CS23 v CS25 take off perf
 

Hi

General question regarding cs23 commuter category (Kingair 200 for example) v cs25 aircraft. What, if any, are the main differences in issues surrounding take off performance, Acel stop/go calculations etc. I would guess it's virtually identical ? Or perhaps it's more a question of how you operate the aircraft eg AOC vs private.

Thanks.

You couldn't be further from the truth....

To simplify hugely:
CS25 - the aircraft should never be endangered by an engine failure during takeoff. At all points it can either stop safely or continue the takeoff.
CS23 - Until the aircraft is clean, there is no guarantee of being able to either stop or climb away in the event of an engine failure. CS23 multi engine aircraft must show some very minimal OEI clean performance, single engine obviously not!
There are CS23 aircraft that are capable of meeting the CS25 requirements, and the manufacturer may or may not give you the graphs to be able to operate it that way, but the underlying principle remains that a CS23 aircraft that loses an engine is quite likely to be in a runway overrun or forced landing situation. There are quite a few pilots flying aound who don't realise this, and think that having a second engine gives them the same safety level as a B777.

But if the aircraft is CS-23 Commuter category like the Jetstream 31 or B1900 then there are very few performance requirements in the take off, enroute and landing phase that are different from the CS-25 requirements.

Most (at least all I ever flew) 25 A/C just have 25 data published and must be operated to this standard, irrelevant to status of ops.
Quite a few 23 A/C (such as the whole 23 Citation-Series) have only 25 T/O data in their manuals. As you don´t have any other numbers, you need to operate as to satisfy these numbers.
You can operate a 23 with published 25 numbers to the 25 standard. Since you talk about the KingAir, Raisbeck offers 25 numbers for their retrofits. You´ll find out, that a KA is a bad 25 performer, relatively speaking.
For AOC ops on a 23 A/C with 23 numbers, you use all engine take off distance to 50ft and multiply that by 1,15 - a complete meaningless number. Good thing that engine failures do happen very seldom in turbine engines. I venture the guess, that exactly this nonsensical number was an argument used by the single engine turbine commercial ops crowd.

Exactly. This became evident when a B200 went in off the end of a local large secondary airport nearby. Much chatter here related to the awesome performance of it on one, some pointed out that it has 25 performance to boot.

But when you actually run the numbers with a accelerate stop and accelerate go suddenly it looked marginal.