The Army's top civilian official has called for an urgent plan to equip Army helicopters in Iraq and Afghanistan with the most advanced defensive systems available, according to a memo obtained by a senator.

Five days after a surface-to-air missile brought down a CH-47D Chinook transport (search) and left 16 dead, the Army's acting secretary, Les Brownlee wrote, "Like other force protection measures, this is URGENT!"

The memo was obtained by Sen. Dick Durbin (search), D-Ill. It is dated Nov. 7, the same day that insurgents downed a Black Hawk helicopter (search) in Iraq, killing six.

Army officials had no immediate comment on the memo, which also say, "Affordability is not a constraint for the plan."

Durbin said the memo was "the right response to our recent helicopter tragedies in Iraq."

The Chinook that went down Nov. 2 was from a joint Illinois-Iowa National Guard unit. It had a standard package of defensive chaff and flares, Army officials say, although more advanced -- and expensive -- versions exist on special operations helicopters. Some of the other Army helicopters in Iraq went for a few months without any defenses.

These defenses can confuse guided surface-to-air missiles if an attack is detected in time.

But the equipment did not save the Chinook. Officials have said the system fired flares but they did not deflect the enemy missile.

Some have noted that the equipment is not 100 percent effective and that there was not much time for the Chinook to avoid the missile; the helicopter was flying low, so the missile hit it quickly.

Officials believe the Black Hawk was brought down by an unguided rocket-propelled grenade. Chaff, flares and jammers would not have affected such a weapon.