Thursday, 8 January 2015


In the inevitable speculation that precedes the DFDR data analysis of the final minutes of QZ8501, the prevailing weather conditions are getting a lot of column inches. Meteorology is always a factor in aviation but there are some things to bear in mind in this debate:
  • As I mentioned in my previous post, severe convective weather is commonplace in equatorial and tropical regions - aviators must cope with it every day;
  • There were several other aircraft in the area when QZ8501 was lost, each of which completed its flight safely;
  • Airframe icing, engine icing, hail, lightning and turbulence may all be present in convective cloud but modern aircraft have systems and/or design characteristics, and ultimately pilot procedures to manage these conditions;
  • Forecast weather conditions are of interest to pilots for planning purposes but in flight they must respond to what they encounter, regardless of the forecast;
  • Pilots know that in general the concentrations of convective activity reduce with altitude but at the same time the aircraft performance margins narrow proportionately (high/low speed buffet);
  • In busy airspace (and most of the world is now busy) level change requests may well be denied due to other traffic - the same is true to some extent of lateral deviations for weather avoidance;
  • Weather radar is the pilot's primary tool for severe convective weather avoidance but it is not 100% effective as it only detects raindrops;
  • Aircraft manufacturers' and industry guidance on weather avoidance generally agrees that pilots should avoid convective cloud by 20 nautical miles laterally and not attempt to avoid by flying over the top due to unpredictable vertical cloud development.
So to say that this accident was caused by severe weather, without any useful supporting data (other than some very red satellite pictures) is more than somewhat premature.

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