Hi bfisk
For driftdown we are talking about the same thing but with different words. When you loose one engine, you set the max continuous thrust and best glide speed (min drag) on the live engine, as consequence a negatif climb gradien (speed decreasing, lift as well as per formula, so driftdown). Ok we are on same level...
Now I don't have any idea about "letdown".
I have to answer to the question: "what's difference between driftdown and letdown?"
Anybody else for this question?
thank you