swh quite so but NONE of those are Transport Category certifications and all the TCDS's in the world aint gunna change that.
The history of SFAR 23 and SFAR 41 is that they were
never ever meant to be any more than attempts by the FAA, to provide in the
then absence of a suitable FAR25 type, a "bridge" for a capacity gap in the "commuter airline" market that was too small for the available Transport Category types and too big for the small Navajo/C402-4 types until something better (smaller FAR25 types) came along OR the market grew to meet them.
You can't change the absolute performance available from any particular type, you can only mandate modification of TO weights to invoke a higher EFATO climb gradient than the minimum required by the certification rules under which it was originally designed.
Or increase the grunt and airspeeds for the same wing area, which leads us up another garden path altogether.
It goes round in circles, to meet the 1-2-3-4 segment Transport Cat gradients required you apply a quasi one say 1.9% requirement after the aircraft is cleaned up. Claytons Cat.
NOTE: there is no V1/2 as described in FAR25 beyond tricking up the TO charts to manufacture something that looks and works like it or fly the certification figures for those requirements. Don't want to do that coz it wont make it in economic or available strip lengths.
To achieve that in your std Navajo/C402-4 the TO weight reduction will often reduce the available payload beyond economic. Bigger engines means more weight, higher speeds for the same wing, more money = need more seats.
So you take an airframe with stretch potential and grow it by grandfathering to a commuter and, thank God for the turbine, we can install enough grunt to overcome the energy equations. To do that costs heaps and you might as well go straight to FAR25 if you can afford it as a manufacturer. Some chose not to go anywhere near it.
But you still can't overcome the fact that the airframe was never designed in the first place to be Transport Category certified. You could maybe put enough grunt on it to maybe give you the performance but then you'd have to beef everything up and increase the size of the vertical stab blah blah blah it all turns to poop.
Any road, the FAA never saw it as anything but a short term fix, the underlying requirement being that RPT pax must fly on Transport Cat types.
To ensure that, they put a sunset clause on the use of SFAR 23 and 41, currently if I recall correctly 2010.
Further and I think it was beyond 1997/8 they embargoed addition/replacement of SFAR23/41 aircraft in
existing fleets with other than FAR25 types and prohibited startup airlines from using them at all.
The economics were so marginal that they even allowed no autopilot ops with an FO who also doubled as the FA requirement for safety briefs etc.
There's been a fire sale going on with these types since and they only have any value as freighters or as long as there are third world countries that allow their use in RPT.
Hence the migration of these types out of the US fleets to many third world countries like Australia, the regulators of which seem most happy with, if not totally oblivious of what it all means.
That last comment is unfair to those in CASA who understand of which I speak, but are powerless amongst the political and other chaos of the recent past to generate a rational and informed debate with the Australian traveller on how they feel about it.
Yes it was the way then, but the 60's and 70' airframes are waaaaaaaay behind us, even 90's airframes are past it in the integration of the modern flight control and nav systems required for operations in the present environment.
One can only guess at the SIDS and CPCP programme costs for continued operations by them.
As for really dumb wannabe airline captains role playing Capt Queeg with pretend airliners in the dark.
I seriously doubt that this fella could follow what we're talking about here. If he could then he wouldn't be.
