RD-33 Engine & Design Problems

Well as a casual observer of the Mig-29M2/MMRCA approaching to land at the AeroIndia 2005 , after performing so magnificently at the show ( I remeber many LCA scientist praising the 29MRCA performance ) and since I was standing at the tarmac , and while the 29 was approaching to land , tail of Black Smoke was clearly visible ( I wouldnt call it a dense smoke ), but neverthless very much visible ones clearly marking the 29MRCA out from other aircraft.

If one looks at the old Mig-29A footage ,it was more densely smoked a clear give away for defence system ( ack-ack , missile etc ) .

Now that was the 29A and this is the 29MRCA at AE2005 , If it was a minor issue it would have been sorted till its latest avtar , Though the IAF uses a low smoke variant of the RD-33 , Think its called RD-333 , But How low smoky is another question.

Also it had reliablity issue and may be design issue since they couldnt solve the problems till now , I am not aware if the latest variant of the RD-33 has completely solved it , But the near latest I saw at AE2005 was smoky.

Also CAG has pointed to the RD-33 engine problem in the IAF Indian Airforce Mig-29 XPerience may be by now they might have solved it by and large.

But Does the RD-33 engine in general faces Design Problems ?????
Something which cannot be overcome completely , Or is it some other reasons like low quality of spares,fuel and maintainence issues which creates this problem ?????????

Since MIG-35 or MMRCA ( what ever may be its avtar ) is a top contender for IAF requirement , It becomes more serious issue.