For the second time this year, India has grounded its Su-30 fighters because one of the aircraft crashed. This time, the grounding of the 98 Su-30s in service is expected to last only a few days. Earlier this year, in May, its Su-30 fighters were grounded for a month after one of them appeared to develop engine problems and crashed. One of the pilots survived, but the parachute of the other failed to open. Four days before the Indian Su-30 went down, a Russian Su-35 also crashed because of engine problems. The Su-35 is an advanced version of the Su-30, and uses a similar engine. Earlier this year, Russia grounded all its MiG-29 fighters to check for structural problems, after one of them came apart in flight. All this is particularly upsetting to Indians, who had been assured by the Russians that the Su-30 was a modern (built to Western standards of reliability) aircraft. Such assurances were necessary because of earlier Indian experience with the MiG-21, and Russian aircraft in general. So far this year, India has lost twelve military aircraft, most of them of Russian design.
India lost 250 MiG-21s to accidents between 1991 and 2003. When consulted, Russia pointed out that India had insisted on manufacturing many of the spare parts needed to keep MiG-21s operational, and many of these parts were not manufactured to Russian specifications. While Russia does not have a reputation for making the highest quality equipment, their standards are often higher than Indias. It's no secret that much of the military equipment made in India is pretty shabby by world standards.
Most of the 110 pilots lost in these MiG-21 accidents were new pilots, which pointed out another problem. India has long put off buying jet trainers. New pilots go straight from propeller driven trainer aircraft, to high performance jets like the MiG-21. This is made worse by the fact that the MiG-21 has always been known as a tricky aircraft to fly. That, in addition to it being an aircraft dependent on one, low quality, engine, makes it more understandable why so many MiGs were lost.
The MiG-21 problems were overcome by 2006, a year in which no MiG-21s were lost. One of the main causes of many crashes was finally traced to bad fuel pumps. India improved maintenance, spare parts quality and pilot training to the point that the aircraft was no longer considered the most dangerous fighter to fly.
But India was not the only one, besides the Russians, who had problems with Russian made warplanes. During the Cold War, the U.S. had several dozen Russian aircraft they used for training their fighter pilots. Despite energetic efforts to keep these aircraft flying, their accident rate was 100 per 100,000 flying hours. That's very high by U.S. standards. The F-22 has an accident rate is about 6 per 100,000 hours, mainly because it's new. F-15s and F-16s have an accident rate of 3-4 per 100,000 flight hours. India, using mostly Russian aircraft, has an accident rate of 6-7 per 100,000 hours flown (compared to 4-5 for all NATO air forces.) The Indian rate had been over ten for many years, and it is still that high, and often higher, with other nations (including Russia and China), that use Russian aircraft designs.
New aircraft always have higher accident rates, which is how many hidden (from the design engineers and test pilots) flaws and technical problems are discovered. The F-22 is expected to eventually have an accident rate of 2-3 per 100,000 flight hours. This is part of a trend.
Combat aircraft have, for decades, been getting more reliable, even as they became more complex. For example, in the early 1950s, the F-89 fighter had 383 accidents per 100,000 flying hours. A decade later, the rate was in the 20s for a new generation of aircraft. At the time, the F-4, which served into the 1990s, had a rate of under 5 per 100,000 hours. Combat aircraft have gotten more reliable and easier to maintain, despite growing complexity, for the same reason automobiles have. Better engineering, and more sensors built into equipment, makes it easier for the user and maintenance personnel to detect potential problems. Aircraft used the computerized maintenance systems, currently common on new aircraft, long before automobiles got them. Unless you have a much older car that still runs, or a real good memory, you don't notice the enormous increase in automobile reliability. But older pilots remember, because such changes are a matter of life and death if you make your living driving an aircraft. And commanders know that safer aircraft give them more aircraft to use in combat, and more aircraft that can survive combat damage and keep fighting.
Unmanned aircraft have a much higher rate, which is largely the result of not having a pilot on board. The RQ-1 Predator has an accident rate of about 30 per 100,000 hours. Older model UAVs had much higher rates (up to 363 for the RQ-2A).