Understanding Departure Procedures and its Two Different Types


I look back to a year ago and remember the lessons I was covering in my instrument training— Fight instruments, Nav-aids, system limitations, etc. We, my flight instructor and I, had not quite reached the point of learning the full details of instrument approach plates, departure procedures, arrival routes, etc. When we did discuss it, it was a lot of terms and concepts to learn. Instrument flying has a great deal of information essential to safe IFR operation, including its many different plates and procedures. Generally, when you are training for your instrument rating, you tend to spend most of your time focusing on holds and instrument approaches and not nearly as much time with the encompassing factors associated with IFR departures.  

Let’s take a closer look at DP’s (Departure Procedures) and the two different types— ODP’s (Obstacle Departure Procedure) and SID’s (Standard Instrument Departure). 

To understand the importance of departure procedures, there are a few standards that need to be recognized. According to the U.S. standard for TERPS (Terminal Instrument Procedures), there is a specific obstacle clearance that must be maintained. Your aircraft must climb at least 200 Feet Per Nautical Mile (FPNM). This is determined through an observed obstacle penetration slope of 152 FPNM. If an obstacle does not penetrate the 200 FPNM climb gradient, the pilot has a minimum obstacle clearance of 48ft.

Side Note* the 152FPNM is the 40:1 ratio often referenced. 1 nautical mile is roughly 6067 feet, therefore 6067/152 = 39.9 or 40 to 1.

When obstacles penetrate that 40:1 obstacle slope, this can increase your required climb gradients as well as none standard takeoff minimums. ODP’s (Obstacle Departure Procedures) are created by the NFPO (National Flight Procedures Office) to ensure requirements are put in place to maintain sufficient obstacle clearance. ODP’s can be published either Textually or graphically. Do not be confused in that SID’s are only graphical (but may have text on them).

Highlighted in red is an example of a textual ODP. In the TPP, it is easy to confuse the ODP section with the “takeoff Obstacle Notes”. These are not the same thing. Takeoff Obstacle Notes are “low-close in obstacles” that are less than 200 ft above the departure end of the runway (DER) as well as within 1NM of the end of the runway. These do not require greater take-off minima. It is the pilot’s responsibility to see and avoid these obstacles.

Highlighted in yellow is a notable feature of graphical ODP’s that differentiate them from SID’s. On the plate, it will state OBSTACLE. Graphical ODP’s have identifiers (Ex. DRAKE2.DRK) which allows them to be filed during your IFR flight plan, while textual ODP’s can not.

Lastly, SID’s (Standard Instrument Departures) require an ATC clearance prior to flying the route. They are used to increase efficiency by expediting traffic flow and alleviating some pilot/controller workload. These are often seen at larger airports where congestion is high. If you received clearance from ATC via the SID, you are automatically cleared for the ODP. But if you are cleared for an ODP, that does not mean you are cleared for the SID. You have to make sure before accepting a SID, that your aircraft can perform to required climb gradients. If it can not meet requirements, put “No SID” in your remarks section of your flight plan.

There are two main types of SID’s — Vector and pilot navigation SID’s.

Vector SID— ATC will provide radar vectors right after takeoff and will continue until you reach your fix charted or an assigned route. As you can see here on the MEADOW FOUR, common to vector SID’s they do not have transitions or departure routes to follow. Depending upon your route of flight, after you follow the initial directions (heading and altitude) ATC will vector you via a Nav-aid in the direction of your flight. 

Pilot Navigation SID— have a set of instructions for every aircraft to follow a particular route. You may see two or more transitions listed on this form of SID. As you see here on the KKIDS ONE it has a visual (graphical or plan view) section and a textual description. This confuses a lot of people because SID’s are only graphical. Textual descriptions simply re-iterate what the graphical depicts but in some simple transitions textual descriptions will not be included. 

To all of the pilots who have personally flown departure procedures, what was your experience with them?