Phil:
"but the avoid region is only applicable for unaccelerated level flight"
Beg to differ - the top half above the knee is for that regime, below the knee is for the climb, where your hand is assumed to be on the collective.
Thanks for the amplification. The test pilot is allowed to respond much quicker on the collective at the knee of the curve and below. However, as far as I know, the test condition is still with power (collective pitch) for level flight, not climb. Since the delay required is almost instantaneous (0.3 second?), having the collective pitch higher (which means the blade drag is higher) than the test condition for establishment of the avoid area results in a quicker decay in rotor rpm for a climbing helicopter, meaning the knee is not, strictly speaking, valid, nor is the rest of the avoid area.
The difference in avoid area for level flight versus climb may be a small and even negligible for most helicopters but for one like the 214B, a single-engine helicopter with enough power, rotor, and tail rotor to hover out of ground effect at something like 11,000 feet, my understanding is that it did make a difference.