Planning an IFR departure
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Departures always require careful planning. Add mountainous terrain, instrument conditions (IMC), or any condition requiring maximum performance from the aircraft, and the stakes are even higher. Factors in departure planning will vary based on the class of aircraft one is flying (piston single, twin, jet, etc.), but there are common considerations that should be followed by all. One rule is to allow plenty of planning time, consider alternates even in good weather, and accept the fact that the best option very well could be to fly another day.
One aspect of IFR departurs is to accept the fact that the best option very well could be to fly another day.
First, use a Sectional Chart or sattelite imagery (even for IFR pilots) to get the “big picture” of surrounding terrain and potential obstructions. As they say, a picture is worth a thousand words, and you need a VFR chart to get that snapshot. The Sectional view also will give you an indication of the possibility of turbulence, by virtue of your departure path’s proximity to higher terrain and how the wind is blowing across those ridges. Take the opportunity to see where the more hospitable terrain is located and consider planning your departure in that direction.
A look at the Sectional Chart near Rifle and Eagle, CO indicate challenging elevations in all directions.
Departure procedures are designed primarily to provide obstacle clearance.
Next, determine whether a departure procedure is available for your airport. Departure procedures are designed primarily to provide obstacle clearance and should be used when published. These procedures come in two varieties: Obstacle Departure Procedures (ODPs) and Standard Instrument Departures (SIDs). SIDs are ATC procedures and always are printed graphically. ODPs can be printed graphically or textually. Departure procedures will be listed by airport in the IFR “Takeoff Minimums and Departure Procedures” section of the Terminal Procedures Publication (TPPs), or approach charts. If the procedure is textual, it will be described in section C of the approach charts; if an ODP has been developed solely for obstacle avoidance, it will be indicated with a “T” symbol on related instrument approach charts.
ODPs should be considered mandatory in any type of marginal conditions or at unfamiliar airports. Provided nothing else has been specifically assigned, ODPs may be flown without an ATC clearance. An important point surrounding the creation of departure procedures is that they assume normal aircraft performance and likely will require climb gradients steeper than those to which you are accustomed so double check your takeoff performance especially at high density altitude. It is up to you as the PIC to determine whether you can comply with the procedural requirements (for your own good) and to consider contingency plans.
At airports without published instrument approach/departure procedures, you will need to ensure that you can climb visually to a safe altitude. To determine a safe altitude, consult the Low Altitude En Route Charts (L-charts), a necessary part of your preflight preparation, which will allow you to determine minimum IFR altitudes for obstruction clearance.
Minimum En Route Altitudes (MEAs) or Minimum Obstruction Clearance Altitudes (MOCAs) are used for published routes, while Off-Route Obstruction Clearance Altitudes (OROCAs) are used for non-published routing. When departing an unfamiliar airport, reaching a published route at or above the MEA is always the safest bet even if it means a circling climb over the airport. It assures not only obstacle clearance, but also acceptable navigation and communication coverage with ATC. Published routes typically follow more friendly terrain, affording you more options for contingencies. MOCAs are lower altitudes that provide the same assurance of obstacle clearance as an MEA but only guarantee navigation coverage within 22nm of the VOR.
The low altitude enroute chart near Rifle Garfield County indicates MEAs and ORACAs above 10,000 feet.
In the event that you’re flying a direct, non-published route, keep in mind that OROCAs almost always will be higher than published MEAs and make no guarantee of ATC communication, radar or navigation coverage–nor do they consider the prospect of more challenging terrain.
The altitudes discussed so far work well when everything is performing normally, but what if something goes wrong? For dealing with emergencies following departure, the target altitude should be the Minimum Safe Altitude (MSA) published on the approach chart. The MSA provides at least 1,000 feet of clearance within a specified distance from the fix upon which a procedure is based. MSAs often are divided into sectors to provide greater flexibility, so take care in the preflight planning to ensure you have the right target altitude in mind, based on flight direction. While studying the approach chart, look for notices that may include advisories related to terrain.
Given the many books, videos and articles produced on weather considerations for departure, there is not sufficient room here to give the topic its deserved attention and respect. That being said, a thorough weather briefing is imperative. The eastern mountains tend to have more complicated weather patterns, which can include mountain obscurations, IFR conditions and slow-moving fronts. Turbulence, as well as updrafts and downdrafts, are of obvious concern near mountainous terrain. Remain upwind of ridges when possible or avoid being downwind and in close proximity to them.
Downdrafts can exceed the climb capability of aircraft. If experiencing a severe downdraft, try to visualize the wind pattern and make a turn out of the downdraft and toward lower terrain. Do not hesitate to use your emergency authority to leave your route if conditions deteriorate rapidly. The winds aloft information and pilot reports will provide good insight as to how the wind might be interacting with ridges.
Downdrafts can exceed the climb capability of aircraft.
In addition to turbulence considerations, utilize METARs, TAFs, and other forecasts to help gain a better understanding of current and forecasted conditions. I find the TAF Forecast Discussions particularly helpful, as they provide candid remarks from the forecaster as to how the report was created, factors considered, and even confidence level in the reports issued for the area.
When preparing to fly your departure, a clearance issued on the ground is always preferred. This is one less task to accomplish in the air and gives you the opportunity to establish airborne communication and radar contact more quickly. ATC does a great job of steering you away from trouble when they are in contact.
The word of caution worth repeating regarding airborne clearance is to be absolutely certain you can climb to an altitude, in visual conditions, that will ensure obstacle clearance and communication with ATC. Plan for a published route, even if this means extra mileage.
The widespread availability of terrain data on installed avionics, as well as on portables and iPads, makes it foolish not to invest in this technology if you’re flying in mountainous terrain. This information is invaluable when you can’t see what’s in front of you.
Finally, in mountainous terrain or challenging conditions, always depart as light as possible and build in extra margin for weather. This will enable your aircraft to achieve greater performance and will offer more alternatives if things don’t go as planned. Also, flying earlier in the day is generally a better option to avoid convective activity.
In mountainous terrain or challenging conditions, always depart as light as possible
Talk to the locals. Pilots sitting at the FBO have a wealth of information and insight that you won’t find published anywhere–a preferred route out of a certain area, unique ATC procedures, or even verbiage helpful in obtaining a clearance. Challenging departures are not the time to be overconfident—or shy about seeking help.
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