Many non-towered airports share the same common traffic advisory frequency and though this is an antiquated system, it mostly works. Where the system starts to break down is when the skies get crowded, like on weekends and holidays. The few CTAF frequencies there are get busy because many non-towered airports share one of two common CTAF frequencies - 122.8 or 122.7. Some new frequencies are beginning to be assigned, but the way pilots determine whether or not a radio call they just heard might affect them is the convention of prefacing all CTAF announcements with the name of the airport. So far so, so good.
Some of the airports within a 100 mile or so radius of the San Francisco Bay Area that share the frequency 122.8 include Halfmoon Bay, Sonoma Skypark, Ocean Ridge, Cloverdale, Rio Vista, Watts Woodland, Colusa County, Kingdon, Rancho Murietta, Westover, Oakdale, Turlock, Tracy, Los Banos, and Wattsonville. Many of these airports are infrequently used, but many are quite busy with training aircraft. It's not uncommon to hear pilots at other airports more than 50 miles away. I often hear jet traffic inbound to Truckee making CTAF announcements while high over the Sierra Mountains and wonder how far their transmissions might be heard. You don't have to be at a high altitude for your signal to carry. I remember making a CTAF call inbound to Visalia at 2000 feet and having someone in Byron (140 nm away) say "Hey John, is that you?"
When the frequencies get crowded, it can be hard to get a word in edgewise and when two aircraft try to transmit at the same time, you get a loud squeal and nobody hears anything. Radio communication, see-and-avoid procedures, and luck are what keep aircraft from hitting one another at these small airports. For their part the FAA has begun to assign new CTAF frequencies to many non-towered airports as a way to reduce congestion on the freqencies and this a great idea. In fact, Rio Vista just got a new frequency on March 1 of this year.
RIU 02/167 O88 COM CTAF/UNICOM 122.725 VICE 122.8 WEF 0903010800
Translate this NOTAM and you'll understand that the old CTAF frequency of 122.8 has been replaced with the frequency 122.725. Then you will hopefully mark up your VFR sectional and A/FD with the new frequency. Since Rio Vista is frequented by many of the part 141 training school aircraft in the area, this new frequency should help a lot. The problem is this NOTAM and the new frequency assignment seem to have been lost on about 50% of the pilots using the Rio Vista Airport. Either they have not gotten a pre-flight briefing since March 1 or they aren't reading the NOTAMs carefully.
I'm not instructing as much since last October, but I've still been to Rio Vista a dozen times since March and each time at least one aircraft is still using the old frequency. And why not? The current San Francisco VFR sectional still lists the frequency as 122.8 as do all the relevant Jeppesen VFR+GPS charts. Heck, even the latest Airport Facility Directory and all the latest NACO approach charts still list the CTAF as 122.8. Why this is I can only guess.
The next San Francisco VFR sectional is due out at the end of August of this year and perhaps the FAA's charting division wants to harmonize the release of that sectional with an updated A/FD and terminal procedures. A great idea to someone sitting at a desk, but not such a great idea for someone flying an aircraft into Rio Vista. I haven't noticed if the airport information signs on the Rio Vista airport actually reference the new frequency or not. I even emailed the folks at Airnav, but they said they don't update their online information until the FAA makes the changes, presumably to the A/FD. So even Airnav still lists the old, wrong frequency. What's a pilot or instructor to do?
My current, preferred procedure at Rio Vista is to tune the #1 radio to 122.725 and use that as the CTAF. Okay, so I'm a boy scout, but heck there's a NOTAM. I don't want to be called on the carpet for not complying with 14 CFR 91.103, but I don't have a death wish either. I tune the #2 radio to 122.8 (the old frequency) and monitor it, too. If I hear someone on the old frequency, I quickly transmit a courtesy explanation of the new frequency in use - if I can get a word in edgewise. Sometimes the old frequency is so busy with calls from other airports that listening to two frequencies becomes a distraction in and of itself. So this new frequency assignment was supposed to reduce radio conflicts and make things safer, but it has actually made things less safe.
One simple solution would have been to wait until a few days before the new San Francisco VFR sectional was to be published and then release the NOTAM. Now that the cat is out of the bag, at least the next versions of the A/FD and the terminal procedures should be updated. For completeness, another solution would be to release a NOTAM retracting the previous NOTAM. Yeah, that sounds about right for the FAA ...
My suggestion for pilots who want to avoid missing these important, but obscure NOTAMs is to get an online briefing from DUATS or DUAT and then use your browser's search feature to locate all the instances of the airport identifiers for places where you plan to operate. DUAT lets you request your briefing output as plain English, which also helps.
RIU 02/167 O88 COMMUNICATIONS CTAF/UNICOM 122.725 INSTEAD/VERSUS 122.8 WITH EFFECT FROM OR EFFECTIVE FROM 0903010800
FltPlan has a nice way of formatting relevant NOTAMs for a particular airport that makes them stand out.
The sad fact is that there really is no substitute for wading through all the darn NOTAMs. For more information that you could ever possibly want on NOTAMs, read this. And even if it's a beautiful VFR day, get a briefing, read those NOTAMs, and keep your eyes peeled.
And don't call me at the old number.