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July 12, 2010: The U.S. Air Force is quite pleased now that that it has reduced the loss rate (an accident causing destruction, or at least a million dollars of damage, per 100,000 flight hours) of its MQ-1 Predators down to 7.5 last year. Although this is twice the rate of manned fighter aircraft (like the F-15 or F-16), and five times the rate of the old, but very reliable, B-52, it's about the same rate as single engine private aircraft (8.2). Only a few years ago, the rate for the 1.1 ton MQ-1 was 30. The 4.7 ton larger MQ-9 Reaper had a loss rate of 16.4 last year, its third year of service. The Predator has been in action since the late 1990s. The design and operation of the MQ-9 learned much from the experience of the MQ-1.

Unmanned aircraft have always had a much higher loss rate, which is largely the result of not having a pilot on board, and not doing all that could be done to compensate for that. Older model UAVs had much higher rates. The 1980s era RQ-2A Pioneer had an annual rate of up to 363 per 100,000 hours. Despite that, the RQ-2 proved very useful during the 1991 Gulf war.

The air force has found that the MQ-1 is not an inherently accident prone aircraft, and that, when the losses were greatest,  80 percent of the losses were caused by human error. Part of this was due to poor user interface, which was only gradually brought up to the standard developed for video game flight simulators (which were eventually used as a model for the most effective operator controls). The MQ-1s were also in the air longer, per sorties, than any previous UAV, and that led to more losses because of unexpected maintenance problems and equipment failures in flight.

So far, between the air force and CIA (a major operator of UAVs over Pakistan, and other places), nearly a hundred MQ-1 and MQ-9s have been lost, out of nearly 500 built. But the troops can't have enough of these aircraft overhead, and this year MQ-1s and 9s will spend over 300,000 hours in the air over Iraq and (mostly) Afghanistan. That's compared to 185,000 hours last year and 151,000 hours in 2008. It took 12 years of service (1995-2007, including development) for the MQ-1 Predator alone to reach its first 250,000 hours. It took another two years (2007-2009) to fly an additional 250,000 hours (500,000 total). As the flight hours increase, the accident rate goes down.

But not always. 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. After the Cold War ended, and many secrets were revealed, it was discovered that the Russians had no better luck with lowering their aircraft loss rates. This was partly due to poorly trained pilots and ground crews, but also to poor design and quality control.

In contrast, the new F-22 has an accident rate is about 6 per 100,000 hours, mainly because it's new. Ultimately, the rate is expected to be 2-3. 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. But as India and China improved the training for pilots and ground crews, the accident rates declined.

Combat aircraft have, for decades, been getting more reliable, even as they became more complex. For example, in the early 1950s, the U.S. 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.