Don't get me wrong. I admire the Cactus crew and said that they did a perfect job.
The decision to ditch was only the second best though.
The only error was that they accepted the HDG 220.
My decision at this very moment would have been: "negative, turning back to La Guardia immediatly." ATC would have needed to clear the way.
The thinking of Sully (“I couldn’t afford to be wrong.”) is absolutely correct. No human being can calculate in a split second if it is enough or not. But if you did your thinking ahead (we call it anticipated decisionmaking), you don't have to do the decision when you need it. The decision is: if you can make it out on two engines, you can always make it back without. Try it out in the sim. It always works!
My "small margin" was ment for the descent planning, not for the safety thinking. It means: plan that you have a little more altitude than you might want to have. But not too much, because if you are too high it's as dangerous as too low. If it still doesn't work: Turn away and make your ditching parallel to La Guardia.
I also don't think that the ditching-decision was more than a small safety margin, because history has shown that a succesful ditching was very unlikely. They only ditched because they had no other option at that later stage. We don't know how the chances where for ditching, probably far less than 50%.
Finally I repeat that I don't want to blame anyone and mostly not the US1539 crew. I just want to share my experience to others who might once need it. The ditching worked this time. Maybe next time not.
Dani