Yep, the Twin Otter on Floats (Straight) can carry about 15 people with luggage and proceed to fly for about an hour and a bit and land with reserves. On Amphibs it carries about 10 to 12 people with bags and can fly around for about 30 to 40 minutes and land with reserves. It’s a huge penalty with Amphibs, especially if you can’t have an up-gross weight increase (13’000 to 14’000 pounds) which would make this mod worthwhile.
Having a aircraft built as an Amphib, with mostly composite structures and higher cruise speed with these engines makes a strong selling point in my view.
The PT6-27 or 34’s are thirsty (SGR) when strapped to a stoll airframe that was made in the 60’s and then rebuild circa 2010. Looking at the numbers the Cessna Caravan would be the winner here hands down except that it’s not a stoll airframe (Yet).
Given the comment about it being better for big water operations is quiet interesting and I hope the trials prove Dornier right. The deep Keels on the Wipline Floats offer a distinct advantage to date for this sort of operation though. Nobody would want to put 6 million dollars worth of aircraft through this sort of punishment on a regular basis if they had any sense. Maybe a 2 million dollar aircraft but 6 million!