'Positve Radar Control'

[bboy]

Hi,

In our ops manual, this is one of the requirements to descend below MSA. However I cannot find a definition or reference to it anywhere.

It seems quite a grey area in my company (Europe) when ATC send you to a waypoint and give you descent. Many will not go to the given cleared altitude unless above MSA or on a heading. Is this prudent and cautious or unnecessary? I dont know!! The way I understand positive radar control is that ATC are controlling your track and issuing descent based on their MVA's and knowing where you are going as they have cleared you to that point or you are on a star or other predicted route. Does it make a difference whether on a heading or not?

Whats the difference between positive radar control and radar vectors??


thanks in advance.

PS searched the topic but nothing found

[HEATHROW DIRECTOR]

Never heard of "positive radar control". Either you are or you are not.... why "positive"

[Loki]

Indeed....though some of my vectors could be a bit vague at times.

[galaxy flyer]

Could it be related to the old FAAism of "Positive Control" which meant what is now Class A airspace where everyone must be on a clearance?

GF

[blissbak]

maybe your manual has been written by a journalist :hmm:

[samotnik]

In a ICAO world, ATC shall not give you descent below MSA, unless you are under radar control and minimum radar vectoring altitude is lower than MSA.

"Positive radar control" - if you were informed that you are identified, or in radar contact, and never heard later on that 'radar service terminated', then you may assume that you are under radar control. Radar vectors can not be provided if you are not identified and under radar control.

[bboy]

[QUOTE]In a ICAO world, ATC shall not give you descent below MSA, unless you are under radar control and minimum radar vectoring altitude is lower than MSA.

Thats exactly what I think too. Is there a ICAO reference to that somewhere??

Do you have to be on a heading to be receiving 'radar vectors' ?? In my company there is a general belief that yo have to be on a heading, otherwise you are below MSA, tracking via your own NAV and therefore not sbject to terrain clearance by atc.

Cheers

[HEATHROW DIRECTOR]

<<Do you have to be on a heading to be receiving 'radar vectors' ?? >>

Think that through v-e-r-y s-l-o-w-l-y!!

[bboy]

ok, I phrased that incorrectly.... What Im looking to understand is that if you are not on a heading (vectors) and under radar control, are you receiving terrain clearance?? In lots of instances in Europe, one can be given direct to an IAF or IF and given descent below MSA. Are you responsible and required to maintain a profile above the MSA even though issued with descent clearance below, as all I can find from ICAO is that ATC are only responsible for terrain clearance when you are in receipt of vectors.

[bboy]

Think is what I was looking for...

PANS ATM (Doc 4444) 8.6.5.2 (also reflected in 4.10.3 Note 3).

When vectoring an IFR flight and when giving an IFR flight a direct routing which takes the aircraft off an ATS route, the controller shall issue clearances such that the prescribed obstacle clearance will exist at all times until the aircraft reaches a point where the pilot will resume own navigation.

[flyburg]

Whoaa bboy,

That is one of my pet pieves and I have discussed this many times.

It is my believe that the only time ATC is responsible for terrain clearance is when you ar being radar vectored! When on your own navigation or a direct to clnc has been issued you are responsible for terrain clearance ( obviously, when being radar vectored you still watch closely and question any rv if in doubt).

I would really like the opinion of an atc expert about this!

Many times when flying for a small outfit in spain, I would get a direct from madrid to bilboa and subsequently a descent clearance witch would place us under the grid mora for that sector, needless to say I would stay above the grid mora until established on an airway or approach procedure! Questioning the clearance was a futile excercise.

I believe, but this was many moons ago, that the US AIM specifically states that terrain clearance rests solely with the pilot unless radar vectored upon which it becomes a shared responsibility.

Again, I would really like an ATC experts opinion on this!

[blissbak]

Direct to is equal to vectoring in my world, and even if you're still flying the standard stuff I must pay attention to the radar monitoring.

[songbird29]

I know the term 'positive radar control' from my contacts with US controllers and the FAA.

IMHO 'Positive radar control' dates back from the time when ATC changed from the mere provision of information to radar based control, with controllers providing 'positive' instructions such as headings, climbs and descents.

The flying community, used to a much higher degree of freedom when ATC was limited to providing information, needed to be convinced that ATC directives should be adhered to. That is how the tautological term 'positive radar control' was colloquially introduced to reinforce the new status of the controller.

Taking the tautology for granted I have always liked the term as it very well reflects the work of the controller, who is not the passive provider of information but the pivotal player in aviation preventing collisions.

[CuitoCuanavale]

"Positive radar control" - archaic & obsolete. FAA (Possibly remnants of the old order) may still at times use it. Yup, even the FAA have moved on!

'flyburg', youre spot on! - Radar Control and left on FLt PLN'd Route/Path - crew responsible for terrain. Once taken off FLt PLN'd Route/Path..i/e; - receiving radar vectors - ATC responsible for terrain.

[Bergerie1]

To a certain extent it depends on where you are in the world. Twice in my flying career I was given clearances that had I followed them I would have bored holes in hills. Yes, when under radar control and being vectored for the approach, ATC have responsibility for terrain clearance. But I would still be very wary and check every cleared altitude and query any clearance that did not correspond to my own navigation (charts and/or ND). Only when you are postively estabilished on an instrument approach procedure should you descend below MSA/SSA. We all can make mistakes and it is good airmanship to check every clearance, however good ATC may be.

[ameet0121]

topic has become very intereting.

ICAO doc 4444 refers two words-1. Radar Service 2. Radar Vectors

In Radar service the acft is identified and monitered. ATC shall give help if pilot asks for it or for some other reasons. But clearly the acft flies with its own navigation and is resposible for terrain clearance even if it has been allowed to go from one point to other as requested by pilot.

During radar vectors the navigation of acft is been taken over by ATC and hence he is wholly resposible for all terrain clearance. This is one of the reason why before when acft is asked to fly direct to a point after being radar vectored he must be given his position with reference to a navaid or way point so that now pilot can navigate of his own and hence become resposible for terrain cleance.

Regarding MSA
MSA is valid within 25NM of Navaid and acft can desend to MSA on QNH. The MSA is decided by the IAP expert based on hight of highest obstruction within 30(25+5 buffer) nm+1000feet. There maybe many other obstruction lower than it near approach path. Hence radar controller is authorised to descend acft to MSA or MVA only and make acft establish on final approach track may it be ILS, VOR or visual approach. In no case he shall descend the acft below MSA or MVA.
The Acft shall descend below MSA once established on Final approach track or Intermediate segment. The FAT and segments are designed by IAP experts taking into consideration obstructions near approach path which radar controller may not be aware of. The acft shall strictly follow the FAT while descending below MSA on her own navigation if unable shall immediately go around.

I wonder if I am able to clear few queries. Apologies for a big writeup.