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I believe vertical distance is more accurate because it is using the flight level broadcast in the mode C (or equivalent mode S) transmission.
Distance is fairly accurate as it uses properties in the signal (that doppler shift thing presumably). However direction is much harder to detect. For an analysis, see http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA293670 (I don't know how directionality is calculated). Most of the time, the error is around 4deg but can be as much as 30deg. The error is installation specific (as the directionality is effected by the shape of the aircraft the detection system is attached to). In the link above, there was very poor detection around the 180 deg bearing due to interference from the aircraft's tail. Perhaps thats why PCAS units only give you a basic 45deg compass point rather than a bearing? Depending where in your aircraft you put it will depend on its accuracy. However in saying that, I still can't see what the problem is with saying that someone is 5 miles behind you when the airwaves are fairly quiet, so long as everyone knows how big a pinch of salt to take that information with. Of course - PCAS is only useful if someone else is actively pinging the mode S transponders in the area (a TCAS unit or an SSR) so you can listen in, and the other aircraft have a working mode S transponder in the first place. |
However in saying that, I still can't see what the problem is with saying that someone is 5 miles behind you when the airwaves are fairly quiet, so long as everyone knows how big a pinch of salt to take that information with. "Visual with traffic" has a defined meaning and can change the way that people can operate. |
If you are asked to say your current position to an information service before you reach your next reporting point, the information is going to be something like "3 miles north of X town, 1300 ft on QNH 995 HPa". That is enough information to provide basic situational awareness to other aircraft, giving them a direction and height to give the Mk1 eyeball a direction to look in. The information provided by PCAS (or TCAS) is as accurate, providing a basic help to situational awareness.
Certainly you don't know whether thats the correct aircraft, and the direction may well be off by 30deg, but it gives you a starting point for the MK1 eyeball. That is useful information. Why not share it? |
Because it is meaningless crap and leads to less educated pilots thinking they have some form of seperation when they don't.
It also means those of us that are going to ignore such meanless crap have to listen to it before deciding its meaningless crap. Then muttering under our breaths "whoopty do" Its in the same league as "your on guard" when folk are doing practise pans. And similar to 500's experence all the TCAS units I have used give way more errors than 30 degs especially with none mode S contacts. The contacts jump from left to right sides on the screen and also forwards and backwards. The slower the traffic the more error there seems to be calculating what it is doing. More to the fact you have been given traffic which you think you have on your screen you declare it. That traffic thinks everything is fine. Actually unless that traffic has been asked you don't have a clue if it has its transponder turned on, your contact could very well be something else. That none transpondered aircraft could then change level with out saying anything and your still looking for that other traffic which is actually on another frequency. |
Originally Posted by piperboy84
(Post 7262837)
MJ,
For sure nothing replaces a visual, and i was somewhat skeptical about the whole TCAS concept as i initially thought it may dilute my visual scans or make me more reliant on the machine as opposed to looking. However in practice its quite the opposite, it really is a net addition to the visual scan and helps target/focus the scan, another thing it is really got for is military jets, not for avoiding them as the closing rate is so quick but merely as a heads up they are coming and so it does not scare the !!!! out of me when they swoosh past (which happens a lot around my home strip) and they are easily identifiable as military on the screen due to the closing rate. Since i started using it ( if i remember correctly i paid about £400 for it) there has been many times when i have been cruising along and it alerts me to traffic in the area i was just looking at, upon refocusing i have been able to pick them out. The SO controller may have ignored the comment but the other traffic immediately acknowledged my call via the controller which gave me a level of comfort. In the particular instance i mentioned the TCAS was really helpful as i was level at 1200 there was a scattered layer between 1700 to 2000 and the other traffic was showing at approximately 2300 to 2600 so a visual may not have been possible. what model is it the XRX? |
Sorry to resurrect this thread, but used SI for the second time ever today and true to form they were great and the service was first rate. A couple of exchanges even gave me a chuckle. Checked in with them over Loch Lomond on my way back from Oban to Forfar and after initial contact the controller asked me to restate my equipment type to which I replied again “M7” there was a slight delay then she advised another aircraft that a “M7” was nearby, he acknowledged this but added that he would need to Google what a M7 was, to which the controller replied that is exactly what she had just done! Further along I got a traffic advisory, I responded that “I did not have a visual but did have them on the screen at my 5 o’clock and 3 miles”. Now I have been dying to say this ever since I bought my handy dandy used PCAS of ebay and I finally got the chance today (it’s the small things in life that make my sad old arse happy !!) Keep up the great work SI |
I was training our new femail FISO 2 s |
Fisbang,
Please thank your female associate for her help on Monday for phoning on my behalf when I should have known better that Fife is shut Mon Tues. My apologies for wasting her time. |
Fisbang, Please thank your female associate for her help on Monday for phoning on my behalf when I should have known better that Fife is shut Mon Tues. My apologies for wasting her time. |
Much apreciated. One day I'll do a D&D practice, I have never called them even during training. Are they still looking for the practice?
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Liam
what model is it the XRX? |
MJ
all the TCAS units I have used give way more errors than 30 degs e.g. if i am on a 090 compass heading and the PCAS says i am on a 030 with traffic at to my left rear quadrant, i am gonna guestimate its at my left front quadrant between 360 and 90 |
Oh gone on then you can make your RT call but just make it factually correct.
"Roger, I have an unidentified contact on my unapproved TCAS unit which may or maybe not be the traffic your on about G-xy" In the open FIR in a none Radar enviroment you haven't a clue whats out there. And have no way of knowing what you are picking up on your box of tricks. Or more to the point what your not picking up. |
MJ
Oh gone on then you can make your RT call but just make it factually correct But the one of the reasons for having is not for making RT calls based on what its showing (or not showing), but for the 50/50 chance of picking up traffic coming up my ass that I have a 100% certainty of not seeing |
Crash one Much apreciated. One day I'll do a D&D practice, I have never called them even during training. Are they still looking for the practice? |
There hasn't been any rear mounting of aircraft in the accident reports and if you are in visual conditions its up to the other pilot to see and avoid. You seeing them on your box of tricks doesn't add anything to the situation. What you going to do steer away based on your box of tricks?
You have no clue at all what is really around you in a none radar enviroment. But really your call means nothing. It spreads miss-information more than anything else. It may sound to you that its cool but actually makes you sound like a clueless pillock. And GA aircraft up north please give scottish info a shout if you fancy a DnD event. Otherwise they start asking commercial aircraft to play there games and you feel a right tw@t at FL180 calling a practise pan on 121.5 unsure of your position. |
Right MJ lets put your money where your mouth is !
I see your in Aberdeen, why don’t I pick you up in the Maule and we will fly around Aberdeen and Angus for an hour and I will bet you lunch that my “box o’ tricks” alerts and accurately locates more traffic quicker than you can visually. |
Nah mate way way east.
4000 hours working with TCAS and know the limits 2000 hours of which is in class G. If it tells you to do something, do it and ask questions later. Apart from that don't do anything. And know that knowbody gives a toss what I can see on it. You are in class G speaking to a none radar information officer. You have zero clue that the contact is the one they are talking about. You have zero clue that the one they are talking about is even squawking, you have zero clue that the one you are picking up is even working that service. Yet you make a pish RT call that you have them on a box of tricks. My TCAS unit is a honeywell $65k installation and it can't do what you think your unapproved ebay special can do. |
Mad Jock......surely anything that is going to assist both your own lookout and any info I as a FISO can tell you about must be a bonus.??.......I think your just getting grumpy being away from Scotland for too long.....about time you were back in that Cub in minus 16 freezing ya knackers off.......anyway whilst your away your missing the delightfull tones of "Ugly Betty" ....:cool::cool::cool:
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Yes it can be used to give a hint of a direction to look out for a visual contact of something who knows if its the one you have passed information on.
I have zero problem with people having such units and would encourage people to get one if they can afford it. Although I must admit I don't have a clue about these unapproved units but they seem to get the thumbs up on here. Its the RT call giving meaningless information that the aircraft has a contact on that unit. Notice I say "a contact" you have no way of knowing that the contact is the one thats being talked about. Its a dirty habit of pilots giving the call, and I freely admit that the commercial pilots are just as guilty as private. With anyluck CAP 413 will get addition on the subject that will put all the flight deck discussions to an end. Most training deptments in Europe are pretty hot on stamping it out these days. |
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