WASHINGTON - “Revolutionary” to some but an “expensive truck” to others, the long-awaited V-22 Osprey aircraft is still polarizing U.S. military observers two months into its first-ever deployment.

Officials say the hybrid aircraft, which takes off and lands like a helicopter but flies like a plane, is doing exactly what it was designed to do: carry troops and supplies over long distances at more than twice the speed of the Vietnam-era helicopters the Ospreys are replacing.

But critics, including the Pentagon’s former top weapons tester, say the 10 Ospreys now in Iraq are being used gingerly to avoid combat situations and accidents.

The Ospreys are “absolutely being used the way they were designed,” Major Erik Dent, a Marine Corps spokesman, said Wednesday. They have flown missions every day since early October and have experienced no technical problems or accidents, he said.

But the Osprey, one of the Pentagon’s most expensive aircrafts to date, has still not been tested in battle, says Phillip Coyle, director of operational test and evaluation in the Defense Department until 2001.

Coyle and others say the aircraft may be vulnerable to attack because it lacks a front-mounted gun. All Ospreys have one rear-mounted machine gun, although the Marine Corps is now considering adding a second.

“From what I understand they’re not using it in combat. They’re using it like a truck, from one relatively safe place to another,” said Phillip Coyle, a former assistant secretary of defense and the Pentagon’s director of tests and evaluation until 2001.

Coyle, now a senior advisor to the Center for Defense Information, calls the Osprey a great concept but believes its high cost and history of technical problems and accidents has made it an unwise investment. The Defense Department has spent $20 billion during the last 25 years to develop the aircraft, which is made jointly by Bell Helicopter and the Boeing Company.

This week, the military placed a flight restriction on the domestic Osprey fleet. The new restriction is related to an engine fire that forced an Osprey to make an emergency landing in North Carolina last month.

Thirty people have been killed during Osprey test flight crashes, including 26 U.S. Marines.

“The last thing they need is a ‘Black Hawk Down’ type of situation,” Coyle said this week, referring to the Battle of Mogadishu in Somalia in 1993, during which two Black Hawk helicopters were downed by militia fire. Eighteen trapped U.S. troops eventually died during street fighting.

Dent confirmed that the Osprey has not yet been involved in a firefight in Iraq or evacuated wounded Marines. Osprey supporters often point out the fact that, with a top speed of nearly 300 miles per hour, the aircraft can move troops to medical care twice as fast as traditional helicopters.

The Osprey has yet to take fire, Dent said, because Iraq has stabilized since the aircraft were deployed, putting Marines in fewer combat situations. The last U.S. Marine fatality due to hostile fire occurred on October 8, according to www.icasualties.org, which tracks all coalition casualties in Iraq.

The Osprey is not a gunship, and was never designed as an attack vehicle, James Darcy, the Osprey program’s spokesman says. Long-distance troop and supply transport are the “bread and butter missions” of the Osprey, he said.

“It’s not being babied (in Iraq),” Darcy said Tuesday. “It’s doing the exact same mission as the helicopter squadron it was meant to replace.”

Darcy says the Osprey’s high cost - each one is about $69 million, or $120 million if total development costs are factored - is worth it.

“What we’re fielding is an entirely new class of aircrafts,” Darcy said at Patuxent River Naval Air Station in Maryland, where the Osprey was developed. “It’s as much of a revolution in technology as fielding the jet or the initial helicopters.”

The military has said they fill a longstanding gap between helicopters and planes, allowing combat-ready Marines to be quickly dropped deep inside of enemy territory. Their mission radius is nearly 500 miles.

“The Marine Corps has pretty much bet the future of Marine aviation on the V-22,” said Nick Schwellenbach, national security investigator at the nonprofit Project on Government Oversight in Washington.

“But the cost per unit of these things is so prohibitive, they’re only going to be able to buy so many,” he said Wednesday. “And will they risk a $120 million machine, that may be hard to replace? I don’t know.”

Last month, Congress appropriated $2.72 billion for 26 new Ospreys, including 21 for the Marine Corps. The rest will go to the Air Force.

“At the end of the day, $120 million is I think too much to pay for this,” Schwellenbach said. “It would be great if it really was revolutionary. I’m doubtful though.”