On Mon, 01 May 2006 01:22:53 GMT, john smith wrote in
::

I never saw traffic that ATC called out to me that passed within two
miles and 1000 feet vertical separation.

I agree. It's difficult to spot conflicting air traffic even when
it's only a mile or two away. No doubt, that's the reasoning behind
the FAA's 250 knot speed limit below 10,000'.

As Mr. Macklin indicates:

Remember, ATC calls traffic in relation to your track, not
heading, so if they say 2 O'clock it can be anywhere to your
right front.

There is another insidious inaccuracy in ATC's traffic advisory
information. Termed 'latency' it is caused by the radar antenna's
rotation rate. Targets are updated on the 'scope' once every six
seconds, so the baring provided by ATC is not real-time, but
historical by up to six seconds. (This rate may vary by facility.)

If one assumes a worst case scenario of 250 knot traffic, six seconds
works out to 4,167'/second, or 25,000' (greater than 4 nautical
miles).

Additionally, radar information is remotely relayed to TRACONs, and
then processed by ATC computers. Surely this induces additional
latency, but I have no information on the magnitude of its
significance.

So, with all this in mind, it helps to look along the flight path of
the traffic (corrected for wind) up to 4 NM out ahead of where ATC
reported it.

If you still don't spot the traffic, request a vector from ATC.

And what ever you do, NEVER rely on ATC to keep you separated in VMC;
separation in VMC is ALWAYS airmens' responsibility even if you're on
an IFR flight plan.

As a wise, old airman once opined:

For instance, a pilot who has no fear of a mid-air is an idiot.
A pilot who flies without being constantly aware that he/she is
the main aspect of the mid-air avoidance equation is misguided.
--Dudley Henriques