Helicopters — their own helicopters — have killed 19 American and British servicemen in crashes in and near Iraq over the last week. Two more Americans were captured when they had to ditch an Army helicopter 50 miles south of Baghdad. Another six died last week in a helicopter crash in Afghanistan. While troubled by these developments, military analysts and historians are not entirely surprised. Helicopters are renowned for being vulnerable to damage from sand and debris, easy to shoot down, irritatingly difficult to fix and maintain and hard to fly when visibility is poor. They are slow, cumbersome and have only modest capacity and range.

But the rotor-winged aircraft is also one of the most versatile and, some say, irreplaceable pieces of hardware in the military’s arsenal — one vital enough to modern strategy that troops have learned to forgive its many weaknesses.

“Helicopters can go in as a weapons platform, bring troops and supplies along with them, they evacuate casualties on the way out — that’s an indispensable role in modern combat,’’ says Gordon Leishman, a professor at the University of Maryland’s Alfred Gessow Rotorcraft Center. “You have to account for is shortcomings, but if you told the military that they were going into battle tomorrow and couldn’t fly any helicopters, they’d say you were crazy.’’

Allied forces today have 500 or more helicopters of different varieties in the Middle East. The army’s main attack helicopter, the dual-engine AH-64 Apache, is regarded as one of the rabbits in the army’s hat, expected to rain havoc on Iraq’s Republican Guard. The Apache’s mission is to destroy enemy tanks before they come within range of American troops. In Iraq, they are also being used against missile launchers and troops.