WASHINGTON - The single biggest killer of American and British troops so far in the war with Iraq is a notoriously dangerous and fickle piece of machinery that coalition forces wouldn't dare go into battle without.
Helicopters - their own helicopters - have killed 19 American and British servicemen in crashes in and near Iraq over the past 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 notorious 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 its 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."
The helicopter first emerged as a viable means of transportation in 1940, when Russian-born aerospace pioneer Igor Sikorsky first flew the VS-300.
The military was quickly impressed, and the U.S. Army Air Corps ordered its own version of Sikorsky's helicopter the same year. But as a military platform, the helicopter is largely a child of the Vietnam War - where the "air cavalry" concept of quickly positioning troops around the battlefield by air was first applied. The Army has been enamored ever since.
Coalition forces today have 500 or more helicopters 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.
Already equipped with Hellfire anti-tank missiles, Hydra rockets, a 30 mm cannon and night-vision sensors, the Apache has gotten an upgrade since the last Persian Gulf war. The new Apache Longbow sports a sophisticated target-tracking radar system that can engage several enemies at once.
Military forces in Iraq also are flush with the Army's UH-60 Black Hawk, a utility helicopter that replaced the Vietnam-era "Huey" and is used as an attacker, a troop transport and for medical evacuation missions. It is perhaps best known for crashing famously in Mogadishu, Somalia, in 1993, and its subsequent role in the book and Hollywood film Black Hawk Down.
A Black Hawk helicopter can carry two door-mounted machine guns, and they are being used in Iraq to guard the supply columns between Kuwait and the front-end tank units approaching Baghdad. They also can carry 11 combat-loaded infantry troops into battle.
The Army's primary transport helicopter is the CH-47 Chinook, a two-rotor, banana-shaped aircraft that can carry 10 tons of cargo, weapons or troops. In the gulf war of 1991, Chinooks ferried American troops north and Iraqi prisoners south - a role envisioned for them again.
"You're talking about resupply, flank security, repositioning troops, an attack role - they're a very, very important part of your attack planning," says retired Lt. Gen. Donald E. Rosenblum, former commander of the Army's 24th Infantry Division, a precursor to the 3rd Infantry Division now advancing on Baghdad.
"I'm an old infantry guy, and let me tell you, the guys on the ground sure are happy that those helicopters are up there."
But keeping them up there is a challenge even in peacetime, and an infinitely more complicated one when the air is heavy with sand, smoke, bullets and stress.
In the desert a helicopter's rotors can kick up clouds of sand that obscure landing zones and confuse the pilot's equilibrium. Unlike fixed-wing aircraft, which glide naturally and tend to stay in the sky once they get there, helicopters require constant inputs from the pilot to stay level and aloft.
The desert is also inhospitable to the aircraft itself. The reduction gears that turn the rotor can fill with sand and seize, and air intake valves can clog and choke off the engine. Rotor blades that whip through sandstorms like a blender can quickly become pitted and split, causing their composite fibers to peel apart. Helicopters operating in the desert are typically grounded and inspected every few hours for signs of rotor wear, and the blades must be resurfaced frequently with paint or tape.
Enemy bullets and anti-aircraft fire will, of course, compound the problem. Military helicopters carry extra plating and heavy-gauge components to make them more "ballistically tolerant," but none of them can be considered tank-like for the simple reason that all of them have to fly.
The reasons for the recent crashes in the Persian Gulf are unclear. Four U.S. Marines and eight British Royal Marines died Friday when a CH-46 Sea Knight - a tandem-rotor helicopter similar to the Army's Chinook - crashed along the Iraq-Kuwait border. The next day, six British sailors and an American died in the Persian Gulf when two British Sea King helicopters collided shortly after lifting off from a Navy ship.
One day later, in Afghanistan, a Pave Hawk helicopter - the Air Force version of a Black Hawk - crashed while on a medical evacuation mission and killed all six Americans onboard. None of those helicopters appeared to have been brought down by enemy fire.
"You'll see a lot of the accidents attributed to pilot error, but that's because helicopters are much more difficult to fly than fixed-wing aircraft - particularly in the harsh conditions in the Persian Gulf," says Joe Horn, an aerospace engineering professor at Pennsylvania State University's Rotorcraft Center.
Only the Apache Longbow helicopter that touched down Monday near the Iraqi city of Karbala was engaged in a fight. The helicopter appeared undamaged in photographs, but its two American crew members were taken prisoner and the aircraft was later destroyed by American forces. The Pentagon has not said why it landed in unfriendly territory. Iraqi officials claim that the Apache was shot down "by a farmer."
Leishman and others say that claim is unlikely. A well-placed bullet from a pistol or rifle could conceivably jam one of the craft's rotor gears or pierce a fuel tank, but Apaches that returned after the mission all sustained much heavier fire. Vietnam-era helicopters were thinner, less powerful and vulnerable to small-arms fire. But modern military helicopters like the Apache have blast shields and Kevlar plating designed to withstand even moderately heavy firepower, such as .50-caliber machine guns.
Nonetheless, Army officials have altered their tactics because of strong Iraqi resistance on the ground, telling pilots to avoid engagements at close range. Modern helicopters can easily spot and destroy targets from several miles away using their rockets or laser-guided missiles, though that tactic increases the risk of unintentional damage to nearby buildings and civilians.
"It's unfair to say that a helicopter is fragile," says Leishman. "They aren't flying tanks, but these helicopters are designed to operate at low altitude under dangerous conditions. It's very unlikely that a stray bullet could cause any kind of catastrophic damage.
"But it's a compromise. The helicopter has its vulnerabilities, but the military accepts those because of the important role it can play."