Basic Gas Turbine theory.
I probably should know, but while searching the Commodore 64 hard drive installed in my cranium I failed to recall why there is a 2nd peak during the start of a turbine engine.
The allison C30 (god bless its oil discharging soul...) has the 2nd peak at 34% N1.
Its been a while since the BGT exam so whats the reason?
Cheers!