A design for a "flapping wing" aircraft hand-drawn by Zhang Dousan, a 61-year-old from Chaozhou, Guangdong province. Xiaoxiao Xu describes Zhang as "the most creative and unrestrained" of all the Chinese aeronauts she met while researching her book. [Photo provided to chinadaily.com.cn]

Photographer Xiaoxiao Xu travelled across China documenting the impoverished farmers striving to build their own aircraft, Dominic Morgan reports.

At 200 meters in the air, terror gripped Xiaoxiao Xu. She was sitting in the back of a rickety autogyro that her pilot, a baby-faced 42-year-old from rural Zhejiang province named Xu Bin, said he had designed and built himself, and she had just made the mistake of looking down.

I felt the wind through my hair and saw the houses, mountains, fields and lakes passing by below my feet, Xu recalls in her recently published book Aeronautics in the Backyard. I started to picture how exactly we were going to crash.

But then I spotted Xu Bin looking down below with the curiosity of a little boy. He was gleaming with intense happiness. I began to appreciate just how much enjoyment he gets out of flying, she continues. My fear faded, and I looked out to enjoy the view with him.

This combination of joy, wonder and just a hint of madness runs through Xu's new book, an uplifting collection of tales and photographs from her experience searching out China's rural dreamers who, against all odds, are taking to the skies in their own hand-built aircraft.

Xu's adventure began on a quiet afternoon in April 2014 at her home in Amsterdam, when an article titled "Air Castles" in the Dutch newspaper Volkskrant caught her eye.