RU2502638C2 - Method of additional braking of aircraft wheels and device to this end - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to aircraft engineering, particularly, to control over aircraft wheels. Proposed device comprises flaps 6 coupled by hinges 7 and plates 8 to follow the shape of fuselage tail bottom 1 so that they turn about each other in release and retraction. Extreme outer flap 6 is hinged with two curved levers 9 hinged to fuselage and with hydraulic cylinders 10. Flaps 6 are retracted into special guide 5 via hinged wheels. In touchdown, high-pressure fluid is forced into hydraulic cylinders 10 to turn their rods actuating curved levers 9 that extend extreme and the next flaps from guides 5 into position whereat they deflect gas flow by 90 degrees upward. At said position said flaps stay at there stroke end; thereafter, the flaps are retracted inside fuselage guides 5.

EFFECT: shorter run on runway.

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Description

The invention relates to aviation and, in particular, to systems for braking the wheels of the chassis of aircraft (LA).

After the wheels of an aircraft, for example, an aircraft, touch the surface of the runway (runway) or the ground (if the airfield is not equipped with a hard surface), the aircraft decelerates, which determines the path length and, consequently, the length of the runway.

There is a method of braking an aircraft using a brake parachute [1], when, when the wheels touch the runway, a brake parachute is released, which, having aerodynamic drag, slows down the aircraft, reducing the path length.

The disadvantage of this method of braking aircraft is that it is effective in the first section of the run, when the speed of the aircraft along the runway is high enough. After this section, the brake parachute is reset (separated from the aircraft).

A known method of braking aircraft reverse engine thrust [1], when, when the wheels touch the landing gear, the engine thrust changes its direction to the opposite.

The disadvantage of this method is the complexity of the device for its implementation and the formation of a dusty or snow cloud when using a dirt airfield or a snowy runway, which makes it difficult for the crew to move the aircraft during the run.

The closest in essence to the proposed is a braking method using the friction force F generated between the wheels (tires) of the chassis and the surface of the runway.

The friction force F is determined by the formula [1]:

$$F=fN=f\left(G-Y\right),\left(\text{one}\right)$$

where f is the coefficient of friction; N is the strength of the normal reaction from the surface of the runway; G is the gravity of the aircraft; Y is the lifting force, which, as the speed of the aircraft on the runway surface decreases, will decrease.

From formula (1) it can be seen that the friction force F depends on the friction coefficient f and the normal reaction force N. The friction coefficient f is a constant for the landing conditions, and its maximum value f _pk is equal to the rest friction coefficient. With mileage, f will be less than at rest. Thus, the friction force between the tire covers and the runway surface depends mainly on the reaction force of the runway surface, which is determined mainly by the gravity of the aircraft and the available lifting force Y: the faster Y decreases, the greater the force N and the greater will be the force F. But, in turn, a decrease in the force Y will determine an increase in the force F. The moment from the force F relative to the axis of the wheel balances the braking torque M _t applied to the wheel from the wheel brake, i.e. [2]

$$M_f=F\left(R-\delta \right),\left(\text{2}\right)$$

Here: R is the radius of the wheel; δ - compression pneumatics of the wheel.

The greater the force F, the greater the braking torque, the more intense the braking of the aircraft.

The disadvantage of this method of braking is that the maximum value of F is limited by the value [2]:

$$F_{m\mathrm{but}\mathrm{to}\mathrm{from}}=f_{P\mathrm{about}\mathrm{to}}N\left(\text{3}\right)$$

If the braking moment M _t is greater than the maximum balancing moment M _F , which determines F _max , then slippage of the entire contact of the wheel (tire) relative to the surface of the runway appears, i.e. “use” will appear, which leads to a decrease in driving resistance and a large wear of the tire covers.

The technical result of the invention is achieved in that an additional friction force is created that slows down the aircraft when, when landing, when the wheels touch the surface of the runway or the ground, the engine thrust vector deviates 90 ° up from its normal direction along the aircraft axis and holds it in this position until the end of the run. This causes an additional reaction from the ground and friction between the tires of the wheels of the chassis and the surface of the runway or the ground. Additional frictional force is an inhibitory force to the movement of the aircraft on the run. As a result, the total frictional force increases, which reduces the mean free path, and hence the runway length.

The inventive method is implemented in a device consisting of several sections, repeating the shape of the lower half of the rear of the fuselage (engine housing), connected to each other and the deflection levers pivotally, which ensures their rotation relative to each other when extending and cleaning so that when cleaning they are pushed into the two guides on both sides of the fuselage (engine housing) by hinged wheels, without interfering with the gas flow from the nozzle, and when extended, with the help of two curved levers They are connected each with its own hydraulic cylinder, so that the gas flow from the engine deviates 90 ° upward, creating an additional reaction from the surface of the runway or soil, causing additional friction between the tires of the wheels of the chassis and the ground.

New features that have significant differences in the method are:

1. Deviation of the engine thrust vector upward by 90 ° to create an additional reaction of the surface of the runway or soil and, as a result, additional friction force between the tires of the wheels of the chassis and the ground.

The salient features of the device are:

- the presence of retractable and retractable sections of the wings in the rear of the fuselage (engine housing), repeating the shape of its lower part;

- the presence of two curvilinear deflection levers connected to the sections of the wings and the rods of the hydraulic cylinders pivotally;

- the presence of hinges between the sections of the wings and levers deviation;

- the presence of two special guides in the lower part of the fuselage (engine housing), where the sections of the wings are pushed on the hinged wheels;

- the presence of two hydraulic cylinders connected by their rods to the deflection levers and causing the latter to rotate around their axis of attachment, pushing or pulling sections of the wings.

The use of new features, together with the well-known, and new connections between them ensure the achievement of the technical result of the invention, namely: reducing the flight path of the aircraft and the size of the runway, as well as unloading the front support, with intensive braking, a large, inertia, aircraft inertia develops, which, turning the aircraft around the center of mass, is balanced by the reaction of the earth from the front support. And the additional force P _y acting on the shoulder L _t , which is much larger than the shoulder h under the action of the thrust along the axis of the aircraft, creates a moment directed opposite to the moment from the inertia force, which reduces the load on the front support.

The invention is illustrated by drawings.

Figure 1 presents a diagram of the forces acting on the aircraft (for example, a single-engine aircraft with an engine in the rear of the fuselage and a three-wheeled landing gear with a front support is taken) during run, view "a". In view "b" the principle of wheel braking is shown schematically. Figure 2 shows a device for turning behind, view "A", and from above, view "B".

In addition to the above forces F, G, Y, N, the forces X, F _yn , P _x and P _y also act on the plane, see figure 1, view "a", where: X is the drag force, depending on the speed of movement LA, - the greater the speed, the greater this force in magnitude, i.e. this force slows down the movement. In practice, it acts while the nose wheel is raised; F _in - the inertia force of the aircraft. It arises, according to Newton’s second law, when there is acceleration. Because on the run the speed decreases, then the acceleration is directed towards the movement of the aircraft, i.e. forward. The greater the acceleration, the greater F _in , and

, $$F_{\mathrm{and}n.}=jm$$

,

where j is the acceleration, m is the mass of the aircraft; P _x - projection of the thrust vector on the longitudinal axis of the aircraft. Usually, when the thrust vector is not rotated upward, then all the engine thrust remaining on the run is P _x ; P _y - the projection of the thrust vector on the vertical axis (Y axis). When the thrust vector is rotated upward by 90 °, all remaining thrust will be equal to P _y .

In turn, the friction force F = F _g.k + F _s.k. , i.e. consists of the friction forces of the main wheels (there are two of them) and the front wheel acting on the aircraft on the run. And the reaction force of the earth is N = N _g.k + N _s.c. , i.e. consists of ground reactions acting on the main wheels and the front wheel. The reaction of the surface of the runway acting on each wheel Q _k = N / 3 (three wheels).

As a result of turning the thrust vector upward, a force P _y appears and, as a response to it, additional forces N _add.g and N _add.p acting on the main and front bearings. As a result, additional friction forces F _add.g and F _add.p acting on the main and front wheels.

In view "b" is a diagram of the forces and moments acting on each wheel. On each wheel, as shown above, the force Q _k (reaction of the runway surface) and the force F (friction force between the pneumatics of the wheel and the surface of the runway) act. The aircraft moves at a speed of V _c (shown by arrow). The wheel rotates with an angular velocity ω. The radius of the wheel is R. The deflection of the pneumatic during its deformation is δ. When the brakes are turned on, the braking moment M _t is created, which tends to reduce the angular velocity of the wheel ω and thereby reduce the aircraft speed V _c . The friction force F creates a moment M _f = F (R-δ), which is directed against the braking moment. This moment should be a little more than the braking moment, because otherwise, the wheel surface will slip on the runway surface (“skid”). If the friction force F is increased, then its moment M _F will increase. Then it will be possible to increase the braking torque M _t . Therefore, when the thrust vector is deflected upward, an additional friction force F _add appears, which will increase the braking torque.

Figure 2 schematically shows the proposed device. It contains sash 6 connected to each other by hinges 7 and plates 8 between them. The shutters follow the shape of the semi-fuselage (the lower part of the fuselage or the engine body), but the size is smaller so that they can fit inside the fuselage by sliding their articulated wheels 7 along the guides 5 located on both sides of the fuselage 4. The outermost hinges 7 of the outermost shutter 6 are also pivotally connected with two curved levers 9, which, in turn, are pivotally connected to the rods of two hydraulic cylinders 10, pivoted by the housing on the structure of the fuselage 1 inside it. The main pillars 3 and the front pillar 2 allow the aircraft to make movement along the runway or the ground.

Thus, the deviation of the thrust vector upward by 90 °, see Fig. 1, view “a”, allows you to get the force P _y , and from it - the force N _add , and from it - the force F _add , resulting in increased braking moment M _t and braking acceleration j. But it is known [1] that the mean free path L LA _pr is determined by the formula 2

$$L_{PR.}=-V_{P\mathrm{about}\mathrm{from}.}/2j_{\mathrm{from}R.}$$

And the average acceleration value j _{cp is} calculated as

$$j_{cp.}=-g{\left(X+F\right)}_{cp.}/G$$

The last equation shows that the average braking acceleration j _cp depends on the average value of the friction force F _cp : the larger it is, the greater the acceleration. But, on the other hand, the greater the acceleration of braking, the smaller the path length L _CR , the shorter the runway length.

A device for additional braking of aircraft operates as follows. The initial position of the device is as follows: it is removed inside the fuselage (engine housing), without interfering with the jet of engine gases flowing out of the nozzle. At the moment the main struts touch the surface of the runway (ground), an inertial (or some other design) sensor is activated (or the crew by a switch) and energizes the electrovalve, which opens the line from the aircraft hydraulic system to the hydraulic cylinders 10. When the fluid enters them under pressure, the cylinder rods begin to be released and act on the curved levers 9, which rotate around their axis of attachment and withdraw from the guide 5, one after the other, the shutters 6, which are set so that the gas stream from the nozzle moves the body deviates upward by 90 °, creating a force P _y , from which there is an additional reaction of the earth N _add and an additional friction force F _add . In this position, the flaps are until the end of the run. The more the engine thrust is left on the run (P _x ), the greater will be the force P _y , and consequently, the additional forces N _extra and F _{extra will be} , which will reduce the path length and the runway length. After the run is completed, the switch stops the power supply to the solenoid valve, which switches the high pressure supply to the other cavity of the hydraulic cylinders 10, the rods of which are pulled into the body and drag along the curved arms 9, which rotate around their mounting axes and move the shutters 6 to clean them in guides 5. The flaps 6 are retracted into the fuselage, without interfering with the gas jet flowing out of the engine nozzle. The aircraft can taxi on the airfield or take off and fly.

The use of the claimed invention can significantly reduce the path length of the aircraft, and therefore the length of the runway.

Information sources

1. Aerodynamics and flight dynamics of maneuverable aircraft. - M.: Military Publishing, 1984. - S. 494-495.

2. Fundamentals of aircraft design. / Ed. professors, doctor of technical sciences Turkina K.D. - M .: Military Publishing House, 1974. - P.133.

Claims (1)

A device for additional braking of the wheels of the aircraft, providing a deviation of the thrust vector of the aircraft, consisting of several wings, repeating the shape of the lower half of the rear of the fuselage, pivotally connected to each other and curved levers, which ensures their rotation relative to each other when extending and cleaning in this way that during cleaning, they are pushed into the two guides on both sides of the fuselage by the articulated wheels without interfering with the gas flow from the nozzle, and when By narrowing, with the help of two curvilinear deflection levers, each connected to the rod of its hydraulic cylinder, they are set so that the gas flow from the engine deviates 90 ° upward, creating an additional reaction from the surface of the runway or the ground, causing additional friction between the tire covers chassis and ground.

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