Common point of confusion.
(a) Part 25 Types have a much higher level of redundancy that applies to Part 23 .. across the board.
(b) For Part 25, providing that
(i) the conditions pertaining on the day reasonably approximate the certification presumptions .. and
(ii) the crew performs similarly .. and
(iiI) the ops eng folk have done their work competently
it is reasonable to presume that the aircraft will survive to fly another day.
(c) For Part 23, there is a range of certification performance criteria.
However, for the typical heavier light twin operation (at limiting weights) an engine failure during takeoff presents extremely significant problems .. until the aircraft is cleaned up and at a speed at or very close to Vyse the probability that the aircraft will live to fly another day is moot. It all depends very heavily on local terrain and pilot competence once the aircraft is in a configuration at least (maybe ?) able to climb.
In the case of lighter light twins ... all bets are off ... the power of prayer is said to be an important part of the pilot's toolkit in such circumstances.
(d) It doesn't matter too much what we call things but, generally, V2 is specified for Part 25 and Vtoss or something similar for Part 23
(e) for BOTH Parts 23 and 25 Vtoss/V2 is concerned with getting a reasonable field performance (while maintaining a margin above stall and Vmc), not optimum OEI climb performance.
For BOTH, the OEI best climb gradient speed will be significantly higher than Vtoss/V2, even if overspeed V2s are scheduled. This reflects the nature of the climb characteristic which is a bit like an upturned tea cup sticking up a little bit above going down conditions ...
- Part 25 sticks up a modest amount
- heavier Part 23 sticks up a tiny amount
- lighter Part 23 should not be presumed to offer any OEI climb performance of use.
Commuter Category is an in-between mongrel (I use the term in a breeding sense) having a modest OEI climb capability.
For more details, one needs to refer to the TCDS for any given Type and then do a bunch of Sherlocking to amass the set of relevant Design Standard documentation.
Even then, one cannot guarantee that one will have the complete and correct set of data due to backroom agreements and deals between the OEM and Regulator as part of the development of the agreed frozen design standard for the project.
[Such should be reflected in the TCDS but getting the data is not always straightforward .. however the TCDS records that there was an issue with a particular requirement so one is alerted to the situation that the published rules probably have been varied to some extent.]