Canadian War Plane activity at CYHM

EJB

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Oct 29, 2002
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Downtown Hamilton
Frequently on weekends there are flights from CHYM, holidays, etc. This morning I put on one of my many scanners and radios and wanted to see if the plane from the museum near CHYM was active and yup, I heard them on 123.450

IIRC is a common pilot to pilot frequency and a rare one in which I hear both sides of comms.

I checked out Flightradar24.com and saw the plane was headed back to CHYM, near where I could see it. I heard pilots talking to be other on 123.45 but only 1 plane on the radar site. As they flew over the lower city, I saw 2 planes.

Why doesn't Flightradar24.com show the 2 planes?
 

derevs

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Dec 4, 2001
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Mississauga, Ontario
I believe that the flight radar sites use AIS to track planes. Maybe the second plane did not have AIS or had it turned off.
This also applies to marine situations. I have never seen the Toronto ferries on the marine site, same can said for Peel and York marine units.
I have seen Toronto police marine units and Hamilton on the marine site, though.
 

ATCTech

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Aug 13, 2002
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Central Halton County, Ontario Canada
The tracking sites use data primarily from ADS-B equipped aircraft fed to them by people on the ground which means the aircraft is transmitting with a Mode-S transponder and the ADS-B option. (GPS position info provided as part of the ADS-B system in other words.) If the aircraft has a Mode S transponder but not the ADS-B add-on, then only the unique hard-coded identification of the aircraft and other basic data like altitude is sent by the transponder but not the GPS position. In that case, the tracking web sites do a calculation called multi-lateration or M-LAT. To accomplish a position plot the ground stations receiving the Mode-S data and sending it to the web site must have GPS data of the receiving ground station included in every packet they send including a precise GPS-derived time stamp. From that the web site can fairly accurately determine the position of the aircraft through triangulation (at minimum 3 ground stations seeing the target aircraft) based on times reported. The more stations reporting the same transponder hit, the more accurate the calculated aircraft position. At major airports in Canada we used M-LAT to display aircraft and vehicle positions on maneuvering areas. Even vehicles have basic transponders to meet this requirement.

Now, if an aircraft does not show up at all on the web-based tracking site it means the aircraft is still using a Mode C transponder. Mode C does NOT send an aircraft specific "hard wired" code from the transponder. (Mode S does send a 6 digit HEX code affiliated directly with the civil registration.) Older mode C secondary radar uses a 4 digit ATC-provided numerical code that's valid ONLY for a specific leg of a flight and can be changed by ATC as required even while the aircraft is in flight by requesting the crew dial in a new discrete "squawk" code, or in the case of a VFR flights, 1200 for all aircraft. Consumer level ADS-B boxes don't have any way of dealing with Mode-C transponder codes as they have no way of knowing the actual aircraft associated with the ATC-assigned code. If and when an ATC radar receives the same 4 digit code from two different targets the controller receives a "Dual Discrete" alarm, alerting them that two (or more) targets are squawking the same Mode-C code. 1200 codes for VFR flights do not cause that alarm.

The last bit? Mode-S transponders and ADS-B specifically are not required in Canada south of 60 degrees north latitude at this point. Mode S is mandatory in the US of A. for trans-oceanic flights plus Europe and other areas of the world. Military aircraft will have Mode-S in many cases but not necessarily have ADS-B, or maybe not have it turned on in many situations for obvious reasons. Tracking sites will typically show you if positions are being derived from ADS-B or M-LAT for every target, civilian or military.
 
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EJB

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Oct 29, 2002
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Downtown Hamilton
I was hoping for your response, are you still working at YYZ?

Thank you for all the responses, much appreciated.
 
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