Takeoff Clearance on a Ground Frequency

[RonR]

Regarding the GLF4 accident at KBED yesterday, if a tower controller is working both ground and tower (when the airport isn't really busy), is it possible that he/she would issue a takeoff clearance to an aircraft while that aircraft was still on the ground frequency?  That seems to be what happened yesterday with this flight since there was no communication with them on the tower frequency around the time of the accident...

Ron

[Rick108]

That is certainly possible, but what I usually see at non-busy Class C airports is the (single) controller transmits everything on BOTH ground and tower frequencies (and often clearance, too) at the same time.  Typically the pilot would switch to tower before reporting ready to depart, so issuing the takeoff clearance ONLY on ground would be strange, unless the controller had requested they stay on ground for some reason.  Or, possibly they forgot to switch, and the controller just answered them where they called, on ground.  Either way, it's very sad...

[RonR]

Now that you mention it, after listening to the clip again, the controller was transmitting on both frequencies at the same time. Thanks for the clarification Rick.  And yes very sad...RIP...

Sent from my SGH-M919 using Tapatalk

[spades]

You're required to broadcast on all frequencies when sectors/positions are combined.  I wouldn't bother switching a pilot to a different frequency that I was also using unless an operational advantage can be obtained.  For example, some frequencies have the ability to be cross coupled so if I have 3 frequencies but only two can be cross coupled, I might put them on a different one to avoid them stepping on each other.  Also, if you're really combined up like on a midnight shift, then the quality of some frequencies deteriorate even before they leave your new combined sector. 

[JetScan1]

spades,

some frequencies have the ability to be cross coupled so if I have 3 frequencies but only two can be cross coupled, I might put them on a different one to avoid them stepping on each other.

My understanding is that in the US (ARTCC) you only have the ability to cross-couple a maximum of 2 frequencies together. Is that still the case, or are you aware of any areas that have the ability to cross-couple more than 2 together ?

Just for my own curiosity I'm compiling a list of Center frequencies that can be cross-coupled. If you can provide them, just wondering what frequencies you have the ability to cross-couple in the sectors you work ?  

[mkbraun1]

I have been flying and heard a controller have 4 separate frequencies. Center controllers. Depending on certain aiports and their volume, amount of traffic, you can hear an approach controller on approach, tower, ground, and clearance. One other thing is that some frequencies are rated air v. Ground. So you may be able to transmit some specific to airborne traffic verses on the ground. It all depends on the FCC.

[JetScan1]

mkbraun1

I have been flying and heard a controller have 4 separate frequencies. Center controllers.

Yes, the Center controller's can work multiple frequencies, but "cross-coupling" the frequency allows an aircraft on one frequency to hear aircraft that are on a different frequency. This is not the case with the old system where the pilot could not hear the aircraft on the different frequencies the controller was working.

I've been told that with the system used in the US they can only cross-couple 2 frequencies together at a time. This is different than in Canada and Europe where multiple frequencies can be cross-coupled together.

From what I've heard it's slowly starting to be used with more sector pairs in the US at certain Centers, but I've still not heard more than 2 frequencies cross-coupled at the same time.

When you heard the controller working 4 frequencies, could you hear all the aircraft on the other frequencies as well ?

[svoynick]

You're required to broadcast on all frequencies when sectors/positions are combined.  I wouldn't bother switching a pilot to a different frequency that I was also using unless an operational advantage can be obtained.  For example, some frequencies have the ability to be cross coupled so if I have 3 frequencies but only two can be cross coupled, I might put them on a different one to avoid them stepping on each other.  Also, if you're really combined up like on a midnight shift, then the quality of some frequencies deteriorate even before they leave your new combined sector.

Yes, the Center controller's can work multiple frequencies, but "cross-coupling" the frequency allows an aircraft on one frequency to hear aircraft that are on a different frequency. This is not the case with the old system where the pilot could not hear the aircraft on the different frequencies the controller was working.

It seems like you and spades are using two different definitions of "cross-coupling".  I believe spades is referring to only having the controller transmitting on the multiple frequencies he is using, so if aircraft A is working on freq A, and aircraft B is working the same controller on freq B, then the controller's instructions to "A" will go out on both frequencies, and B will hear the controller, but can not hear replies from "A".

You seem to be describing what is called in radio hardware terminology, a "repeater" function, in the sense that when aircraft A transmits, and that audio is received at ATC, thenin addition to presenting that audio to the controller's ears, the ATC radio hardware also retransmits it out onto frequency B.  

I'm not meaning to contradict you - I admit I don't know - but do you have any references explaining this technical detail?  Whether ATC "cross-coupling" is just when ATC transmits on multiple frequencies being worked by one controller (spades' usage), or whether it includes the repeating of received aircraft audio transmitted back out onto a second frequency being worked at a given position (JetScan's usage)? I'd like to read up on it to educate myself.

Does anyone else have any details to add here?

[JetScan1]

svoynick,

It seems like you and spades are using two different definitions of "cross-coupling".

I believe we are both talking about the same thing.

FAA definition ...

"Cross-Coupling - a feature wherein the received voice on one frequency in a pair of frequencies is transmitted over the other frequency of that pair without operator intervention."

Reference: page 368 from this document

https://faaco.faa.gov/attachments/NVS_Specification_v0_09-BL-2011-09-13.pdf

I think what spades is saying is he can transmit on multiple frequencies (the old system) but also at the same time has the capability to "cross-couple" 2 of those frequencies together (the new system).

[spades]

Cross coupling allows an aircraft's response to be broadcasted on the other frequency that it is coupled with.  Whether cross coupled or not, all frequencies will hear the controller regardless of who the controller is trying to talk to.  However, the real advantage of having aircraft responses be relayed is to reduce the amount of times that aircraft step on each other.  A perfect example is when you're trying to understand a foreign carrier and then in the middle of it, somebody on another frequency starts talking because they simply don't know that you're in the middle of something and then you end up having to have everyone repeat themselves. 

JetScan, I'll get back to you with the frequencies.  I'll try to find something in writing that says I can list those things.  I know it seems harmless but there was a big thing earlier this year when a guy posted something he shouldn't have so I just want to make sure I don't do something that would jeopardize myself.

[JetScan1]

spades,

JetScan, I'll get back to you with the frequencies.  I'll try to find something in writing that says I can list those things.  I know it seems harmless but there was a big thing earlier this year when a guy posted something he shouldn't have so I just want to make sure I don't do something that would jeopardize myself.

Thanks for the reply. It's not a big deal so don't worry about it if there is any concerns. Cheers,

[davolijj]

I would just add that the use of multiple frequencies in the tower is a common practice.  The only restriction I know of is that controllers are not allowed to use ground control frequency to communicate with airborne aircraft.

2-4-1. RADIO COMMUNICATIONS

Use radio frequencies for the special purposes for which they are intended. A single frequency may be used for more than one function except as follows:

TERMINAL. When combining positions in the tower, do not use ground control frequency for airborne communications.

NOTE-
Due to the limited number of frequencies assigned to towers for the ground control function, it is very likely that airborne use of a ground control frequency could cause interference to other towers or interference to your aircraft from another tower. When combining these functions, it is recommended combining them on local control. The ATIS may be used to specify the desired frequency.

[svoynick]

Sorry I didn't see these responses earlier.  Thanks to both of you, JetScan and spades, for educating me on cross-coupling!  I can definitely see how this would help cut down on aircraft stepping on each other in the controller's ear.

[FLLflyboy]

At my first facility, we frequently had CD/GC/ and LC combined at one position, usually early in the morning at in the evening hours. I was able to transmit on all three simultaneously. I do remember a few instances where I did clear someone for takeoff on GC. Usually it was me not realizing he was still on GC but it happens and since I was the one working all frequencies, it was a non-issue.