Start

If you ever have to start without an N1 gauge (we had one that stuck in really cold weather), 15% is about the point at which the blades start turning just on airflow through the engine. 58% is about 25% rotor RPM.
External Start Battery Start
25 Secs On 40 Secs On
30 Secs Off 60 Secs Off
25 Secs On 40 Secs On
30 Secs Off 60 Secs Off
25 Secs On 40 Secs On
30 Mins Off 30 MIns Off

No  Item  Action 
1  Area and  Clear, switch anti-collision light on 
rotors 
2  TOT  Below 150 degs C 
3  Starter  Press 
button 
4  Throttle  Open at 15% N1 and when TOT is less than 150 degs C (that’s what the book says). 
Light-up should occur within 20 seconds. With C20 and C20R engines, you can start 

No Item  Action
earlier than 15%—in fact, between 12-15%, provided the N1 is accelerating in that
range, in these temperature ranges:
-18 12%
-18—+7 13%

> +7 15%

Expect a higher than normal TOT, but not usually above the top end of the yellow band.
Do not attempt to start below 12%, or if the N1 RPM peaks at any point inside the
above range, because the engine still relies on assistance from the battery until a very
late stage in the cycle, and you will be wasting power unnecessarily. If the engine is
going too slowly to provide proper cooling airflow, you will get a hot start and a melted
back end. A good start should take only 25 seconds from when fuel is introduced to
reaching Ground Idle.

Expect to see the temperature peak twice.
You now have to check for three other things at the same time:
5 TOT  Should stay in the yellow band, although when starting, you can enter the range 793-927 degs C for 10 secs. Not above 927. You can do this because the engine is not spinning fast enough to cause turbine blade creep.
6  Eng Oil Rising pressure
7 Blades  Turning by 25% N1. A corollary of this is that if you start with the blades tied down, as all of us have at some stage, as long as you stop before 25%, you can keep it a secret. Any later than that may cause a strain on the transmission and a scorch on the blade over the tail boom.