I've noticed that sometimes pilots tend to present the next ATC frequency in the standby radio, and when required to switch frequencies, they can just push the frequency transfer switch to switch the preset frequency to the active radio. When do pilots preset frequencies? I.e. tower or ground frequencies are known through the briefing material (i.e. Jeppesen charts), so they could be preselected to accelerate operations. Are there any rules as to when preselect the next frequency, is it also done during cruise flight or only in the terminal area?
I'm not aware of any rules, hopefully others can contribute, but you can usually predict the next frequency with a high rate of precision.
For example (exact stations will differ depending on airport and airspace type) a typical IFR sequence of stations.
- Clearance delivery
The initial tuning will put delivery in live and ground in standby. Then as you say, just press the toggle. When the next frequency gets dialled in is not, as far as I know, governed in anyway and is probably not even in SOPs since it is just about using the equipment more efficiently.
Say delivery has given you a clearance. They will probably follow up with something like "call ground 129.7" for push and start". When you are ready for push and start, toggle to ground then put the tower into the standby frequency and so on.
Frequency changes are certainly made in cruise, when passing from one ACC sector to the next. These frequencies are published in the national AIP's and visible on en-route charts. For a sector handoff, I'd probably dial the next frequency in when the current sector instructs me to contact xyz.
It's really not a big deal if you have to contact someone unexpected. Modern boxes with push button tuning are almost as quick to tune manually as to toggle.
The saying is that you Aviate, Navigate and then Communicate, so if there is a rule it is that you fit setting the next frequency in when you have time. I generally list the frequencies I will be using in order during my pre-flight preparation so I don't have to hunt for them, and in flight I enter the next frequency on the list soon after changing frequency, but that's just what works for me.
Some avionics systems let you enter in all the frequencies you will use in the order you need them before you fly, you then call them up one by one during the flight with the push of a button.
This is one of range of tricky problems that makes piloting challenging. In a small plane, often the pilot has only a single backup channel, so there is the active channel and the backup channel. If a flight condition involves more than two different frequencies need in rapid succession, it can be hectic to set the radio.
In the basic case, taking off or landing at a single airport, there is usually no problem. You might have two frequencies, tower and ground. Then, after you take off, you swap ground for ATC. This is easy.
Where it gets tricky is when there are multiple airports close to each other, so the pilot is required to do a handoff. In this case there can be a bunch of different frequencies and the pilot has to switch between them rapidly, while doing a bunch of other tasks like setting the transponder. Not only that, but the aircraft will simultaneously be doing an ascent or other maneuvers, making it even more complicated. Now, factor in that when you are taking off you have to be doing all of this, yet also be constantly alert and looking out for other aircraft.
When you have overlapping airspace, the general plan is to start with tower and ground, then you will switch to clearance delivery. As soon as you have the clearance, you set the transponder. Then you immediately switch out again for the tower in whatever airspace you are flying into. Note that this frequency cannot be programmed ahead of time, because often it is given to you by the tower you just left. So, for example, the Nashua tower will clear you to take off and say, "Contact Manchester on XYZ", so immediately after you take off and leave Nashua airspace, you switch to Manchester Tower on the frequency they give you. Eventually, when you get clear of all towers, you switch to the ARTCC.