I am working on a trajectory optimisation program for commercial, large aircraft, in which I want to incorporate realistic air traffic control regulations. One of the constraints I want to incorporate is that of ATC requiring step-climb cruise at specific flight levels.
Specifically, the hemispheric rule, though not universal, is a good example of how air traffic is managed by enforcing that westbound flights take even flight levels (FL020, FL040, etc.), whereas eastbound flights take odd flight levels (FL010, FL030, etc.).
So, aircraft should fly at one of these flight levels during cruise, when in level flight, thus resulting in a step-climb cruise, as opposed to a continuous-climb cruise profile. E.g., if an aircraft flying east starts its cruise at FL330, it would want to increase its altitude at some point for increased fuel efficiency. If cleared by ATC, it should climb to FL350 (maybe even FL370, if feasible), and so on.
My question is; are there any restrictions on how long the climb part between each of the level portions can take, at maximum (in terms of distance, time, or some other measure), and if so, what is the specific FAR/JAR or CS25 chapter that mentions it?
One could imagine that if such regulations aren't imposed, the climb segment in between level steps could take up so much time, theoretically, that effectively the cruise would still be continuous-climb. Although this is probably not too much of a problem in real life, it is a problem in my trajectory optimisation program. I.e., without proper bounds on the duration/length of this in-between climb leg, the solution always tends towards a continuous-climb solution by making the level flight portion short and the climb portion large.