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Flight 214 Crash Happened Despite Fact That Runway 28L Threshold Moved Further From Sea Wall Recently

As a pilot, I can well imagine how Asiana Flight 214 hit the sea wall rather than landing on the runway. Approaches over water are always dangerous, especially in visual conditions, because of how difficult it is to tell how high above the water you are. This is especially true when the water is extremely calm with no waves or other disturbances on the surface. Pictures from various news media clearly showed that the water was extremely calm when the crash happened.

Add to that the fact that the threshold of the actual runway was only displaced from the sea wall by about 640 feet. This means that under the conditions of a normal approach, which has a glide slope of about 3 degrees, the aircraft would only clear the sea wall by about 36 feet. This may sound like a lot, but it is not much when you are dealing with an aircraft as large as a 777. Add to this the fact that the water level appears to be about 12 to 20 feet below the level of the runway. This means that the aircraft, while on that normal 3 degree approach path, would need to be about 50 to 60 feet above the water. If the pilots got a bit lower than that, it is easy to see how they could have hit the sea wall on approach. In fact, I am surprised that this has not happened more often.

It is interesting to note that the runway threshold was moved about 300 feet further from the sea wall at some time in the last year. This can be ascertained by noting the appearance of the approach to runway 28L shown below. This was taken from Google Earth. The image was time stamped August 23, 2012. In this image, the runway threshold was only about 375 feet from the sea wall. In this case, a 3 degree approach slope would bring an aircraft over the sea wall edge at an altitude of only about 18 feet! Again, I am surprised that there have not been similar accidents on this runway in the past.

When you look at the next image, which includes the image of the crashed 777, you can clearly see that the runway threshold has been moved an additional 300 feet from the sea wall. Since the Google Earth image was time stamped August 2012, it is obvious that the threshold was moved within the last 11 months. You can also clearly see how the runway has been repainted to accommodate the threshold movement.

We know that the ILS (instrument landing system) was not in service at the time of the crash. Thus, the pilots would not have had a working glideslope. They would still have had the VASI (visual approach slope indicator) which is a ground-based directional light system that appears green to the pilot if the pilot is above the appropriate glide slope and red if the aircraft is below the glide slope. Thus, this would clearly have been telling the pilots that they were low. But, a VASI is more visible in darker conditions and this crash occurred in bright daylight, so the VASI may not have been as visible as it might otherwise have been. However, these were highly experienced pilots and they surely had working radar altimeters and other instruments that should have told them that they were too low. (Actually, so far I have only seen information on the captain. He reportedly had over 9000 hours. The co-pilot may have had far fewer hours. And, given the fact that the weather was so good, it is entirely possible that the co-pilot was actually flying the plane at the time of the accident so as to gain experience.)

Obviously, we won’t know what went wrong until the NTSB has had a chance to listen to the cockpit voice recorder and review the flight data. But, this certainly looks like a tragic case of pilot error. Also, the airport planners may want to think about moving the threshold even further from the sea wall, especially since this is one of the longest runways in the country, anyway, at a bit more than 11000 feet. I wonder why it took so long to move the threshold.

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