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Sunday, February 17 2013 20:18

Full Circle – Zero/Zero Landings, Part Two

Written by  Thomas Block
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July 2012

My column in the May issue of Piper Flyer had been prompted by a copy of a letter I’d received from a fellow who had flown with me as copilot on a great many of my international airline flights in the 1990s. Capt. Scott Reynolds (now retired) was a prince of an aviator to have sitting beside me in those days while I plied back and forth across the Atlantic in widebody jets. His recent letter reminded me of a particular flight from Rome, Italy to Philadelphia in a Boeing 767 when deteriorating weather, increasing ATC delays and lowering fuel reserves caused us some interesting moments.

The outcome was an approach and landing from which I had no intention of executing a missed approach; we were going to land this airplane on that runway, irrespective of what the ceiling and visibility might prove to be. In effect, we had mentally committed ourselves to a zero/zero landing. We would, if necessary, have made one—but it turned out that the actual weather remained at the legal minimums, so no zero/zero touchdown was necessary. Like I said, we were ready.

Let’s look again at the definition of what I’m talking about. A zero/zero landing would literally mean landing the airplane while the ceiling was absolutely zero and the visibility was absolutely zero, too—a condition we hardly ever encounter. In reality, zero/zero means “hardly any” ceiling or visibility to work with.

It’s interesting to note that modern jetliners can do autolands regardless of what the cloud ceiling and the forward visibility might be, but the rules still require that the captain and crew have a slight chance of verifying that there really is a runway beneath them at least a few heartbeats before the wheels actually touch. For that reason, most full autolands require a few hundred feet of forward visibility so that the glow from the runway and centerline lights can be briefly seen by the flight crew before the rubber meets the concrete. In the vernacular it’s called “decision height,” and the pilot has a fraction of a second to decide to either keep things going just as they are or to make an autopilot missed approach.

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