Radar information - what's the altitude?
Join Date: Mar 2006
Location: Montréal, Canada
Posts: 75
Likes: 0
Received 0 Likes
on
0 Posts
... and now back to the topic...
Riverboat,
I use this practice where I work simply to avoid an uncommanded climb. You shouldn't have to do math from it though. If we report traffic that's 1,000 feet above you, then that's all you really have to know. You don't even have to know your own altitude even; you know the traffic is a thousand feet above you.
I use it too when someone is climbing to 7,000 and another is level at 8,000. I'll say to the one that's level: "Traffic will stop a thousand feet below", especially, in an approach environment, if the pilot might be expecting descent soon.
It would be unwise to use it when the traffic is inconflict and at an incertain altitude or if it is unclear whether it is climbing, or level. So if I see traffic ahead of you at 2,700 and you're level at 2,500, I'll say the altitude since that traffic might be on the way up or down or level and either way still a conflict since he's within IFR and VFR sep minima.
I always found that "He's at the same altitude as you headed straight for you" works better than giving the altitude, position and direction and letting you figure it out a second later.
This being said, you won't hear me give out traffic info unless you cross the pond...
Cheers,
SAO
To get back to the main thread. It was indeed changed because there had been incidents where aircraft under RAS had climbed or descended to the level reported. There is nothin wrong with providing a direct readout but, sometimes it is easier to say indicating 500' below. If you are military you are also taught that indicating means unverified and at means it is verfied so no need to add those phrases on the end of the transmission.
Also, setting the QNH is all well and good for terminal issues but if you are providing a radar service across a number of ASRs then 1013 is better.
Also, setting the QNH is all well and good for terminal issues but if you are providing a radar service across a number of ASRs then 1013 is better.
Join Date: Jan 2003
Location: S coast
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
I believe we are dealing with 2 phrases here for 2 situations:
1) KNOWN trafic which is said to 1000 feet above, 1500 feet below, etc, and
2) UNKNOWN traffic which should be said to be above/below/slightly above, etc..
MATS Pt 1 E (attach) refers
Tori
1) KNOWN trafic which is said to 1000 feet above, 1500 feet below, etc, and
2) UNKNOWN traffic which should be said to be above/below/slightly above, etc..
MATS Pt 1 E (attach) refers
Tori
You need to be careful to differentiate between procedures and available standard phrases.
UK MATS Part 1:
15 Traffic Information
15.1 Traffic information shall include the following:
• Bearing from the aircraft in terms of the 12 hour clock (when the aircraft is turning,direction of the unknown aircraft by compass points);
• Distance from the aircraft in miles;
• Direction in which the unknown aircraft is proceeding, e.g. 'traffic is opposite direction/crossing left to right', etc.
• Height information when available, this may include the unverified mode C of unknown aircraft.
15.2 Under some circumstances, controllers may consider it prudent to inform a pilot of other traffic which is separated from his aircraft. In such cases, to prevent any possible confusion, no reference should be made to the actual level of the other aircraft. If necessary, the pilot should be informed that the other aircraft is '(number) thousand feet above/below'.
UK MATS Part 1:
15 Traffic Information
15.1 Traffic information shall include the following:
• Bearing from the aircraft in terms of the 12 hour clock (when the aircraft is turning,direction of the unknown aircraft by compass points);
• Distance from the aircraft in miles;
• Direction in which the unknown aircraft is proceeding, e.g. 'traffic is opposite direction/crossing left to right', etc.
• Height information when available, this may include the unverified mode C of unknown aircraft.
15.2 Under some circumstances, controllers may consider it prudent to inform a pilot of other traffic which is separated from his aircraft. In such cases, to prevent any possible confusion, no reference should be made to the actual level of the other aircraft. If necessary, the pilot should be informed that the other aircraft is '(number) thousand feet above/below'.
Join Date: Jan 2003
Location: S coast
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
Thanks 2sheds, point taken, but the phrases, which you acknowledge as Standard Phrases, in the part E should be used if applicable, and you're using the available unverified mode C information to make your assessment of "indicating above, below" etc.
Of course we could always have a clear ruling from SRG!
Tori
Of course we could always have a clear ruling from SRG!
Tori
Join Date: Jun 2007
Location: Earth
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
Transponder outputs altitude report in 100ft (or 25ft if Mode S and capable) based upon 1013.25 mB pressure. Setting QNH on altimeter, etc, will have no effect on the transponder. This will lead to transponder reported height being different to altimeter report based on QNH. Some of the more advanced radar processing and display systems will QNH convert the transponder altitude report when below transition altitude to give aircraft altitude in feet based on QNH rather than a Flight Level on 1013.25mB
What will be consistant is the difference in height between targets using the same 1013.23 mB pressure reference. So it is probably more correct to state differences in height of local traffic rather than their actual height AMSL that the radar display shows.
oh, and before someone makes a smartarse comment about transponder altitude reports being called Mode C, Mode S equipped aircraft (88%+ of all transponder equipped aircraft) do not use Mode C when responding in Mode S - hence I didn't call it Mode C.
I'll get off my Mode S soapbox now.........
What will be consistant is the difference in height between targets using the same 1013.23 mB pressure reference. So it is probably more correct to state differences in height of local traffic rather than their actual height AMSL that the radar display shows.
oh, and before someone makes a smartarse comment about transponder altitude reports being called Mode C, Mode S equipped aircraft (88%+ of all transponder equipped aircraft) do not use Mode C when responding in Mode S - hence I didn't call it Mode C.
I'll get off my Mode S soapbox now.........
If the Mode C information is unverified, one cannot state that a particular aircraft is actually above or below. I think it is possible to read too much into the application of standard phrases - I suspect that this particular one is a leftover from the days of heightfinders!
ShyTorque, I may have missed the point of your response, but ATC and the radar have no way of knowing what pressure setting the unverified 2400 traffic is on. It would make sense that it is either local QNH, RPS or 1013, but who knows.
I don't like the indicating above/below, and will always say "indicating xxxx unverified."
Widger: I read
as '...providing a radar service for a number of ARS*S....', but that is probably more to do with the day I have had!
I don't like the indicating above/below, and will always say "indicating xxxx unverified."
Widger: I read
.......but if you are providing a radar service across a number of ASRs then 1013 is better
Join Date: Nov 2006
Location: .
Posts: 284
Likes: 0
Received 0 Likes
on
0 Posts
It was indeed changed because there had been incidents where aircraft under RAS had climbed or descended to the level reported.
Avoid imitations
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 14,576
Received 433 Likes
on
228 Posts
RAC/OPS,
I'm not sure which response you mean as you didn't make that clear.
I think I agree with your statement - but his encoder and mine work from the same datum, 1013.2, irrespective of the subscale setting in either cockpit.
Sorry, it's been a hard week for me too!
I'm not sure which response you mean as you didn't make that clear.
I think I agree with your statement - but his encoder and mine work from the same datum, 1013.2, irrespective of the subscale setting in either cockpit.
Sorry, it's been a hard week for me too!
Join Date: Oct 2004
Location: South of UK
Posts: 273
Likes: 0
Received 0 Likes
on
0 Posts
From what I've read somewhere, the transponder doesn't pass an actual level, it passes the current pressure it reads at it's level, whatever it may be. Maybe I've misunderstood something, feel free to correct me.
The transponder will relate a measured pressure to an altitude based on a fixed "QNH" of 1013.2mB. It will then provide a message in either a Mode C reply or Mode S DF=5 reply to a Secondary Radar with an altitude measured in feet to 25 or 100ft resolution depending on aircraft capability.
"...to an altitude based on a fixed "QNH" of 1013.2mB..."
"...to the pressure datum 1013.2 mb..." would be a better way of expressing it. With respect, the reference to "altitude" and "QNH", albeit in quotes, only serves to confuse!
"...to the pressure datum 1013.2 mb..." would be a better way of expressing it. With respect, the reference to "altitude" and "QNH", albeit in quotes, only serves to confuse!
Join Date: Jan 2003
Location: S coast
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
2sheds you're putting words into my mouth. The book says "indicating above/below/ etc." for the same reason you say indicating XXXXft in your traffic information.
As nicevectoring points out, the altimeter encoder encodes and transponds based on 1013.2, and any local conversions are done on your radar based on your local settings and Transition Altitude, so irrespective of the pilot's setting, the readings will be equivalent for all contacts.
This shows when a pilot hasn't reset his sub-scale, and is flying (typically) an altitude with (typically) 1013 set and is a few hundred feet adrift from his stated level. A technical bonus which I have used a few times to some pilots' advantage to prevent their further embarrassment
Also to re-state Widger's point, this phraseology doesn't date from heightfinding equipment, but from the mid-air at (Delhi??) when the quoted level was taken as a level to descend to and - surprise, surprise - they met. The ICAO guidance thereafter was to refer to relative levels (known traffic) or no level at all (unknown traffic).
Tori
As nicevectoring points out, the altimeter encoder encodes and transponds based on 1013.2, and any local conversions are done on your radar based on your local settings and Transition Altitude, so irrespective of the pilot's setting, the readings will be equivalent for all contacts.
This shows when a pilot hasn't reset his sub-scale, and is flying (typically) an altitude with (typically) 1013 set and is a few hundred feet adrift from his stated level. A technical bonus which I have used a few times to some pilots' advantage to prevent their further embarrassment
Also to re-state Widger's point, this phraseology doesn't date from heightfinding equipment, but from the mid-air at (Delhi??) when the quoted level was taken as a level to descend to and - surprise, surprise - they met. The ICAO guidance thereafter was to refer to relative levels (known traffic) or no level at all (unknown traffic).
Tori
Join Date: Apr 2001
Location: Sometimes north, sometimes south
Posts: 1,809
Likes: 0
Received 4 Likes
on
1 Post
If you are military you are also taught that indicating means unverified and at means it is verfied
NS
Join Date: Dec 1999
Location: LHR/EGLL
Age: 45
Posts: 4,392
Likes: 0
Received 0 Likes
on
0 Posts
Verified means that the Mode C height information on the radar screen that the ATCO reads off is accurate, to within +/- 200 feet of what the pilot said his level was.
Unverified means that the height information has not been checked for accuracy.
Unverified means that the height information has not been checked for accuracy.
Join Date: Jan 2003
Location: S coast
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
radarspod
basically - yes. Obviously unknown A/c squawking 7000 with mode C will by definition be unverified (also referred to as "indicating") because you're not talking to the pilot to effect verification!
tori
basically - yes. Obviously unknown A/c squawking 7000 with mode C will by definition be unverified (also referred to as "indicating") because you're not talking to the pilot to effect verification!
tori