Weather conditions at Changshui Airport

Firstly, this paper briefly introduces the ILS instrument landing system and its program implementation method, introduces the types of visibility, the factors affecting visibility and several weather phenomena that are easy to form low visibility weather, and analyzes its harm to actual flight. Then, based on the characteristics of ILS approach procedure in low visibility, the implementation methods of ILS approach in low visibility are summarized, including approach preparation, five-sided approach cut-in and five-sided track descent control. Attention distribution skills from instrument to vision, continuous approach or missed approach, etc. Combined with my own flight experience, the matters needing attention in each stage of approach and the related crew cooperation are put forward.

Keywords: blind approach and low visibility landing

China Library ClassificationNo.: V2 12 Document ID: A DocumentNo.:1672-3791(2012) 06 (a)-0029-02.

1 Basic landing method of instrument landing system

(1) Before landing, when requesting permission to land through clouds from the ground commander according to the instrument, apply for opening the ground equipment of ILS system, use other radio equipment to enter the site, and master the position of the aircraft.

(2) Adjust the frequency of the landing airport heading beacon in the left and right control boxes in advance.

(3) Turn on the signal lamp and audio lighting power supply.

(4) Point the channel pointer to the landing magnetic heading on HSI.

(5) The autopilot is connected with ILS system for automatic approach and cloud landing. For landing on a large route, turn on the autopilot before the third turn at the latest, use the heading preselection pointer to make the third turn at an angle of 30 ~ 40, and then move the HSI heading deviation lever from the full deviation scale to the center. When it moves to the center, it means that the plane enters the channel.

(6) Usually, make the plane fly horizontally below the standard glide path to intercept the glide path. When the glide slope indicator is in the center or in the grid of 1/2, it means that the aircraft basically enters the glide slope. Turn on the glide slope button and the aircraft glides along the standard glide slope.

(7) When the relative height is 300 m ~ 400 m, check whether the monitoring flag and GP flag of ILS system are stable. If it is unstable, cancel the automatic driving and change to manual operation.

(8) When the relative altitude is 60m, turn off the autopilot and land visually.

2 the concept of visibility

Generally speaking, visibility has two meanings. One is the maximum distance that a person with normal vision can distinguish a target. The second is to observe the clarity of the target within a certain distance.

In aviation activities, pilots need to observe obstacles, other flying objects, lights and other targets, and distinguish their types and determine their types and positions. To distinguish the target, the most basic condition is to see the outline of the target clearly. Therefore, the visibility used in aviation is defined as: the maximum distance for people with normal vision to see the outline of the target during the day, and the distance for people to see the luminous point of the light at night.

3 The influence of low visibility on blind approach

There are eight weather phenomena that affect visibility: fog, smoke, haze, sandstorm, floating dust, snow blowing, low clouds and precipitation, but fog and low clouds are the most common and influential.

Air from unsaturated state to saturated state is the basic principle of water production in the atmosphere. There are two ways for air to reach saturation: one is the increase of water vapor; The second is the cooling of air. Because fog and low clouds are the products of the near-surface atmosphere, these two factors play an important role and are greatly influenced by the surface conditions. There are several ways to increase water vapor in the near-surface atmosphere: evaporation of water on the underlying surface, turbulent mixing, horizontal transportation and precipitation evaporation of upper clouds. Generally speaking, fog and low clouds are more likely to appear in areas with wet underlying surface and rich water resources. The cooling modes of near-surface atmosphere are mainly turbulent mixing and radiation. Surface radiation cools at night, and turbulent mixing expands this cooling upward. Through the above physical processes, fog and low clouds are formed under certain conditions.

3. 1 fog

Water droplets and crystals suspended in the near-surface gas layer, resulting in visibility less than 1 km, are called dense fog; Light fog causes visibility between 5 and 9 kilometers. When the pilot changes from instrument flight to visual flight, if he sees broken fog or uniform fog, the plane looks like he is looking up, and the pilot often pushes the ejector pin unconsciously, which increases the descent rate and causes the rear section of the Pentagon to be lower than the glide line.

3.2 Low-level cloud

The cloud bottom is even as a curtain, fuzzy as fog, and very low. When approaching at night, the pilot may have a high sense of the plane; In the process of flattening the plane, the pilot may have a feeling of falling under the runway.

4 Blind descent approach method under low visibility conditions

4. 1 approach expectation under low visibility conditions

When it is known that the weather situation and forecast of the destination airport are low visibility, the captain and crew should first make mental preparations, including understanding the reserve fuel quantity, take-off fuel quantity, approach precautions, go-around procedures, etc. of the selected alternate field, so as to foresee the flight situation monitoring that may be caused by low visibility.

4.2 Preparation for Blind Descent Approach under Low Visibility Conditions

ILS approach preparation pays the most attention to the close cooperation between the crew, requiring clear division of labor, coordinated action and strict procedures to ensure flight safety. The airport with ATIS is prepared according to the information of ATIS. Airports without ATIS should be prepared according to the effective information received or the weather conditions. Its main contents are as follows.

(1) Read ILS/DME approach map.

(2) The setting of 2)ILS and DME stations and the identification of call sign.

(3) Set 3) Minimum descending height MDA of 3)ILS/DME.

(4) Adjustment of channel and landing reference speed.

(5) Clear the method of interrupting approach, go-around and lifting.

(6) Complete the approach project and briefly describe it.

During the flight, the flight guidance system receives the heading signal, pitch tilt signal, channel deviation signal and HSI pre-selected channel signal. After computer calculation, ADI provides pitch and tilt control instructions to pilots or automatically controls the flight state of aircraft through A/P. In order to ensure that the aircraft can glide down the glide path accurately and not deviate from the fairway, and ensure the safety of the aircraft, during the ILS approach, it should quickly descend to the specified height (below the glide path) and cut into the fairway, and then cut into the glide path. RMI and RBI are used to check whether the ILS works normally, control the progress of each flight stage, and reduce the frequent correction and correction actions of the five sides.

4.3 Method of cutting into pentagons

The planned approach route provides the transition from the route structure to the terminal area anchor point or waypoint, which is the process from the route flight to the initial approach anchor point (IAF).

When the remaining heading MH = 45, look at RMI or HSI when the heading is windless.

When the RMI indicator value is QDM5, the aircraft continues to turn normally.

When RMI indicates QDM5, you can't turn. You should continue to fly on this course until RMI indicates QDM5. At this time, you can establish the slope and start turning normally.

If there is crosswind in the Pentagon approach, there are two ways to correct it. One way is to advance or postpone the recovery appropriately, as shown below.