Lost Arts 2 – Diversion to the Alternate

I have been learning to use the new technology and along the way I have discovered a few situations where the old technology is not only still relevant, it’s more important that ever. One of these situations is planning to divert to an alternate airport…

The “diversion to the alternate” is a skill that has always been vital. The simple fact is that you can’t always land at the airport you planned on when you took off. Many variables could change during the flight that could force you to a different airport than planned — weather being the most likely variable. When a pilot must switch to an unplanned destination, they must be able to literally think on the fly. Now this is where new technology comes in. Many GPS navigation systems have a feature that will, at the touch of a button, display the nearest airports to your current location. The pilot then only has to make a selection, push another button, and their entire route of flight to the alternate airport is displayed. Easy, simple, accurate, and fast. The diversion to the alternate should now be a “no-brainer.

But wait, the technology in the airplane may have changed, but the FAA’s practical test standards have not. The FAA is either behind the times on this, or they are not yet willing to completely turn over to automation the ability of a pilot to divert to an alternate — knowing the FAA, I’m sure its some of each.

The Private Pilot and Commercial Pilot practical test standards both list “Diversion” as a required task and both have identical standards. They both say that in order to pass this part of the test the examiner must “determine that the applicant makes an accurate estimate of the heading, groundspeed, arrival time, and fuel consumption to the alternate airport.” Notice it says that the “applicant” not the applicant’s GPS system, must accomplish this task. This means that you still must use a chart and plotter to pass either test. While you are making these calculations the airplane must be flown within +/- 200 feet for Private Pilot applicants and +/- 100 feet for Commercial Pilot applicants. Then once the decision to divert has been made and a new heading selected, the Private Pilot applicant must fly that heading with +/- 15 degrees and Commercial Pilot applicants within +/- 10 degrees.

Now here is what the examiners in my area are doing. Note: despite the FAA’s best efforts to standardize the oral and flight tests, we all know that there are variations from examiner to examiner, but this testing technique came from an examiner’s required conference, so if your local examiner is not doing this yet, they may start soon. If the Private or Commercial test is given in an airplane that has an advanced navigational system in it, the applicant must know how to use it, but the applicant (at least in the diversion part of the test) must also demonstrate that they don’t completely rely on it.

How it works: When the diversion to an alternate part of the test comes up, the examiner does not turn off the GPS system, but instead changes the screen to the largest possible scale. This means the system will show that your airplane is somewhere in North America but no more information than that. The examiner then tells the applicant that they need to divert to another airport. Sometimes the examiner will select an airport; sometimes they leave that up to the applicant. The applicant must now meet the test standard of estimating the new heading to the alternate airport, and calculating a new groundspeed. With the new groundspeed calculated the applicant must give an estimated time of arrival at the alternate airport and most important of all, must give a fuel consumption estimate. The fuel needed to get to the alternate must then be compared to the available fuel in the airplane.

The real test: Now here is the part where the examiner makes sure that you are not relying on your GPS navigation system too much. All these calculations must be made using a chart, plotter, and old-fashioned flight computer (E-6B). And then finally, your GPS system that works so well and has always told you exactly where you are where you are going, is actually turned against you. After all the estimates have been made, and the airplane turned to the new heading, the examiners returns the screen’s scale to a more normal size, selects the alternate airport in the GPS computer, and hits the button labeled “direct.” The GPS system will then display the exact heading, groundspeed, and time to the alternated airport. If your estimate of heading disagrees with the GPS’s heading by more than 15 degree for Private Pilot applicants (or 10 degrees for Commercial Pilot applicants) then you would fail this task and consequently fail the checkride. In this way, the examiner uses the GPS system to check your work. The GPS is usually your friend, but in this procedure, it becomes an electronic test grader — a grader that is very accurate and cannot be talked into lenience.

THE BOTTOM LINE: Have a great time with the new GPS navigation system, but do not forget your charts, plotters, and flight computers. Practice the diversion often. It is an acquired skill to spot a suitable alternate on the chart, and draw a line across that chart while you are simultaneously flying the airplane (remember you must hold altitude within 200 feet for Private and 100 feet for Commercial). Then take the heading, apply the wind, use the “wind face” side of the flight computer to determine groundspeed, then flip to the “computer” side to calculate time of arrival and fuel consumption enroute. You will rightfully feel that you are juggling more balls than you can handle, so practice, practice, practice. By maintaining this skill you will be ready to pass the checkride — more importantly you will be prepared to safely get back on the ground even if perhaps a solar storm interrupts the new technology when you need it most.