Originally Posted by
MightyGem
Would also depend on whether they are private or commercial aircraft. Commercial twin engine helicopters are required to do the backup take off, whereas private aircraft are not.
Not true. In simple terms commercial aircraft are required to fly the CAT A profiles as prescribed in the RFM.
Generally Airbus (and it's predecessors) have published a 'back-up' profile for ground level helipads, whereas Sikorsky favour a vertical profile. Elevated helipad operations, such as those found offshore, also use a vertical profile.