Tuesday, March 24, 2009

"One-One Thousand, That's Eleven Thousand"

On my northbound commute from DC to Bridgeport, I get routed over Kennedy Airport (KJFK) and so get to listen to the estimable New York Approach controllers doing their thing. In assigning altitudes to their departures and arrivals, they state the numbers twice, in different ways, like: "American 79 Heavy, climb and maintain one-one-thousand, that's eleven-thousand." (The flight crews will usually read back the instruction using the same phraseology.)

A question showed up on another blog concerning the rationale behind this phraseology, which got me to googling -- and led me to the ASRS analysis that I've linked to the title of this post. It turns out that the "(varied) numbers twice" procedure is a tool to minimize miscommunicated and misunderstood altitude assignments. Click on the title and read the analysis -- good stuff there.

By the way, Order 7110.65 (the Controller's Bible) permits but does not require use of this phraseology.

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