Why don't Transport Category aircraft have a listed Vy? I was talking with a pilot about an inability to maintain the targeted climb rate in a particular situation and asked him what the Vy was for the jet.  He curtly replied "Vy is only for Part 23 aircraft." (FYI for those outside the US:  Part 25 aircraft are commerical planes, while Part 23 are usually general aviation planes. You can find more details here.)

Yet, I know for a fact that there is a maximum excess thrust speed, because at a certain speed drag is at a minimum. This should be close to Vy.  I also know that rate of climb is frequently listed for these aircraft. However, the optimal speed for gaining altitude isn't usually listed for commercial aircraft like it is for GA aircraft.   In fact, many of the v-speeds like Vmca and Vdec are harder to find for larger aircraft.



Why is this?  I can think of several possibilities:


Commercial aircraft speeds are defined by ATC and operating procedures, not by performance considerations
Commercial aircraft have enough thrust that climb performance limits isn't an issue (which I doubt from my experience).
Commercial aircraft use other parameters for similar purposes like rate of climb, v2, or long range cruise speed
Jets don't list this speed but propeller planes do
Large commercial jets operate within a much wider range of weights than most GA aircraft do, and since Vy varies with weight, it wouldn't make sense to publish "a" single Vy speed for them. The crew can get a best rate or best angle of climb speed from the FMC (which "knows" the current weight of the aircraft, based on current fuel &amp; an entered Zero Fuel Weight). 

From an empty aircraft with minimum fuel to a loaded aircraft with max fuel, the weight probably won't quite double for most commercial jet aircraft, but the one might be 170% or more of the other. With that much range, any single Vy you publish would be way far off in a lot of cases. On a GA aircraft, without an FMC and operating in a much narrower weight range, publishing a single speed makes much more sense as the delta between published and actual becomes smaller and the consequence of being a couple knots off is probably slight.