan

[tj80]

Hi Alan,

Many thanks.  I understand how important the antenna placement is, although the unit I have built will just about fit on the coming it does obstruct more sky than I would like so yesterday I just plonked it on the back seat (rented PA28).  I was happy to see a GPS fix with 10 satellites and, later, a much smoother GPS track with less "noise" than the ones from the internal iPad receiver.

As you say, this placement meant plenty of metal and "bags of water" in the way.  I've also got a short extension lead and a stubby antenna on the DVB tuner, so overall sensitivity is something of an unknown.  That's why I am keen to see how long PAW could pick up the helicopter for - it may be that it picked it up behind me but didn't alert because of the range setting.  If that's the case I can just increase the range!  However if it didn't detect it at all until it was in front of me I will need to think a bit harder about placement.

As an aside, something which was of no practical use but greatly pleased the geek in me was seeing a long line of perfectly spaced airliners on final to Heathrow! 

Thanks,
Tim

PS. I wonder if there is a way of recording the iPad screen for post-flight analysis?  That would mean being able to go back to see what was actually happening while eyes-out (where they should be!).

[Ian Melville]

I did run the log through the post-processor, but I couldn't find the Kingair or any Mode-S contacts.

Finally, am I right in thinking this is another PAW?
$PAWRT,EA8935,0,0,0,0,1,0,*42

If so, how can I tell where and when this was?

Yes, that looks like a PAW generated P3I sentence.
To tell where and when we will need the $GPGGA line above the sentence you posted above and the $PFLAA line immediately below(which will also have EA8935 within it)

[tj80]

This is from the track log - is there documentation explaining what all these log entries mean?

$GPRMC,172559,A,5120.963,N,00033.717,W,9.000,23,040816,,,A*49
$PAWRT,EA8935,0,0,0,0,1,0,*42
$PFLAA,3,103,-89,9,1,EA8935!EA8935,10,,0,,8*7B

Thanks,
Tim

[Ian Melville]

That's just over 100m from you? Do you have two PAW units as the odds on someone else being that close are very slim. The other unit is also not set up fully as default Hex-ID and no Flight-ID. Hempstead area of Luton?

$GPRMC is the Reccomended Minimum, I prefer the $GPGGA as that gives height as well. Was this in flight? Just 9 knots heading 23 degrees true?

$GPRMC and $GPGGA are international standards for NMEA http://www.gpsinformation.org/dale/nmea.htm
$PFLAA is a Flarm standard and available in Flarm documents from their website. We are not allowed to link to Flarm Documents from this forum, but easy enough to Google.
$PAWRT is a new Pilot Aware sentence which Lee has briefed on in Reply #31 of this page http://forum.pilotaware.com/index.php/topic,535.30.html

[Admin]

PAWRT explaination

http://forum.pilotaware.com/index.php/topic,535.msg7015.html#msg7015

[tj80]

Hmm.  Definitely a "glitch" somewhere then - I only have one PAW and that log was from a flight from Fairoaks down to the south coast and back, nowhere near Luton!  Also a bit strange there's only one PAW message received?

[Ian Melville]

I'll double check when I get home.
Bad day yesterday, spent the whole morning writing code to map the flight path of PAW and targets the accidentally overwrote the whole lot. :-( Going to start again but changing to a faster code environment.
Can you email me your Trk file?

Cheer
Ian

[tj80]

Hi Ian,

Have sent you a message.

Cheers,
Tim

[Ian Melville]

Hi Tim,
I did make an error in my rush this morning. You were in fact taxying at Fairoaks, and the transmission was from the buildings to the north west, perhaps second floor. Sorry don't know which room :-)

Odd that it is just the one, perhaps some one with a new toy. The signal may have been transmitting continuously, but too weak to get out of the buildings walls, and got out through a window as you passed!

[tj80]

Thanks, Ian - amazing!  At least I know my PAW bridge is working!