Nyal Williams wrote:
We are considering short-handed operations in the early
hours of the day and will have just a wing runner.
Is there a standardized phrase or a recommended best
phrase to radio the tow pilot to begin the launch?
We need something that is specific for the tow pilot,
short, unambiguous, and easily understood.

The winch site here uses "Full Power, Full Power" on the field telephone
to the winch.

The other phrases are "Take up slack, take up slack" and "Stop, stop,
stop, stop!"

There's also "Would you like a break?" We don't need to say that twice!

Please don't say 'Go, Go, Go!' It violates almost
all the requirements.

Ours might too but it works for us.

GC