Published on : 26/05/2024

On 26 May 1956, the first lead transport plane from Beijing to Lhasa flew smoothly over the "Roof of the World" and landed safely at the airfield near Lhasa, signifying the success of the test flight of the Beijing-Lhasa route.

In order to fly over the Tibet plateau, referred to as an "air restriction zone", Chinese Air Force pilots underwent countless flight trials.

They piloted convoy transport aircrafts over the Kunlun Mountains, the Bayan Har Mountains, Tanggula Mountains, and the Hengduan Mountain Range, enduring high-altitude gales at over 100 kilometres per hour, turbulent vertical airflows, and bouts of hail in sub-zero temperatures. They conducted repetitive flight training and rehearsals.

Before this, the pilots had already conducted test flights with the "Ilyushin IL-12", testing this aircraft's high-altitude performance. It turned out that the "Ilyushin IL-12's" maximum altitude reached 9,040 metres, which met the flight requirements.

After the flight altitude standard was tested, an airport survey team of 15 people, consisting of air force maintenance staff, Soviet experts of the time, surveyors, meteorologists, doctors, and flight personnel, conducted a field investigation. They also further researched multiple flight plan options, and eventually decided to build a temporary grassland airport, Lhasa Airport, in Dangxiong.

In order to ensure that the flight to Lhasa was infallible, the famous Chinese physicist Qian Xuesen penned the continuous mathematical function of flight curves for pilots during landing and take-off from high-altitude airports.

Using Qian Xuesen's formula as the basis, the pilots combined the take-off and landing characteristics of the high-altitude airport and contrasted the technical theories of aircraft taking off and landing at sea level airports and high-altitude airports from different perspectives.

In this way, they mastered key data such as the necessary runway time, runway distance, take-off and landing speeds on high-altitude airports.

After all the preparations were made, the test team flew the "Ilyushin IL-12" to Yushu Airport in Qinghai for several test flights in order to accumulate flying experience.

Meanwhile, in view of the performance of the test flights, the experts modified the aircraft for the test flights, laying a solid foundation for the success of the test flights on the Beijing-Lhasa route.