Every time a pilot lands in a flight, he encounters the concept of landing distance. First, it is the performance landing distance obtained by looking up the table according to the actual flight conditions. Then, the actual landing distance produced by the pilot in the air during the landing of the aircraft, the QAR on the aircraft records the radio altitude of 50 feet to the ground distance.
Many pilots mistakenly believe that the aircraft is flying 50 feet above the runway entrance according to the ILS 3¡ã glide path, and are not clear about the relationship between the radio altitude indication and the aircraft. The following is to analyze the landing distance according to the regulations, test flight verification, manual and QAR.
First of all, when the flight is below the decision altitude, the barometric altimeter is no longer referred to because the barometric altimeter is affected by low-altitude airflow and ground effects, and the indicator error becomes larger and needs to be switched to visual flight, while the approach of instruments above class II is based on the radio altimeter.
After receiving the altitude signal, the radio altimeter is converted to the height between the undersurface of the main landing gear and the ground (vertical fuselage longitudinal axis) according to the aircraft’s own coordinate system. If the aircraft’s short five-side runway extension surface of the approach airport is flat enough, it can refer to the radio altitude approach and leveling landing.
We all know that the glide path receiving antenna should be strictly on the ILS glide path in the process of five-side approach, so that there is a certain distance between the main wheel and the glide path according to different types of structures (see the example of A330, see Figure 1). When the pilot approaches the runway entrance according to the 3-degree glide path light, the relative relationship of the aircraft (see Figure 2 of A330).
Figure 2 shows that the A330 at the runway entrance the pilot’s line of sight is 59 feet and the main wheel ground is 32 feet, so the pilot’s line of sight at 50 feet is 27 feet away from the main wheel.
Therefore, when the main wheel of the aircraft enters the runway according to the glide line indicated by the ILS glide path or the glide path indicator, the distance between the main wheel and the ground is less than 50 feet, and there will be altitude differences among different types of aircraft.
Medium, mainframe and heavy aircraft all display different main wheel inlet heights, with larger and longer aircraft having lower ground height.
The altitude of the aircraft at the beginning of leveling is basically the same, and the difference of approach speed leads to different landing distances. According to the runway entrance speed, the aircraft can be classified into class A, B, C (121-140kt) and D (141-165kt). Class E belongs to military aircraft and will not be discussed.
Civil aviation transport enterprise aircraft are basically C class and D class.
The requirements of CCAR25 concerning aircraft landing distance are as follows: CCAR25.21, CCAR25.101h i, CCAR25.109f, CCAR25.125a b Test flight method: a) Ensure the maximum tire pressure and check the maximum brake pressure before the test;
b) Conduct the test according to the recommended landing procedure, control the approach glide Angle between -2.5¡ã and -3.5¡ã, and control the ground point sink rate between 2 and 6ft/s;
c) After the aircraft touches the ground, decelerate the aircraft according to the deceleration measures required by the test until it stops completely, and keep the stopping state for 5s;
d) During the test, the anti-slip system works;
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