Are the brakes able to hold the aircraft completely stationery at 70% for 30 seconds?
- yes, unless the runway is completely covered in ice, in which case skill is required and one engine at a time can help. No need for an intermediate 40% since uneven spool-up will not be a problem. I should add that it is always a good idea to let ATC know also that you will be 'sitting on the potty' for longer than usual.
Denti - that is amazing - can you give me an example - OAT/Pressure Altitude/Assumed temp/Engine fit? You'll have SSG snapping at your heels with 75% N1.