I have a question about a specific departure proceedure:

http://155.178.201.160/d-tpp/1209/00081CICERO.PDF


This is the Cicero Five Departure out of MDW/Chicago. I've been assigned it a few times by clearance (Though you cannot file it), but upon departure I am assigned a completely different heading and altitude.

Why am I being assigned this departure if I will just be given a completely different assignment? Im assuming that I should fly the assigned heading/alt on takeoff and not this departure then? That's what I did and half expected to be yelled at.

You should always fly the assigned in a case as you used as an example.
One difference is the departure is used for planning. The directions are issued based on real time requirements. That's one possible explanation.

USMCFLYR

In Chicago, it's all about O'Hare. That's why they assign you different headings and altitudes coming out of Midway, they're keeping you away from the traffic going into/out of O'Hare.

SIDS like this save clearance delivery from having to provide you with the initial and expected altitudes, as well as the departure frequency, so it's just a work-saver for ATC.

ATC assigned headings and altitudes take precedence over the DP,
however the controller may later assign a heading or a fix to join the DP.
Keep in mind that this does not relieve you from other requirements on the DP,
in particular the 250 KT restriction in the center of the page. Pilots get caught on this one daily as they either select speed FMS, or accelerate past 250 out of 10,000 FT.

An easy fix for this is to keep the speed on manual and 250 kts, also cover this restriction in your departure brief.

Think of it this way if you had a Comms failure and you can proceed VFR now you have the departure and can follow communication failure procedures.

Ok, thanks guys. I think that I was still given an initial assigned altitude with my clearance but everything you're saying makes sense. It is all about O'Hare...haha. Im flying an SR-22.. so I don't have to worry about 250 kts.

It also helps in prep for a "lost comm" situation.

Yeah....what he said. ^^^^^^^

First, the reason you can't file this DP is because it has no assigned headings to take you to the enroute structure. You've got some pre-published standard initial turn after takeoff but no where to go after that. To summarize, the DP has you fly a heading (or group) up to 13, 15, or2400' (based most likely for the anticipated routing of other traffic) after which vectors take over.

Like every other DP, it's shorthand to make taking it down and reviewing it more easy (a picture paints a 1000 words). And like any other clearance, short-had or long winded, it's subject to be overridden by more current and specific ATC instructions.