http://www.strategypage.com/htmw/htatrit/articles/20140730.aspx
July 30, 2014: As long ago as 2009 Russian engineers knew they had some serious problems with the AL-31 family of engines that powered so many of the most modern (and exported) jet fighters. Introduced in the early 1980s to power the Su-27, a later version was used for the Su-30 in the 1990s. An even more improved version, called the AL-41, was developed for the Su-35 fifth generation fighters. But in early 2009 one of the two prototypes of the Su-35 cashed from what were later found to be "engineering defects" in one of the two AL-41 engines, which failed during takeoff. At least two Su-30s have been lost so far because of this problem.
Now India, the largest user of the Su-30, has gone public with demands that Russia do something about the high failure rate of AL-31s. India did not reveal the exact numbers of such failures (as that would reveal how low the reliability was of India’s Su-30s) but was emphatic that the failure rate was too high. The Su-30 has two engines and the loss of one in flight does not automatically result in a lost aircraft because the Su-30 can land on one engine. But that puts the Su-30 out of action for a week as the incident is investigated and a new engine installed. India pointed out that the loss of one engine in combat would often be fatal. India did reveal that it now rebuilds its AL-31s after 700 hours of use instead of the recommended 1,000. AL-31s are supposed to be good for 3,000 hours and that extra rebuild is expensive and takes time.
Indian pilots are understandably nervous about the safety of the many Russian warplanes they fly. The older MiG fighters are the most dangerous and nearly half have been lost to accidents, usually because of equipment failure. The more recent Su-30 models were believed to be a lot safer. Recent problems indicate this may not be the case, thus the very public demands for Russia to fix the problems. Air force leaders are under tremendous pressure to solve the problem. Pilot training has increased, especially on how to fly a Su-30 on one engine, as have efforts to increase maintenance and safety standards. But it’s all for nothing if Russia cannot fix basic design flaws.
Russian engines have long been noted for their low reliability, and short service lives. There are currently two Russian engines being built for fighter aircraft. The $4 million AL-31 (for the Su-27/30, and the Chinese J-11, J-10) and the $3 million RD-33/93 for the MiG-29 and the Chinese JF-17 (a F-16 type aircraft developed in cooperation with Pakistan) are big export items and a major source of income for the Russian firms that build them. The AL-41 is supposed to be good for 4,000 flight hours (compared to 3,000 hours for the AL-31). Accidents like the one in 2009 are expected during aircraft development, although in the last decade, Western aircraft developers have avoided such losses by doing a lot more testing via computer simulation. The AL-31/41 has been the cause of several Su-30 mishaps recently and the Russians are still seeking answers. It’s is obviously not easy. The Al-31 itself is five meters (16.3 feet) long and weighs 1.6 tons. They are complex bits of engineering with thousands of precision parts. There is a lot that can go wrong. India understands this but the abnormally high number of engine failures in 2012 and 2013 and Russian inability to fix problems that have been present since before 2008 is very worriso
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