ramana wrote:My take.
Kaveri -!(the one that was tested in Russia) has noise at high rpm per DRDO chief Dr. Christopher.
To me this indicates turbine blade vibrations at high speed.
This means a blade stiffness issue.
You can either increase stiffness or reduce mass to get above the resonant frequency.
All this would need new test data.
So K-1 test data is interesting but not wholly germane to the K-2 after blade fix.
Anyway Dr. Christopher is confident it will be solved in a couple of years and will fly in an LCA.
He must have good basis for his confidence.
We have waited for so long and a wait of two more years wont affect our sanguinity.
Flutter in the booster stages (low pressure compressor). It happens only on certain points - at altitudes (my guess) and at high power op points (Dr Christopher). I am told GTRE resolved this issue already. They claimed they can fly it in LCA without help from Snecma. Take this one FWIW though.
Here is what we know already. Kabini core works well, as expected. How we can conclude this?? Kaveri has achieved targeted dry trust. There has been no dispute on this, reported anywhere that I have seen. UCAV program was linked to Kabini since quite a few years. They would not have done it without good confidence over Kabini's performance. Also Kaveri performed rather well in Marine avatar KGMT. This also indicates that the issue with flutter is at higher altitude point (amd thus it was uncovered only during flight testing in Russia. If only we atleast had our own High altitude test facility this problem could have been seen much earlier). The shortfall in wet thrust was due to AB performance. It has screech issue as well. (Now GTRE claim they have overcome this issue as well). From all the info I have seen, the problems are/were only for the LPC and AB.
Adding to this, French reviewed Kaveri and concluded about 20% work is remaining to make it flight-worthy. The ground tests, high speed taxi tests and actual flight tests itself is a huge task and I suspect it constitutes major portion on this 20% remaining tasks. Connecting the dots, I think, there is not much to be rectified in Kaveri. All measure issues must have been taken care of already. If there was any issue with the Kabini or major redesign on LPC/AB was needed, there is no way any one in the work can make Kaveri flight worthy in 2years. And there is no question of replacing Kaveri core with M88 core, since you can't just take one core and stick it to another engine's LP system without good 4-5yrs of work on it. I initially thought Scecma might do this but after some pondering and adding 2+2, I came to conclusion that there seems to be no reason why Kabini be replaced at all.
Even if we choose not to believe GTRE's claim that the design thrust for dry as well as wet conditions has been achieved already, still from the estimations/timelines/budgets given by Snecma, there seems to be no major technical issue to be resolved. Its mainly to add finishing touches, plucking some low hanging fruits and complete the rest of the test program.
BTW another tidbit for jingos - currently Kaveri's stall margin is 19-20% as against design target of 22% while GTRE wants to achieve 25%. This is one thing yet to be achieved, they said in AeroIndia.