@ gameover,
Lot of posts, but regarding your question, driftdown in a 73 or airbus once again is not such a big deal!
law states that if your SE ceiling is less than the route mea or grid mora, whatever you name it you have to have a driftdown procedure.
Generally speaking for the above mentioned types it is just a dispatch exercise. the SE driftdown rate and speed will allow you to descend clear of all terrain in almost all places I can think of.
For example, the 73 will SE driftdown at approx 300 to 500 fpm. given an speed of 5 to 6 miles per hour it would take you close to 132 miles to descend from FL330 to FL 220 in worst case scenario!!! Enough to cover almost all places in the world. That is not what escape routes are for.
Escape routes come into effect for emergency descents, even in the alps this can be an issue. the 73 has pax oxygen for 12 minutes. You have to be able to descent to 14.000 in 12 minutes. With an average speed of 6 miles pm you have to be able to descent to 14.000 within 72 miles, can be done over the highest parts of the Alps but you have to know where you are at, some other places in the world this may be an issue, hence the escape routes.
Hopes this helps