Don’t Block That Frequency

20 Nov 09 5 Comments

I’m on the road this week but never fear! The well-known aviation blogger Plastic Pilot has kindly taken command of Fear of Landing for the day. I asked him to tell us what it is like in Air Traffic Control and he responded with the following post.

ATC Behind the Scenes

by Vincent, the Plastic Pilot

I’ve been working for ATC companies for the last nine years and gained a good understanding of how the whole system works, from both sides. Knowing what a controller working position looks like and how the guys on the other side of the radio are working makes the cooperation easier. This is what I’d like to share in this post to make you feel better when you talk to ATC…

Controllers are supported in their tasks by different systems: surveillance systems (radar, ADS-B and others) inform them about the aircraft positions, this information is linked with flight plan data.

NewcastleOther systems provide controllers with so called “environment information”:

  • weather,
  • runway in use,
  • military airspace,
  • NOTAMs,
  • and so on.

But all this nice technology becomes totally useless if the controller loses his ability to communicate with the pilots. This is why the radio system is the most important for controller.

The radio system on the ATC side is exactly the same as in the cockpit: a controller can transmit or receive, but not both at the same time. If you talk, the controller must listen and wait till the end of your transmission. There is no override or bypass system. This is why controllers hate it when their frequency get blocked.

StrasbourgLet me tell you a short story I saw once, directly from the tower…

An Airbus 320 was lined-up, ready for take-off. The controller was waiting for the preceding landing to vacate the runway before issuing the take-off clearance. A Boeing 737 was on short final. The timing was short, but not critical. At the very moment where the controller was ready to clear the Airbus for take-off, an incoming VFR pilot started a transmission.

The pilot did not use the standard “Tower, Call-sign, good morning” initial contact message. Instead, he started a very long transmission, not using ICAO phraseology. I don’t remember the very words he used, but it was something like “Tower good morning, this is HB-XXX… a PA28 we took off from LSXX and we are requesting landing clearance. We have two persons on board. We also copied airport information Quebec and are approaching VRP N”. The message was excessively long, and sounded anything but professional. During the time the frequency was blocked, the 737 on final had to go around, because the A320 was still standing there, by lack of landing clearance.

AngoulemeWithout a radio, a controller becomes a simple spectator…

If the VFR pilot had use a short initial contact, the controller would have answered with a “Stand-by”, and then cleared the 320 for take-off, and the 737 to land, shortly after. I’m sure you don’t want to be this kind of pilot, so please use standard phraseology and keep your messages short.

VFR pilots mostly use ground, tower and approach frequencies, where pilots can hear each other, thanks to the relative small size of the airspace served by these frequencies. It is a good radio practice to wait for a couple of seconds before initial contact on a new frequency, to make sure you won’t interrupt some other radio exchanges. When contacting an “Information” frequency, an additional problem exist: given the size of the areas served by one single controller, possibly using multiple frequencies, the risk of simultaneous transmission is increased.

MarrakeshDepending how sophisticated the radio system is, it is possible for a flight information service officer to work several frequencies simultaneously, but this is not always the case. When you make your initial contact, it is possible that the guy on the other side must try different transmission frequencies to answer your call. He can also be talking to someone else on a frequency you don’t monitor.

One more thing for VFR pilots… Remember that if you fly without a flight plan, controllers do not have any clue who you are and what you want to do. They have to note down everything you say on the fly, so please don’t talk too fast when you pass your message. It’s much better to transmit once, slowly and clearly, than too fast and have them requesting all information again.

Finally, if you have the opportunity to visit a local ATC facility… just do it. You will be well received and will learn a lot. Controllers like to talk to pilots, even if this is a bit more complex than before September 11th. Look for ATC open house day at your local airport and don’t miss it.

Be sure to visit PlasticPilot’s General Aviation Blog and thank him for this insider’s view of the tower. Also take a look at his exciting initiative Flying Across America with a plan to fly from Daytona Beach, FL to Catalina Island, CA and back.

Category: Miscellaneous,


  • Dear Sylvia, I am finally coming to the end of my UK PPL training; just my Qualifying Cross Country (when the weather eventually permits) and Skills test to do. This article reminds me of an incident this summer. I was to do a solo short navigation excercise flying from Shoreham to a local landmark and back. Unusually the wind direction made the grass runway 25 active and as it was the firs time I had taken off Solo from grass I was understandably a little nervous. Once take off clearance had been given I gripped the joystick of the Diamond DA40 and probably my teeth as well and proceeded to take off. Fealing quite pleased that it had gone so well, I climbed to 600 feet turned left onto crosswind and then At 1000 feet when I was just about to leave the circuit I suddenly realised that I had been squeezing the Joystick and the Transmit button a little too hard! I immediately released the transmit button to hear the ATC calling my callsign suggesting that my transmitter had jammed open. I made a mental note to try and fly more relaxed from then on.

  • Oh no! I talked to myself throughout my first solos, like a radio dj: and now we’re turning onto crosswind, height looking nice, another nice turn, keep it up. The thought of broadcasting that – well, it would have been interesting. But it is stressful, alone in the plane! If you were going to press a wrong button, there are certainly worse options.

  • my first solo was a mix of surprise and disappointment. I felt no difference when flying solo. it was the same feeling with or without my flight instructor. so nothing special happened. I did my circuits, landings and radio as usual. but the last landing turned out to be without flaps and the aircraft refused to touch down at the intended spot.

  • I’ve been the victim of this sort of story a few times. Almost did a go-around once because somebody tied the frequency up, thus delaying the previous airplane’s takeoff clearance.

    I’ve also had my conversation ‘interrupted’ a few times by pilots who jump on the mic without listening first.

  • I’ve had the same occur to me – once with a French pilot who was lost and describing in great detail where he wanted to be and what route he wanted to take. ATC were more than happy to help him but he wouldn’t take instruction and talked at length at every opportunity. I was heading for airspace and had to divert as I couldn’t get a word in edgewise to get transit approved.

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