So supposing a pilot is communicating with approach on comm1,
but has comm2 monitoring the tower, what happens if a stronger
tower transmission is received at the same time as an approach
transmission? Will the audio panel loose it, or play them in
sequence? And would a pilot actually set his radios up like that, or
simply have the tower frequency in comm1 standby ready to switch
over?
Nonono; the radios are independent all the way through to the audio that
could feed directly into the speakers so signal strength is irrelevant.
The panel will play all selected inputs over the top of each other.
The current FGFS behavior with the NAV1/2 and ADF idents is a good example.
If IFR on an NDB approach, you are required to monitor the ADF receiver
continuously while using it for navigation. Thus, you are listening to
the morse beeping (MY for DEORO for example) while also talking to the
approach controller and (afterwards) to the tower people. Irritating.
You almost never listen to two controllers at once, operationally, because
IFR you are always under the control of exactly one sector/position.
Transitioning from approach to tower is a handoff like any other handoff.
However, when it's quiet, I might listen to the next sector along to get
some idea what it's like up ahead. ... and other similar situations.
When VFR, life is a lot more complicated and I often have two towers on.
Some of the more modern panels allow you to specify that certain input
channels are non-operational, i.e. should be suppressed whenever the pilot
speaks or one of the operational input sources (such as the radios) makes
a noise. Back seat passengers and the CD player are usually good choices.
IFR, I normally have COM1 on approach/center and COM2 on tower/atis/fss.
On aircraft with flipflop, the other side of COM1 is the last frequency
(unless I know we're about to cross a boundary and I know the next freq)
and the other side of COM2 is the unselected one of the tower/atis pair.
I usually use the radio 1/2 select to choose which I'm talking and listening
to, so they don't talk at the same time which is difficult to listen to.
However, any time I hit the both button or press the COM1 and COM2 buttons
(depending on panel design), I can potentially hear two controllers talking
at the same time. If the volume is about equal and their voices are
distinctive, it is just like being in a room with two people talking at once.
I'm told that some of the advanced panels, that support stereo headsets,
can place COM1 in the left stereo position and COM2 in the right position.
This makes it much much easier to listen to the two sources at the same time.
For example, when over Lake Hodges at 4k' enroute KCRQ to KMYF, I'm about
to get switched from 127.3 to 132.2 so the former is COM1 active and the latter
is COM1 standby. I know that the next sector's controller is going to have
to read the atis for KMYF to me (unless I've already picked it up).
So, I'll put 126.9 into COM2 with the volume down and listen to both;
when the controller isn't talking, I can hear the atis and (after a few
repeats) I can get the information copied down onto paper. On average,
the 127.3 channel is in use about half the time, and if those transmissions
happen to line up with the same bit of the atis repeat, you can end up
listening to rest of the atis repeat a large number of times. However, if
the two voices are distinctively different, you can pick up the atis content
while still being able to listen and understand the controller. When done,
I take the radio off the both setting, tune 119.2 into COM2 standby and
hit the toggle to put it into COM2's active because I'll need it in 15 min.
When I get the handoff, I just hit COM1's toggle and listen to see whether
the frequency is clear then announce something like ...
SoCal Approach, Cessna 6291R level 4 thousand heading 1 0 0
with information charlie at montgomery
PS ... airline purists will point out that I've got excess words in that,
which is true but irrelevant (since the FAA recommends it) since I'm doing
this on initial contact to confirm the control instruction that I'm subject
to. Unlike airlines that follow fairly rigid routes and STARs, I can end
up doing unusual things and prefer the controllers to have no assumptions.
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