The Experimental Military Unit (EMU) was a joint Australian-American company-sized helicopter assault force which operated during the Vietnam War.

Although the RAN contingent was significantly smaller than the rest of the unit, the Australian personnel frequently found themselves in senior positions, due to having more extensive training and experience than their American counterparts.

[6] A typical daily deployment consisted of ten Slicks (plus a spare), two teams of two gunships, and a Command and Control helicopter (designated 'Charley Charley').

[8][11] Other duties performed by the EMU, particularly from 1970 onwards, included dawn and dusk assaults; night hunter-killer patrols, which consisted of one Slick armed with flares, two gunships, and a Charley Charley armed with a high-power searchlight and a twin 0.50 calibre machinegun; and joint operations with the United States Navy SEALs, which typically involved locating and capturing senior Viet Cong (VC) personnel.

[13] In mid-February, while delivering the ARVN 9th Division to a landing zone near Mỹ Tho, the EMU encountered multiple companies of heavily armed North Vietnamese People's Army of Vietnam (PAVN) soldiers.

9 Squadron RAAF were invited to fly with the EMU for two-week stints: although officially conceived to promote knowledge-sharing between the Royal Australian Navy, Royal Australian Air Force and the United States Army aviation branch, the plan also helped counteract pilot shortages in the EMU as United States personnel completed their twelve-month draft period and were not immediately replaced.

[17] During the landing, the force was ambushed by VC: ten aircraft were hit and several ARVN were killed or wounded, although the only injury suffered by EMU aircrew was a bullet through the earlobe of an American pilot.

[22] The VC commenced sporadic mortar attacks on Bearcat on 22 February, forcing the EMU to evacuate their helicopters and support personnel to Blackhorse six times over the next seven days.

[22] On 31 May, an EMU gunship escorting a formation near Đồng Tâm Base Camp came under heavy fire and crashed, killing all aboard.

[22][23] On 16 June, an Australian gunner aboard a Slick was wounded while providing covering fire for a medical evacuation of South Vietnamese soldiers near Cái Bè.

[24] On 19 December, following a VC ambush in Bình Đại which killed half of an ARVN unit, the EMU successfully deployed a blocking force in the path of the PAVN withdrawal, which inflicted heavy casualties.

[26] This was compounded by shortages in new American personnel to replace those who had completed their draft, spare parts, and aircraft, forcing the EMU to borrow helicopters and aircrew from other units.

[26] In early March, an EMU helicopter landed on a booby trap, seriously wounding the Australian pilot and killing two South Vietnamese passengers.

[26] Later that month, an American gunship crewman died from wounds received from enemy fire, while in a separate incident, five Slicks were damaged by gunfire.

[28] The pilot, Sub-Lieutenant Andy Perry, was later awarded the United States Silver Star, the South Vietnamese Cross of Gallantry, and was mentioned in despatches.

[28] Two days later, an EMU gunship crashed after being fired on by a .50 caliber machine gun, killing the American aircrew, while its companion was heavily damaged.

[28] In August, the EMU was relocated to Đồng Tâm Base Camp, which also housed elements of the United States Navy SEALs and the Mobile Riverine Force.

[30] On 11 November, the EMU was required to drop four waves of South Vietnamese soldiers into an engagement with a VC battalion near the U Minh Forest.

[30] The vulnerability of the UH-1 was demonstrated in late 1970[clarification needed], when five EMU helicopters were shot down in the Kien Hoa province by a single VC soldier armed with an AK-47 rifle.

[31] On 4 December, an Australian EMU pilot rescued a South Vietnamese patrol boat, which had been disabled and was drifting towards the VC force that had attacked it and sunk a companion craft.

[32] The American pilot was killed, but the other personnel survived the crash, linked up with South Vietnamese troops fighting in the area, and remained with them until helicopters of the 1st Cavalry Regiment drove the PAVN off.