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I think this stems from a common misconception that ATC is “in charge.” Yes, compliance with ATC is mandatory, but in an emergency, priority number one is to fl

I think this stems from a common misconception that ATC is “in charge.” Yes, compliance with ATC is mandatory, but in an emergency, priority number one is to fly the airplane. ATC can’t help you there. Communication with ATC is priority number three. ATC cleared the airspace for her and has her on radar; there’s nothing else they can do.

weaksauce 9y ago
Aviate, navigate, communicate... in that order.
- dingaling 9y ago
  That's an axiom, not a law. For example it would be inadvisable to navigate a stricken aircraft through an airport's terminal manoeuvring area without prioritising communication with ATC. Quick way to make things much worse. Or trying to navigate to a diversion airfield without first communicating to ensure that it is usable. Aviate, then navigate and communicate.
  - lutorm 9y ago
    Not at all; once you declare an emergency, it's ATC's job to get everyone else out of your way. It's obviously better if you tell them what you're going to do, but that takes a backseat to actually handling the emergency.
barty1 9y ago
Last thing a controller wants to do is to get in the way of the pilot flying the airplane in the event of an emergency. I worked a light aircraft that had iced up a couple of months ago, and the only thing I really did was to relay whatever information I had to help the pilot find his way out of the ice.
tialaramex 9y ago
I don't think it's correct to say that compliance is "mandatory". The set of circumstances in which a pilot ordinarily must disobey direct instructions from ATC is small, but it's not empty. And ATC rarely gives direct instructions anyway, a lot of what is said by ATC is phrased in terms of permission for the pilot to do things they should probably choose to do. If they respond "Unable" the ATC isn't going to write them up for violating some rule, they're going to look at how to work around this. A very obvious example where the Rules explicitly tell pilots to disobey ATC is instructions from local technology that isn't co-ordinated with the ground, such as Ground Proximity Warning System and Traffic Collision Avoidance System. If these systems decide that overall "Climb, Crossing Climb, Climb Now!" is the correct instruction, but your controller suggests descending, the Rules are clear that you should all obey the machine and it will probably be fine because the machine is doing its own real time conflict resolution and re-assessing the local situation. The Rules say you should tell the controller why you didn't obey their instructions but again, not as a greater priority than flying the plane.
- danaliv 9y ago
  I think we’re in agreement. :) I was referring to § 91.123 (a), which reads in part (emphasis added): “When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory.” I.e. when ATC tells you “turn left heading 135,” unless you have a very good reason not to, you must turn left to heading 135. The part I didn’t emphasize is of course exactly what you’re saying. I suppose another way to phrase what I meant is that while ATC is the boss “in the small,” the PIC is the boss “in the large,” and I don’t think non-pilots think of it that way.
mncharity 9y ago
> Yes, compliance with ATC is mandatory, but in an emergency, priority number one is to fly the airplane. https://www.ecfr.gov/cgi-bin/text-idx?node=se14.2.91_1123 https://www.ecfr.gov/cgi-bin/text-idx?node=se14.2.91_1123 : (b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised. (c) Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible. https://www.ecfr.gov/cgi-bin/text-idx?node=se14.3.121_1557 https://www.ecfr.gov/cgi-bin/text-idx?node=se14.3.121_1557 : (a) In an emergency situation that requires immediate decision and action the pilot in command may take any action that he considers necessary under the circumstances. In such a case he may deviate from prescribed operations procedures and methods, weather minimums, and this chapter, to the extent required in the interests of safety. https://www.law.cornell.edu/cfr/text/14/91.3 https://www.law.cornell.edu/cfr/text/14/91.3 : §91.3 Responsibility and authority of the pilot in command. (a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft. (b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

weaksauce 9y ago

Aviate, navigate, communicate... in that order.

dingaling 9y ago
That's an axiom, not a law. For example it would be inadvisable to navigate a stricken aircraft through an airport's terminal manoeuvring area without prioritising communication with ATC. Quick way to make things much worse. Or trying to navigate to a diversion airfield without first communicating to ensure that it is usable. Aviate, then navigate and communicate.
- lutorm 9y ago
  Not at all; once you declare an emergency, it's ATC's job to get everyone else out of your way. It's obviously better if you tell them what you're going to do, but that takes a backseat to actually handling the emergency.

barty1 9y ago

Last thing a controller wants to do is to get in the way of the pilot flying the airplane in the event of an emergency. I worked a light aircraft that had iced up a couple of months ago, and the only thing I really did was to relay whatever information I had to help the pilot find his way out of the ice.

tialaramex 9y ago

I don't think it's correct to say that compliance is "mandatory". The set of circumstances in which a pilot ordinarily must disobey direct instructions from ATC is small, but it's not empty. And ATC rarely gives direct instructions anyway, a lot of what is said by ATC is phrased in terms of permission for the pilot to do things they should probably choose to do. If they respond "Unable" the ATC isn't going to write them up for violating some rule, they're going to look at how to work around this. A very obvious example where the Rules explicitly tell pilots to disobey ATC is instructions from local technology that isn't co-ordinated with the ground, such as Ground Proximity Warning System and Traffic Collision Avoidance System. If these systems decide that overall "Climb, Crossing Climb, Climb Now!" is the correct instruction, but your controller suggests descending, the Rules are clear that you should all obey the machine and it will probably be fine because the machine is doing its own real time conflict resolution and re-assessing the local situation. The Rules say you should tell the controller why you didn't obey their instructions but again, not as a greater priority than flying the plane.

danaliv 9y ago
I think we’re in agreement. :) I was referring to § 91.123 (a), which reads in part (emphasis added): “When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory.” I.e. when ATC tells you “turn left heading 135,” unless you have a very good reason not to, you must turn left to heading 135. The part I didn’t emphasize is of course exactly what you’re saying. I suppose another way to phrase what I meant is that while ATC is the boss “in the small,” the PIC is the boss “in the large,” and I don’t think non-pilots think of it that way.

mncharity 9y ago

> Yes, compliance with ATC is mandatory, but in an emergency, priority number one is to fly the airplane. https://www.ecfr.gov/cgi-bin/text-idx?node=se14.2.91_1123 https://www.ecfr.gov/cgi-bin/text-idx?node=se14.2.91_1123 : (b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised. (c) Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible. https://www.ecfr.gov/cgi-bin/text-idx?node=se14.3.121_1557 https://www.ecfr.gov/cgi-bin/text-idx?node=se14.3.121_1557 : (a) In an emergency situation that requires immediate decision and action the pilot in command may take any action that he considers necessary under the circumstances. In such a case he may deviate from prescribed operations procedures and methods, weather minimums, and this chapter, to the extent required in the interests of safety. https://www.law.cornell.edu/cfr/text/14/91.3 https://www.law.cornell.edu/cfr/text/14/91.3 : §91.3 Responsibility and authority of the pilot in command. (a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft. (b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.