RU223804U1 - Airplane with emergency landing flaps - Google Patents

Abstract

The utility model relates to aviation technology, and more specifically to aircraft that have a flattened wide section of the lower surface of the central part of the fuselage formed by the landing gear fairings. The advantage of the utility model is that it simplifies the design of aircraft emergency landing flaps and reduces their weight and size. The aircraft contains two emergency landing flaps installed on the side surfaces of the landing gear fairings, on the left and on the right, vertical to the fuselage horizontal plane, behind the center of mass, across the incoming water flow, symmetrically to the base plane of the fuselage. When the emergency landing flaps enter the water, the hydrodynamic drag force arising on them creates a diving moment, compensating for the pitching moment from the hydrodynamic lift force arising on the flattened central part of the fuselage bottom. This prevents the aircraft from being thrown out of the water with an increase in pitch angle (leopard), and the further movement of the aircraft through the water becomes stable. At the same time, the loads acting on the aircraft fuselage are reduced, which reduces the possibility of damage to the fuselage. The utility model can be used to reduce loads on the fuselage during an emergency landing of an aircraft on water.

Description

The utility model relates to aviation technology, and more specifically to aircraft that have a flattened wide section of the lower surface of the central part of the fuselage formed by the landing gear fairings (for example, the ATR-42 aircraft). During an emergency landing on water of such an aircraft, the hydrodynamic lift force acting on the flattened lower surface of the central part of the fuselage leads to the aircraft being thrown out of the water with an increase in the pitch angle - leopard (leopard is the ejection of an aircraft from the water at high planing speeds with a change in trim angle). The movement of such an aircraft through water can be a series of leopards, which indicates longitudinal instability of the movement. The values of hydrodynamic loads on the fuselage during secondary splashdowns after leopards can significantly exceed the values that arise during the initial contact of the fuselage with water.

There are known devices (emergency equipment used in aircraft) designed to prevent fuselage impacts on water and destruction of the fuselage during an emergency landing on water. Such devices include deflectable hydraulic flaps, hydroskis and hydrofoils installed under the fuselage.

As a prototype, we will consider an aircraft with installed hydraulic shields (US Patent No. 2676771, Cl.244-105, 1954). Hydraulic shields are plates hinged under the fuselage in the nose and deflected at an angle of about 30° during a forced landing of the aircraft on water.

In fig. Figure 1 shows the aircraft chosen as a prototype, where 1 is the fuselage, 2 is the hydraulic shield, 3 is the hydraulic shield release diagram. Hydraulic shields can be of various shapes in plan: rectangular, triangular and trapezoidal. When the flaps enter the water, they are subject to a hydrodynamic lifting force, creating a pitching moment sufficient to prevent the fuselage from hitting the water.

The disadvantages of the prototype are the complex design of the hydraulic shields, which requires a device for their release, and their large size and weight. Thus, based on the results of testing the aircraft model, it was found that the trapezoidal hydraulic shield installed on an aircraft weighing 22 tons, fuselage length 20 m and width 3 m has a length of 1220 mm with trapezoid bases of 600 mm and 300 mm [Fisher L.J. and Hoffman E.L. Ditching Investigations of Dynamic Models and Effects of Design Parameters on Ditching Characteristics. NACA Report 1958, N 1347, 28 p. Bibl. 2 NN. (Technical translation of TsAGI No. 9885, 1959)].

The task and technical result of creating a utility model is to reduce the hydrodynamic loads acting on the aircraft fuselage during an emergency landing on water.

The solution to the problem and the technical result are achieved by the fact that in an aircraft with emergency landing flaps, containing a flattened wide section of the lower surface of the central part of the fuselage, formed by landing gear fairings, on the side surfaces of which two emergency landing flaps are installed behind the center of mass of the aircraft symmetrically to the base plane of the fuselage, in this case, the emergency landing flaps are made protruding beyond the lower surface of the landing gear fairings vertically to the building horizontal of the fuselage.

Figure 1 shows the aircraft chosen as a prototype.

Figure 2 is a diagram of the installation of emergency landing flaps, front view.

Figure 3 is a diagram of the installation of emergency landing flaps on an enlarged scale.

Figure 4 is a diagram of the installation of emergency landing flaps, seen along arrow A.

In fig. 5 - graphs of the dependence of splashdown parameters on time for the model with and without emergency landing flaps.

To reduce the loads acting during a forced landing on water on the fuselage of an aircraft having a flattened wide section 4 of the lower surface of the central part of the fuselage 1 (Fig. 2), formed by the landing gear fairings 5, and to reduce the possibility of damage to the fuselage, two emergency landing flaps 2, for example, made in the form of plates. The flaps 2 are installed vertically to the building horizontal of the fuselage, across the incoming water flow, symmetrically to the base plane of the fuselage on the left and right on the landing gear fairings 5 behind the center of mass 6. Flaps 2 (Fig. 3) are attached to the landing gear attachment points and protrude beyond the lower surface of the fairings 5. The emergency landing flaps are permanently installed and do not require a retraction and extension mechanism.

For example, the dimensions of the shields for an aircraft weighing 30 tons, with an equivalent fuselage diameter of 3 m and a fuselage length of 25 meters are: shield width of about 100 mm and height of about 150-200 mm. The dimensions of the shields are small enough so that they do not increase the aircraft's drag during flight.

When the emergency landing flaps enter the water, the hydrodynamic drag force arising on them creates a diving moment, compensating for the pitching moment from the hydrodynamic lift force arising on the flattened central part of the fuselage bottom. This prevents the aircraft from being thrown out of the water with an increase in pitch angle (leopard) and the further movement of the aircraft through the water becomes stable. At the same time, the loads acting on the aircraft fuselage are reduced, which reduces the possibility of damage to the fuselage.

The studies have shown the effectiveness of emergency landing flaps. As can be seen from the graphs shown in Fig. 4, the installation of emergency landing flaps leads to a reduction in normal overloads and longitudinal angular vibrations of the aircraft.

Claims (1)

An aircraft with emergency landing flaps, made with a flattened wide section of the lower surface of the central part of the fuselage formed by the landing gear fairings, on the side surfaces of which two emergency landing flaps are installed behind the center of mass of the aircraft symmetrically to the base plane of the fuselage, while the emergency landing flaps are installed vertically, protruding beyond the lower surface of the landing gear fairings.