I agree with your comment that it depends upon where you are located…my location here is at a Class D shared Military / GA airport (KPSM) in Portsmouth New Hampshire about 60 miles north or Boston. Pease has no radar of their own - radar is provided by Manchest NH approach which is 45 miles to the West - below 1500’ can be a probem. This presents a bigger problem about 30 miles North (KSFM) which is on the fringe of Manchester radar - and the overlap fringe of Portland Maine’s coverage – busy non towered field with two runways (old WWII filed) in the triangle from the 40’s - lot’s of “non - talkers” landing on any runway they feel like that day ! This is where the Ryan BX is exceptional - without all of the “false positives” as the 9900 Ryan or the Skywatch…and when the BX is in approach mode - it shrinks the safety cone to 1.5 - 3 miles so that you are not hearing about other traffic which does not concern you during pattern operations. Just some idle thoughts 
Just returned from Hartford Ct (KHFD) where my friend picked up his Tiger with a new 330 installation coupled to a 530. He said he had no data/traffic until above 2000’ & then it worked fine.
Meanwhile my Skywatch worked fine even in the pattern but then failed completely on the way back to KISP
When ATC suppresses VFR traffic to declutter his/her scope, would that affect what the 330 sees? As you can surmise, I know nothing about this
John
That sounds greta Scott. Too bad it is not an option for a Cirrus.
As they say in Jamaica — Soon Come mon – Soon Come
At san jose the coverage starts between 300 and 400 feet…
In reply to:
When ATC suppresses VFR traffic to declutter his/her scope, would that affect what the 330 sees?
John,
The actions of a controller would not affect the data sent. This is all a separate system.
In a terminal or en route environment, controllers have three levels of data they can display.
- Full track datablock for those he or she is actually controlling.
- Partial track datablock for those flights that are under the control of the ATC facility or of interest to the controller
- Limited track datablock for everything else such as VFR traffic not controlled by the facility (1200 code) that would display the mode C altitude data.
Then there are primary returns with no altitude data and no transponder that just appear as a target (plot).
Likewise at PAO I get coverage in the pattern and at least a few hundred feet below that.
In reply to:
Is this something that is documented somewhere? I’m puzzled because the FAA does have 3-D radars that would give both range and height.
I have never heard of any altitude appear on a scope other than Mode C altitude from an airplane’s transponder, which of course won’t be there on a primary target.
In reply to:
I have never heard of any altitude appear on a scope other than Mode C altitude from an airplane’s transponder, which of course won’t be there on a primary target.
Gordon,
In the case of 3-D radars, the altitude data is available (without a reinforced beacon) in the radar message. It is not as accurate as the mode C data, but it is available. It has been a while since I worked on the software that captures this data. When I get into work tomorrow, I’ll check on it. I can’t remember how this is displayed to the controller (I believe the altitude is tagged so the controller can tell the difference).
I just wanted to know if you had seen this documented somewhere as a limitation?
In reply to:
In the case of 3-D radars, the altitude data is available (without a reinforced beacon) in the radar message.
Are these units in use by civilian ARTCCs (as opposed to joint-use)? Do you know how accurate the altitude data is? I would imagine it is somewhat dependent on the distance from the antenna.
Gordon,
I checked with our radar experts who build many of the Air Route Surveillance Radar - Model 4s (ARSR-4s). This is a long-range, three-dimensional (3D), rotating phased array, primary radar system with coverage of 250 nm. It is part of the Joint Surveillance System (JSS) used in conjunction with ARSR-3 coverage as part of the nationwide air defense command surveillance network. In addition to functions particular to the military, the ARSR-4 performs the same basic functions of the ARSR-3, by providing primary long-range surveillance data, including slant range and azimuth data for en route operation. Generally, the long range radars are accurate to within about 500 ft in the vertical. Much of this depends on how recently the radar beams were aligned and how well the radar is maintained.
In reply to:
Generally, the long range radars are accurate to within about 500 ft in the vertical.
So I assume that they would not use it for separation even if it were available for display on the scope. I don’t think it is. These aren’t in use by garden variety ARTCC’s, are they?
In reply to:
So I assume that they would not use it for separation even if it were available for display on the scope. I don’t think it is. These aren’t in use by garden variety ARTCC’s, are they?
Many “kinds of altitudes” are utilized to control and separate air traffic. This includes the primary radar data, pilot reported altitude and mode C altitude. I don’t know specifically how controllers make use of this data. I wanted to chat with one of our ATC guys, but didn’t get a chance. However, it wouldn’t be any different than any unverified altitude. If this is an aircraft under ATC control, they can check it with a pilot reported altitude.
Is this the kind of information lying behind a controller callout such as, “traffic 3 o’clock, altitude 4500 feet unverified” ??
In reply to:
Is this the kind of information lying behind a controller callout such as, “traffic 3 o’clock, altitude 4500 feet unverified” ??
Kevin,
I’m fairly sure that type of callout is associated with a VFR target, squawking 1200, mode C, that the controller is not talking with. In other words, he sees the 4500 ft mode C readout on his scope, but since he has not verified the altitude with the pilot, he can’t be 100% sure.
I would suspect that the type of primary altitude information Scott is referring to is too rough (500 ft or so, as he said) to be of that type of use to controllers.
Steve
In reply to:
Is this the kind of information lying behind a controller callout such as, “traffic 3 o’clock, altitude 4500 feet unverified” ??
That would be what you’d hear if the target is squawking a VFR code and has Mode C turned on (Alt). The target will show the Mode C altitude, but since the controller is not talking to that airplane s/he cannot verify that the Mode C is correct, thus the “unverified” qualifier. This is why whenever you call up on a new freq you always state your altitude, whether VFR or IFR. If you forget, the controller will always remind you, because s/he’s required to verify the Mode C for your airplane.
It is also important to note that ATC is required to provide for separation between all IFR aircraft and participating VFR aircraft. In both of those cases, they will have a “Verified” mode C altitude or a reported altitude by the aircraft.
In IMC, there should be no VFR aircraft. In Non-IMC, all aircraft are responsible to see and avoid.
In the ATC world, it is better to give less info than erroneous info, so by not acknowledging any altitude, they are being ‘safer.’
It’s the Government. What can I tell you. there is always a reason, but it doesn’t have to make any sense.
Marty
In reply to:
This is why whenever you call up on a new freq you always state your altitude, whether VFR or IFR. If you forget, the controller will always remind you, because s/he’s required to verify the Mode C for your airplane.
Gordon,
I could be wrong but I believe you only need to do this once per facility.
In other words, if (for example), Baltimore Approach on 128.7 hands you off to Baltimore Approach on 125.52, you don’t have to state your altitude. But if Baltimore Approach hands you off to Washington Center, then you would have to state your altitude.
I normally say my altitude every time anyway, since it’s just easier. But on those extremely busy days where it takes a couple minutes just for enough air time to check in, I’ll sometimes abbreviate it and leave out my altitude, if I’m not contacting a new facility.
Steve
Steve, I think you don’t have to report altitude when the controller says, “Change to my frequency…” When you get handed off to another person, even in the same facility, you still should.
Either way, your practice is what I do, and unless they say the above, I give them the altitude.
BTW, I also try to ask for a Mode C check at least once a flight to ensure that I am transmitting accurate info.
Marty
Steve,
You definitely should provide your altitude when switching facilities (however, ATC can communicate between facilities to verify your altitude as well). When contacting the same facility I also provide my altitude, such as “Baltimore approach, Arrow 8392V, level 3,500.” Otherwise I’m met with, “Ah, Arrow 8392V, say request.” They think I’m a new VFR aircraft requesting advisories. When I’m with a student pilot, the student often omits the altitude and this happens all of the time.
From FAAO 7110.65:
5-2-17. VALIDATION OF MODE C READOUT
Ensure that Mode C altitude readouts are valid after accepting an interfacility handoff, initial track start, track start from coast/suspend tabular list, missing, or unreasonable Mode C readouts.
a. Consider an altitude readout valid when:
-
It varies less than 300 feet from the pilot reported altitude.
-
…not pertinent…
-
You have correlated the altitude information in your data block with the validated information in a data block generated in another facility (by verbally coordinating with the other controller) and your readout is exactly the same as the readout in the other data block.
b. When unable to validate the readout, do not use the Mode C altitude information for separation.