From what values \u200b\u200bthe critical angle of attack depends. Angle of attack and aerodynamic forces. We reveal a little secret. Aircraft landing configuration

With an increase in , the value of the force R grows and it deviates more and more backward due to an increase in air resistance, but the angle of attack  cannot constantly and with impunity grow, in the end the branch breaks off and the flow from the wing stalls.

When the flow breaks down, the wing loses its bearing capacity and is not much different from a conventional edged board. In addition, stall occurs non-simultaneously throughout the entire wing and is accompanied by shaking followed by aircraft rotation.

Each wing has its own critical angle of attack , after exceeding which there is a stall. Thick profiles have more  cr than thin ones because of the smoother flow around the profile.

 cr depends little on the flight speed.

It should be understood and firmly remembered that a breakdown occurs due to an excess of  cr, loss of speed is only a special case of reaching  cr.

On  cr, you can bring the aircraft in a wide range of speeds, with intensive maneuvering.

After the aircraft stalls, a headroom is required to return to normal flight mode.

Failure of an aircraft near the ground due to a lack of height leads to a collision with the ground.

Stalling at low altitude is the cause of 80% of all accidents and disasters among amateur pilots. There is a special device "Angle of attack indicator", which is installed on all modern aircraft. It shows the current real angle of attack.

11. Total aerodynamic force r. Its components. Center of pressure.

Figure: 12

Full aerodynamic powerR is called the resultant of all frictional and pressure forces acting on the body in flight.

The point of intersection of the force R with the chord is called the center of pressure (CP).

The R force formula is the main aerodynamic formula of all times and peoples, however, not only the R force, but in general ALL aerodynamic forces acting on airplanes, diesel locomotives, falling bricks and cars. It is simple and ingenious and consists of three factors:

1) S - wing area

2) - high-speed head

3) the coefficient (in our case C R - tse er) of the total aerodynamic force.

If the force R is expanded along the axes of the high-speed coordinate system, then we get 3 (three) components: X, Y and Z.

X is the force of frontal resistance;

Y - lifting force.

Z is the lateral force.

Angle  (beta) - slip angle. This is the angle between the longitudinal plane of symmetry of the aircraft and the oncoming flow velocity vector.

The Z force occurs only when slip occurs. Without sliding, the force R is expanded only into Y and X.

12. Lift force and drag.

Lifting force arises due to the flow around the wing and the formation of a pressure difference under the wing and above the wing.

Frontal drag of the wing is the aerodynamic force that slows down the movement of the wing in the air and is directed in the direction opposite to the movement.

The formulas for these forces are the same, the difference is only in the coefficients.

Y \u003d C y S

X \u003d C x S

The values \u200b\u200bof these coefficients are obtained by blowing the wing in a wind tunnel.

The graph of the approximate dependence of C y on  is as follows:

As can be seen from the graph, Cy grows almost linearly with increasing , up to  cr, that is, until the flow stalls from the wing.

The C y value ranges from 0 to 2 on most aircraft. In essence, the C y coefficient characterizes the wing's ability to convert velocity head into lift. There are aircraft equipped with powerful mechanized wings to reduce the landing speed and reduce the take-off distance; they have higher C y values. However, more than C y \u003d 6 man failed to reach, while C y of the great eagle, when taking off with prey from the ground, reaches 14.

The C x coefficient, as well as the X force, consists mainly of 3 components. The wave - 4th component appears when the numbers M are close to the critical M, about M \u003d 0.8.

C x tr (friction) - arises from air friction against the aircraft.

C x pressure (or vortex) - arises from the pressure difference in front of the wing and behind the wing.

C xi (inductive) - arises from the so-called flow bevel. When the oncoming stream meets an inclined, lower, wing plane, it changes the direction of movement parallel to the plane, that is, it inclines somewhat downward. The lift force is deflected along with the flow at the same angle back, since it is a derivative of the flow that has changed direction. The resulting component of the lift force on the X-axis is the inductive component.

C xi also arises from the flow of air through the wing ends and from the pressure difference under the wing and above the wing.

C xi depends on the aspect ratio of the wing  and the angle of attack .

The shorter and wider the wing, the more intense the flow overflow and the greater the inductive resistance.

The more , the more intense the overflow occurs and X i increases. This is why sport gliders have such narrow and long wings - to reduce inductive drag.

C x friction and C x pressures within the operating  practically do not change, and the coefficient C xi, depending on по, changes according to the parabolic law.

In this article, we will look at the basic principles of a large jet aircraft applicable to our conditions. Although the Tu-154 was chosen as the basis for consideration, it should be borne in mind that, in general, similar principles of piloting are applied on other types of aircraft. The information was taken based on real equipment, and we will tempt fate while in MSFS98-2002, Microsoft has such a computer simulator, you may have even heard ...

Aircraft landing configuration

Airplane configuration - combination of positions of wing mechanization, landing gear, aircraft parts and assemblies, which determine its aerodynamic qualities.

On a transport aircraft, even before entering the glide path, wing mechanization, landing gear should be released and the stabilizer shifted. In addition, at the decision of the aircraft commander, the crew can turn on the autopilot and / or autothrottle for automatic approach.

Wing mechanization

Wing mechanization - a complex of devices on the wing, designed to regulate its bearing capacity and improve the characteristics of stability and controllability. Wing mechanization includes flaps, slats, flaps (spoilers), active boundary layer control systems (for example, its blowing off by air taken from the engines), etc.

Flaps

In general, flaps and slats are designed to increase the wing bearing capacity during takeoff and landing.

Aerodynamically, this translates into the following:

flaps increase the wing area, which leads to increased lift.
flaps increase the curvature of the wing profile, which leads to more intense downward deflection of the air flow, which also increases lift.
the flaps increase the aerodynamic drag of the aircraft, and therefore cause a decrease in speed.

The increase in wing lift allows the speed to be reduced to a lower limit. For example, if with a mass of 80 t stall speed Tu-154B without flaps is 270 km / h, then after the flaps are fully extended (by 48 degrees), it decreases to 210 km / h. If you reduce the speed below this limit, the plane will reach dangerous angles of attack, there will be stall shaking (buffeting) (especially with the flaps retracted) and eventually stall.

A wing equipped with flaps and slats forming profiled slots in it is called slotted... The flaps can also consist of multiple panels and have slots. For example, Tu-154M uses two-slot, and on Tu-154B three-slot flaps (in the photo Tu-154B-2). On a slotted wing, air from the area of \u200b\u200bincreased pressure under the wing at a high speed enters through the slots to the upper surface of the wing, which leads to a decrease in pressure on the upper surface. With a smaller pressure difference, the flow around the wing is smoother and the tendency to stall formation decreases.

Angle of Attack (AoA)

The basic concept of aerodynamics. The angle of attack of the wing profile is the angle at which the profile is blown by the incoming air stream. In a normal situation, UA should not exceed 12-15 degrees, otherwise there is stall, i.e. the formation of turbulent "burunches" behind the wing, as in a fast stream, if you put your palm not along, but across the water stream. Stalling results in a loss of lift on the wing and stall aircraft.

On "small" aircraft (including the Yak-40, Tu-134), the release of the flaps usually leads to "Swelling" - the plane slightly increases vertical speed and lifts its nose. On "big" planes there are systems for improving stability and controllability, which automatically parry the arising moment by lowering the nose. There is such a system on the Tu-154, so there is little "swelling" (in addition, there the moment of flaps release is combined with the moment of shifting the stabilizer, which creates the opposite moment). On the Tu-134, the pilot has to extinguish the increase in lift by deflecting the steering column away from him. In any case, to reduce "swelling", it is customary to extend the flaps in two or three steps - usually first by 20-25 degrees, then by 30-45 degrees.

Slats

Except for the flaps, almost everything transport aircraft also have slats, which are installed in the front of the wing, and automatically deflect downwards simultaneously with the flaps (the pilot hardly thinks about them). In principle, they perform the same function as the flaps. The difference is as follows:

At high angles of attack, the slats deflected downward like a hook cling to the incoming air stream, deflecting it downward along the profile. As a result, the slats reduce the angle of attack of the rest of the wing and postpone the stall moment to higher angles of attack.
Slats are usually smaller, which means less drag.

In general, the release of both the flaps and the slats is reduced to an increase in the curvature of the wing profile, which allows the incoming air flow to be deflected more downward, and therefore to increase the lift.

As far as we know, slats are not separately selected in the air file.

To understand how such sophisticated mechanization is used on planes, watch the birds land. You can often notice how pigeons and crows like them sit down with their wings fluffed up, tucking their tail and stabilizer under themselves, trying to get a wing profile of large curvature and create a good air cushion. This is the extension of the flaps and slats.

Mechanization B-747 landing

Spoilers

Interceptors, they are spoilers are deflectable brake flaps on the upper surface of the wing that increase aerodynamic drag and reduce lift (unlike flaps and slats). Therefore, spoilers (especially on "silts") are also called lift dampers.

Interceptors are a very broad concept, which is stuffed with many different types of absorbers, and on different types they can be called differently and located in different places.

As an example, consider the wing of the Tu-154 aircraft, which uses three types of spoilers:

1) external aileron-spoilers (spoilerons, roll spoilers)

Aileron spoilers are a complement to ailerons. They deviate asymmetrically. For example, on the Tu-154, when the left aileron is deflected upward by an angle of up to 20 degrees, the left interceptor aileron is automatically deflected upward by an angle of up to 45 degrees. As a result, the lift on the left wing decreases and the aircraft rolls to the left. Ditto for the right wing.

Why can't you get by with just ailerons?

The fact is that in order to create a roll moment on a large aircraft, a large area of \u200b\u200bdeflected ailerons is needed. But since jet aircraft fly at speeds close to sound, they must have a thin wing profile that would not create too much drag. The use of large ailerons would lead to its twisting and all sorts of bad phenomena such as aileron reversal (this, for example, can take place on the Tu-134). Therefore, a way is needed to distribute the load on the wing more evenly. For this purpose, aileron-spoilers are used. - flaps installed on the upper surface, which, when deflected upward, reduce the lift on this wing, and "drown" it down. The roll speed increases significantly.

The pilot does not think about the spoiler aileron; from his point of view, everything happens automatically.

In the air file, the aileron spoilers are, in principle, provided.

2) medium spoilers (speed brakes)

Medium spoilers are what are usually understood as simply "spoilers" or "spoilers" - ie. "air brakes". The symmetrical engagement of spoilers on both wing halves leads to a sharp decrease in lift and deceleration of the aircraft. After releasing the "air brakes", the aircraft will balance at a higher angle of attack, start to decelerate due to the increased resistance, and gradually descend.

On the Tu-154, the middle spoilers are deflected at an arbitrary angle up to 45 degrees using the lever on the middle control panel of the pilots. This is the question of where the plane has a stop crane.

On the Tu-154, the outer and middle spoilers are structurally different elements, but on other aircraft the "air brakes" can be structurally combined with the spoiler aileron. For example, on IL-76 spoilers usually operate in aileron mode (with a deflection of up to 20 degrees), and, if necessary, in braking mode (with a deflection of up to 40 degrees).

It is not necessary to release medium spoilers during the landing approach. Actually, retracting spoilers after landing gear is usually prohibited. In a normal situation, spoilers are issued for a faster descent from the level with a vertical speed of up to 15 m / s and after the aircraft has landed. In addition, they can be used for rejected takeoff and emergency descent.

It happens that the "virtuals" during the landing approach forget to turn off the throttle, and keep the mode almost at takeoff, trying to fit into the landing pattern at a very high speed, causing the controller's angry cries in the style of “Maximum speed below ten thousand feet is 200 knots! " In such cases, it is possible to briefly release medium spoilers, but in reality, this is unlikely to lead to anything good. It is better to use such a rough method of damping in advance - only on descent, and it is not always necessary to release the spoilers to a full angle.

3) ground spoilers

Also "brake flaps"

They are located on the upper surface in the inner (root) part of the wing between the fuselage and the landing gear nacelles. The Tu-154 automatically deflects at an angle of 50 degrees after landing when the main landing gear is compressed, the speed is over 100 km / h and the throttle is in the "idle" or "reverse" position. The middle spoilers also deflect at the same time.

Internal spoilers are designed to absorb lift after landing or during a rejected takeoff. Like other types of spoilers, they do not so much dampen the speed as they dampen the lift of the wing, which leads to an increase in the load on the wheels and improved traction. Thanks to this, after the internal spoilers have been extended, it is possible to switch to wheel braking.

On Tu-134, brake flaps are the only type of spoilers.

In the simulator, internal spoilers are either absent or are recreated rather conditionally.

Pitch balancing

Large aircraft have a number of pitch control features that should be mentioned. Trimming, centering, balancing, stabilizer shifting, steering column consumption. Let's consider these issues in more detail.

Pitch

Pitch- angular movement aircraft relative to the transverse axis of inertia, or, more simply, "bully". The sailors call this garbage "trim". Pitch opposed bank and yaw, which respectively characterize the position of the aircraft during its rotation around the longitudinal and vertical axes. Accordingly, the angles of pitch, roll and yaw (sometimes called Euler angles) are distinguished. The term "yaw" can be replaced by the word "heading", for example they say "in the course channel".

The difference between the pitch angle and the angle of attack, I hope there is no need to explain ... When the plane falls completely flat, like an iron, its angle of attack will be 90 degrees, and the pitch angle will be close to zero. On the contrary, when a fighter is in a set, afterburner, with good speed, its pitch angle can be 20 degrees, and the angle of attack, say, only 5 degrees.

Trimming

To ensure proper piloting, the effort at the helm must be perceptible, otherwise, any accidental deflection could lead the plane into some kind of bad spin. As a matter of fact, this is why on heavy aircraft that are not designed to perform sharp maneuvers, control wheels are usually used, not handles - they are not so easy to accidentally roll over. (The exception is Airbus, which prefers joysticks.)

It is clear that with prolonged control, the pilot's biceps will gradually develop quite decent, moreover, if the plane unbalanced in effort it is difficult to fly because any relaxation of effort will push steering column (SHK) in the wrong place. Therefore, so that in the course of the flight, the pilots can sometimes slap the stewardess Katka on the ass, trimmers are installed on the planes.

A trimmer is a device that, in one way or another, fixes the steering wheel (control stick) in a given position so that the papelats can descend, gain altitude and fly in level flight, etc. effortlessly on the steering column.

As a result of trimming, the point to which the steering wheel (stick) is pulled will not coincide with the neutral position for that steering wheel. Than further from the trim position, the big efforts have to be made to keep the steering wheel (handle) in a given position.

Most often, a trimmer means a trim in the pitch channel - i.e. elevator trimmer (PB). Nevertheless, on large planes, trimmers, just in case, are installed in all three channels - there they usually perform an auxiliary role. For example, in the roll channel, trimming can be applied in case of longitudinal unbalance of the aircraft due to asymmetric production of fuel from the wing tanks, i.e. when one wing pulls over the other. In the course channel - in case of engine failure, so that the plane does not yaw to the side when one engine is not running. Etc.

Trimming can be technically implemented in the following ways:

1) through a separate aerodynamic trimmer, as on Tu-134 - i.e. a small "knob" on the elevator, which holds the main rudder in a given position by means of aerodynamic compensation, i.e. using the force of the incoming stream. On Tu-134, to control such a trimmer is used trimmer wheel, on which the cable is wound, going to the PB.

2) through MET (trim effect mechanism)as on the Tu-154 - i.e. simply by adjusting the tightening in the spring system (more correctly, spring loaders), which purely mechanically holds the steering column in position. When the MET rod moves back and forth, the loaders are loosened and stretched. To control the MET, small push switches on the handwheel handles are used, when turned on, the MET rod, and behind it the steering column, slowly move to a given position. There are no aerodynamic trim tabs as on the Tu-134, but on the Tu-154.

3) using adjustable stabilizerlike most western types (see below)

In the simulator, it is difficult to recreate a real elevator trim, for this you will have to use a fancy joystick with a trim effect, because what is called a trimmer in MSFS, in fact, should not be taken as such - it would be more correct to cover the joystick with plasticine or chewing gum, or just put mouse on the table (in FS98) - here's the trimmer. I must say that management is generally a sore spot for all simulators. Even if you buy the most sophisticated steering wheel and pedal system, it is still likely to be far from real. An imitation is an imitation, because in order to get an absolutely exact copy of a real plane, you need to spend as much effort and process as much information as to build a real plane ...

Centering (CG)

Center of Gravity (CG) position- the position of the center of gravity, measured as a percentage of the length of the so-called mean aerodynamic chord (МАХ, Mean Aerodynamic Chord, MAC) - i.e. chord of a conditional rectangular wing, equivalent to this wing, and having the same area with it.

Chord - a straight line segment connecting the leading and trailing edges of the wing profile.

position of the center of gravity 25% of the average

The length of the mean aerodynamic chord is found by integrating over the lengths of the chords along all wing profiles. Roughly speaking, MAR characterizes the most common, most probable wing profile. those. it is assumed that the entire wing with all its variability of airfoils can be replaced by one single averaged airfoil with one single averaged chord - MAR.

To find the position of the MAR, knowing its length, you need to cross the MAR with the contour of the real wing and see where the beginning of the obtained segment is. This point (0% MAR) will serve as a reference point for determining the alignment.

Of course, a transport plane cannot have a constant balance. It will change from departure to departure due to the movement of goods, changes in the number of passengers, as well as during the flight as fuel runs out. For each airplane, an admissible centering range has been determined, which ensures its good stability and controllability. Usually distinguish front (for Tu-154B - 21-28%), average (28-35%) and back (35-50%) centering - for other types the numbers will be slightly different.

The centering of an empty aircraft is very different from the centering of a fueled aircraft with all cargo and passengers, and for its calculation a special one is filled in before departure. centering chart.

An empty Tu-154B has a centering of about 49-50% of MAR, despite the fact that at 52.5% it already capsizes on the tail (the engines on the tail pull over). Therefore, under the aft fuselage, in some cases, it is necessary to install a safety bar.

Balancing in flight

Swept-wing aircraft wing center of lift located at a point of approximately 50-60% of MAR, i.e. behind the center of gravity, which in flight is usually located in the region of 20-30% of MAR.

As a result, in horizontal flight on the wing there is lift leverwho wants to tip the plane onto the bow, i.e. normally the aircraft is under the influence dive moment.

To avoid all this, during the entire flight, you will have to parry the resulting diving moment. balancing deviation PB, i.e. the deflection of the elevator will not be zero even in level flight.

Basically, to keep the plane from "diving" will need to create pitch-up moment, i.e. PB will need to deviate upward.

Cabriolet - from fr. cabrer, "rearing up".

Always only up? No not always.

As the speed increases, velocity head will increase, which means that the total lift on the wing, on the stabilizer and on the elevator will increase proportionally

F under \u003d F under1 - F under2 - F under3

But the force of gravity will remain the same, which means the plane will go into a set. To rebalance the papelats in level flight, you will have to lower the elevator lower (move the control wheel away from you), i.e. reduce the term F under3... Then the nose will go down, and the plane will be balanced again in horizontal flight, but at a lower angle of attack.

Thus, for each speed we will have our own balancing deviation of the PB - we will get a whole balancing curve (dependence of the RV deviation on the flight speed). At high speeds, you will have to move the steering column away from you (PB down) to keep the female from pitching up, at low speeds you will have to take the steering column towards you (PB up) to keep the female from diving... The steering wheel and elevator will be in neutral only at one specific indicated speed (about 490 km / h for the Tu-154B).

Stabilizer (Horizontal Stabilizer)

In addition, as can be seen from the above diagram, the aircraft can be balanced not only with the elevator, but also with the adjustable stabilizer (term Fpod2). Such a stabilizer can be completely set to a new angle using a special mechanism. The efficiency of such a transfer will be approximately 3 times higher - i.e. 3 degrees of PB deflection will correspond to 1 degree of stabilizer deflection, since its area of \u200b\u200bthe horizontal stabilizer at the "carcass" is approximately 3 times the area of \u200b\u200bthe PB.

What is the advantage of using a movable stabilizer? First of all, in this case the consumption of the elevator decreases... The fact is that sometimes, due to too forward centering, to keep the aircraft at a certain angle of attack, you have to use the entire course of the steering column - the pilot has chosen to control completely, and then the aircraft cannot be lured up by any carrot. This can especially be the case on a fully forward centering landing where the elevator may not be sufficient when attempting to go around. As a matter of fact, the value of the maximum front centering is set so that the available deflection of the elevator is sufficient for all flight modes.

Since the PB deviates relative to the stabilizer, it is easy to see that the use of the adjustable stabilizer will reduce steering wheel consumption and increase the available centering range and available speeds... This means it will be possible to take more cargo and arrange them in a more convenient way.

In level flight at flight level, the Tu-154 stabilizer is at an angle of -1.5 degrees to pitch up with respect to the fuselage, i.e. almost horizontal. Takeoff and landing, it is shifted further to pitch-up at an angle of up to -7 degrees relative to the fuselage in order to create a sufficient angle of attack to maintain the aircraft in level flight at low speed.

A feature of the Tu-154 is that the rearrangement of the stabilizer is carried out only during takeoff and landing, and in flight it is retracted to the -1.5 position (which is considered to be zero), and the plane is then balanced with one elevator.

At the same time, for the convenience of the crew and for a number of other reasons, the combined with flaps and slats extended, i.e. when the flap handle is moved from the 0 position to the release position, automatically slats are released and the stabilizer is shifted to the agreed position. When flaps are retracted after take-off - the same, in reverse order.

Let's give a table that hangs in the cockpit to constantly remind him that they have a pancake in figs produced ...

Thus, everything happens by itself. On a circle, before landing at a speed of 400 km / h, the crew only has to check whether the balancing deviation of the PB corresponds to the position of the stabilizer dial and, if not, then set the dial to the desired position. For example, the arrow of the indicator of the position of the PB in the green sector, then we put the dial on the green "P" - everything is quite simple and does not require significant mental effort ...

In case of automation failures, all releases and shifting of mechanization can be done in manual mode. For example, if we are talking about a stabilizer, you need to flip the cap on the left in the photo and move the stabilizer to the agreed position.

On other types of aircraft, this system works differently. For example, on the Yak-42, MD-83, B-747 (I find it difficult to say for the whole of Odessa, but this should be the case on most western aircraft) the stabilizer deflects during the entire flight and completely replaces the trim tab... Such a system is more perfect, because it allows to reduce drag in flight, since the stabilizer, due to its large area, deflects at smaller angles than PB.

On the Yak-40, Tu-134, the stabilizer is also usually adjusted independently of the wing mechanization.

Now about MSFS. In the simulator, we have a "trim stabilizer" situation, as in Western types. There is no separate virtual trimmer in MSFS. That rectangular thing (as on "cessna"), which Microsoft calls "trimmer" is actually a stabilizer, which is noticeable by the independence of its work from the PB.

Why is that? Probably, the whole point is that initially (in the late 80s) FS was used as a software base for full-featured simulators, on which there were real steering columns and real METs. When MS bought (stole?) FS, she did not delve deeply into the specifics of its work (and perhaps did not even have a full description of it), so the stabilizer began to be called a trimmer. At least, I would like to make such an assumption while studying MS + FS, because the description for the air file has not been published, and by the quality of the default models and a number of other signs, we can conclude that Microsoft itself does not really understand it.

In the case of the Tu-154, it is probably necessary to set the microsoft trimmer once before landing in level flight so that the elevator indicator is approximately in neutral position, and no longer return to it, but work only with the trimmer of a joystick, which no one has .. Or work with a "rectangular thing", close your eyes and repeat to yourself: "This is not a stabilizer, this is not a stabilizer ...."

Auto Throttle

In the helm mode, KVS or 2P controls the engines using RUD-s (engine control levers) on the middle control panel or by giving commands to the flight engineer: "Mode such and such"

Sometimes it is convenient to control the motors not manually, but using automatic traction (auto throttle, AT), which tries to keep the speed within acceptable limits, automatically adjusting the mode of the motors.

Turn on AT (Shift R key), set desired speed on US-I (airspeed indicator), and the automatics will try to maintain it without pilot intervention. On the Tu-154, the speed with the AT-6-2 can be adjusted in two ways 1) by rotating the rack on the left or on the right US-I 2) by rotating the regulator on PN-6 (\u003d remote control STU and autothrottle).

Varieties of landing systems

Distinguish visual entry and instrument approach.

A purely visual approach is rarely used on large aircraft and can be difficult even for an experienced crew. Therefore, usually the approach is carried out by instrument, i.e. with the use of radio engineering systems under the control and supervision of the air traffic controller.

Air Traffic Control (ATC, Air Traffic Control, ATC) - traffic control of aircraft in flight and on the airfield maneuvering area.

Radio engineering landing systems

Consider approaches using radio-technical landing systems. They can be classified into the following types:

"By OSB", i.e. using DPRM and BPRM

"By PMC", i.e. using ILS

"By RSP", i.e. by locator.

Approach to OSB

Also known as "drive by drive".

OSB (landing system equipment) - a complex of ground facilities, including two drive radio stations with marker radio beacons, as well as lighting equipment (STO)installed at the aerodrome according to the approved standard scheme.

Specifically, the OSB includes

"distant" (locator beacon) (DPRM, Outer Marker, OM) - a distant drive radio station with its own marker, which is located 4000 (+/- 200) m from the runway end. When the marker passes in the cockpit, a light and sound alarm is triggered. The Morse code of the signal in the ILS system has the form "dash-dash-dash ...".

"near" (locator beacon) (BPRM, Middle Marker, MM) - a near drive radio station also with its own marker, which is located 1050 (+/- 150) m from the runway end. Morse code in the ILS system has the form "dash-dot -..."

Driving radio stations operate in the range of 150-1300 kHz.

When flying in a circle, the first and second sets automatic radio compass (ARK, Automatic Direction Finder, ADF) are tuned to the frequencies of the DPRM and BPRM - while one arrow on the ARC indicator will point to the DPRM, the second to the BPRM.

Recall that the arrow of the ARC pointer always points to the radio station, just like the arrow of a magnetic compass always points to the north. Therefore, when flying according to the scheme, the moment of the beginning of the fourth turn can be determined on the heading angle of the radio station (KUR)... Let's say, if the DPRM radio station is exactly on the left, then KUR \u003d 270 deg. If we want to turn on it, then the turn must be started 10-15 degrees earlier (i.e., with KUR \u003d 280 ... 285 degrees). The flight over the radio station will be accompanied by a turn of the arrow by 180 degrees.

Thus, when flying in a circle, the heading angle of the DPRM helps to determine the moments of the beginning of the turns on the circle. In this regard, the DPRM is a kind of reference point against which many actions are calculated during the approach.

Also attached to the radio marker, or marker beacon - a transmitter that sends up a narrowly directed signal, which, when flying over it, is perceived by aircraft receivers and causes an indicator light and an electric call to work. Thanks to this, knowing at what height the DPRM and BPRM should be passed (usually this 200 and 60 m, respectively), you can get two points along which you can build a pre-planting line.

In the west, at airfields of category II and III with difficult terrain at a distance of 75..100 m from the runway end, they also install internal radiomarker (Inner Marker, IM) (with Morse code "point-to-point-to-point ...."), which is used as an additional reminder to the crew about approaching the moment of the beginning of visual guidance and the need to make a decision about landing.

The OSP complex refers to the simplified landing systems, it must provide the aircraft crew with a drive to the aerodrome area and a maneuver to descend to the height of the visual detection of the runway. In practice, it plays a secondary role and does not usually replace the need for an ILS or landing radar system. Purely on OSB they enter only in the absence of more advanced landing systems.

When approaching only by OSB, horizontal visibility should be at least 1800 m, vertical visibility at least 120 m.If this meteorological minimum is not observed, it is necessary to go to dispersal field.

Please note that the DPRM and the BPRM at different ends of the band have the same frequency. In a normal situation, the radio stations on the other end should be turned off, but this is not the case in the sim, therefore, when flying in a circle, the ARC often starts to glitch, clinging to one radio station, then another.

Call by PMC

Also say "system entry"... In general, this is the same as an ILS call. (see also Dmitry Prosko's article on this site)

In Russian-language terminology radio beacon landing system (RMS) is used as an umbrella term that includes various types of landing systems - in particular, ILS (Instrument Landing System) (as a western standard) and SP-70, SP-75, SP-80 (as domestic standards).

The principles of RMS approach are quite simple.

The ground part of the RMS consists of two radio beacons - localizer beacon (KRM) and glide path beacon (timing), which emit two oblique beams (equal signal zones) in the vertical and horizontal plane. The intersection of these zones forms the approach trajectory. Aircraft receiving devices determine the position of the aircraft relative to this trajectory and issue control signals to pKP-1 flight controller (in other words, to the artificial horizon) and planning and navigation device PNP-1 (in other words, to the course pointer).

If the frequency is adjusted correctly, then when approaching the runway, the pilot will see two moving lines on the large artificial horizon - a vertical command arrow and horizontal glide path command arrow, as well as two triangular indices indicating the position of the aircraft relative to the calculated trajectory.

Today is a small article to restore order in concepts. Although the main principle of my stories is the maximum simplicity, but, apparently, we still cannot get away from a couple of aerodynamic definitions. However, we certainly won't get into the jungle, I think ... 🙂 So let's start.

Determination of the angle of attack

For convenience, we will talk about what is already known to us, and you already know that this is true for the wing as a whole.

In one of the previous articles, we talked about the lift generated when flowing around an asymmetric airfoil, located parallel to the flow for ease of understanding (i.e. a simplified version). In fact, any wing (i.e. the profile itself) is located at an angle to it. Thus, there is such a very important concept as. Let's define it more precisely.

The minimum straight-line distance from the nose of the airfoil to its tip (between points A and B) is the chord of the airfoil. And the angle between the chord and the direction of the incoming flow is the angle of attack α ... In this case, we consider the flow calm, that is, undisturbed. For the future, I note that the flow can be laminar when it flows smoothly, without mixing the adjacent layers, and turbulent when vortices and mixing of the layers appear.

Aerodynamic force

And here you can reveal little secret :-). In fact, there is no lifting force as an independent quantity. But I certainly did not deceive you. Just besides the lifting (Y), there is one more aerodynamic force. This is the force of air resistance (X). The resistance is of considerable magnitude and, especially in the presence of an angle of attack, it cannot be ignored. Both of these forces add up to a quantity called total aerodynamic force (R). It is she who just affects the wing profile. It is applied at a point called the center of pressure. Why pressure? Because the air "presses" on the profile by means of this very force.

With the introduction of the concept, one more thing appears, which is very important and cannot be ignored. When the airfoil moves at an angle to the incoming flow, this flow seems to be mowing and acquires some downward movement. Since air has a certain mass, then, according to the law of conservation of momentum, a force directed in the opposite direction (i.e., almost upward) will act on the profile, and depending on the magnitude of this mass. It will also participate in the formation of the full aerodynamic force, and hence the lift force of the profile, although it is clear that it itself has a somewhat different nature of formation than the one we spoke about.

When flowing around an airfoil (both asymmetric and any other), these two types of lifting force seem to complement each other, and the decisive role (in magnitude) is now played by the force, resulting from an angle of attack... The lift arising according to Bernoulli's law plays a secondary role, which is what happens on a real aircraft.

Thanks to this phenomenon, almost any plate, even a flat plate, can fly. For this, one requirement: there must be an angle of attack. As soon as the plate becomes non-parallel to the incoming flow, the aforementioned aerodynamic forces immediately appear and the process has begun ... This is an important concept in general, it turns out.

In concluding this article, I will say as before. We have mentioned just a few terms and definitions from the aerodynamics queen of aviation sciences today. Just mentioned! In fact, this science is as difficult as it is interesting. However, the amazing beauty of aviation is available to anyone, even those ignorant of aerodynamics ... 🙂

P.S. In conclusion, I propose to watch a short video that illustrates well the flow around the profile, depending on the angle of attack and the forces acting on it. High blood pressure is shown in red, low pressure in blue.

P.S.S. Two illustrations used in this article are taken from the resource http://www.rcdesign.ru/articles/avia/wings_profile. Thanks to their author Konstantin Bochkov.

Attack angle

Attack angle (the common designation is the letter of the Greek alphabet alpha) - the angle between the direction of the speed of the flow (liquid or gas) oncoming the body and the characteristic longitudinal direction chosen on the body, for example, at the wing of an aircraft it will be the wing chord, in the aircraft - the longitudinal construction axis, at the projectile or rockets - their axis of symmetry. When looking at a wing or aircraft, the angle of attack is in the normal plane, as opposed to the slip angle.

Attack angle aircraft - the angle between the chord of the wing and the projection of its velocity V on the plane ОХY of the associated coordinate system; is considered positive if the projection of V onto the normal OY axis is negative. In the problems of flight dynamics, the spatial U. is used: (α) n - the angle between the axis OX and the direction of the aircraft speed.

Angle of attack sensors for an air-to-air missile.

Wing and stream

As long as aviation exists in the world, so many aircraft are threatened by one of the most frequent and terrible dangers - stalling into a tailspin, because the angle of attack of the aircraft becomes higher than the critical value. Then the smoothness of the air flow around the wing is violated, and the lift is sharply reduced. Stall usually occurs on one wing, as the flow is almost never symmetrical. It is on this wing that the plane falls, and it's good if the stall doesn't go into a spin.

Why do such situations occur when the aircraft's angle of attack increases to its critical value? Either speed was lost, or the maneuvering overloaded the aircraft too much. This can also happen if the height is too high and has approached the "ceiling" of possibilities. Most often, the latter occurs when a thundercloud is bypassed from above. The high-speed pressure at high altitudes is small, the vessel becomes more and more unstable, and the critical angle of attack of the aircraft can spontaneously increase.

Military and civil aviation

The situation described above is very familiar to pilots of maneuverable aircraft, especially fighters, who have theoretical knowledge and sufficient experience to get out of any situation of this kind. But the essence of this phenomenon is purely physical, and therefore it is characteristic of all aircraft, of all types, of all sizes and of any purpose. Passengers do not fly at extremely low speeds, and vigorous maneuvers are not provided for them either. Civilian pilots often fail to cope with the situation when the angle of attack of an aircraft wing becomes critical.

It is considered an unusual situation if a passenger ship suddenly loses speed, moreover, many believe that this is generally out of the question. But no. Both domestic and foreign practice shows that this happens not even very rarely, when the dumping ends in a disaster and the death of many people. Civilian pilots are not well trained to cope with this aircraft position. But the transition to a tailspin can be prevented if the angle of attack of the aircraft during takeoff does not become critical. It is almost impossible to do anything at low altitude.

Examples of

This happened in the disasters that occurred with the TU-154 aircraft in different time... For example, in Kazakhstan, when the ship descended in stall mode, the pilot did not stop pulling the steering wheel towards himself, trying to stop the descent. And the ship should have been given the opposite! Lower your nose to pick up speed. But until the very fall to the ground, the pilot did not understand this. Roughly the same thing happened near Irkutsk and Donetsk. Also, the A-310 not far from Kremenchug tried to gain altitude when it was necessary to gain speed and all the time to observe the angle of attack sensor in the plane.

Lift is generated by an increase in the flow rate that flows around the wing from above compared to the flow rate under the wing. The more speed the flow has gained, the less pressure in it. The difference in pressure on the wing and under the wing is the lift. The aircraft's angle of attack is a measure of normal flight.

What do we have to do

If the vessel suddenly rolls to the right, the pilot deflects the steering wheel to the left, against the roll. When on the console, the wing deflects downward and increases the angle of attack, slowing down the air stream and increasing pressure. At the same time, on top of the wing, the flow accelerates and lowers the pressure on the wing. And on the right wing at the same moment the opposite action takes place. Aileron - up, the angle of attack and lift are reduced. And the ship goes out of heel.

But if the angle of attack of the aircraft (when landing, for example) is close to critical, that is, too large, the aileron cannot be deflected downward, then the smoothness of the air stream is disturbed, starting to swirl. And now this is a stall, which sharply reduces the air flow speed and also sharply increases the pressure on the wing. Lift quickly fades away, while everything is fine on the other wing. The difference in lift only increases the roll. But the pilot wanted the best ... But the ship begins to descend, spin, spin and fall.

How to proceed

Many practicing pilots talk about the plane's angle of attack "for dummies", even Mikoyan wrote a lot about it. In principle, everything is simple here: there is practically no complete symmetry in the air flow, and therefore even without a roll, a breakdown of the air flow can occur, and also only on one wing. People who are very far from piloting, but who know the laws of physics, will be able to figure out that this plane's angle of attack has become critical.

Output

Now it is easy to draw a simple and fundamental conclusion: if the angle of attack is large at low speed, it is impossible, categorically impossible to counteract the roll with the ailerons. It is retracted by the steering wheel (s). Otherwise, it is easy to provoke a corkscrew. If a stall does occur, only military pilots are able to get out of this situation, civilians are not taught this, they fly according to very strict restrictive rules.

And you need to teach! After plane crashes, the recordings of conversations from And never once in the cockpit of a plane crashed in a tailspin did not sound "The helm from yourself!", Although this is the only way to escape. And "Leg against the roll!" didn't sound either. not ready for such situations.

Why is this happening

Passenger aircraft are almost completely automated, which certainly makes it easier for the pilot. This is especially true for adverse weather conditions and flights at night. However, this is where the greatest danger lies. If it is impossible to use the ground system, if at least one node in the automatic system fails, then manual control must be used. But pilots get used to automation, gradually losing their piloting skills "the old fashioned way", especially in difficult conditions. After all, even the simulators for them are set to automatic mode.

This is how plane crashes happen. For example, in Zurich, a passenger plane could not land normally on the drives. The weather was minimal, and the pilot did not taxied, collided with trees. All died. It often happens that it is the automation that causes the stall into a tailspin. The autopilot always uses ailerons against spontaneous roll, that is, it does what cannot be done in the event of a stall threat. At high angles of attack, the autopilot should be turned off immediately.

An example of autopilot actions

The autopilot is harmful not only at the beginning of a stall, but also when the aircraft is taken out of a spin. An example of this is the case in Akhtubinsk, when an excellent military test pilot was forced to eject, and realizing what was the matter. He attacked the target with the autopilot on, when he fell into a tailspin. Twice he managed to stop the rotation of the plane, but the autopilot stubbornly manipulated the ailerons, and the rotation returned.

Problems like this, which constantly arise in connection with the widespread distribution of the programmed automatic control by aircraft, are extremely worried about not only domestic specialists, but also foreign civil aviation... International seminars and rallies dedicated to flight safety are held, where it is certainly noted that the crews are not well trained in controlling an aircraft with a high degree of automation. They get out of dire situations only if the pilot has personal ingenuity and good manual piloting technique.

The most common mistakes

Even the automation that the ship is equipped with is often not well understood by pilots. This played a role in 40% (of which 30% ended in disaster). In the USA, they began to compile evidence of disharmony among pilots with a highly automated aircraft, and a whole catalog of them has already accumulated. Very often, pilots do not even notice the failure of the autothrottle and autopilot in general.

They also poorly control the state of speed and energy, therefore this state is not preserved. Some pilots do not realize that rudder deflection is no longer correct. You need to control the flight path, and the pilot is distracted by programming automatic system... And many more similar errors occur. The human factor accounts for 62% of all serious air accidents.

Explanation "on the fingers"

Probably everyone already knows what the angle of attack of an aircraft is, and even people who are not related to aviation are aware of the importance of this concept. However, are there such? If there is, then there are very few of them on Earth. Almost everyone flies by air! And almost everyone is afraid of flying. Someone internally worries, and someone right on board falls into hysterics at the slightest turbulence.

Probably, it would be necessary to tell passengers about the most basic concepts related to the aircraft. After all, the critical angle of attack of the aircraft is not at all what they are experiencing now, and it is better if they understand it. You can instruct flight attendants to convey such information, prepare appropriate illustrations. For example, tell that there is no such independent quantity as lift. It just doesn't exist. Everything flies thanks to the aerodynamic force of air resistance! Such excursions to the basics of science can not only distract from the fear of flight, but also interest.

Angle of attack sensor

An aircraft must have a device capable of determining the wing angle and the horizontal air flow. That is, such a device, on which the well-being of the flight depends, should be shown to passengers at least in a picture. With this sensor, you can judge how far the nose of the aircraft is looking up or down. If the angle of attack is critical, the engines do not have enough power to continue flying, and therefore a stall occurs on one wing.

It can be explained quite simply: thanks to this sensor, you can see the angle between the aircraft and the ground. The lines should be parallel in flight at the already gained altitude, when there is still time before the descent. And if a line running along the ground tends to a line mentally drawn along the plane, an angle is obtained, which is called the angle of attack. You cannot do without it either, because the plane takes off and lands at an angle. But he cannot be critical. This is approximately how it should be told. And this is not all that passengers need to know about flights.