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Now It Makes More Sense

Maria Antonova who writes at Global Post has committed journalism by talking to people and consulting open sources to provide a more reasonable picture of the crash at Smolensk.

The most important piece of the puzzle she provides is the fact that the Ground Control Approach system at the Smolensk North airport did not have a working glide slope radar, so the aircraft was using its altimeter. In the same vein she reports that there was only one landing attempt, not the four that have been reported by other sources. The pilot told the ground controller that he would make one pass and if it was unsuccessful, he would divert to another airport.

The other piece of information needed was to locate the airport on a topographical map and see what the terrain was like around the airport.

With those pieces in place, the landing was pretty much guaranteed to be a disaster.

The airport sits on land that is more 200 meters above the surrounding lowlands. There are hills on both sides of it. If you are using your radar altimeter, it won’t react to the higher ground until it is too late to correct. If you set you regular altimeter to the barometric reading of the airport and compare your standard altimeter with the radar altimeter, it will look like your standard altimeter is off. Visibility was 400 meters in fog, so there was no way of seeing the problem until it was too late.

The ABC reports on the preliminary data from the “black boxes”. Essentially, Russian sources are saying that the data indicates that the aircraft was descending faster than is recommended, and continued to drop after the pilot tried to level out.

This effect is common in a lot of aircraft types, but is more pronounced in the Tu-154/Boeing 727 design. Jet engines have to spin up to increase power, so there is a time lag there, and the lower speed of landing is a bit tricky in those aircraft. Many of the design features that increase their in-flight speed, complicate low speed handling.

My personal opinion is that the pilot should not have attempted the approach in the absence of the glide slope radar.

April 19, 2010   4 Comments