It is really not easy to test flights in China, before the test flights in the 60s, there was no refueling truck, and the basin could only be refueled again and again, and the oil was very dirty and could only be filtered with gauze. One MiG-17/19 with full fuel, required

It is really not easy to test flights in China, before the test flights in the 60s, there was no refueling truck, and the basin could only be refueled again and again, and the oil was very dirty and could only be filtered with gauze. A MiG-17/19 is fully fueled, and it takes more than half a day for multiple people to work together, and it is in such a difficult environment that Chinese test pilots have flown out generations of advanced fighters.