Flight Planning Guide
last updated Saturday, March 13th, 2010 @ 19:00 UTC

The process of planning a commercial flight under IFR procedures is a meticulous series of steps requiring a large number of resources. Even the process which appears below is simplified to a substantial extent (and thus should not, in any way, be mistaken for advice for planning a real-world flight of any kind). Please keep in mind that flying with TransGear Airways does not necessarily require you to follow this checklist! You are free to navigate visually, using Atlas or the FlightGear Multiplayer map, or using a direct path via the FlightGear Flight Manager menu (if your aircraft type supports it). If you are insistent upon following an IFR flight route, pre-built ones for each leg are available in the Charts and Resources page. This guide is intended for those who should choose to do their own flight planning over any of the aforementioned, easier, methods.

(DISCLAIMER: please feel free to correct me on any factual errors that may be contained below. My knowledge is all hobbyist-level, and therefore I may be slightly off on a few details here and there, especially as they pertain to real-world procedures.)

Step 1 -- Determining your Route

"Airways" are paths in the sky defined by connecting navigational aids with lines which trace specific magnetic headings, called "radials". The "Victor" airways are primarily for low-level aircraft, while "Jetways" are designed for Turbofan-powered, (primarily commercial) jet traffic. A "direct-to" segment in a flight plan is part of the intended route which is not on an airway, but can be followed by arriving at one point and then pointing "direct to" another. A "SID" is a Standard Instrument Departure; a pre-defined path that connects the departure point of an airport with one or more major airways. A "STAR" is the opposite; a Standard Terminal Arrival Route, which is a pre-defined path for transitioning from airways to arrival points.

The real method for determining a route from your origin to your destination would be to consult the SIDs and STARs for your departure and arrival airports, and sectional charts which cover the space between, to see which combination allows for the "jetways" that most efficiently connect them. You would then need to work out your transitions from one jetway to another; sometimes they intersect at a particular navaid, or other times you'll need to hop from one to another by creating a "direct-to" segment in between. You would then indicate intended altitudes for each segment of the path (see below steps) and file this "flight plan" with the agency governing air traffic (in the USA, this is the "FAA", the Federal Aviation Administration) and hope that it is "approved as filed" -- i.e. that they didn't have to make any changes to accommodate other traffic. Prior to departure, you would contact an FAA representative by radio on a "Clearance Delivery" frequency to recieve the status of your filed flight plan, and scribble down any changes they rattle off.

TransGear pilots have the freedom to use any routes they like, don't have to file their flight plans with anyone, and certainly don't have to worry that they might not be "cleared as filed." A shortcut to obtaining a complete route, from departure airport to SID to jetway(s) to STAR to touchdown, is to visit a website designed for generating instant flight routes. One such website is flightaware.com -- under their "Pilot Resources" tab is a subsection called "IFR Route Search" and a link marked "recently used IFR routes." Under this link, you can enter an origin and destination airport, and generate a list of recent, actual flight routes used, sorted by popularity. These routes will include the SID from the origin airport, the various waypoints along the path, the STAR used to navigate into the destination, and the cruise altitude used. (NOTE: if you plan to fly using traditional radio navigation rather than a GPS-style method, you'll need to stay away from SIDs and STARs marked "RNAV", standing for "Area Navigation", which include GPS fixes which aren't locatable by VOR/DME recievers.)

To further expand the route into a complete list of waypoints, you will need to look at the SID for the departure airport, sectional charts for the enroute path, and the STAR for the arrival; at some point, possibly after you are advised of the active arrival runway, you'll need the Instrument Approach Procedure for that runway as well. The SIDs, STARs, and IAPs can be found on the faa.gov site under their "Air Traffic" tab and "Flight Information" menu option, there is a link called "Aeronautical Charts"; the resulting page has an option on the left called "Free Downloads" and a link entitled "digital - Terminal Procedures Publication (d-TPP) and Airport Diagrams". A list of current publication versions, with their effective dates, will be displayed; click on the one relevant to the expected date of the flight. Once here, you will be at a map of the US. Below that is a box containing search options. Since you will know the ICAO for the airport in question, the easiest thing to do is click the radio button for "ICAO" and enter the ID of the necessary airport. This will bring up a chart containing links to every published procedure available for that airport: "DP" stands for "departure" (a.k.a. SID), "STAR" is self-evident, "IAP" is an Instrument Approach Procedure, and "APD" is that field's official Airport Runway and Taxiway Diagram. (The "Minimums" documents listed there, if any, can be ignored for our purposes.) Keep this website in mind, because you'll return to it later when it comes time to plan for arrival at your destination.

For each waypoint, you will need to know:

Certain procedures may include one or more "direct-to" waypoints, meaning that the path you take to it is not specified, and you can simply direct your navigation systems to point you straight at it from wherever you are. In fact, for our purposes, and especially because fully-functional GPS navigation in FlightGear is still being realized, it's probably sufficient to navigate a "direct-to" path from each waypoint to the next. In reality, though, pilots would approach and depart each waypoint from a specific heading, and the CDI (Course Deviation Indicator) on their NAV instrument would help them correct their inbound path prior to arriving at the waypoint.

Each SID and STAR may contain more than one path leading to or from the airport. These variations are called "transitions". To glean a list of waypoints from a SID or STAR, you have to determine which transition applies to this flight route. Generally speaking, the last waypoint in the indicated SID will be the first waypoint along the flight route's list; and, the last waypoint given before the STAR is the entry point for that STAR's particular transition. Follow the arrows to determine which waypoints are a part of your comprehensive, consolidated, full route.

CAUTION: Some SIDs and STARs are general, and can be used no matter what the active runway is at the associated airport. Others have different variations depending on the takeoff or landing direction. Still others are completely specific to one particular takeoff or landing direction. Before proceeding with the whole entire process listed below, you will probably want to get a quick weather briefing at your departure and arrival airports via The National Weather Service METAR Search Page and check to ensure your SID and STAR are appropriate for the surface wind direction. Otherwise, you may have to substitute a different arrival or departure procedure, and in fact, that could also affect the jetway paths that connect the two. So you might just have to choose one of the other route variations FlightAware gave; this is the main reason there are such variations.

There is a website called simroutes.com that will do some of the work for you; however, it might be better just to use the actual charts and published procedures to get a more complete understanding of what's going on. It's up to you.

At the completion of this step, you should have a list of specific waypoints (in the form of fixes, VOR's, and other nav-aids) that form your complete route from departure to arrival.

Step 2 -- Determining a Cruise Altitude

Real pilots determine their preferred cruise altitude and fuel load simultaneously, in a complex dance of mathematical catch-22s: generally, better fuel efficiency is achieved at higher altitudes, but it takes more fuel to get the plane up higher. Adding extra fuel increases weight, which makes climbing more difficult and thus burns more fuel. Thus, finding the best cruise altitude is about knowing where the trade-off of burning more fuel to get to higher altitudes pays off by burning less fuel once you get there. To further complicate matters, especially on longer flights, more fuel efficiency can often be gained by climbing first to an "initial cruise", burning off some of the fuel and thus some of the weight, and then climbing in one or more "steps" to higher cruise altitude(s) as the flight progresses. Of course, this trade-off point is different for each aircraft, and is also affected by the passenger and cargo load aboard at the time.

If you know all of the calculus involved in figuring that out, or just happen to have an E6B aviation calculator at your disposal (and the training and knowledge to know how to use it), congratulations. You should probably consider getting a job doing this for real.

TransGear pilots can estimate a reasonably good cruise altitude using several different methods. One is to refer back to the flight path generated by flightaware -- each flight plan it displays includes the actual, real-world cruise altitudes that were used. Of course, whether these altitudes make sense for your aircraft type and passenger/cargo load is anyone's guess. So here's a guideline that should get you close enough.

One thing you want to know is that, typically, Westbound flight legs (which are defined as headings of 180-359) are assigned altitudes 500 feet above an even thousand up to 16,500, and an even round thousand at or above FL180. Eastbound flight legs (000-179) are assigned to altitudes 500 feet above an odd thousand up to 15,500, and odd round thousands at or above FL190. (NOTE: North- and South-bound flights often have to change altitudes on each leg, given the exact heading of that leg, to remain in compliance with this guideline!)

So here's what I suggest. Take the total trip length (whether you add up the mileage in each segment, or just use the point-to-point mileage from the origin to the destination as an estimate, it's probably fine either way), add two zeroes, and adjust to the closest valid level per your direction, and there's your cruise altitiude. For example -- if the flight is Eastbound at 263 nautical miles, the desired cruise altitude will be somewhere around 26300. The closest Eastbound altitude to that is FL270. That should work perfectly fine for a cruise altitude for your flight. I recommend that you cap things at about FL350 or so, or perhaps less depending on your aircraft type and load, as climbing any higher (i.e. approaching the service ceiling of the aircraft) will certainly be less fuel-efficient at high load levels.

After this step, you should have in mind a definitive cruise altitude you intend to use for your flight.

Step 3 -- Assigning Intermediate Altitudes

Once you have your cruise altitude determined, you'll want to assign an intermediate altitude to each of the waypoints along the route. Especially if the aircraft you're using supports a Flight Management System that automatically loads the new target altitude into the autopilot settings as you cross each waypoint, this can make the flight a largely automated process.

Take your long list of waypoints, and start with the ones from the SID. Go back to that SID chart and you'll notice there are altitude markings along most of the paths between listed fixes. Most of the time, those are guidelines, or even minimums -- not necessarily assignments -- and we're going to ignore those for the moment. However, there will be some that are listed with an altitude that is underlined (a minimum), "overlined" (a maximum), or both (a firm assignment). Also, some will be accompanied by a notice reading "VERTICAL NAVIGATION PLANNING INFORMATION: Expect clearance to cross at {x,xxx}." For any such points on your SID or your STAR, go ahead and list those associated altitude restrictions for reference.

The next thing to do is to take those firmly assigned points and work forwards or backwards between them, up to and including your cruise altitude, to fill in the gaps. This is where it becomes important to know a little bit about the climb and descent performance of your aircraft.

Real pilots have access to performance charts about their aircraft that predict its climb performance when flying under certain parameters. They also fly according to strict guidelines in a very tightly defined flight envelope, meaning that the exact pitch angles and thrust settings are precisely laid out and followed. This makes calculating the climb or descent rate a matter of plugging a couple of variables into a formula, or consulting a performance data chart, or some such.

TransGear pilots can estimate these rates: the average climb and/or descent rate is about 1,500 feet per minute for a jet transport, and upon departure it's traveling at 250 knots, which is just over 4 nautical miles per minute. That means, using rounded figures, that for every nautical mile forward your plane moves, it climbs or descends just about 400 feet. At cruise speeds, this is more like 300 feet per nautical mile. If your aircraft climbs or descends at a rate radically different than that, you can adjust the preceding as needed. Given that your SID and STAR charts should indicate the distance between waypoints in nautical miles by a number below the route line segment enclosed by parenthesis (such as "(3)"), you can work out how much your altitude can reasonably be expected to change from one waypoint to another. Now you can go back to see which of the minimums make sense, and which need to be ignored because of a firm altitude at a subsequent waypoint. Thus you can fill in reasonable expectations for altitudes at each, ensuring to leave each firmly assigned one as-is.

Clearly, you should mark all of the waypoints along the jetways (the "cruise path") with the cruise altitude. If you are employing the step-climb technique, you can use certain waypoints as your markers for your next step, and increase by intervals of 2,000 or 4,000 (to remain on the correct altitude for your direction of travel). Real-world pilots would naturally have to gain permission from ARTCC ("Center") controllers to do so; but, since Center controllers are rare in FlightGear, and non-existant within TransGear events, pilots can manage their own step-climbs (if desired) in this, probably automated, fashion.

At the conclusion of this step, you should have a long list of waypoints, each with an assigned altitude.

Step 4 -- Determining Fuel Load

Real-world pilots, to reiterate from above, determine fuel along with cruise altitude. They have detailed charts which lay out the expected fuel burn rates from ground to various cruise levels, and at cruise at various levels, and probably at various weights as well.

TransGear Pilots have a variety of options when it comes to shortcuts that can be taken. One part is already done, since the cruising altitude has already been set.

For one, if you wish to avoid the messy question of fuel altogether, you can simply fuel their aircraft to capacity, reduce your passenger and cargo load to ensure the aircraft is under its maximum takeoff weight, and consider this step done.

However, if you want to take a more realistic (yet still heavily simplified) tack for fuel loading, the below is a process that has worked very well for me. Here's what you will need.

First, you will have to have some sort of data regarding the fuel your aircraft burns getting to altitude, and how much it burns at cruise at various altitudes. If you don't have this data, a simple and fairly quick test flight at max takeoff weight, climbing to a high cruise and taking note of the fuel burned to altitudes in various intervals, then descending in steps and noting the fuel flow rate at each level (by checking the fuel flow gauges, if equipped, or by checking the difference in weight over a six-minute interval and multiplying by ten for an hourly rate), can get you some pretty reasonable figures. I have done this for a couple of aircraft and the resulting chart is posted on the Charts and Resources page. (No, this process isn't exact; less so for the cruise than the climb data, as the weight of the plane is decreasing slightly as you drop from level to level. However, the result will be a chart of estimated fuel burn rates to and at a variety of cruise altitudes, and these numbers will be plenty close enough for our purposes.)

Now that you have the data, you can determine the fuel load for your flight. To do this, you need to know the total distance. You should add up the nautical miles in each route segment if you can, but a close-enough estimate can be made with a simple point-to-point distance between the departure and arrival airports. I found using data from TransGear's USA West hub (events 5 through 8) that using a charted IFR flight path added an average of 13% additional mileage to each flight over its direct distance, so you can estimate by multiplying the straight-line amount by 1.13. Once you have this, your total fuel load will consist of three separately estimated steps:

Certain aircraft have detailed specifications for how the fuel load should be distributed for good balance and handling. However, if your aircraft lacks these procedures, the best way to handle it may be to take the total fuel load divided by the total fuel capacity (to get a decimal representation of the "percent full" your plane will be), then multiply that by the capacity of each tank to determine how much to fill that tank. For example, if the fuel load you come up with is 12,000, and the plane's tanks hold 8,000, 8,000, and 4,000, then the percent full is 12,000 / 20,000 or 0.6; the larger two tanks should be filled to (8,000 x 0.6 =) 4,800, and the smaller tank should be set to (4,000 x 0.6 =) 2,400. Thus, all three tanks will be at 60% capacity, and the plane should be fairly balanced.

Once this step is complete, you should have a figure for total fuel needed, and have an idea how it should be distributed.

Step 5 -- Preparing to Follow Your Route

At this point, you have all of the routing information you need. The question is, what do you do with it?

The answer depends on the aircraft you're using, and possibly the version of FlightGear as well. If you are using an aircraft which works with the Flight Manager options in FlightGear, or that has its own Flight Manager/Flight Director implemented, this step essentially encompasses a bit of "data entry" -- starting FlightGear and then entering in each waypoint in succession, with its associated altitude if your aircraft's system supports that. Ideally, you should also indicate the inbound and outbound radials, but that may not be possible in most of FlightGear's navigation systems just yet. In the future, some systems will support (or even require) that the entire SID and STAR be loaded as whole units. Also, depending on aircraft and software version, you may need to select "Slave NAV to GPS" in order to get one of your NAV instruments to show course deviation information.

On the other hand, if you are planning to use standard radio navigation, you have your work cut out for you, and are about to discover why older flight crews included one person whose sole responsibility was flight navigation.

Take your list of waypoints and grab those SID and STAR diagrams and sectional charts. Hopefully you've read my earlier caution about SIDs and STARs marked "RNAV", and thus any waypoints that are designated by a five-letter name are Intersections, which are represented on the diagram by a triangle. Otherwise, five-letter named waypoints may also be GPS Fixes, designated by a four-point star, which you can't locate using traditional radio navigation. Three-letter locations are VORs, and are shown on the SID and STAR charts by a hexagonal symbol; on the sectional, they're shown as circles with gradients marked in five-degree intervals.

For each VOR, if you haven't already, you'll need to make a note of its frequency, and the radial you are supposed to approach it from as well as the one you should depart it by. Intersections, though, can be substantially trickier. Some are locatable by tracking a given VOR radial to a certain DME; others, you can only accurately locate by tuning a second VOR and selecting a given radial off of this cross-reference point. When both of your NAV radios are set to the correct VORs and radials, and both of the Course Deviation Indicator needles are centered, you're at the intersection of the two radials. For those instances, you'll want to jot down BOTH VOR frequencies and radial settings needed to locate this point.

Once you start FlightGear, set your NAV radios for as many of the first few waypoints as you can, utilizing both radios' active and standby frequencies. Once you're airborne, the first few points in the SID may rattle by pretty quickly; thereafter, you should have some time on each leg to set the next, but it's nice to have done all of the research on the correct frequencies and radials ahead of time, since your attention will be divided once you're underway. (NOTE: Again, the reason for a 3-man crew is starting to become evident, isn't it? Heaven forbid you encounter weather enroute, and have to divert to a whole new flight path, while still safely flying the plane!)

After completing this step, you should be ready to start FlightGear and begin setting up for your flight.

Additional Resources

There are numerous tutorials available on the web for simulator pilots learning to follow real-life published procedures. Here are two in particular that are very helpful; in fact, both were instrumental in developing this checklist. Both are designed with MicroSoft Flight Simulator and VATSim in mind, but are perfectly applicable to FlightGear and TransGear Airways as well. The first is a PDF file, which is especially useful because it focuses on KSLC in particular. The second is a four-part video series.

The PDF is available here: http://www.dc3airways.com/technical/files/dva%20How%20to%20Read%20Charts.pdf

Here are the links to the video, in four parts: