Why is the plane to Lhasa different from the ordinary plane?

Lhasa has a civil aviation airport, namely Gongga Airport. From the nature of use, Gongga Airport is a dual-use airport, with a standard grade of 4E, and has a runway and terminal with a length of 4000 meters. The local altitude reaches 3600 meters, which is a typical plateau airport among domestic civil aviation airports, but it is not a more difficult plateau airport.

From the perspective of civil aviation aircraft, flying to a plateau airport like Gongga in Lhasa has the following three main impacts on flight performance requirements:

1, takeoff and landing performance;

The biggest change of air parameters in plateau area is the sharp drop of air density, which leads to the decline of aircraft lift at the same speed. In this case, the length of the take-off and landing runway of civil aircraft with the same model and passenger capacity is much longer than that of plain airport. This is why the runway length of Lhasa Gongga Airport should be increased to 4000m, while the runway length of Hongqiao Airport (4E) at the same level is only 3400m.

On the contrary, for civil aircraft, it is necessary to make their own weight as light as possible, so that they can have better plateau acceleration and landing deceleration performance under the same engine thrust. Even if an accident occurs in the air, the distance and time of gliding flight will be longer. To carry out professional performance parameters, it needs ETOPS, that is, the longest time for an aircraft to fly safely under the condition of single engine failure, which is generally required to be 120 minutes instead of the common 60 minutes.

2. Stability of plateau mountain area when encountering airflow;

The airflow in the plateau mountainous area is more complicated, and the airspace around the airport will encounter all kinds of sudden strong winds and wind shear. In this case, on the one hand, the pilot's operational ability is tested, on the other hand, the stability of the aircraft is tested. Generally speaking, the length of aircraft fuselage is shorter, and the vertical and horizontal tail areas of aircraft are larger. Of course, if there is a flight control system, the software part needs to be readjusted.

3. Cabin pressure maintenance requirements;

When a civil aircraft flies normally in the air, the pressure in the cabin is generally maintained at a height of 2000-2400 meters, and the pressure is constantly adjusted during the landing process to keep it consistent with the ground pressure outside the cabin. However, after switching to the plateau area, it is necessary to adjust the cabin pressure mode. We can't copy the requirements during the plain area, but we should keep the air pressure in the cabin as high as possible to make passengers feel comfortable.

In fact, there is no high requirement for the realization of specific models. As long as the runway is long enough, ground navigation equipment can take off and land. However, for domestic flights to Lhasa, considering the comprehensive factors such as flight safety, performance, cost and route density, it is generally completed by smaller aircraft. In the 1970s and 1980s, four-engine aircraft like Boeing 707 were generally used to fly. In the 1990s, it was replaced by wide-body aircraft like A330 and low-density narrow-body passenger aircraft like Boeing 737-700, and Soviet-made aircraft like Tu-154 also flew in.

After 2000, Airbus carried out altitude adaptation transformation on the short fuselage model in its A320 series, and thus launched this A3 19 passenger plane, which was known as the "Little Prince of the Plateau", and was purchased in large quantities by domestic airlines such as Tibet Airlines and Sichuan Airlines, and specially flew to Xizang Autonomous Region.

Therefore, generally speaking, the requirements for civil airliners flying to Lhasa are "small, light and stable" models.