Friday, June 22, 2012

Correction on FAA pilot data

As several readers pointed out in yesterday's comments, I was a bit uncritical in my willingness to accept the FAA data straight out of the spreadsheets.

If I'd looked carefully at the numbers I published, I would have seen that the number of FAA certificates for glider pilots took an unexpected jump between 2001 and 2002.  Here's the change between 2001 and 2002 for glider pilots.  (Note that the "air transport" glider pilots is an entirely new category.)  This data is from "Table 8" in the Civil Airmen Certificates data set, labelled "Estimated Active Glider Pilots by Class of Certificate."    

So what's strange about this is that for the previous 5 years, the growth in glider pilots had been very modest--maybe 200 pilots added / year.  To pick up more than 13K in one year is clearly a recalibration and not an actual event.  

One thing to know about all data sets is that this kind of change in the way you count is happening constantly.  (It's sometimes called "changing the basis," where "basis" refers to the "basis on which your making your measurements.)  

Usually there's a metadata note, and I missed footnote 2 in the original spreadsheet which says: 
 2/  Glider and lighter-than-air pilots are not required to have a medical examination.  Beginning with 2002, glider pilots with another rating  but no current medical  are counted as "Glider (only)".
As you can see, reclassifying "gilder pilots with another rating (but no current medical)" as Glider moved a bunch of people into the glider pool.  

I'm not sure what the "air transport" label refers to.  Do any of my pilot readers happen to know? 

In any case, the 'doubling' I'd been asking about seems a bit artificial. 

So to all of you who guessed that it was an increase in rotorcraft pilots, we'll have to hand you the award for the week.  

Search lesson:  Read the darn footnotes, especially when there are strange, unexplained jumps in the data! 

Thanks to all of the sharp-eyed (and critical) readers who commented.  Much appreciated!  

1 comment:

  1. Air Transport refers to a Pilot who has an Airline Transport Pilot License as well - this authorizes a pilot to serves as a pilot-in-command of an aircraft with more than 9 passengers. To get an ATPL, you have to have your Commercial Pilot License as well, so not sure if those Commercial numbers include the ATP, or if they are just a separate category.