Monday, April 2, 2012

Navigation

I'm working with a commercial pilot candidate for the first time in quite a while, and the process is raising some interesting questions. The flying part hasn't changed much in the past 75 years or so, but in the USA commercial pilots candidates are required to have two hours each of day and night cross-country (navigation) training.

And I don't know what to teach him.

When confused about how to proceed there's often an axiom that starts things moving in the right direction. For commercial pilots, the axiom is "planning - anticipation - orientation -- efficiency." The commercial maneuvers themselves (steep turns, lazy 8s, chandelles, etc) are really just a vehicle for a pilot to plan and execute a complicated series of tasks. Many other tasks might do.

And so the goal of commercial navigation training must be to give the pilot practice planning and executing a complicated series of (navigational) tasks.

The rise of database navigation has been a true paradigm shift. (What most call GPS navigation and a few call RNAV is really database navigation: it's less important to know how the unit determined your position than it is to know that it has a database of fixes and elevations and procedures.)

So database navigation has to be part of the curriculum. It's very likely that his handheld has an expired database (truth to tell, my handheld has an expired database), so it is extra important to carry current charts. This used to mean a subscription to paper charts, but now the various iPad apps make it really easy to have current charts.

Route planning fits the axiom. An acceptable daytime route may be unacceptable when it's dark. Day or night, choose alternatives along the way, and beyond. Always plan the fuel realistically; for example, if anti-ice requires more fuel, you plan on using anti-ice the whole way. Know or anticipate what controllers will do, especially in airplanes whose fuel burn depends on altitude.

He needs to know how to program the route he chose (how do you get a lat/long into your handheld?), and how to reprogram a route. It would be nice if he knew what RAIM is, but this is VFR flying so there is no real requirement. I'll mention it, but only provide details if he asks.

The textbooks (unless there is one that I have yet to see) still include a lot of E6B problems. I don't think the need to adjust for the wind is going to disappear anytime soon, although GPS track and groundspeed make it much easier to find the proper wind-correction angle. But even without GPS, I am finding less and less use for the E6B. Since I don't fly high altitudes anymore, I don't need it to figure True Air Speed. But I also don't need it to figure wind correction angles: all of my E6B calculations have been replaced by the Rule of 60, an interesting little bit of mathematics that few pilots know even though the FAA requires it for every knowledge test except maybe parachute rigger.

The Rule of 60 says that if you are off-course by 1 degree then after 60 miles you will be 1 mile off course. This is a proportion, so after 30 miles you'd be half a mile off, and after 120 miles you'd be 2 miles off. The proportion still works for "small" angles, so after 60 miles with a 2 degree error, you're 2 miles off course, and with a 3 degree error you'd be 3 miles off.

(For the math nerds out there, the reason is that the sine of a small angle is approximately the angle, when the angle is measured in radians. One radian is about 60 degrees, so 1 degree is 1/60 of a radian. 'Nuff said.)

So when there's a 20 knot wind 15 degrees off the bow in our 140 knot Cherokee Six, the crosswind component is about 5 knots (20*(15/60)), the wind correction is about (5/140)*60, or 2 degrees, and the groundspeed is a little over 120. Close enough.

He needs to plan his descent carefully to avoid shock-cooling the engine, and to anticipate what pattern entry will work. This means knowing the forecast winds, and knowing the NOTAMs about runway closures. Runway slope or obstacles might be an issue, so the Airport/Facility Directory is a must (Have you noticed that the Electronic Flight Bags have resurrected the A/FD as the primary source of airport information?).

Departing from a strange airport means reviewing terrain, slope, SIDs and DPs, and the like.

I think he's going to be busy...

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