This article originally appeared in IFR MAGAZINE and is reproduced here by permission of Belvoir Publications.
If you've looked at the instrument written booklet lately, you'll notice that although there are some new questions here and there, not much has changed. The written is heavy on regs, theory and weather but light on the real meat-and-potatoes grit of IFR flying. This is especially true of how the feds treat SIDs and STARs.
Consider, for example, the elaborate time en route problems involving standard instrument departures. Instrument-pilots-to-be spend hours sweating over these things, only to learn that (a) the multiple guess answers are too close to be resolved by an E-6B and (b) no one ever does these calculations in the real world anyway. In fact, apart from the test writers in Oklahoma City, maybe no one ever has done such calculations.
Even though it's misdirected, the emphasis on SIDs and STARs is not misplaced. These procedures are a part of everyday IFR flying and if you routinely pencil in "NO SIDs/NO STARs" on your flight plan, you're denying yourself the occasional shortcut or, at the least, missing an opportunity to learn how ATC works. So, how do you use SIDs and STARs? Should you use them at all? What are the pitfalls?
SIDs (standard instrument departures) and STARs (standard terminal arrival routes) appear in both Jeppesen and NOS publications. Jeppesen bundles them together with the approaches. NOS groups the arrivals at the front of the booklets while the SIDs are paired with the approaches.
Personally I like the way the STARs appear, since it saves duplication. But why didn't they do the SIDs the same way? I didn't check carefully, but I saw the Regional Six departure printed on 10 different pages in the same NOS booklet. Jeppesen does the same, of course, meaning you might get to file one SID 10 times.
Even though we consider them instrument procedures for pilots to use, SIDs and STARs aren't there primarily to make the pilot's life easier. SIDs and STARs exist chiefly to make it easy on ATC. The idea is this: It's a lot easier for a controller to say "cleared to Kansas City via the San Jose Seven Departure, J12," than it is "cleared to Kansas City via runway heading to the San Jose VORDME 1.8, then right to heading 110, to cross the San Jose 47-degree radial at or below 5000 feet, intercept the Oakland 121degree radial to MOONY, J12..."
The point is, SIDs and STARs allow ATC to codify commonly used clearances and procedures. Essentially, they buy frequency time and, for that reason, SIDs and STARs make it easy on both controllers and pilots. Also, SIDs and STARs give ATC a means to communicate to the pilot what his or her routing is likely to be when departing or arriving. By reviewing that ahead of time-or by filing the procedure in the first place-the pilot can plan accordingly.
Light aircraft IFR pilots routinely encounter SIDs. They're used almost everywhere, at towered fields served by some kind of approach control. Some are complex-such as the previously described San Jose Seven- while others consist of nothing more than "runway heading" to a specific altitude. Why such a simple clearance requires a SID is beyond us. We don't make the rules, we just try to avoid breaking too many of them.
As fully described in section 5-26 of the AIM, SIDs come in two types: pilot nav and vector SIDs. In practice, some SIDs seem to be a little of both. Pilot nav SIDs imply that the pilot is equipped to navigate the SID and that he or she will do so without any intervention from federal authorities. If the clearance reads "via the San Jose Seven departure," the pilot is authorized and expected to follow every little twist and niggle in the route, unless ATC comes up with another plan.
Pilot nav SIDs are clearly labeled as such, in the title on both NOS and Jeppesen plates. Not that you could get confused. Pilot nav SIDs usually have a fat slug of type describing the various courses and altitudes the pilot is supposed to fly. Vector SIDs, on the other hand, usually give a heading and maybe a fix or two before the word "thence, " which is ATC's rather biblical way of saying expect vectors or resume own navigation.
SIDs are really pretty simple. So simple, in fact, that we wonder why so many pilots duck them by adding "NO SIDs" to the remarks. There are a few traps to worry about, however. One obvious point is to make sure you have and follow the correct and current SID. Many airports have several SIDs for the same runway and pilots have been known to fly the wrong one. Watch out for expired-plate syndrome, too. Altitudes, courses and frequencies on SIDs change more often than you might think. Expired plates just won't hack it.
Some SIDs are performance based, meaning that you're expected to be able to maintain a minimum climb gradient in order to accept the SID. The gradient may be necessary for terrain clearance or to meet an ATC crossing restriction. If you fall short of the gradient, you could become part of the local topography or, at the very least, get spanked by ATC for messing up the departure sequence. Either way, check the chart carefully and use the gradient-to-rate table to convert the required climb to a feet-per-minute value. If no special climb gradient is specified, the assumed climb gradient is 200 feet per mile, or about 333 feet per minute at 100 knots. The same assumed gradient, by the way, applies to ordinary unnamed instrument departure procedures found at towered and non towered airports.
Pilot nav SIDs always (well, almost) specify the initial altitude. Vector SIDs sometimes do, too. But often that altitude comes with the clearance. Some pilots have been thoroughly confused by a clearance with an altitude other than that given in the SID. Which altitude takes precedence, that on the SID or the one given in the clearance? Frankly, we don't know. We've been told that local custom applies to this one. When an altitude other than that on the SID is given, most controllers are careful to emphasize it. But you can't count on that. The best way to sort it out is to ask the controller to clarify the clearance.
Standard terminal arrival routes are largely the province of heavy jets or al least relatively fast traffic descending from the flight levels. Some even say as much. Notes such as "applicable to turbojets only" or "all aircraft operating 11,000 feet and above" tell the story. If you're a piston driver operating at low altitude, you can forget flying those STARs. Even if you're a high falutin' Mooney 252 pilot used to cruising at FL240, you might be too slow to keep up with the jets populating the SIDs. You'll either get turned off the route or, more likely, descended and brought in under the jet traffic.
But that doesn't mean you should forget STARs entirely. These procedures do offer important clues about the traffic flow into major terminals, information that's useful for flight planning, whether you're VFR or IFR. In some parts of the country, such as Dallas-Fort Worth, where I operate, STARs are used commonly for low altitude traffic. It really depends on the whim of the of local ATC facility, since that's where the procedures originate.
Let's examine the Acton Two Arrival (AQN.AQN.2) for DF/W to see how it can work. Let's assume we're flying a piston single on a short 50-mile trip coming into the D/FW area from Waco. Let's say we file 5000 feet, direct to our destination, Arlington, Texas. In case you're wondering, there's no chance we'll get that routing. IFR traffic into DF/W is routed over one of four "gatepost" VORs that form a square around the metro area.
With that in mind, clearance delivery will come back with something like this: "Cleared to the Arlington Airport, via Victor 17 Acton, the Acton Two arrival, maintain 5000 feet, departure frequency 135.2..." Pilots not accustomed to flying low-altitude STARs may be surprised by that clearance, since the STAR goes to small muni field with no tower.
Step one is to make sure the STAR goes to your destination. If it doesn't, you can't get there from here, period. Step two is to forget about the picture and go to the text on the back of the page. For this particular STAR (and many others around Dallas) the map is a nightmare. The arrival description cuts through the clag, though. It lists various categories of aircraft: Turbojets landing at Dallas. ..that's not us. . .Non-turbojets landing at Dallas...closer, but no cigar. Finally, under "All aircraft landing at Arlington," we see these instructions: "From over AQN VORTAC, R-079 to BRITY, expect vectors final approach course."
So, remembering that STARs are meant to simplify clearance delivery procedures, all we really needed to know is that Victor 17 takes us to Acton VOR and from there, we're going to track the R-079 outbound and get vectors. If you had used NO SIDs/STARs in your flight plan, that's exactly what you would have gotten anyway.
Does the clearance actually pan out in real life? Nope, probably not. Often, an amendment is tacked on by Center: "Cherokee Three Four Charlie, join the arrival east of Acton." Then, as soon as Regional approach gets hold of you, you get vectors to the final approach course, never having gotten near the published STAR route. Why? Local traffic, probably. Could be there was faster traffic closing up behind and it just worked better not to use the STAR.
So why do they bother specifying it? ATC procedural inertia, mainly. The Letters of Agreement have been written and the controllers generally follow them, even though they know the routing won't stand. What they don't know (at least when you depart) is what the traffic picture will be when you prepare to enter the STAR, which is why they don't cobble up a new route to begin with.
Lost communications is another reason. Say you lost comm before the shortcut. You could turn east on the R-079 at the VOR, stay out of everybody's way and safely continue to Arlington. If you lost radios after the shortcut, same story.
Is it possible to figure out in advance if STARs are in use and if so, is it worth doing? Yes, it is possible and it 's also worth doing, to the extent that it always makes sense to know as much as you can about ATC 's plans. I can't think of any circumstance where it's better to be in the dark.
The easiest way to plan is to look at the index of the approach plates in NOS booklets. Look up the airport you're going to and see what applies. The key is to read the arrival description to see if low-altitude traffic is included. As I said earlier, make sure your destination airport is served by the arrival. If it isn't, don't bother filing it. ATC will hand you the preferred routing anyway.
Most STARs (and SIDs) have transitions that are best thought of as branch routes feeding the main procedure. The Acton Two, for example, has the Wink, Abilene and EDNAS transitions, flown, respectively, from the two VORs and an intersection. These transitions join the STAR, then lead right to the Acton VOR. If you're expected to fly the transition, the clearance will say that: "Cleared to...via the Wink transition, Acton Two arrival...etc."
If you want to file a transition, the filing code is given right on the chart. Let's say you were filing for Arlington from El Paso, with the Wink transition. The route would read: ELP V16 INK.AQN2 F54. The computer would probably accept the routing, but whether ATC would stick to it is anybody's guess. DUAT, by the way, is supposed to accept SIDs and STARs, but will do so only if the procedures appear in its database.
One last point about both SIDs and STARs: They provide the approach and departure frequencies you will need. It's funny to listen to the tower at Houston Hobby, where every clearance gives the Hobby Eight, and no departure frequency is given. After takeoff, the tower ships pilots to departure and some have to ask for the freq, forgetting that it appears right on the SID. (The same applies to STARs) Just remember to look it up before you take off.