Target torque is the minimum power that should be available from an engine (at the 2.5 minute OEI rating) that has passed a power assurance check.
It is a factor of density altitude.
The relevance of it depends on how you are operating.
For example, if you are correctly loaded (and rigged) as per the Category A supplement the target torque should be sufficient to enable you to:
- Land back on the take-off area if the engine fails before TDP
- Continue the take-off if the engine fails after TDP
- Land at the intended landing area if the engine fails after LDP
- Fly away if the engine fails before LDP
(if flown in accordance with the relevant profiles).
Similarly, Class D external load operations make use of the target torque figure in establishing whether you can maintain an OEI hover.