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Tim Blagg

Blagg: Landing all in the approach

July 11, 2013

July 11, 2013

That crash out in San Francisco has me pondering the problem of landing. Getting an airplane off the ground isn’t that hard ... almost anyone can do it. But bring them down again is a different story ... and that’s in good weather, when you can see the ground and the runway.

Ever since humans began to fly, the problem of how to get back safely to earth in bad weather has been a problem.

Back in the early days, if you were unfortunate enough to be aloft when the clouds, rain or fog closed in you were in a real pickle.

Early mail pilots, for example, who had to “push” the weather because of the urgency of their mission, too often found themselves staring helplessly down at a gray, featureless mass with no guiding lights or terrain features visible to help them find the airport. Charles Lindbergh, for example, had to parachute out of his war surplus DH-4 biplane twice because he couldn’t land.

In an effort to help pilots, the U.S. government built a series of towers across the country, each with a rotating beacon — pilots flying at night could follow them to their destination. This was the beginning of the air traffic control system.

Then, radio beacons were added. Some were simple broadcasting stations, each with its own Morse code identifier, which airplanes equipped with a radio direction finder “loop” antenna could tune in.

Others sent out a “beam” with two lobes. One broadcast a Morse N (dash-dot) over and over again, while the adjacent lobe carried an A (dot-dash). A pilot knew he or she was “on the beam” when the two signals merged into a single steady tone.

When my father was flying C-47 transports across the Sahara, from Ghana on the West Coast of Africa to Karachi in India, those beams and beacons were the only navigational aids he had.

But the beams didn’t help in that final descent into the airport.

In Britain during World War II, giant gas torches were lit on either side of runways in an effort to burn off the omnipresent fog, so bombers and fighters could land even in England’s terrible weather.

Toward the end of the war, another landing aid was introduced. It consisted of two high frequency radar beams, aligned with the runway. One could “see” an approaching aircraft and tell if it was on the centerline of the runway. The other was angled up along the correct approach path.

Highly trained operators talked the pilot down to a safe landing, telling him if he was lined up properly, and giving him corrections if he was left or right, or high or low.

This “Ground Controlled Approach” or GCA, was used for several decades after the war, until it was replaced by another system, called ILS. It is still used in Europe, however, on a limited basis. The famous science fiction author Arthur C. Clarke was involved in the development of the system, and wrote a novel about it called “Glide Path.”

ILS, or “instrument landing system” puts the burden on the pilot. It uses two tight radio beams to control an instrument on the aircraft’s panel. One needle shows the pilot if he or she is on the glide path, the other if the airplane is lined up with the runway.

It works in all weather, and when coupled with a sophisticated automatic pilot can literally fly the airplane right to a landing.

Still newer systems using satellite information are now replacing ILS systems.

So how, with all this help, did an Asiana airlines Boeing 777 manage to get so far below the glide path at San Francisco’s International Airport the other day that it actually crashed into the seawall at the end of the runway?

That’s really the 64-dollar question, isn’t it?

That airplane has ground avoidance radar, an automatic pilot that can use GPS information to fly halfway around the world, and ILS system ... multiple backups and layered protection designed to keep pilots from flying into the ground.

And yet that’s exactly what happened.

Apparently, the glide slope transmitter for that particular runway was out of operation, which could have been a factor. But the pilots (there were three!) would have been notified of that long before they approached the airport.

But what really rocks my boat is that the weather was good. It was clear, so the pilots could see the runway — the left-most of two parallel strips of concrete some 10,500 feet long — stretching out in front of them.

The NTSB is investigating the crash, which killed three passengers and injured scores more, and we’ll find out more when they’re finished.

It’s possible that something in the aircraft’s super-sophisticated software malfunctioned and, say, failed to deliver power when demanded.

Or the pilots may have been relying on another landing system and were misled.

But my mind still boggles at the thought that three experienced Asiana pilots sat chatting among themselves, staring at the runway gradually looming larger and larger and failed to see that they were too low and too slow to make it.

Flying by airliner is incredibly safe today, and the Frisco crash doesn’t change that. But as a long-time student of aircraft and pilots, I can’t wait to find out what the heck went wrong.

Blagg has been Editor of The Recorder since 1986. He lives in Greenfield and is a military historian with an interest in local history. He can be reached at: tblagg@recorder.com or 413-772-0261, ext. 250.

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