Hi Spad:
Uh, you might have an out-of-date book, or perhaps a Series 100 or 200 book.
For the Series 300, in principle, the engines are started in feather. The exception to that rule is when the air is considerably denser than normal, which is defined as temperatures below 50° F (10°C) and pressure altitudes less than 3,000 feet. When those two conditions exist, the propeller levers should be moved to the MAX RPM (full forward) position prior to engine start.
When the air is quite dense, the engine may hang up on 'minimum flow' fuel (thus yielding about 48% Ng) after start if it is started with the propellers in feather. This is undesirable; the goal is to always have the engine idling on 'governing' fuel (the FCU being the fuel governor) at the end of the start if governing fuel is > minimum flow. The governor is rigged to idle at about 51 to 52% Ng at ISA. At high elevations, the engine will idle faster than that, but when that happens, it is idling on minimum flow, not the governor.
There is no published limitation for maximum torque when the propellers are in feather. I have seen references in some training publications that suggest that 17 PSI torque should not be exceeded (on the -27 engine) when the propeller is in feather, but I have been unable to substantiate these references with PWC, the engine manufacturer. Certainly there is no harm in increasing gas generator speed sufficient to bring a generator on line (idle +15%) with the propeller in feather. I cannot imagine any circumstance that would require Ng greater than that when the propeller is feathered.
Michael (the guy who writes the book...
)