Why do I not always hear ATC read back by pilots (on required instructions)?

KORD4me
  • Why do I not always hear ATC read back by pilots (on required instructions)? KORD4me

    I enjoy tracking air traffic at my local KORD. I listen on LiveATC and use my private virtual radar setup to get "real-time" traffic info.

    I understand which instructions need to be read back by the pilots per this question however on more than one occasion I don't hear read back on critical vector info on departure, despite the visual confirmation of instruction (pilot making proper vector and speed adjustments).

    I tend to notice this with bigger birds (777,747,340), however smaller regional jets almost always promptly read back.

    Questions:

    1. Is there an alternative way of ATC instruction acknowledgement? (Other than read back?)

    2. Is it possible that the reply is somehow on a different frequency?

    3. Is this just a problem with LiveATC? (One theory is that A/C leaves receiver coverage area and that's why I don't hear reply, however on approach side much bigger distances are heard in my area)

    Thank you


    I did verify that indeed the aircraft that I don't hear read back from receives special departure frequency by tower.

    Once tower clears aircraft for take off and hands them off to departure controller they use "departure" frequency to read back instructions. It is typically different from standard departure frequency.

    The only thing that is not clear is if there is any rhyme or reason for which aircraft gets this special departure frequency and which doesn't.

    As pointed out in the question for some reason mostly it is "big" aircraft that gets this preferential treatment, but I am not 100% sure why.

  • At my airport, KCOS, tower has split frequencies for the east and west runways. 90 percent of the time both are handled by the same controller. They transmit and receive on both frequencies, but you are only listening to one.

  • The O'Hare Eight Departure is the only departure procedure out of ORD. This is what it looks like:

    O'Hare Eight Departure Chart

    Notice that there are three departure control frequencies:

    • Chicago Dep Con West: 125.4
    • Chicago Dep Con East/North: 125.0
    • Chicago Dep Con South: 126.635

    Airplanes are usually given the frequency appropriate for the sector that their first departure fix is located in. If they are very busy, each sector will have its own departure controller and they will be talking to different people. If it isn't as busy, they pilots will still be talking on their individual frequencies, but one controller may be listening to and transmitting on two or all three frequencies at once.

    For instance, if a particular aircraft is cleared over POLO VOR (due west of ORD) they will be given a departure frequency of 125.4 as part of their clearance. Let's say that the traffic is slow and only one controller is being used to cover all three frequencies. If you are listening to the East/North frequency on 125.0, you will hear the departure controller issue a clearance to the aircraft, but never hear the response because the aircraft is transmitting on 125.4.

Related questions and answers
  • by the pilots per this question however on more than one occasion I don't hear read back on critical vector info on departure, despite the visual confirmation of instruction (pilot making proper vector... and that's why I don't hear reply, however on approach side much bigger distances are heard in my area) Thank you I did verify that indeed the aircraft that I don't hear read back from receives special departure frequency by tower. Once tower clears aircraft for take off and hands them off to departure controller they use "departure" frequency to read back instructions. It is typically

  • or VFR approach, or the appropriate missed approach procedure if we're on an instrument approach However, in the US, I often hear the pilot saying "going missed" when breaking off an instrument approach. Is this standard phraseology in the US, or another one of those non-standard phrases which have gained footing? The 7110.65 only mentions the instruction "go around" (which incidentally is analogous.... (I also often hear just "missed approach", which I suppose would be appropriate when checking back in with approach, but not with the tower, although feel free to clarify that for me as well)

  • These are calculations which I use to know when to descend and the Rate: Multiply the ALT of feet to lose by 3 and $Groundspeed\div2\times10$ will give you your required rate of descent for a 3° glide slope. For example: FL350 to FL100 => 25,000 ft down $25\times3=75$, so start at 75 nm GS = 320 kts => $320\div2\times10=1,600$ => -1,600 fpm is your desired rate of descent. How do I calculate without using tangents for degrees, other than 3: 2,5; 4; 5 ...? In my last question I got it wrong, even though through math the answer was correct.

  • Are airspace violations (e.g. entry to class B without clearance) based on primary radar and/or Mode C transponder, or something else? I read that Mode C altitude is based on pressure altitude, i.e., set to 29.92" ... but presumably that's adjusted at the ATC facility based on the current pressure before being used for altitude enforcement. This begs the question, what would stop one (hypothetically), just winding back the altimeter pressure reading to appear to be at a lower altitude? So to summarize: How are airspace violations detected: What data input is used? If Mode C reading

  • Air Force One is obviously a big deal. We close terminals and implement other seemingly crazy safeguards against terrorist attacks while the president is en-route to an airport. How does ATC protect the president whilst in the air? I have heard of TFRs for "VIP in the area" reasons — is that for AF1? I am guessing that the aircraft identification is blocked, but wouldn't they still need... jet was close to Air Force One and was unresponsive to calls. "As we got over Gainesville, Fla., we got the word from Jacksonville Center. They said, 'Air Force One you have traffic behind you

  • I know aircraft commonly have rotary actuators to extend and retract the flaps. I am not sure how many but I think I read two per flap on a 747. My question is what is the result if one actuator fails? I don't know if more then one needs to fail in order for a flap not to extend or retract. I am mostly wondering if could cause an aircraft turn-back because somebody told me it could. However... to landing that would be the other scenario and am not sure what the worst impact on a pilots ability to land would be (assuming one failed unit would prevent a flap extension?). Any experienced pilot

  • I'm in the process of getting my private pilot's license, and I've come to the point where it's probably time to think about buying a headset. As I understand it there are a few options ranging from a standard mic and speakers, to passive noise cancellation, active noise cancellation, and even bluetooth for use with iPhones/MP3 players, which I think is awesome, however I'm concerned about... to some sweet tunes, is there the possibility that having music will exacerbate the aforementioned issues, or what if ATC comes on, and I hear them, but I don't register what they say because I was jamming

  • So the answer in my mind is "of course pilots can fly circling approaches at non-towered airports" (seriously, I could swear that I've done it before, but then again I can't think of any specific examples....). That is, until I ran across this little tidbit in the Air Traffic Control Order while researching another question: 4-8-6. CIRCLING APPROACH a. Circling approach instructions may only be given for aircraft landing at airports with operational control towers. So then the question becomes, why do they have circling minimums at non-towered airports?? No tower here. ATC

  • ATC will sometimes give pilots the instruction to maintain visual separation from nearby traffic. I have a couple questions about this: There is a related question here about traffic separation. Is the required separation in this case different, and how can they judge this? (I would like a bit more detail for this specific case than was provided on the answer there) Normally pilots will follow their flight plan and ATC instructions. What actions should pilots take to maintain separation? I mean, obviously whatever is necessary, but is there any standard method? Should they anticipate

  • I was looking through my virtual radar logs one of the days and found this "glitchy" ADS-B behavior. I am almost 100% sure that this is not due to my antenna or setup since two independent different radars confirmed this weird behavior from FlightRadar24. Also A/C before and after this one did not exhibit this behavior. Does anybody have any thoughts as to what may be happening??? Why... of occurrence is approximately: 3/16/2014 6:09pm CST I have also verified FlightAware is ALSO showing the same weird glitch. See below "yellow" highlighted airplane: Same A/C from FlightRadar24

Data information