Postby anand_sankar » 03 Dec 2009 14:17
Here is my two cents on the latest Su-30 MKI crash.
In the first crash as soon as information about the loss of control surfaced, it was clear it was an avionics issue. But this one is a lot more baffling.
It took a bit of time to think hard and assimilate lots of different scraps of data on the MKI, that I have researched over the years.
Random fires in modern turbofan engines are extremely rare. And the standards for combat fighters are higher than commercial aircraft because they have to survive battle damage. So, unless someone messed up real bad at the factory (considering this is a new aircraft), you can absolve the fuel feed system and hot innards of the engines. Also, MKI can be reliably be expected to have state-of-the-art fire suppression in these areas. Further, both engines will be completely independent of each other, further enhanced by barriers including thermal isolation, to ensure redundancy. Its hard to see a failure here bringing down a twin-engined aircraft. Even in the worst case scenario, the pilot would have had time to assess the damage, make a report and bail out.
For me something that disturbs is the way the overhaul and manufacture of the AL-31F engines were supposed to be taken up by the Indian manufacturer. MKI literature says the radar will be manufactured in Russia, and the last item to be transferred to HAL will be the engines. First overhaul facilities were built and then the manufacture. Overhaul has begun and in manufacture we all know they have had problems with making the fan blades, but are said to have overcome that. But the trickiest part with the engines is the nozzles. I remember reading an interview about AL-31F's nozzle development and its makers struggled to get the nozzles right. The challenge was to ensure structural integrity in the moving parts of the nozzle at high temperatures, especially when on afterburner. It is common knowledge that nozzle overhaul interval is radically reduced if the burner is used too much while vectoring thrust. So, if the entire engine, including nozzles were made in India, I would run my eye through this, because quality control here is critical. A nozzle failure can be catastrophic.
I can imagine a scenario where they were pulling up hard after a bombing run. But again both engine nozzles giving way at the same time? And at that exact juncture? What are the odds on that?