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Instrument Tip: Trust, but verify

Was that clearance really for you?

In instrument flying your clearance is everything. It serves as your route map, your guide, and your permission slip. Since flying on instruments in controlled airspace is completely dependent on your clearance, getting it right is critical.
Instrument Tips

Clear communication between pilots and air traffic control is always important, and a clearance represents one of the most critical types of communication. When it goes wrong and the pilot doesn’t do what air traffic control is expecting, a tongue lashing is the least of the pilot’s worries. Certificate actions or safety-related problems are very real possibilities.

For decades this clear communication was a joint responsibility between pilots and controllers. The controller gave the clearance, the pilot acknowledged the clearance, and the controller confirmed the proper receipt or issued a correction. This procedure is laid out in the Aeronautical Information Manual. There it says the pilot’s responsibilities are to acknowledge receipt and understanding of an ATC clearance; read back any hold short of runway instructions issued by ATC; request clarification or amendment, as appropriate, any time a clearance is not fully understood or considered unacceptable from a safety standpoint; and promptly comply with an air traffic clearance upon receipt except as necessary to cope with an emergency.

On the other hand, controllers are expected to issue appropriate clearances for the operation to be conducted, or being conducted, in accordance with established criteria; assign altitudes in IFR clearances that are at or above the minimum IFR altitudes in controlled airspace; ensure acknowledgement by the pilot for issued information, clearances, or instructions; and ensure that readbacks by the pilot of altitude, heading, or other items are correct. If the readback is incorrect, distorted, or incomplete, the controller makes corrections as appropriate.

All pilots, but especially those on instrument flights, must be 100 percent sure of any clearance before taking an action.That last point, ensuring readbacks are correct and taking action if incorrect, seems like a critical part of the relationship. And for the most part it works well. Yet in 2000 the FAA took action against a pilot after he violated a clearance he had read back incorrectly and the controller didn’t catch the mistake. In short, the pilot acknowledged another airplane’s clearance and took action based on his belief that the clearance was for him. The controller didn’t correct him, and the FAA took away his certificate.

There are a number of important lessons from this precedent. The FAA’s interpretation of the rules made the point that the pilot is the final authority as to the flight, and that the regulations are clear that he or she must abide by a clearance unless an emergency exists. Nothing else matters.

Effectively, this means all pilots, but especially those on instrument flights, must be 100 percent sure of any clearance before taking an action. The good news is that rarely is an action required immediately. Before making a turn, changing altitude, putting a new fix in the GPS, or anything else that will change your current trajectory, ask yourself if what you heard was genuinely meant for you, and question things that don’t make sense. A clearance to a fix well off your course should raise alarm bells, as should unusual altitude changes. And especially if another airplane with a similar N number is on the frequency, verify everything you hear by repeating back, taking notes, and so on.

As surprising as it is that the pilot was violated, it’s comforting to know that this is an unusual case. Controllers are just as invested in making sure the clearance is received correctly as the pilot is, which means they are usually patient with questions and clarifications. Regardless, the case is one of many examples showing it’s the pilot’s sole responsibility to make sure the flight is conducted safely and within the regulations.

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Ian J. Twombly

Ian J. Twombly

Ian J. Twombly is senior content producer for AOPA Media.

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