“Pawn to E4.” I can remember back to when I was first learning the game of chess. Lots of discussion was had about how each piece could and couldn’t move. That first day I was overwhelmed with the rules I had to follow, procedure was the only matter on my mind. As far as I knew, you just moved your pieces around the board looking and hoping for an opening to take a shot at your opponent. As you can probably guess, I lost my first several matches that day. In fact, I can’t remember ever winning a match of chess. My lack of practice combined with a complete ignorance of chess strategy has surely led to this string of defeats. Most of us know though, that strategy is a huge part of chess, in fact the strategies behind chess are probably more of what makes chess chess than the pieces and squares on the board.
This relation between procedure and strategy also holds true when it comes to navigation. I can remember back to my first cross country planning lesson and the automatic headache I received. True courses, true headings, calibrated airspeed, outside air temperature, variation, deviation, and the list went on. I was so weighed down with terms and numbers that all I could do was try to follow the procedures and processes I was being taught to fill a navigation log with scribbles. My first cross country flight was a debacle of botched radio calls, missed checkpoints, and chicken scratch addition. On my first solo cross country flight I was terrified of missing my one and only destination that was within spitting of the interstate I had followed to get there. Lets just say it took many many hours of cross country experience to wean myself off of the GPS and finally be comfortable just sitting back and watching the scenery go by waiting for the next landmark to appear over the horizon.
Before we even cover the multitude of factors and procedures involved in cross country planning and flying, we need to first talk about strategy. This is a lost subject in our modern era of the “Magenta Line”. In this and future articles I hope to share some strategies I’ve stumbled upon while out stooging around over the last few years. I think you will find that these concepts will give you some added confidence while out and about on the sky streets.
We recreational pilots are always looking for excuses to go fly. The “exactly 50 nautical mile” airport is of course one of the most sought after destinations, especially if there is food on the other end. We pilots spend a lot of time and effort flying to places that we immediately return from; we don’t leave the home nest empty for long. It’s easy to have the tanks topped off on the rental 172 on a nice day and pop out to some place for a $100 burger. Not much thought required. However, in flying older and smaller airplanes on longer trips, I’ve found more consideration is required before just jumping in and going.
For example, a little problem slapped me in the face two separate times before I finally sat down with pen and paper and figured it out. I used to go out to my glider club all the time in my Luscombe. My tiny fuel tank held just enough gas to legally make it round trip without having to stop for gas. Then one day I had quite the tailwind going out and without much more than a second thought I assumed that boost going out would help get me back even-Steven even with a homebound headwind. It didn’t, and I had to divert for fuel fifty miles short of home. Here’s an explanation of what was happening.
Picture two airports exactly 100 nautical miles apart. Your airplane travels at exactly 100 knots and you need to make a round robin trip for the aforementioned burger. If the winds are calm it’s pretty easy to see that the ground speed both ways is 100 knots and that each leg should take exactly one hour for a total trip time of two hours.
Now imagine you have a ten knot tailwind going out. Groundspeed would be 110 knots and 90 knots on the return. Of course it will take less than an hour going out and more than an hour coming back but how long is the total trip? The first time I looked at this I assumed it would average out and be exactly two hours. So has everyone else I’ve ever posed the question to but in fact this isn’t the case. You may be shocked to find that it actually takes a little longer, two hours, one minute, and thirteen seconds.
To see what I’m getting at here, spool those winds aloft up to fifty knots. Now our outbound groundspeed is 150 knots and fifty knots coming home. At those rates it takes forty minutes going out and two hours coming back for a grand total of two hours and forty minutes. At this point you are probably thinking I’ve broken math or am playing some evil trick with the calculator. Hang in there for two more examples and we will get to the explanation you probably want.
Now consider a ninety nine knot wind for ground speeds of 199 and 1 knot, respectively. Going out takes thirty minutes and nine seconds while the trip home takes one hundred hours. That’s a roundtrip time of one hundred hours, thirty minutes, and nine seconds. That's a long trip for one burger.
Finally, think about the implications of a 100 knot wind. That gives us a ground speed of two hundred knots going out but zero for a return. In pure mathematical terms that means our trip would take an infinite amount of time. None of us have time for that.
What you might notice first from this example, is that a steady wind on an “out and back” cross country never helps, it only hurts. Strangely enough that means the best wind conditions for this type of trip are calm winds. It’s better to have no wind both ways than a steady wind that is a tailwind on one leg and a headwind coming back.
This alludes to the surprising fact that headwinds hurt worse than tailwinds help. To get a grasp on this you have to “start slow”. Imagine your car is having serious issues and can only go one mile per hour. It’s going to take a whole hour to go one mile. Now double your speed to two miles per hour. You just cut your trip time to go one mile down to thirty minutes.
Now let’s take this example from one extreme to another, think of a jet going 500 mph. Push the power up to get 501 mph. You’ve added one mph but that one mph is pretty insignificant to the other 500 mph you already have. On a 500 mile trip that extra mph will save you eight seconds. Basically what I’m trying to say here is that each extra knot you add to your speed gets less and and less significant. Start taking speed away and each knot you lose results in a significantly slower speed.
In summary, we’ve arrived at the first of many important little strategies to keep in mind when out and about. Never assume all things to be equal on a round-robin trip when wind is at play. At the least, on a typical student cross country you may be five minutes late. Unfortunately, when the stakes are higher the outcome could be much worse. In short, always be sure of how much time a potential trip is going to take. Next time we will dig deeper into some more peculiarities of time, speed, and wind.
