Aviation In Canada

Tuesday, April 19, 2005


Radio communications is, in my opinion, an art. You don't have body language to help express your feelings, just your words and tone. Essential to effective ATC communications is proper phraseology, along with some non-standard words to get ideas across. Another item that is important is technique. The title for today's post gets at one of the main points with technique.

Many people new to working radios end up making a common error. Even "old hands" at radio work occasionally goof up this way. "Clipping" is the term used for the inadvertent cutting off of words in a transmission, typically at the front end of a statement. For example, you key your mic to say, "Hi, how are you?" and all the receiver hears is, "How are you?" This is typically done, by mistake without even realizing it, by starting to speak before the mic is keyed. In the previous example, losing, "Hi," isn't all that critical, but other words lost can be.

The most common example that ATC will hear is when issuing an altitude to an IFR airplane. The transmission goes something like, "Alpha Bravo Charlie, maitain four thousand," and the typical readback has the pilot say the altitude, then the callsign, sounding like, "Four thousand, Alpha Bravo Charlie." There is one controller I work with who is absolutely adamant that a pilot responding is "dead wrong" to respond like this and even claims to have seen it written somewhere. I don't buy his arguement. In any case, if clipping comes into play here, ATC will only hear, "-thousand, Alpha Bravo Charlie." This is an incomplete readback, and if this is what we hear, we have to go chasing after it to ensure the right altitude is readback. Traffic may be a factor, whether climbing or descending, and if descending on a vector for an approach, terrain may be a factor. I don't absolve ATC for blame in this regard, either. I've already had to beat the tendency out of three of my own ATC trainess, and a few others that I've sat with in a "babysitting" sense while their regular instructor is away. It's awfully hard for a pilot to hear a transmission aimed at him when less than his full callsign is used. Though I do have to credit many pilots for hearing what my trainees were saying to them, despite their best efforts at clipping part of their callsigns.

I understand how it happens, too. Sometimes things are busy and a rushed transmission is made. Sometimes it's just a slip of the finger on the button. But it does make a difference. Even a split second pause while going for the button can make a difference in the usefulness of a transmission, regardless of which side of the radio conversation it comes from.