Aviation In Canada

Wednesday, October 26, 2005

Altimeter Readbacks

This question arises every now and then as well: Do I have to readback an altimeter. I've done some research on it in Canadian books and have yet to find anything written about it. There is, apparently, no requirement to read back an altimeter setting to ATC, whether you're IFR or VFR.

Having said that, the vast majority of pilots will readback altimeter settings issed them by ATC, and it just seems to have become one of those work practices. As a controller, I'll listen to the readback as dilligently as I listen to a clearance readback. In fact, I've caught more errant altimeter readbacks than IFR clearance readbacks that were in error. This said, I think the practice of reading back altimeters by IFR aircraft should continue, personally.

I say IFR, since IFR aircraft are often operating in cloud, and this becomes especially important for aircraft on approach during IMC. Even with an ILS to guide you, where the glidepath covers you for altitude guidance, the altimeter is used as a cross check at the FAF as well as the guage you generally look at for determining when you're at the Decision Height. As such, it is vital, even with vertical guidance, to have the correct altimeter setting.

For VFR, however, the altimeter setting is secondary, since a VFR pilot's main way of flying is by looking out the window. Sure, there are gauges which are truly important (ASI, tachometer, altimeter, compass, etc) but mostly, you're determining how high you want to be (in a general sense) by what's out the window, using the altimeter as a reference point once in a while. Is the altimeter setting important to you? Sure. But not as critical as for IFR flight.

As a controller, I have never chased an aircraft for an altimeter readback. I'll definitely say that when a pilot doesn't read it back, I do feel like something is missing in his transmission, and it's almost an urgent feeling, too, one that I often tell myself to let go of. I quite readily listen for them, though, and given the number I have caught, I think a readback is an appropriate practice and hope it continues.