Jumped on this thread a bit late. A few points:
1. Vy does corrospond to best glide in a jet just as in any other aircraft, L/Dmax as it were. The speed varies
in each aircraft type, but usually you can sort it out by the recommended speeds with more than
one engine out in an aircraft with more than 2 engines, for twins, I think it is published somewhere.
For example, in the MD-11, it works out to be 1.3 stall +30 kts, approximately.
Glide ratio is quite good, as that is dependent on the forward speed and cleanliness of the design,
so glide ratios tend to be signifcantly better than light aircraft. The larger aircraft actually has
less surface area and frontal area for the volume of the aircraft, and that also reduces the drag a bit.
The climb speed profile is not really indicative of the Vy, as it is a tradeoff between the forward speed
and climb rate. A higher forward speed in climb can result in less overall fuel burn for the flight,
as well as time savings. Depends a lot on the cost index the individual carrier wants to use.
Yes, you can do full stalls in all transport jets out there, and they are done routinely both during
initial flight test and any time the aircraft comes out of a heavy maintenance check, as the
amount of warning the stick shaker is giving must be recorded and stall characteristics must be
good. There are configurations where the stall characteristics are bad, and there are normally
operating limitations placed on the aircraft such that line pilots will not encounter those regimes.
Descent speeds are often closer to the L/Dmax, but vary for the carriers, and due to traffic flow
are generally a compromise to allow for consistent speeds into the airport. The farther you are
from L/Dmax the greater the angle of descent. More operators descend at speeds well above
L/Dmax. The heavier you are, the higher the L/Dmax IAS will be, consequently, the aircraft will
be closer to L/Dmax at higher weights, and so a higher rate results in a better glide at the
same IAS than a lower weight will.
Finally, yes, power on takeoff varies. Max power is a function of OAT, pressure, etc., but normally
we use a reduced power that reduces the thrust by assuming a higher temperature that still allows
us to meet Part 25 performance requirements.