VFR navigation


VFR

One of the most fun things to learn in both theory and practice when flying, is VFR navigation. Below I'll try to make a summary on how to do, both in real world as in a sim.

VFR means Visual Flight Rules. Although the rules may differ a bit considering the airspace you are flying in, it basically consists of a minimum horizontal distance to clouds, a minimum vertical distance to clouds and always having view of the ground. In short: you are navigating on your surroundings and landmarks. This also means that no form of instrumentation is necessary to navigate (but you do need some to fly and keep to the rules of the airspace you are flying in). In practice, only a compas and an altimeter are all that is needed. this leads to the most fun to be had and training to be gained by using an aircraft without much more than those two instruments. In FSX I'd suggest the Piper Cub (A2A or default). In real life I fly the Scheibe SF25 Motorfalke.

Preparation

As you may find yourself flying lands not yet visited, you will not be familiar with the surroundings. Therefor, a navigational plan is in order to make you feel comfortable. Usually this too falls under the 6 P's: Proper Planning Prevents Piss Poor Performance. And while navigating "under de horizon" is relatively easy, doing so "over the horizon" requires a certain amount of trust in your own planning in order not to go panicky (trust me, I've been there...) when your surroundings become completely unfamiliar to you, and unexpected at that certain time.

To start, you need to know the indicated cruising speed of your aircraft. Next, you need to measure distance between your chosen landmarks. Third, you need a watch. A great way to plan is to use a flight map, on which you can pencil stripe your course or legs between chosen landmarks. Usually it's a mix of straight A to B navigation and A to B via C navigation based on a landmark at C. Another great help is google maps, showing you before even flying how a landmark looks exactly. A nice application to use while sim flying is skyvector.com. No only convenient for IFR flying, as programmable waypoints are also in there, it holds a ton of information for the VFR flyer.

Also, to calculate stuff, a handy "E6-B flight computer" or "whizz wheel" can be obtained. You can usually buy a cardboard one for around 15 euros, which is sturdy enough to last you years. There's also online versions to be found (http://www.csgnetwork.com/e6bcalc.html) which I'll use below, and naturally apps for your mobile. I normally use it for calculation of time vs distance and wind drift correction, but you can use it for a ton of other applications. If you're interested, I'd recommend buying one or using the online version a lot, as with some exercise it will help you get precise numbers on the fly, even when flying instead of preparing.

So how to prepare?

Step 1: where to go today?

The most important question! For this exercize, I'll choose Morgantown KMGW, to Parkersburg Mid Ohio Regional KPKB. The first part is over open country, without much landmarks. We could just set a straight line course and time it, but if we would stray, especially to the south, we would wander endless green surroundings. So I chose a mid solution: do a limited time over featureless green until we hit a good landmark, and continue over feature rich terrain towards our destination. Yes, that takes more time, but gives confidence, security and fun. As such, our plan is seen in Picture 1.

Step 2: calculations

We basically have 2 legs: from Morgantown West to New Martinsville and the Ohio river; and from there South West towards Parkersburg, loosely following the Ohio River.

The first leg is basically a course over relatively featureless terrain. Relatively, because we will be crossing roads, railroads and powerlines. But, because we lack a crossing of any one of those, the navigational value of them is moot. That's why bridges, crossings, cloverleaves and such are such excellent landmarks to navigate on, with crossings of water the best, since water can be seen from far away as opposed to roads only.

Our leg to New Martinsville is 44nm on a track of 279 degrees. Around halfway we will cross highway 250, from Cottontown south to Mannington. This provides a mental note, and could be used as a time mark point on our navigational plan. We also know that our aircraft cruises at 60KIAS. to be very thorough we should convert that to TAS, but our low altitude and short flying time will not yield large differences. Using the online E6-B, we can see that 60KIAS at 3500ft gives us 64KTAS: 4 kts, being 4 nm/h, on an estimated 40min track. But ok, let's use the 64KTAS. We also know that the wind in general on our planned flying altitude is 12 kts coming from 060 degrees: on the left of our tail. This will mean 2 things: our ground speed will be higher than our indicated flying speed, and the wind will drift us right of our planned track.

To conclude: distance = 44nm
track = 279 degrees
speed = 64 kts TRUE
wind = 12 kts from 060

Add this all together in our E6-B "heading, ground speed and wind correction angle", and we get:

Heading = 286 degrees

GS = 73 kts

Wind correction = 7 degrees (as you see as a difference between track heading)

Note that I'm not using stuff around magnetic variation. My real world experience is that this is good to use when you have a course finder, but not so much with a whisky compass see-sawing around on our plane's every move in the wind, making anything out of 3 degree margins pointless. In real life I never do so.

We now also can calculate time over target.

With a ground speed of 73, we'll spend a rounded 36 minutes te cover the 44nm. That also means we'll fly over the aforementioned highway 250 in about 18 minutes. In a well featured terrain, time is not so important, except on your fuel burn vs fuel carried. But in highly wooded areas time is essential. You can discover the wind is a little off in heading or speed, meaning 1-2 minutes faster or slower over your intended target. Any more and you're likely just flying in the wrong direction...

Step 3: further calculation on all legs

Rinse and repeat on the other leg(s). Our second leg takes us from New Martinsvill South West towards our goal.

We can basically follow the river here, keeping it on our left hand side as it meanders to the South South West. Once it turns sharply to the right, we know the airport is right behind that turn. We also have a whole scale of landmarks, the most prominent being hills and their accompanied heights. Don't count too much on those though, since in wooded area's hills tend to blend in the background, making flying from hill to hill highly prone to errors. There are several towns also. St. Mary is a good reference point, as it stradles the river on the east bank, just before a sharp kink right of said river. Further on there are some lighted stacks of 1633ft high. Probably a factory of some sorts, but nice to know. Both town and stacks I will not use as navigational points. But they are great for reference as I follow the river versus time spent. Other things pointing out are minor roads and power lines. Again: unless they cross a waterway or eachother, they are for reference only.

So rinse and repeat: distance = 32nm
track = 244 degrees
speed = 64 kts TRUE
wind = 12 kts from 060

Into our E6-B again:
Heading = 245
GS = 76 kts
Wind correction = 1 degree.
--> Time to spend = 25 minutes.

Using the same track, I'll pass the town of St. Mary around 18min on my 9 o'clock, and 3 min after that the stacks on my 9 o'clock. Beware to use your relative position of 3 and 9 o'clock only. Why? Because 10 o'clock can easily be 1030 or 0930. It's a bit of dead reckoning. In most slower aircraft the wingtip is straight from your fuselage, so your wingtip is always precisely your 3 or 9 o'clock. Don't guestimate!

After that it becomes easy enough. The navigational part now over: contact tower, enter traffic pattern and land.

If you practice this enough, you'll notice your flying becoming very fullfilling and way more fun than a set-heading-bug-and-engage-AP kind of thing. See the pics below for further matchings of our plan and the landmarks we actually encounter during our trip.

Have fun, and I hope more of you will join me on the trek across the USA in a Piper Cub to practice this.