The American CH-47 helicopter that was shot down recently by an Iraqi SAM-7 portable missile apparently had a malfunctioning countermeasures system. Helicopters like the CH-47 are equipped with the ALQ-156 missile warning system (a small radar that spots oncoming missiles and triggers the release of flares.) The downed helicopter also had the M-130 flare dispenser. The investigation is not completed, but it is suspected that the countermeasures system was not being maintained properly. Helicopters, especially older models like the CH-47, require sixteen hours of maintenance for every hour they fly. After every 200 flying hours, the CH-47 is supposed to be partially disassembled and carefully inspected for problems. The CH-47 entered service in the 1960s, although the ones flying now were built in the 1980s and 90s. 

The attacks on American convoys has made air travel more popular, and the hundreds of American helicopters are being used heavily. In situations like this, the maintenance crews are under pressure to keep the choppers flying. In combat situations, and peacetime emergencies, aircraft can be flown with some equipment inoperable. Obviously, in the United States, the CH-47s can be safely flown with the ALQ-156/M-130 countermeasures inoperable. But over Iraq, it's dangerous to fly with a flaky countermeasures. But it's not suicidal. Not many (about a dozen) SAM-7s have been fired, as against thousands of flights by U.S. helicopters. So the investigation may reveal that an aviation officer, under pressure to get the CH-47 in the air for a particular mission, let it go even though the countermeasures had problems. Perhaps the ALQ-156 was just cranky, not totally inoperable. In such situations, the people in charge take chances. Often the flight itself is a matter of life and death. Perhaps to pick up a medical emergency, or get reinforcements to a firefight somewhere. In war time, there's always a lot of risk. And sometimes the risk turns to tragedy.