SEOUL -- The supply of the Surion utility helicopter to the South Korean Army has been suspended due to a failure in critical airworthiness tests, according to the Defense Acquisition Program Administration (DAPA).

The twin-engine, troop-carrying rotorcraft, codenamed KUH-1, was co-developed by Korea Aerospace Industries (KAI) and Airbus Helicopters, formerly known as Eurocopter, in 2009 to replace the aging fleet of UH-1Hs and 500MDs, which have been in service for decades.

KAI has supplied the Army with 54 Surions since 2013 and is supposed to manufacture some 200 more by 2023 under a contract with the DAPA.

The helicopter, however, failed a cold-weather test taken in northern Michigan between last October and March, according to the arms agency.

"The Surion failed the test carried out to see the impact of ice generated during flight under humid and freezing conditions on the engine and several other components," a DAPA spokesman said, adding the helicopter failed to satisfy 29 of the 101 requirements concerned.

The test was carried out at 5 to minus 30 degrees Celsius and found that more than the permissible level of ice built up at the air inlet of the engine, he said.

KAI plans to redesign the failed elements, including heating systems, and put the aircraft under the same test again within one-and-a-half years.

"The anti-icing test is just a tiny part of airworthiness evaluations, and the Surion had already been cleared to fly on the peninsula for war operations," KAI spokesman Lee Myung-hwan said. "We'll resolve the problems with anti-icing elements at the earliest date and push forward deploying the helicopters in the field."

While seeking to get full-scale airworthiness certification, Lee said, KAI is expected to export the Cougar-based helicopter to Southeast Asian countries, where winters are warm and dry.

Besides the troop-carrying version, KAI has redesigned the Surion to perform various duties and roles, such as law enforcement, aerial observation, maritime support, and search and rescue.