From Graybeard:
Right, JW, and the required acceleration to get to the advisory climb rate is gentle. It should be barely noticeable to the SLF.
Not quite, the assumed response for initial RA (Climb, Descend etc) is 0.25g. Not exactly pull-the-wings-off stuff perhaps, but a lot more than people should experience in normal flight (a steady 30 deg banked turn is only 0.15g), the response to an enhanced RA, Increase Climb etc, is 0.35g. So the target vertical rate should be achieved in under 5 secs.
This really matters, if you look at the
Uberlingen accident report appendix 4, you will see that the DHL 757 got nowhere near these figures, it took nearer 13 secs to get to 1500 ft/min, but if it had done it right it would probably have missed the Tu 154, despite the latter's complete foul up of its RA. For a discussion on how to achieve the target acceleration accurately (a far from trivial question that has received too little attention) see
Eurocontrol ACAS Bulletin 12
A Eurocontrol study about 10 years ago found that at the time, none of the sample RAs they studied were flown correctly (roughly half were too slow, the rest too fast); I gather more recent work suggests the figure of correct responses is now....60%, still a long way to go.