Australia grounded its fleet of five CH-47D Chinook helicopters, including two in Afghanistan, under a "precautionary suspension of flying operations" note.

The grounding was ordered because of concerns over the aircraft's advanced flight control system in certain flight conditions, a statement from the Ministry of Defense said.

Brig. Neil Turton, the military's director general Aviation, said the suspension was to ensure safety and is consistent with Army Operational Airworthiness procedures.

"The precautionary suspension will remain in place pending technical analysis of flight data by Defense and Boeing," Turton said.

Boeing manufactures the CH-47 helicopters.

Turton gave no further details of what technical concerns the army had.

Grounded are the two Chinook aircraft deployed in Afghanistan in support of the NATO-led International Security Assistance Force operations. Both aircraft are based at Kandahar Air Field and perform combat and logistic support missions, as well as quick-response tasks.

"The grounding of the aircraft is not expected to have an impact on the conduct of operations," Turton said.

Because Australia's Rotary Wing Group is part of the U.S. 101st Combat Aviation Brigade in Afghanistan, there is no shortage of military and contracted aircraft that can be called up. This allows greater redundancy, synchronization of maintenance and improved mission planning when situations arise such as Australia's grounding of its Chinooks, the Ministry of Defense statement said.

"Military operations staff will offset the loss of capability and readjust schedules and support arrangements to ensure that rotary wing assets are prioritized in accordance with mission requirements," Turton said.

Australia has one Chinook deployed in Papua New Guinea and one on Horn Island in Torres Strait, between the extreme northern tip of Queensland state and Papua New Guinea.

The fifth Chinook remains at the fleet's home base in Townsville, in Queensland.

The grounding comes after a Chinook crash in May when Lt. Marcus Case, a member of the 6th Aviation Regiment, died during a resupply mission in Afghanistan. He was the 83rd ISAF soldier to die in a Chinook crash in Afghanistan up to then, The Canberra Times reported.

However, the grounding of the Chinooks wasn't related to the May accident, the Ministry of Defense said.

The Chinooks, some of which date to the 1970s, are among the oldest airframes operated by the Australian military.

Australia has seven new Chinook CH-47F on order, expected to cost around $142 million each. The first of the CH-47F choppers will be combat ready by 2016, two years after Australia's scheduled withdrawal from Afghanistan.

The grounding of the Chinooks has left Australia without a battlefield airlifter cargo helicopter.

The military's aged twin-engine, fixed-wing Caribou cargo aircraft, made by de Havilland Canada and which saw service in Vietnam, were retired two years ago.

The DHC-4 Caribou -- known in the U.S. military as CV-2 and C-7 Caribou -- is a short takeoff and landing cargo plane first flown in 1958 and mainly retired from military users.

Australia has announced no decision on a replacement for the Caribou.