Army Apache helicopters grounded for over a month after US transmission warning

South Korea's Army Apache attack helicopters have been grounded for more than a month after the United States notified Seoul that the aircraft required technical inspections due to a transmission problem.

Army public affairs chief Bae Seok-jin said at the Ministry of National Defense's regular briefing Tuesday that the Army received a flight-safety notice from the US side regarding the Apache's transmission and has temporarily suspended flights since early October to ensure safety while conducting phased technical inspections. "We plan to resume operations sequentially based on the inspection results," Bae added.

Bae drew a line on concerns about a capability gap, saying the US flight-safety notice includes recommendations for operating the Apache's essential combat assets and that there are currently no problems with emergency standby or operational readiness.

The measure stems from a US Army decision to ground its own fleet. On Oct. 2, the US Army ordered an immediate, temporary flight suspension of AH-64E aircraft equipped with the Improved Drive System transmission until required inspections and corrective actions are completed. About 400 of the roughly 700 Apaches in the US Army's inventory are affected, and the grounding is expected to last several months.

According to the US Army's investigation, the transmission in question can lose auxiliary gearbox drive due to an internal failure, which in turn can cause a loss of tail rotor thrust, electrical power and hydraulics. The cause of the failure has not yet been clearly identified, however.

Taiwan, which operates the same model, also grounded its Apaches after receiving the US technical notice. Taiwanese Defense Minister Gu Liuxiong disclosed the suspension at the legislature on Oct. 29. AH-1W Cobra attack helicopters and OH-58D Kiowa reconnaissance helicopters are filling in for the Apache during the inspection period. Taiwan is reported to have halted operations of 29 of its 30 AH-64E aircraft.

Uncertainty within and outside the military is growing over when flights will resume. Boeing technicians are in South Korea this month to inspect the Army's Apache fleet, leading some to expect the grounding will continue for now.

The Army operates 36 Apaches. In the event of a contingency, the helicopters are tasked with destroying North Korean tanks near the MDL and hovercraft infiltrating the northwestern islands.