Rosetta Stone

If you’re instrument rated and current, you almost certainly own at least a modest complement of IFR charts and approach plates. But the odds are that you still make a number of flights under visual flight rules, and if you’re like me, you probably always have a couple of current local sectionals in your flight bag. And then there’s the other half of us who only fly in visual conditions, and who don’t ever so much as look at an IFR chart or approach plate (or quite truthfully for new pilots, those who haven’t yet seen one). If you’re in that latter half, you might be missing out on a few things.

Flying under instrument flight rules can be quite demanding at times. (In a way though, one thing about IFR flights that isn’t as demanding, especially around the Washington DC area where I live, is the planning aspect and dealing with airspace. Part of that is the familiarization process with the National Airspace System that comes along with earning this rating, and part of it is simply how IFR flights are handled.) When I got my private pilot certificate in 1990, the percentage of aviators holding an instrument rating was somewhere around a third. Now it’s close to half. Part of the reason more pilots now acquire that IFR ticket however is precisely because of the increasing complexity of the airspace through which (as well as the rules under which) we fly. If you’re among those with an IFR ticket, none of this is news to you. But there’s one aspect of flying in both the VFR and IFR worlds that may not have occurred to you, which is that there are some advantages to using some of the information contained in IFR charts, for VFR flight planning.

As a greater percentage of pilots earn instrument privileges (or when, in the fullness of time, our airspace evolves and societal freedoms devolve to the point where not having an instrument rating becomes a handicap), this will all become academic. At the present time though, there are still two formats for visually presenting aeronautical information, one being primarily oriented towards literal portrayals for visual flight rules, and the other involving much less pictorial and instead more symbolic depictions, for the ‘IFR world’.

Typically, pilots acquire a visually oriented skill set before continuing on to learn the ropes in the IFR world, i.e., you get your private pilot certificate first, and then add on the instrument rating. However, before I continue, I must acknowledge one fairly recent and also prescient response to the aeronautical evolution I had just mentioned (as well as the broader phenomenon of the information revolution) and that is Professor Paul Craig’s own SAFER project in flight education research, at MTSU: Budding pilots may not always be learning VFR skills first, and only later acquiring IFR skills. For the present though, that’s still mostly the way it is, so let’s see how these two formats might be combined during the flight planning process to disclose some Greater Truths.

Here are two similar areas shown on first a VFR sectional (Washington), and then a Jeppesen Low Altitude Enroute chart. If you had never seen either type of aeronautical chart before, one thing that would immediately strike you would be the abundance of information crammed into the VFR chart vs. the fairly austere appearance of its IFR counterpart. As it turns out, adorning these expanses of unused white space is a great deal of other stuff which, while not cartographic, can still prove very useful nonetheless. I’ll choose a fairly short flight from Hagerstown MD out to Cumberland, MD along Victor 438. We’ll compare the available information about altitudes, distances along the route, and communication frequencies.

It’s not exactly the Rockies, but there are several areas of higher terrain and potential obstacles along this route. The Maximum Elevation Figures on VFR charts (such as those at 2700 and 3400 feet MSL for the quadrangles along the eastern and western halves of this airway) are based on the highest terrain or feature in each entire quadrangle, plus another 100 to 300 feet, and are in turn rounded to the next higher 100 foot level. If you really want to play it safe though, you can use a ‘minimum enroute altitude’ (MEA) shown on IFR charts, which represents the lowest altitude along that airway and which gives you 1000 feet of obstruction clearance. (In mountainous areas, that becomes 2000 feet.) You can see the magenta numbers along V438 which are 4000 feet between HGR and FLINT intersection, going up to 5000 feet the rest of the way to GRV. You’ll also notice that next to each MEA are lower numbers. Each one is followed by a ‘T’ and is a minimum obstruction clearance altitude (MOCA), which tells you that these are the altitudes you could go down to and still have adequate obstruction clearance, but you might not be able to receive a useful signal from the navigational facility at either end of the airway, if you were further than 22 nautical miles away from it. (IFR pilots are actually only allowed to descend to a MOCA only when within 22 nmi of the facility to which they’re navigating.) Also, a general disclaimer: these minimum IFR altitudes (and there are several others such as Minimum Reception Altitude, and Minimum Vectoring Altitude) are intended only for IFR flights; the hemispherical rule for VFR cruising altitudes should still be observed. (You could just ’round up’ to the next VFR altitude above an MEA, for example.)

On the VFR chart there’s a good checkpoint about two nautical miles eastward of the town of Hancock MD (and Potomac Airpark in West Virginia) where V438 crosses the Potomac River. (It just about coincides with TOMAC intersection.) There’s another about nine nmi to the west, where the airway crosses Sideling Hill Creek to the south of I-68, then another crossing a southward loop in I-68, and another at a rather prominent peak (Boyer Knob) at the west side of the Green Ridge State Forest. (This one about coincides with FLINT intersection.) Shortly after that is the destination, Cumberland Regional Airport, at the southern end of the town. On the sectional we can only guess (or hopefully measure) the distances along V438 to TOMAC and then FLINT, but on the IFR chart, distances for each route segment are given precisely. These are great cross-references for VFR flight planning, of course. You should be crossing TOMAC 13 nautical miles after passing over HGR, and then FLINT another 19 nmi later (although in this case even if you had two VOR receivers on board, you would still need a DME to know that, as this is a ‘DME intersection’). The point is that although both VFR and IFR charts show total airway lengths as well as inbound and outbound bearings to the navaids at either end, there is just more related information that you could use to your advantage. Another benefit to these intersections has to do with communications. (Yes, it’s hard to separate these things into distinct categories, because they’re all related!) Whenever you call ATC for assistance such as requesting VFR flight following, it can be advantageous to reference your position to an IFR waypoint, such as an intersection. Controllers are talking to transport category aircraft all the time, and like the Big Guys (basically all of which are in the IFR ‘system’), they are themselves fluent in IFR-speak. You’ll come across as being a bit more savvy, but you’ll probably also make their job a bit easier than if you had said ‘Um, I’m a few miles to the east of the DUH VOR…’

Now we come to the ‘communication’ part of flight planning (and the actual flying). Here is where the IFR chart can be quite helpful. I don’t know how many times-it was a lot-that I’d desperately searched my sectional chart (in flight, mind you), hoping to find a frequency to identify what facility was in charge of the airspace through which I was flying, for radar advisories, or whatever. You can see the boxes near HGR and also below GRV that show frequencies for the Washington Air Route Traffic Control Center, or ARTCC. Granted, you could get this information from your local Flight Service Station, but it’s right here for the taking. (Note also the other ARTCC information box at the lower left, along with the ARTCC boundary line running up to the upper right, revealing that towards the end of your trip you would be approaching Cleveland Center’s airspace.) There’s another item depicted on IFR charts which involves communication, although it might be also related to altitudes (or obstructions, or other influences that could degrade a navigational signal). Although there aren’t any along this particular route, IFR charts show something known as a frequency changeover point (COP) which you might find useful someday. Typically we navigate from one VOR to another, switching from the one we passed to the one we’re approaching at about the halfway point. Sometimes though, especially in mountainous areas, navigation signals from a VOR at one end can be degraded well before those at the other, nowhere near the halfway point. The changeover point on V268 just to the north of V438 for example shows that one should switch from using HGR to Indian Head (IHD) only 21 miles along that 71 nmi long airway.

I hope I’ve given you some food for thought here. I’m not advocating that we all go out and buy twice the number of charts we’re each now using. (In fact it’s perfectly legal to use an IFR pilot friend’s expired charts for ancillary flight planning information; just don’t dare take them up with you!) I assure you that I haven’t gotten any kickbacks from instrument chart publishers…(And I haven’t even begun to extol the advantages of the so-called IFR approach plate for the familiarization of a VFR pilot with his or her destination airport.) But I’m sure that if I’ve had a part in accelerating any VFR pilots’ familiarization with and interest in the IFR system, I may have made their transition into the realm of IFR flight at least a little less painful!

above: image from part of the Washington Sectional

above: section of the Jeppesen Low Altitude Enroute Chart, 47-48