IFR DEPARTURE PROCEDURES: Complicated, critical, and often misunderstood

If you remember nothing else about IFR departures from uncontrolled airports, remember this:

If you depart an airport into uncontrolled airspace, which includes all airports other than those with controlled airspace (Classes E, D, C, B or E to the surface) responsibility to avoid obstacles and terrain on your initial climb into controlled airspace rests entirely and solely with you, the pilot. Unless and until you reach a published segment of the IFR route system and attain the safe altitude published for that route segment or you receive a vector from ATC,[1] responsibility for avoiding impact with terrain and obstacles rests solely with you the pilot.   Do not rely on controllers. You will not be warned of obstacles nor terrain by ATC nor advised how to avoid them.

Guidance, in one of several forms, notably an obstacle departure procedure, may be available to you, but you must know where to find that guidance and how to interpret it — the responsibility is yours alone.[i]  (AIM 5-2-8, “When used by the controller during departure, the term “radar contact” should not be interpreted as relieving pilots of their responsibility to maintain appropriate terrain and obstruction clearance which may include flying the obstacle DP”)

That guidance is in the form of Obstacle Departure Procedures (ODP), found in the U.S. Terminal Procedures Publication.  Do not confuse Obstacle Departure Procedures with Standard Instrument Departures, known colloquially as SIDs.  The latter are intended to expedite communication between controllers and pilots and are assigned by ATC.  The former are intended solely to guide pilots away from obstacles and terrain when departing uncontrolled airports and are never assigned by ATC.  Collectively, they are called simply Instrument Departure Procedures (DP).  To reiterate, because the phraseology is confusing and has been altered over the years:  Instrument Departure Procedures include both Obstacle Departure Procedures and Standard Instrument Departures, but they are different creatures.

DEPARTURE PROCEDURE NOMENCLATURE

Because the naming of departure procedures has been changed over the years and has led to confusion and occasional tragedy, let’s briefly review the history.   Keep in mind that all departure procedures are one of two types:  those intended solely to assist pilots to maintain obstacle and terrain clearance and those developed for what the FAA calls “system enhancement,” essentially to reduce pilot and controller workload by assigning a predetermined departure path, altitude assignment, and departure frequency in one package.  The names have changed over the years and there are multiple subdivisions in each category, but all departure procedures are of one of these two types.   They are for distinctly different purposes and every pilot should be very clear about those purposes.  Pilots have not been helped toward this clarity by the changes in nomenclature over the years.  Once upon a time, before 2000, we had IFR Departure Procedures — the first type — and Standard Departure Procedures (SIDs) — the second type.  In 2000, the FAA dropped the term SID and began to call all of these procedures, including both distinctly different types, simply Departure Procedures (DPs).   The elimination of the well-known term SID caused confusion and eventually the FAA reintroduced the term for the system enhancement procedures and began to use the term Obstacle Departure Procedure (ODP) for those procedures intended to provide obstacle and terrain clearance.  To make it further confusing, most ODPs are textual only, found in the front matter of the Terminal Procedures Publication (TPP), but some are published in graphic form  embedded with the approach charts and airport diagrams in the main section of the TPP.  I recommend a close reading of the preamble of the front matter of the Takeoff Minimums and (Obstacle) Departure Procedures section in the TPP.

DEPARTURE PROCEDURES generally known as STANDARD INSTRUMENT DEPARTURES (SIDs)

Departure procedures intended primarily to simplify communications and routing at busy airports are always presented graphically and are found adjacent and following the instrument approaches for a given airport in the U.S. Terminal Procedures.  The term SID or Standard Instrument Departure does not appear in the publication.  Each Departure is labeled and known by its unique name.   Thus we have the Hickory One Departure from Hickory or the Panther Eight Departure from Charlotte or the Blue Devil Four Departure from RDU. (Yes, there is a PACKK Departure from RDU also.  Many departure procedures have cute names somehow associated with the locale, in this case local universities.)  These were once called Standard Instrument Departures (or SIDs) and instrument pilots of some years’ experience may remember when they were published in a separate volume by the NOS.  The term Standard Instrument Departure (SID) is no longer used in the title of the charts or procedures, but the AIM still refers to these ATC procedures as Standard Instrument Departures and most pilots still use that term.  The critical thing we must understand is that these Departures are assigned by ATC, unlike Obstacle Departure Procedures, which are never assigned.

These Departures, which we will call SIDs for clarity, will be assigned to you by ATC.  They exist and will be assigned at controlled (towered) airports when departing into controlled airspace, such as B, C, D or E airspace to the surface..  You may file one if you wish, but ATC will assign it if they find it useful or necessary.  If you are not assigned a SID, don’t worry.  Simply follow the ATC instructions from the tower and the departure controller.  If you are assigned a SID, look it up, study it, and note that it probably includes your departure frequency which will then not be read to you as part of your clearance. When the tower says, “Contact departure,” it will expect you to have learned the frequency from the SID chart.  The SID will be found following the approach charts and airport diagram for your specific departure airport.  It will often occupy several pages and will include three elements:  a chart, a textual description of the departure route , and a list of take-off obstacles.  Initial instructions will usually be specific to each runway.   This is the straighforward Blue Devil Four Departure from RDU.  The second page includes the critical textual description, the runway-specific instructions, and any obstacles of concern.   Note that the textual description always prevails; the graphic is for positional awareness.  Note also that many, probably most, departures have transitions, which are simply different routes to different fixes intended for launching traffic in different directions.  Some transitions are intended for pilot navigation and provide specific courses and altitudes.  Other transitions rely on radar vectors and a clearance to a charted fix in your direction of flight.  The symbology looks like this:  BLUUE4.DAN is the Blue Devil Four Departure Danville transition.  Transitions are often assigned as part of the departure procedure. Some SIDS have complex routings that must be followed closely.  Others are what we sometimes call vectored departures or radar departures.  They simply instruct the pilot to fly a certain heading and expect vectors to an assigned fix or transition.  The Raleigh Seven Departure from RDU is a classic vectored departure.  Note the textual description, which promises radar vectors to the transition fixes, each one of which is a VOR in the en route structure.  Note also the two different departure frequencies, labeled “South Departure” and “North Departure.”  We are expected to note the appropriate departure frequency from the departure chart.  The tower will instruct us to contact departure, but will not typically provide the frequency.  And we now have RNAV SIDS, most prevalent at larger airports.  (For examples, see Charlotte Douglas CLT. )   This is the KRITR THREE DEPARTURE chart, with the accompanying textual description and the obstacle notes.)  These have complex routings that require RNAV equipment and are often, although not always, designed for turbojet departures.     Note that to accept a SID you must possess either the charted or textual description of the SID and to accept an RNAV SID the procedure must be retrieved from a current database.  This was more of a problem in years past when SIDs were published in separate volumes and we did not always subscribe or carry them, in which case we noted “No SIDs or STARs” in the remarks section of the filed flight plan.  Now they are bound in the same volume as approaches and included with approaches for each airport in programs that incorporate digital electronic charts, so we usually have them on board.  If not, you must advise ATC, either by noting “No SID” in the remarks section of your flight plan or verbally to ATC.

OBSTACLE DEPARTURE PROCEDURES

Obstacle Departure Procedures are intended solely to provide guidance for obstacle and terrain avoidance when departing into uncontrolled airspace.   These procedures may be charted or, more often, are merely described in text to be found in the U. S. Terminal Procedures – known in the vernacular as “approach plates.”  If you use NACO (formerly NOS) instrument charts, these textual Obstacle DPs are found in the IFR Take-off Minimums and Departure Procedures section of the Terminal Procedures and the less-common charted Obstacle DPs will be found following the approach charts for the specific airport.

Confusion about Obstacle Departure Procedures, particularly an inability to distinguish between Standard Instrument Departures and Obstacle Departure Procedures, has been a contributing cause to at least one notorious accident, the 1991 crash of a Hawker departing San Diego with the band of country singer Reba McEntire aboard.  All died in a collision with a mountain in the darkness.  This article by our editor Sarina Houston provides background and analysis.

Here is how, simplified for brevity, the need for an Obstacle Departure Procedure is determined.  If an instrument approach procedure (IAP) exists for an airport, that airport has been surveyed for obstacles and terrain in the departure paths from its runways.  The question is whether an airplane can depart a specific runway, pass over the departure end of the runway at a reasonable altitude, turn in any direction, and climb at a reasonable angle without impacting an obstacle or terrain. This is the Diverse Departure Assessment.  Each runway is considered separately.  An obstacle identification surface (OCS) is surveyed, beginning at the departure end of the runway (DER) and sloping upward at 152 feet per nautical mile until reaching the minimum IFR altitude or entering the en route structure.  This is the obstacle climb surface (OCS) defined in the TERPS and is based on a 40:1 ratio, the equivalent of a 2.5 percent slope, which works out to 152 feet per nautical mile.  On top of this surface is added the required obstacle clearance (ROC).  The ROC slope is 48’/NM.  Add the OCS to ROC and this becomes the familiar 200ft/NM standard climb angle, which is somewhat steeper than a 40:1 plane. (NB:  This is not feet per minute, which will vary with ground speed.  If you don’t want to do the arithmetic, look at the table on the inside back cover of the TPP.)  ROC increases along this slope until the next phase of flight minimum obstacle clearance is met. Pilots know this as the MEA, MOCA, Grid MORA or minimum holding altitude. [ii]  Just to make this more complicated, many obstacle departure procedures were evaluated under an older criteria that allowed an obstacle to be as high as 35 feet at the departure end of the runway.  So, for the sake of safety, assume that we should pass the DER at least 35 feet above the ground.

This plane is extended outward 25 nautical miles in non-mountainous terrain and 46 nautical miles in designated mountainous areas.  If no obstacle penetrates this plane, a Diverse Departure area is considered to exist for this runway.  For the pilot, this means that if we can cross the DER at 35 feet, climb straight ahead to 400 feet, turn in any direction and climb at 200 feet per nautical mile (note: not 200 feet per minute) we will be free of obstacles and terrain.  Note that beyond the diverse obstacle assessment area (25 or 46 NM) there may be significantly higher obstacles.  This is slightly better than a 40:1 plane.  If an obstacle or terrain penetrates this plane, then an Obstacle Departure Procedure for that runway will be published.  This may involve a minimum climb angle, a minimum visibility, a specific route or some combination of these.  Consider it a means to avoid impacting unyielding things.

Now we know the nomenclature, a bunch of acronyms, and the basics of the TERPs (another acronym) criteria for obstacle departure procedures.  How do we, as pilots, use this information when departing on an IFR flight?

Here is a decision tree to follow.  When departing from an uncontrolled airport into uncontrolled airspace, think systematically about the situation and follow this logic:

  • Is the weather good VMC from the ground to a published enroute altitude and fix?
    • If yes, then a safe departure will be a matter of seeing and avoiding terrain and obstacles.  And, if you choose, flying any obstacle departure procedure that exists.  I would advise following an ODP, particularly at night.
    • If no, then careful planning will be required.
      • Does the departure airport have an instrument approach?
        • If no, then it has not been surveyed for departure obstacles.  You are on your own to navigate from takeoff to the enroute system without impacting obstacles or terrain.  Get out your sectional and study it carefully.  As a Part 91, non-commercial flight, you are entitled to make an IFR departure from an airport without an instrument approach.  Whether or not you deem it wise will depend on its topography, the climb performance of your airplane, and the prevailing weather.
        • If yes, then the airport will have been scrutinized for hazardous obstacles and terrain in the departure area and if they are present, guidance will be available, so you must ask:
          • Is an obstacle departure procedure published for this airport?  Look in the front matter of the TPP for it.  If an obstacle departure procedure exists for that airport, it will be published as either a textual description or in chart form. Obstacle departure procedures associated with GPS or RNAV approaches or which are particularly complicated will be charted.  Others will be published in textual form.
          • If it is published in textual form it will be found in Section C (IFR Take-off Minimums and Departure Procedures) of the front matter of the NACO (formerly NOS) Instrument Approach Procedures (known in the vernacular as “approach  plates”).  You will find it listed under the departure airport, which is listed alphabetically by city name.  (Consult the index if you know only the name of the airport and not its city.)  This text will also mention the height and location of low, close-in obstacles that penetrate the 40:1 plane
          • If it is published in graphical form, it will be found following the instrument approach procedures for the departure airport in the Instrument Approach Procedures.  How can we distinguish it from a Departure Procedure (formerly a SID) intended simply for traffic and routing simplification?  Both will be charted, but the departure procedure intended for obstacle avoidance will include the word “Obstacle” in the title, ie., “Obstacle Departure Procedure.”  (These remain relatively rare, but may become more common as GPS or RNAV approaches become more common and may already be more common in parts of the country with daunting terrain.)
          • If a “T” symbol (a white “T” on a black triangle) is on the approach charts for the airport, there may be an obstacle departure procedure published for the airport. (One or both of two conditions prevail for this airport: alternate takeoff minimums or an obstacle departure procedure.) Takeoff minimums are a subject for another discussion. Both are an indication of a problematic departure.
        • If no . . . If no departure procedure is published for your departure airport, you may assume that no obstacles exist in the departure area (other than those noted below) and that upon crossing the departure area of the runway at or above 35 feet AGL and climbing straight ahead to 400 feet you may turn in any direction and continue to climb at a reasonable rate, defined as 200 feet per nautical mile) to your first en route fix. One last point: it’s not quite that simple.  If what are called “low, close-in obstacles” penetrate the 40:1 plane within 1 NM of the DER they are accounted for by notes in the obstacle departure procedure warning of their location relative to the DER and their AGL/MSL height.  We must avoid them by any means necessary.

Users of Jeppesen charts will find the textual Obstacle DPs at the bottom of the airport diagram chart and graphical, or charted, Obstacle DPs will be found with the approach charts for the airport.  This is one of the several ways in which many pilots find Jeppesen charts to be less obscure and more convenient.  The information in the NACO and Jeppesen charts should be identical; Jeppesen simply makes it easier to find.

To simplify further, good IFR hygiene suggests that when departing IFR from an uncontrolled airport one should always check for an obstacle departure procedure.  Obstacle departure procedures will never be assigned by ATC.  Make it part of your departure briefing.

References:

AIM section 5-2-8

AC 120-91 Airport Obstacle Analysis

CFR 91.177

Instrument Procedures Handbook, FAA-H-8261-1, Chapter 2, “Departure Procedures”

Online resources we suggest:

Pilotedge workshop IFR Departures Demystified     Another Pilotedge workshop, this one addressing IFR departures, a much-misunderstood aspect of IFR operations.  Several notorious IFR accidents have been caused by a pilot’s failure to appreciate the difference between SIDs and ODPs   See below.

1991 Departure Procedure crash involving Reba McEntire band report  An iconic accident revolving around a misunderstanding about the distinction between an obstacle departure procedure (then called simply a departure procedure) and a SID.  In those days the SIDs and STARs were published in a separate book; we would write in the remarks, “No SIDs or STARs.”  Read the transcript; it is, along with the Pinnacle crash, one of the saddest examples of the wages of ignorance.  (The Reba McEntire crash) The NTSB report of the 16 March 1991 fatal crash)

AC 120-91 is the Advisory Circular outlining the means by which obstacle avoidance is determined for commercial (135, 121, 125) operations.  It is not applicable to Part 91 operations but serves as an illustration of the complexity of these issues.

 

It is easy to understand the need for pilots and operators to develop their own contingency procedures. This is universally applied inside TERPS and PANS-Ops.[iv]

[1] AIM 5-2-8, “When used by the controller during departure, the term “radar contact” should not be interpreted as relieving pilots of their responsibility to maintain appropriate terrain and obstruction clearance which may include flying the obstacle DP”

[i] The AIM, section 5-2-8 is a good source for further study.

[ii] TERPS Volume 4, Chapter 1, “General Criteria”

    TERPS Volume 4, Chapter 2, “Diverse Departures”

 

 

 

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