Hi,Have been wondering about this for a while. I like flying vfr but have no real world experience so don't know about this:If I'm flying below some seriously controlled airspace which I don't want to enter how close can I fly to it before I risk an Airbus flying 10ft above my head?? If the vfr chart for example says CTR from 2500-fl180 does this mean I can fly at 2500ft or do people normally leave an accepted gap for safety?? What's the lowest that an airliner might be directed to in such airspace for example??ThanksPierre

I fly in the St. Louis area. At Parks, IIRC the shelf is 3500MSL where the airport is. I never climb above that until getting farther south or east, and give a margin of about 500' below while in that area. Some local airports are under this shelf and there are a lot of approach corridoors in the area. You don't want to get in their way.Usually they will not bring down an airliner below the glideslope intercept altitude. Depending on where you are, 2500' is pretty low for an airliner to intercept. On the other hand, smaller business jets and turboprops may well fly close to the bottom of the shelf in IFR while awaiting higher altitudes from a controller.

Hi,Thanks for the info, a 500ft gap for vfr sounds like the kinda thing I should be doing. Once saw a tv program about a guy who amazingly landed a light aircraft after a collision with a heavy jet which pretty much almost destroyed his tailplane. Just as amazingly the jet apparently carried on and completed its scheduled flight as normal!!.Thanks againPierre

At many controlled airports, the control zone starts at surface level and graduates upwards as the zone gets farther from the airport. On Terminal Charts, you can see the zone bands marked in blue or red with the altitude requirements marked as 40/SFC, meaning Surface to 4000, or 100/60 meaning 6000 to 10000. They also tell you which agency to contact and at what distance to get clearance for the zones.Larry S.

I fly under the Class Bravo in the Denver area regularly. In the vicinity of my airport the floor of the overlying Bravo is 8,000' (airport elevation is 5,670'). I would never get closer than 7,500', allowing for a full 500' buffer. I would prefer to be at 7,000', in fact. As this is less than 3,000' AGL, the rules governing east/west odd/even altitudes do not apply. However, at 7,000', one may have to ensure visual seperation of any IFR traffic- usually the tower at Jeffco clears traffic initially to 7,000' on an IFR departure.Bruce.

Well, if I had to keep 500' below the floor of some of the airspace around here, I'd not have enough clearance from the ground.Around NZCH, there is a lot of 2500' ceiling, and the rules for the overlying airspace say that aircraft are not cleared below 3000'. That means we can safely fly *at* 2500' and have clearance, especially since the controllers will be giving the traffic in the control zone reports about us even though we're outside the zone.Just another way that international practice varies. We have published VFR procedure approaches too, which I gather is quite rare elsewhere. Those usually have only 500' vertical clearance from IFR tracks inside the control zone too; we essentially never get cleared above 1500' inside the NZCH control zone, even though it extends to 3500', because they may need the space for IFR traffic.

Hi Andrew,I'm actually from Greymouth originally (not far from you). :) I never flew there though, have done all my flying here in the US.Bruce.

i routinely fly at 2400' under a 2500' class B floor and everybody else around here does, too. no "vertical separation" to maintain. 2500' means 2500'. just watch your transponder, not the altimeter, that's what "they" see.

Maybe I should ahve clarified that no specific vertical seperation is required. My 500' limit is a personal limit, not a mandated seperation from Class B.Bruce.