When making an IFR flight in Germany, i read the AIP for an airport, and there is written that my initial.....

Question

.....altitude is 4000 ft (i think that in the US you do not have such a SID chart where you have initial altitudes). However, for another SID from the same airport (i mean Frankfurt), the initial altitude is about 5000 ft. So, why do you have SID departures with different initial departure altitudes? What is the reason there?

Answer 1

SID's or standard instrument departures are designed for overall traffic flow out of the airport,  which may be predicated on STAR's -standard arrival procedures, which will have different routing to maximize the efficiency of both arrivals and departures.

However, some arrivals and departures will overlap in some conditions, so that an SID in one direction may or may not have an initial altitude restriction... and if it does, it's usually because of arrival or departure traffic that would cross the SID routing.  

So, the airspace on a SID departing in one direction will see different airspace design in that direction than it will in an alternate direction...therefore the different altitude restrictions.  

Some departure procedures won't have any restriction at all, because there are no traffic conflicts due to routing designs.