Tuesday, January 6, 2015

Aviation Experts!

Some time ago during the sad – and ongoing, situation with MH370 I mentioned that the World fills with aviation experts.
For some inexplicable reason everyone suddenly has an important facet that they feel should be introduced into the search or investigation.
These ideas range from the most fanciful conspiracy theory to the more down to earth and considered thoughts.
None of these conjectural inputs, as I said at the time, are helpful.
The only thing that matters here is that “we do not know”. The full stop (or ‘period’ as our transatlantic friends would have it) marks the point at which we cease to converse.
No more should be said until we have more knowledge; more facts.
There are still no more facts than we had before in that instance.

So we move on to Flight QZ8501.
It has started again.
I did mention that conspiracy theories arose on day one but now we have inputs from people who should know better.
Let me quote from a source that a few people regard as being a ‘news’ paper (‘The Guardian’, it said on the top of the web page):
“Weather was the “triggering factor” in the crash of AirAsia flight QZ8501 with icing likely causing engine damage, Indonesia’s meteorological agency said on Sunday, as bad weather continued to hinder rescue efforts.”
“The most probable weather phenomenon was icing which can cause engine damage due to a cooling process. This is just one of the possibilities that occurred based on the analysis of existing meteorological data.”
‘Cooling process’? Suddenly the meteorological office is a source of expertise on thermodynamics and the operation of the Brayton cycle (jet engine – for those who are not aviation people).
The problem, let me set you straight, with icing is twofold.
1.            The formation of ice on the rime of the airframe intake and the first stage fan blades may create problems when it breaks off and goes down the intake duct.
2.            Icing on the airframe intake rim may cause a disruption of the airflow into the engine. A smooth airflow is necessary for the efficient operation of the compressor. Turbulence can cause surge that can seriously damage the compressor components.
In the first instance one would imagine that these pilots, who were experienced fellows, would have selected anti-icing to ‘ON’ before entering inclement conditions.
This would preclude ice forming on the airframe intake.
Ice formation on the fan blades will, on most high by-pass engines, pass down the cold air duct if it breaks off. That said, ice formation on the fan blades is a fairly remote possibility considering the angular velocity of any section of the blades.
The engine choices for the A320-200 are the CFM56 and IAE (International Aero Engines V2500).
[Note: The Pratt & Whitney PW6000 engine choice is available only on the A318 variant.]
Both the CFM and the IAE engines have been around for a considerable time. Both are renowned for reliability – as they must be for aircraft that can be certified for ETOPS (Extended-range Twin-engine Operational Performance Standards).

Happily the Meteorological Office seems to know better. How fortunate we are to have their insight and recommendations.

Remember what we said about that ‘full stop’?

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