“Unable” by Deanna Wallace

“Unable” by Deanna Wallace

“Unable” by Deanna Wallace

Air traffic controllers are a mystery to some. Through time and experience, most pilots become comfortable talking to air traffic control (ATC) and operating fully within the national airspace system. They adeptly navigate through normal and special use airspace, arrival and departure procedures and instrument approaches into airports. As pilots, we take pride in being able to communicate professionally, effectively and efficiently. This includes being attentive to radio calls, filtering the information down to what needs read back, making those readbacks timely, and carrying out the given instructions as prescribed. There is no small amount of satisfaction that comes with a callback well done. But what happens when you receive an instruction that causes you to pause and wonder if you can, or should, comply?

As students, we are groomed to believe controller instructions are as good as law and the final say in what we are allowed to do when within a controlled environment. The law of primacy tells us that which is learned first tends to stick in your mind better so, because your very first instructor instilled the fear of the ATC gods and compliance in you early on, many of us never learn to appropriately question or act contrary to an ATC instruction. Let us take a look at the regulation governing ATC clearance compliance, FAR 91.123, and see how we, as pilots, are really required to act.

91.123(a) clearly tells us once a clearance has been issued, we cannot deviate from it unless:

  1. We have prior permission through an amended clearance;
  2. We have an emergency that requires a deviation from the original clearance for safety of flight;
  3. We are operating in response to a resolution advisory from an installed traffic alert and collision avoidance system … (Note: this is not referring to all traffic awareness systems, such as is installed in many general aviation aircraft, but rather to those systems that provide generated traffic resolutions with specific instructions on traffic avoidance);
  4. If operating under an IFR flight plan in VFR conditions, the pilot may cancel the IFR flight plan and proceed under visual flight rules, as long as they are not in Class A airspace (above 18,000 MSL); and
  5. Perhaps one of the most underused clauses, “when a pilot is uncertain of an ATC clearance, that pilot shall immediately request clarification from ATC.” Gentlemen and ladies, please, if you don’t understand what is expected of you, think you may have misunderstood an instruction (did they say turn right or left to that heading?), or simply didn’t hear (and/or write) the entirety of the clearance down as it was read to you, ATC would much rather you take up a few more seconds of air time on frequency to get it right than not do as instructed because of a misunderstanding or lack of clarification and create a collision hazard.

The way all that reads, our primary instructors were correct in telling us that ATC instructions (within controlled environments, such as Class A, B, C and D airspace) must be complied with, and it is likely they also stated you could deviate in the event of an emergency (if you’re willing to risk the paperwork, if asked). But any pilot who has operated within the airspace system for any length of time knows controllers, though quite good at what they do, aren’t infallible and don’t always have insight into the specific needs of our mission and our aircraft. So why don’t we hear pilots ask for clarification or use the phrase “unable” more often? Not asking for clarification can be attributed to several factors, including not wanting to be a nuisance by asking a busy controller to repeat or having to admit you may not understand the directions as stated. As far as not saying “unable” to a clearance a pilot feels is outside the scope of their personal or aircraft limitations, the cause can vary from our inherent nature to not question “authority,” as ATC is made out to be from an early stage in our training, to not wanting to admit we or our aircraft may not be capable of something. This is not a trap that only low-time pilots fall into; you are just as likely to see professional pilots in high performance aircraft with the same thought process.

For example, on an IFR flight plan, I have come to expect and know particular descent clearances on routes I fly regularly. Having flown some routes many times, I also know to ask for my descent when the descent clearance isn’t given within a certain timeframe past the usual point because I will otherwise have a difficult time getting the aircraft down by assigned crossing points and altitudes. The first time I flew a familiar route in a turbine aircraft at a much higher altitude, I neglected to ask for this clearance when it wasn’t given to me because I thought I might be assigned something different. It turns out the controller simply got busy, neglected to issue the clearance at the appropriate time, but still expected me to make the same crossing clearance and altitude that I had come to expect.

The beauty of turbine engines is you don’t have to worry about shock cooling them like some pistons and you can somewhat “chop it and drop it” to make a wide range of descent profiles, as long as your pressurization system can keep the cabin comfortable for your passengers. I quickly did the math and determined there was no way I was going to make this descent profile happen and informed the controller I was unable to comply with the crossing restriction but would do the best I could. Did it mess up his arrival flow? Possibly. Was there anything that could have been done about it? Short of a full-blown emergency descent procedure, doubtful. I gave him a solid 2,000-plus fpm descent and still did not make my crossing altitude but, as PIC, I was not willing to ask the aircraft for more, adding unnecessary discomfort to my passengers and putting an undue strain on the pressurization system to keep up. While, as pilots, we try to be as accommodating as possible within the limitations of our aircraft, it is not up to us to be wholly responsible for correcting a lack of planning on a controller’s part … just as it is not up to them to correct for our lack of planning in the manner we would prefer.

While there are many more opportunities for mistakes or miscommunication within the IFR environment, VFR pilots are not immune and should certainly remain vigilant for communication or misdirection errors. Accident and incident reports show pilots can and will blindly follow a controller’s instructions into the side of a mountain, onto a runway another airplane has been cleared to land or take off from, or off in the opposite direction of their destination leaving controlled airspace. Controllers are human after all, and they, in turn, rely upon a pilot’s experience and knowledge to question when something isn’t correct or to tell them when the pilot or aircraft is incapable of performing a clearance. Trust me, they would much rather give you an alternative than to have accident reports to file later.

As a last note, don’t let fear of reprisal or the dreaded “submit a detailed report … if requested” directive mentioned in section (d) of the same part keep you from deviating if necessary for an emergency or questioning a given instruction. Your responsibility as pilot in command is to make the best decision regarding the safety of your flight and passengers over accommodating an ATC clearance. In some rare circumstances you may have to explain your actions in more detail, but most of the time, both pilot and controller adapt, move on, and keep our airspace operating safely and efficiently without any undue hardship to either.

Deanna Wallace has amassed over 6,000 flight hours since she started flying in 1997 and is a 20-year Gold Seal CFI/CFII/MEI with more than 2,000 hours dual given. She holds a Bachelor of Aviation Management from Auburn University and a Master of Aeronautical Science from Embry Riddle Aeronautical University. Deanna is single pilot typed in the King Air 300/350 and flies all King Air variants regularly, including the B100 with TPE-331 engines. Through her East Texas employer, Casey Aviation, she flies Part 91 managed King Airs, ferries aircraft worldwide and actively instructs owner-pilots in the PA46 piston and turbine series aircraft.

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