This is going to be a no-brainer for a pilot, I am sure. I am not one, however, only an enthusiast.

Scenario is: I am flying under the directions of ATC, into a relatively busy Class-B airport and am given a change of heading by them.

Piper N1234A, fly heading 235 ...

The radio is full of communications, and I cannot seem to be able to squeeze in to confirm receipt of heading change. I assume I would start the standard-rate turn immediately, and acknowledge as soon as possible, even if I've already completed the course change?

  • $\begingroup$ ATC is not supposed to assume you received any instructions without hearing a readback. The communications in busy airspace move quickly so incomplete instructions are common, but if you can't squeeze in a readback ATC will usually issue the instruction again $\endgroup$ – TomMcW Mar 27 '16 at 3:12
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    $\begingroup$ SMSvonderTann: sorry, but your edit changed my question from what I wanted to ask to something a bit different. The question isn't about an incomplete instruction from ATC. I stipulate the instruction was received in its entirety, just that the pilot is unable to acknowledge receipt. I wanted to ensure that the pilot is supposed to make the change immediately, and not wait until able to respond with an acknowledgment. Like I said, this is a no-brainer, but I wanted to know I understood the procedures correctly. $\endgroup$ – CGCampbell Mar 27 '16 at 19:00
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    $\begingroup$ If other aircraft are interrupting between the giving of an instruction and its acknowledgement that's a massive violation of radio procedures by them, isn't it? Does that happen significantly often? $\endgroup$ – DJClayworth Oct 14 '16 at 17:24

You are correct, you should turn to the assigned heading immediately unless you aren't sure of the instruction (was that 100 assignment a heading or a speed?).

When ATC gives you a change, it is based on a continuously changing environment and they want you comply right away, as long as it was clear. Usually, doing the wrong thing is worse than doing nothing at all.

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  • $\begingroup$ What if the controller said: "turn right heading 235, climb and maintain...." because of obstacles? So you've turned but you are flying into a sector where you are now below the MVA $\endgroup$ – rbp Mar 27 '16 at 16:49
  • $\begingroup$ Isnt that the pilot's ultimate responsibility to maintain safe flight? Doesnt he always able to say 'unable' and wait for further instruction? $\endgroup$ – vasin1987 Mar 28 '16 at 4:36
  • $\begingroup$ @rbp Then you are in a pickle, because where are the obstacles? Straight ahead? After you turn, but you are okay if you start to climb? This is where your situation awareness becomes even more valuable than normal. As you know, you have options, even up to declaring an emergency so that everyone else shuts up if it is needed. $\endgroup$ – Lnafziger Mar 28 '16 at 17:34
  • $\begingroup$ @vasin1987 Yes, but what if going straight isn't safe? Maybe the instructions were given to prevent an unsafe situation from developing (pretty common). The controller continues to monitor everyone though, and if you don't turn when they expected you to, they should get back to you before it becomes a major problem. $\endgroup$ – Lnafziger Mar 28 '16 at 17:35
  • $\begingroup$ Yeah typically the instruction will come through well before it becomes urgent in order to give time to repeat it if misheard, and react regardless. If it's urgent, you can probably expect an "expedite" to accompany the instruction. $\endgroup$ – Jon Story Mar 29 '16 at 16:54

Your are correct, but I'll offer a different reason than Lnafziger.

  • Aviate
  • Navigate
  • Communicate

Those are your priorities when flying. It is more important that you fly the plane first than it is to answer, in terms of prioritizing your actions.

In class B, you are most likely in radar contact with that controller. Your change in course will become apparent to the controller, and your eventual reply, when you can get it in, will confirm that you have correctly heard/read back the heading he gave you ... or that you have not!

Why it is necessary for flight safety to reply:

"Cougar 355, fly 030, maintain 4000."

You turn towards 300 (because you made a mistake) and you finally get in a radio Call

"Cougar 355, Roger, fly 300, maintain 4000"

The controller is now alerted that you went the wrong way, and he'll issue supplementary instructions (and also check to see if you are about to fly into someone else he has on the scope) ...

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