Police in eastern China have asked a local inventor to stop testing a homemade helicopter after he had a friend take off in the rudimentary aircraft earlier this month.

The crude one-seater designed by Chen Ruihua, 59, was assembled with basic parts sourced both locally and off the internet. The authorities in the town of Miaoquan, in Changshu in Jiangsu province, deemed it a "potential safety hazard," according to a statement released on WeChat last Friday.

Local police, who had come across a video of previous test flights, visited his workshop to prevent another. Building homemade aircraft isn't against the law, they said, but it is unlawful to pilot one without authorization from the civil aviation authority, and without the requisite training and qualifications.

Chen, whose family owns a plastic mold plant, has neither an engineering degree nor a pilot license. He told the police he had been making aircraft as a pastime for a decade, but said he had no intention of selling any and didn't allow any observers to watch his test flights.

His latest invention weighs 375 pounds and measures nearly 12 feet long. It has a folding fuselage and was able to reach an altitude of "several hundred meters," he said. Chen said it was the third generation of the same design, after two previous versions had failed to leave the ground.

He didn't disclose how much time and money he had put into his working model, but suggested it wasn't a small sum.

In its statement, the Changshu Public Security Bureau said Chen's simple helicopter was based on an unspecified Russian rotorcraft. It was powered by a boat engine, said the police, who also released footage of the aircraft taking off and landing at different locations.

"The person test-flying the aircraft wasn't me, but rather my partner," Chen told Chengdu's Red Star News on Monday. He plans to upgrade the helicopter's equipment and turn it into a drone for crop dusting.

Gong Jian, an officer with Miaoquan police, praised Chen's work ethic and courage, but said the law had to be observed in order to ensure public safety.

"The aircraft is crude and has no safety equipment," said Gong. "Careless test flights could threaten the life and property of the operator himself and those of nearby residents, and will also hinder air traffic management."

Local police said Chen promised never to test his homemade helicopter again. It apparently took some convincing.

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