My new favorite word: “unable”

Sometimes one word can speak volumes. This is especially true when there’s a well-defined and mutually understood vocabulary that all parties in a conversation are using– which is exactly what happens when you talk on the radio with an air traffic controller. Although it often sounds bizarre to outsiders, the back-and-forth between pilot and controller can be incredibly information-rich. The FAA has a standard glossary that pilots and controllers are supposed to use, and you can’t go far wrong by sticking with it. Many of the terms in the glossary compress a great deal of meaning into a few syllables, which is important when you’re busy– which, as either a pilot or controller, you will be!

For example, the controller at a busy training airport such as Palo Alto (which usually has between 500-700 takeoffs/landings per day, a lot for a small airport with a 2500′ runway) could say “One Tango Golf, there’s a 172 on final. If you go right now, then you can take off on runway 31”, or he can say “One Tango Golf, landing traffic, expedite, cleared for take off, 31”. Now consider the workload of a pilot flying into an airport like Atlanta or Dallas, or a controller in the tower cab at Chicago-O’Hare or Newark, and you see why brevity is so important.

My favorite of all these expressions is simple: “unable”. The glossary defines it thus:

Indicates inability to comply with a specific instruction, request, or clearance.

Depending on how you use it, it can mean “I won’t do that” or “I can’t do that.” Rather than provide a long explanation, all you have to say is “unable.” Suppose I’ve filed a route from point A to point B and the controller wants to have me deviate to point C, and I happen to be low on fuel? “Unable.” Want me to turn towards an area of built-up clouds? “Unable.” Because the pilot in command has ultimate responsibility for the safety of flight, as PIC you have unlimited authority to accept, or reject, controller requests or instructions– with the very significant caveat that you may be required to account for doing so. If the controller tells me to sidestep to a parallel runway on approach, and I don’t, and I cause an accident, having said “unable” isn’t going to get me out of trouble.

The magic word works both ways, of course: when you ask a controller for something (“Niner Eight Mike, request lower” to get a lower altitude, for example) the controller can merely say “Unable” and that’s it. Of course, whoever receives the U-word can always ask for something different, or explain why they want whatever it is.

Now I just need to brief the people I talk to most frequently so they know what the word means to. “Dad, can you take me to the mall?” “Unable.”


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