A typical TCAS II maneuver requires crew response to the initial RA within 5 seconds and G-forces of ± .25 G.This force is similar to that experienced when initiating an enroute climb or descent. Because of this G-force requirement, the response to the RA cannot be flown using the autopilot. The autopilot must be disconnected prior to responding to the RA.When the initial RA
is changed,the crew must respond within 2 1/2 seconds.
In the latter case:-
You are expected to initiate the change from <one maneuver> to <the opposite> maneuver within 2.5 seconds
using an acceleration of .35 Gs.
Source:
www.honeywelltcas.com/pdffiles/tcas2guide.pdf
Don't quite see what they mean about the G-force being the same as that required to initiate an enroute climb or descent as obviously we normally initiate those through the autopilot, but anyway the timeframes for response (and increased G requirement for RA reversal) are worthy of note eh?
Cheers