Vertical seperation LFPG area

[EMB170]

Today we were inbound to Le Bourget RWY 27 and cleared down to 2000' . Established on the localizer 20 miles out we had traffic 500' below and we were in IMC.
Checking with ATC, they told us that aircraft was VFR traffic and 500' seperation would be normal at this area.

Of course a few seconds later we had an RA , monitor vertical speed .

We reported to ATC , who were still insisting that 500' would be standard for VFR traffic at that area.

One thing is for sure that VFR traffic was for sure not in VFR conditions .

My question is, is 500' vertical seperation really normal ???

Thanks very much .

[flightsearch]

Wich Airspace Class?

[BrATCO]

EMB170,
As far as I remember, 20 NM East of LFPB, you were in a Class A (Paris TMA), in contact with CDG APP.

500' below, the VFR was in class G (1500' QNH and below). The VFR was either in contact with LFPE which controls the RWY pattern on your left, or in contact with LFPT to the NE or LFPM to the S (radar information in class G given by a full qualified APP controller). Or he was in contact with LFPP (air/air information, on your right) to enter the runway pattern, due to descend.

VFR pilots in this area are very-very aware (now) that they must contact an radar APP controller, even though in class G.
I mentionned LFPT and LFPM. The guys there know their job in making VFR fly straight, even in G airspace.


One thing is for sure that VFR traffic was for sure not in VFR conditions
VMC in class G, close to the ground, are sometimes... special.

Hope this helps.

[Spitoon]

Don't know anything about LFPG personally but a quick look at the AIP suggests that the airspace in the area is class A, perhaps with base of 1500ft - although the only chart I could find is not that clear.

Obviously there can be no VFR flights in class a airspace which lends support to the idea that the base was 1500ft. If this is the case it would make sense that the lowest level assigned by ATC is 2000ft thereby providing a minimum of 500ft vertical distance (note, not separation) from any traffic outside CAS.

TCAS does not consider the class of airspace and so a VFR flight operating quite legitimately outside CAS could generate a TA or RA for an aircraft operating on a clearance issued in accordance all the rules inside CAS.

Of course, if my assumption about the airspace structure is wrong, the situation may be completely different.

HTH



(Edited to say that BrATCO beat me to it - and will have a far better understanding of the environment.

[BrATCO]

Spitoon

If this is the case it would make sense that the lowest level assigned by ATC is 2000ft thereby providing a minimum of 500ft vertical distance (note, not separation) from any traffic outside CAS.

It is the case, but the problem was dealt with the other way round.
2000' is in fact the Minimum Radar Safety Altitude. Thus, as IFR flights can't descend lower before the glide, VFR flights benefit a corridor below 1500' all around the Paris CTR, below the TMA.
15 - 20 years ago, they also had a possibility to transit through Le Bourget CTR, but this was removed due to the proximity of CDG : 2 or 3 NM (ish) from southern RWY at the closest.

So, to sum up :
- CDG Northern RWY : 4000' Class A
- CDG Southern RWY : 3000' Class A
- Le Bourget : 2000' Class A
- VFRs : below 1500' Class G, heavily informed.

I stand to be corrected as I left the region a few years ago.

[makosa]

Exactly, base of Class A airspace is 1500 ft QNH, 2000 ft is the lowest level for an IFR flight (intercept alt. for LFPB), below 1500 ft QNH it's Class G airspace.
So a VFR flight at 1500' ? He's in Class G airspace and does NOT have to be in contact with anyone.

So 500' IFR/VFR separation is normal. (same that you would find on an airway in lower airspace)

[chevvron]

I believe the TCAS 'envelope' is 600ft in the vertical plane, thus anything legally 500ft below transmitting mode C will give a TA. Worse still, if his encoder is slightly out, he could legally be transmitting a Mode C readout only 400ft below you, the tolerance being +/- 200ft, albeit he is actually 500ft or more below.
In the UK, where class A airspace has a notified base of 1500ft, if you fly at 1500ft you are deemed to be infringing thus most pilots would fly at 1400ft to avoid it and hence would be 600ft below ergo no TA unless there was a vertical speed element.

[EMB170]

all i can say is , we had had an RA ! he was for sure not in VMC conditions !!!!

[fisbangwollop]

Dont know the airspace but if he was in class G airspace below you in class A he is not required to talk to anyone and he could also be operating in IMC!! :cool:

[BrATCO]

fisbangwollop,
I like this idea ! :ok:

Unfortunately, regarding French rules, if the traffic was IFR (VMC or IMC) he couldn't cruise below 3000' QNH in class G. As class A begins at 1500', he would have had to ask for an IFR clearance before take-off, the controller would have known him and EMB170 wouldn't have been cleared 2000', first available (potentially already assigned) level for the potentially climbing IFR.

So I think this was a VFR.
Below 3000' QNH, VMC in non-controlled airspace are (roughly) : out of the clouds, in sight of the ground, under pilot's renponsability (controllers are not on-board to check).

I really like this idea of an IFR cruising IMC at FL12 with no contact, no FPL... :)

Another possibility would be a Mirage or a C160 cruising in this OAT corridor, en route to/from LFPC, the airbase few miles to the north... But they would have been lower then...


PS : I'd like to edit my first post in this thread :
VFR pilots in this area are very-very aware (now) that they must contact
I meant : "they are kindly informed that it is highly recommanded to keep active 2-way communications with any suitable ATS in this area."