ferris / chesty:
That's a feature, not a bug. Introduced in version 7.0 together with a number of RVSM driven enhancements over the previous 6.4.
Yet this function is fact not RVSM related.
There are several triggers that will set off the TA and RA warnings, the most commonly observed would be time-to-CPA*. In a vertical plane if the CPA falls inside 700 feet of vertical separation, the RA is "armed". The alarm activates when the aircraft are 35 seconds from the CPA. ... and now ...
To reduce the number of false positives, commonly referred to as "nuisance" warning during 1000 ft level-off manoeuvres, the above described logic is somewhat modified:
For the aircraft in level flight, the start of RA indication by on-board system is delayed until 25 seconds to CPA. The idea is that if somebody's climb vector penetrates your proximity zone, both of you will get a TA at -45 seconds, but at -35 seconds the RA is generated only by the intruder's computer. The RA on your aircraft - as long as you maintain level - is delayed until 25 seconds to CPA. This gives a chance for the shirts to stay white, coffee to remain in cups and ceiling panels live unbroken.
The 10 seconds delay is designed to be enough
- a) for normal level-off geometry to take over (alt capture) when the CPA moves outside the "close proximity" zone
- b) for the crew to correctly follow REDUCE CLIMB** RA
Google should be capable of digging an Eurocontrol ACAS II / RVSM implementation presentations, one picture is really better than all of my description. Try "Project ACTOR".
I do not think 7.1 changed in this respect, but did really not check.
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*CPA: closest point of approach
**still speaking of v 7.0