Landing gear - Aircraft support system (Aircraft), providing its parking, movement on the airfield or water during takeoff, landing and taxiing.
Usually consists of several racks equipped with wheels, sometimes skis or floats are used. In some cases, tracks or floats combined with wheels are used. “Chassis” is a general term. As a rule, they distinguish “supports” (“struts” or “legs”) of the chassis, specifying which one. For example, they say: right main landing gear or right main landing gear.
- FROM tail wheel (two-post chassis). The main supports or support are located in front of the center of gravity, and the auxiliary (tail) is behind (see Douglas DC-3, An-2). As a tail support, a “crutch” was often used earlier - a structure without a wheel that works on gliding over the ground (airfields were unpaved).
- With front wheel (three-post chassis). The front (nose) wheel is located in front of the center of gravity, and the main supports are behind the center of gravity. The rack in the nose of the fuselage usually accounts for 10-15% of the mass. Gained distribution during the Second World War and in the postwar years. (see, for example, Boeing 747, Tu-154). Sometimes (see IL-62, Tu-144), it is supplemented with a small additional tail stand to prevent the aircraft from tipping over to the tail at the aerodrome when passengers are improperly moving around the cabin.
- Bike type. The two main supports are located in the fuselage, in front and behind the center of gravity of the apparatus. Two lateral support legs are mounted on the sides (usually on the wingtips). It is used to remove nacelles for landing gear and engines on the wing, that is, to create an “aerodynamically clean” wing (see M-4 and Myasishchev 3M, Boeing B-47 Stratojet, Boeing B-52 Stratofortress, Lockheed U-2, Yak-25, -27, -28). The consequence of this arrangement is the complicated technique of landing the aircraft and the difficulty of modernizing the bomb bay, as well as the use of external weapons.
A variation of the bicycle chassis is the airframe chassis with a single dorsal semi-recessed wheel.
In heavy aircraft, sometimes the number of landing gear wheels is several tens, combined into carts. Chassis carts are usually uniaxial, biaxial or, less commonly, triaxial. A pair of wheels is usually mounted on each axle. They are called that: front pair, middle or back pair. Paired wheels reduce pressure on the aerodrome coating, and also duplicate each other in case of pneumatic puncture. Sometimes on one axis put not two, but four wheels.
Also on heavy aircraft can often be not two, but several main racks. For example, on the Boeing 747, in addition to the left and right main racks, there are two middle dorsal racks. Two main racks are installed longitudinally on the IL-76 from each side. And on Mi-14, Ka-32 helicopters there are two front and two main landing gears.
A kind of ski. Serve for landing on snow. They can be used together with wheels.
Also widely used in helicopters.
The Importance of Standard Operating Procedures (SOPs)
It is vital that you have a firm knowledge of the sequence of procedures before entering airport traffic. You should know what actions need to be performed at each stage of being in the airport traffic. You should learn to cultivate individual stages of awareness of your successes. Keep asking yourself the following questions: Is the speed too high in this area? We fly slowly, high? Is it still far from the strip or close? Am I flying right along a rectangular route? If so, where? Did I send radio calls? Self-tests of this kind will help you to develop high standards of piloting and make fewer mistakes in developing skills or making decisions. Standard operating procedures will help you find answers to questions, including to determine your success and your safety.
This issue is closely related to SOPs. The control values allow you to control the plane at each stage of your stay in the airport air traffic and calmly distribute your attention between flying planes, control the traffic and determine your speed, distance, height relative to the ground, guided by the space closest to the airport.
You have probably heard before that a good landing is the result of a good approach and approach. It's true. As a result, you will fly at a constant speed value, constant descent control values and constant power control values.
Thus, a stabilized flight is a path to the point of contact, a point on the path that should be in the first third of the runway distance (runway).
All this will also have a certain impact on you: you need to concentrate on the wind course corrections, make sure there are no deviations of the flight parameters from the stabilized profile, and reduce the engine power.
Manipulating airspeeds in large ranges by acting on a power plant, accompanied by ups and downs, is clearly a bad idea. This indicates that you are not feeling the aircraft and are not following SOPs. Through inhuman efforts, you may be able to get closer and make an acceptable touch, but this is unlikely. Going to the second round in this case would be the most correct decision.
Not one step, but three
That is how you should think about the moment just before touching the landing strip chassis. At the beginning of leveling, you are somewhere at an altitude of 3 meters (for ultralight slow aircraft) to 15 meters (for faster and heavier aircraft) above the ground, having passed the control speed value, having completed all preparations for approaching your chosen place. Alignment is the process of reducing the vertical speed of an airplane to zero.
Aging. Now you are just a meter above the strip. Make sure that you switch to low throttle and raise the nose of the aircraft to take a landing position, which will ensure a decrease in airspeed. At this point, flight instructors are often advised to hold this position.
Air speed drops, but it’s not at all scary in good weather, because the screen effect is affected, and landing speed will be lower.
Touching the ground. Chassis touched the runway. Use ailerons to compensate for crosswind and rudder to hold the aircraft on the axial landing strip. After landing, remove the flaps to prevent the aircraft from breaking off during high-speed taxiing or when the wind is very strong.
In a gusty wind
Adjust the engine power so that when approaching you have an extra margin of speed when landing in case the wind deprives you of the opportunity to significantly slow down. Add one second impulse value to your normal approach speed for more safety when sitting down and more steering sensitivity. For example: if the wind blows at a speed of 15 knots, with gusts up to 25, then increase the approach speed by 5 knots. Be prepared for going to the second round if you have not passed at least one of your control parameters or SOP, and also if you think that something went wrong.
Side wind like spinach
You may not like the side wind as much as spinach, but the practice of taking off and landing with a side wind will be very useful for you. Experienced pilots argue that being caught by an increasing wind is not as high a risk as landing with a strong crosswind. This is also indicated by statistics. In approximately 48 percent of all weather-related incidents, the main factor was wind, while only half of them were related to the pilot losing control while landing with a crosswind. Therefore, problems can be avoided only through constant practice.
Landing: how can it finally be planted!
You will laugh, but the first time I was on the plane at the age of 26, when my girlfriend persuaded me to fly with her on vacation to Turkey. Probably, the vast majority of modern, constantly flying somewhere, people are hard to believe. But that was the very first flight in my life, and he made a completely indelible impression on me, already an adult. And in the end, even changed my life, for which I am very grateful to fate.
I am ashamed to admit, but then I was a little scared. On the eve of our flight, I was nervous, tossing and turning, and could not sleep. Is it a joke to fly somewhere by plane! As much as 10,000 meters!
Needless to say, how much I was struck by IL-86, this huge flying house, when it began its run in the runway. I could not imagine that this huge heap of metal could so quickly take off. But as soon as we gained altitude and switched to horizontal flight, another problem began to concern me: “Well, good,” I thought, “It seems we are flying. But how now this house will return back to earth. “This thought did not leave me all four hours of our flight. And finally, we started the approach, releasing various fancy pieces of iron from the wings (I didn’t know exactly what the elements of wing mechanization are called). The ground outside the window is approaching, the turbines are howling, the passengers are fidgeting, the scoreboard is on, even the stewardesses have sat down and buckled up ... I am prepared for the worst. :)
Imagine my surprise when all this flying Noah's Ark suddenly took, and rolled on concrete. Here is the current that flew - and is already going. Gently and imperceptibly, he returned from heaven to earth without even jumping! To say that he was surprised is to say nothing. I was just shocked! To the depths of my soul, I was shocked by the skill of those two or three men sitting somewhere far ahead in their cabin who so gracefully at great speed touched the ground with the hefty wheels of a hundred-ton flying bandura! Gracefully. And as I understand it now, even a little dude, slightly protruding the little finger, ostentatiously, at ease, playfully. Like, look how we can! See from envy, for you, the worms not flying, can never do that!
In such moments, when someone shows his mastery to the world, people are divided into two groups. For those who continue to chew their gum, tryndet and not hear the Music, and those who shut up, completely stunned by it. You say that I have spread too much pathos here? No, perhaps you will not say that. You do not just come to this site. :)
Different people see beauty in different ways. Some in painting, some in music, some in mathematics, and some in cooking or even in financial frauds. So if you have not heard Music in the weightless landing of a huge liner, then just try yourself in something else. :)
Well, so, in my case, the bait turned out to be correct. I heard and understood something that I did not hear and did not understand before. I physically felt that there was something very large and important nearby, and I would not touch it and did not learn to do something like that, then my life would be completely ineptly wasted! :) Of course, I did not plan to land the IL-86 (although who knows!), But the goal was set. I told myself that if at least once I could tear off an aircraft heavier than air and return it back to earth safe and sound, then I will have to respect myself for that. From this moment, I had to change a lot in my life. Too much ...
How long it is short, but my path lay in the flying club. Where suddenly it turned out a few not very pleasant things. Firstly, according to my flying abilities, I’m not Valery Chkalov at all (and I never will be). Secondly, that I am not young Valery Chkalov. :) Learning to pilot (as well as any difficult skill in general) is best at a very young age. At the age of 30 it is still possible, but memory and reflexes are not quite the same as in youth, and there is already more fear than at age 18. Fear spoils everything, especially when landing.
So, now about the most interesting - about landing (in the Canadian KULP it is Exercise 18).
Someone already in the second or third flight grabs the landing technique, but it was not given to me for a very long time. And in the 10th flight, nothing came of it. I was very nervous and this did not work out even more. This went on endlessly, until after another unsuccessful attempt, I got angry with the plane. “But how can you finally be planted !!” I thought. And from evil I forgot about fear, brought the plane closer to the ground, thrusting it almost more confidently, pulled out the helm more confidently and flew above the ground at a very low altitude, trying to “hang over the strip longer”, as the instructor asked me. The plane hung, hung and ... sat down, infection! It was just awesome! I did put him. It was a happy day, and I am infinitely grateful for it to my instructor, Pavel Yuryevich Kalugin, who abandoned his affairs for me and arrived at the airport on a weekend to work out “individually” when no one else flies. An individual lesson was a success! I caught the necessary movement at the helm, the leveling level and stopped being so afraid of the approaching land. The spell was lifted and at the very least, through one, the landings began to turn out.
You can write about the landing technique endlessly, constantly rewriting what has already been written. But I will try, not particularly blurring my thoughts on the tree, to emphasize the most important and complex points, the development of which was given to me with the greatest difficulty. And then let’s do it yourself - practice is more important than any chatter. As one well-known character once put it, "I ask you, where is the landing?" Exactly where? Fly more and everything will start to work out. :)
As I said, the success or failure of a landing is largely due to your approach. If the approach is completed correctly, if the arrows are gathered in a heap in advance and the approach to the ground occurs “like on rails” - landing will work out. If until the leveling you are still struggling with the three-dimensionality of space and speed, then most likely the landing will be rough and unsafe. You will see for yourself.
At the same time, we rarely fly alone. Usually, several more planes take off and land at the airport, and often we are simply forced to make calls that are different from the ideal, but provide safe intervals with other planes. This process is always associated with an element of surprise. You are acting according to the plan and suddenly you hear the dispatcher’s command “make your circuit tight”, that is, actually diving a stone down from the third turn to enable the large airliner, hanging on a straight line 5 miles from the airport, to sit right behind you. Ok, heating, low throttle, bend, maximum glide to reset altitude and ... Landing is safe, but non-bulky. Too much fuss. Well, well, "the pilot is safe - the flight was a success." There is no beauty and grace in this, but it is not worth annoying either. Under the proposed conditions, this is a normal working landing. We just have to strive for a beautiful landing, and it is possible only with an equally beautiful, stable approach. :)
So, we were finally lucky, we made a beautiful approach, dropped half the height of the circle after the third turn (base leg) and went straight. There are three options: we are on the glide path, above or below it. Glide path (glide slope / path) is called an imaginary sloping straight line along which the plane descends to the threshold of the runway. The slope of the normal glide path is approximately 3 degrees.
At large airports, we can visually determine our position relative to the normal glide path using the VASIS or PAPI lights, but at a small airport you only have to use your own eye.
First of all, you need to try to remember how the strip is projected in the windshield when the plane is higher, lower or exactly on the glide path. But there is one more trick. The fact is that the glide path ends at the “leveling point,” that is, the place where we must stop the descent and level the plane, proceeding to landing. It is desirable that this point is either at the very beginning of the strip, or even slightly in front of it, so that we can maximize the length of the strip for braking on the run. Such would be an ideal, 3 degree glide path. But how do we know how far we are from the ideal? But very simple. Carefully look at the strip for a second or two: you will find that one part of the image in front of you “floats” up, the other part - down. And some part remains motionless. It is here that you will fly after a while! The perception of perspective by the human eye is so structured that objects that are exactly on the line of our path visually remain motionless.
When this motionless “point” is far behind the threshold of the runway, we are above the normal glide path (a flight is planned), when in front of it is lower (under-flight).
If the point is exactly where we would like (ie, before the threshold of the strip or at the very beginning, above the “numbers” or “signs”), then we are on a normal glide path. In this case, we just keep going, as we went from the third to the fourth, with the same vertical. But we add one more element to this - we keep on the axis. The wind, the infection, we will be blown away, and we are against it with a roll, and with a pedal to the other side (side slip), or with our nose towards the wind (crab).
Если мы ниже глиссады, тут тоже все понятно: увеличиваем режим. Плавно, но быстро: внизу могут быть препятствия, в том числе такие, которых издалека не видно, например, провода. Если мы уж очень низко, то нос можно и поднять, хотя обычно для возвращения на глиссаду достаточно только увеличения режима. Глиссада ведь наклонная прямая. Если просто «прыгнуть» вперед горизонтально, то рано или поздно окажешься на глиссаде. Но если земля уже совсем близко, то не помешает и поднабрать, от греха.
If we are above the glide path, we must act decisively (it is advisable to specially work out these actions by flying conveyors with an instructor). This is due to the fact that it’s simply impossible to lose altitude by removing gas and lowering your nose: the plane is a heavy piece of iron. If it is too steeply directed to the ground, then airspeed will inevitably begin to grow. It is unacceptable! This means that we will not sit down!
Axiom: it is impossible to land a plane flying over a strip at a speed higher than landing. Remember this. NOT. There will be a soaring or a goat, and then you do not have enough stripes.
I had an “amazing” case. I carefully “ground” the plane to the strip at a speed higher than the landing one. He ran along the asphalt, ran 50-80 meters, and then ran into a bump and took off, because this innocent tubercle slightly increased the angle of attack of the wing, and there was still enough speed to lift more than the weight of the aircraft. And then what? That's right, "goat." :)
So, we want to approach the ground at a landing speed. Only with boarding. Not less (dangerous: we’ll fall!), But no more (dangerous: we’ll get out and either roll out or fall!). So, if we go above the glide path, blunt lowering of the nose does not suit us definitely.
What to do? Well, there are two options. Slipping or releasing flaps.
1. At first gliding (forward slip) looks pretty dumb, although in fact it is a fairly safe maneuver. Simply put, we (both of these actions are very important) turn on the carburetor heating and set a small gas. Then we roll the plane (always to the side where the wind is blowing from) and completely (!) We reject the rudder pedal in the opposite direction (the ball will clog in fear in the corner - but we only need this). Now you can lower your nose, but not lower than the position at which the recommended approach speed (for example, 60 knots) will be maintained. In this configuration, the aerodynamic quality of the aircraft is extremely poor, which means that the maximum vertical speed of descent will be achieved and the glide path will become very steep, while the air speed will remain within the recommended range. Now we most likely have time to decline to the strip, but it is better (only in this case!) To slightly shift the alignment point “to ourselves”. This is due to the fact that as soon as we remove the glide on the leveling, the plane will necessarily “swell” and just enough to reach the previous leveling point parallel to the ground. And then it will fly, keep this in mind.
2. Release flaps. This method is used much less often, but it is also possible with a great desire to show off. Flaps have a twofold effect on the aerodynamics of an airplane. They increase the lifting force and increase the force of aerodynamic drag (which affects the aerodynamic quality as well as sliding). It is important to understand that up to 20 degrees the flaps increase the lifting force more than the drag force, and after 20 degrees the drag force grows much faster. Conclusion: if you already release the flaps to reset the height, then at least 30 degrees (with a release of up to 40 on a short straight line, when there is 100% certainty that you will reach the strip).
Caution 1. Do not release flaps at a speed exceeding the permissible limit (white area on the speed indicator).
Caution 2. Do not release flaps in one sweeping motion from 0 to 30, and even more so up to 40. First 15-20 degrees, then 30, then only 40 already on a short straight line.
Caution 3. Do not slide with flaps at 30 or 40 degrees. There is a strong opinion of experienced pilots that you can fall. Hence the danger of flaps extending 30 or 40 degrees into a strong crosswind: if at some point you have to slide to correct drift, this may end badly.
Caution 4. Do not put light gas with flaps 40 degrees until you level the plane above the ground. Otherwise, with a high probability, the landing will be rough. A Canadian instructor taught me that with such flaps, the plane flies like a rock (flies like a rock). Very close to the truth.
Now, after all these warnings, do you understand why the slip method is much more popular? :) Also, do not forget that when flying conveyors, the flaps will need to be hastily removed during the take-off run, otherwise with 40 degrees there is a chance not to get off the ground at all, this is not a joke at all.
Well, having figured out the height and speed, we nevertheless approached the alignment point. Now the hardest part. Actually, landing. :) In fact, it is more complex psychologically than in the sense of technology, because any normal person is afraid to fuck the plane on the rushing towards the ground. This leads to a high leveling, when the cadet subconsciously stops the approach of the earth by premature movement of the helm toward himself. It’s clear that when the plane crashes too high and the small gas has already been set, the speed will start to fall rapidly and if nothing is done, the plane will inevitably fall off. A fall from three to four meters does not bode well.
Therefore, first of all, you need to force yourself not to be afraid of the earth. This comes with experience, but all the same, you will first have to grit your teeth and fly to the ground until the “blades of grass flicker”. Now is the time. :)
To correctly determine the alignment height, it is recommended to look not forward, but slightly to the side, 20 meters ahead. For a long time I could not understand why. They told me something about peripheral vision (which is true), but I still doubted and looked forward. Until he started flying on the Yak-18T. It simply does not show anything on landing: the hood obscures the entire review. A common thing for radial aircraft, and there are still aircraft with a tail wheel, you can’t even see anything on the taxi ahead. In general, yes, you need to get used to looking away. At the same time, the illusion is such that yours, sorry, ass, is falling, and the horizon around, visible with LATERAL VISION, is slow at first, and then quickly rises. Here's how it started to climb fast - it's time to level the plane. This is my vision of the situation, and someone sees and aligns the blade of grass. If you feel something else - try to formulate it for yourself, it is not easy. The main thing - do not be afraid of the earth. Be wary of her approaching too quickly.
And here is how the famous American instructor and showman Rod Machado describes the moment when the alignment begins: “when the strip visually begins to expand dramatically - align”. I highly recommend watching this video (in English).
Now that we are sure that the time has come, we begin to choose the helm for ourselves, in most cases (attention!) In small double movements. Centimeter on yourself - half a centimeter back. Pause. Centimeter on yourself - half a centimeter back. These small movements create the correct landing position of the aircraft and, most importantly, the angle of attack of the wing gradually increases, which leads to a further decrease in speed (due to the growth of aerodynamic drag). Just don’t try to “land the plane” at this moment - that’s the whole trick! On the contrary, your task is to gradually select a helm, don't let him sit down! Let it “freeze” and rush over concrete, losing speed at a very low and therefore completely safe height. Then a soft landing will be a pleasant surprise for you. Exactly the same as a shot from his own weapon for a master of sports shooting. He, too, while aiming, does not press, but only slightly increases pressure on the trigger so that the weapon does not flinch at the most crucial moment. And suddenly “bang!” - and “ten.”
Try to feel the force on the helm with your fingers - as the speed drops, its resistance to your movements will fall, it will begin to “soften” - here you can pull two centimeters and return it by one. About here you touch the strip.
The question "when to put small gas" is very important, the answer depends on specific conditions. It can be placed both before alignment, and during the alignment process, or you can even sit down with a small mode (1500 revolutions on the Cessna 150). Accordingly, we will get the softest landing when landing with the regime, but the mileage with such a landing will be the largest. If we have a huge 3 kilometer lane ahead - why not. If we have only 400 meters of concrete, then small gas can be delivered even before crossing the threshold of the strip, “above the grass”.
Now the most unpleasant thing for me personally is landing with a side wind. After all, if there is no wind, or it is strictly in a strip, then the longitudinal axis of the aircraft is parallel to the axis of the runway. But if the wind blows from the side ... Again, there are two correction methods, either crab (nose to the side of the wind, wings in the horizon) or roll against the wind to stop drift, and the opposite pedal is exactly so that the axis of the plane is parallel to the axis and the plane did not turn toward the roll. The last method is called side slip, which is, in fact, a subspecies of normal slip (forward slip), but here the pedal does not deviate all the way, but according to the need to maintain direction on the runway. In the particular case, a complete pedal deflection may be required. Worse, with a very strong crosswind, rudder efficiency may not be enough, the pedal will go all the way, but the roll counteracting the drift will be so large that the plane will begin to turn. This means that the landing characteristics of the aircraft in the crosswind are exceeded and it is NOT possible to land with this course - roll out at best, in the worst roll over on the run.
The Western school loves the side slip method, because it clearly demonstrates whether there is any possibility of sitting down in such a wind and, in addition, provides constant parallelism between the plane axis and the runway axis. However, the crab method is also not bad and is used mainly on heavy equipment, where it is simply forbidden to use the rudder pedals for a number of reasons. But heavy equipment has self-orientating struts, which makes landing easier. It is important for us to prevent lateral load on the chassis. Therefore, in fact, at the last moment, on leveling, in any case, we will be forced to switch from the crab method to the side slip method, using the pedal to align the plane along the axis, and creating a small roll on the windward leg with ailerons (against the wind). If we touch the strip with this foot earlier - it does not matter, it’s even better.
It is clear that if we immediately used the side slip method, then we approached the ground with the same roll, and again, most likely, touch the ground with the same windward foot.
Usually, when the main wheels touched the ground, the cadet considers the task completed. And lets go of the helm. Nose stance nasty plop on concrete. This is wrong and ugly.
Nose against the wind, and wings in the horizon (Crab and slip) or roll against the wind (slip)
In the AOPA Regulation (Association of Aviation Equipment Owners and Pilots), the Crab and slip method is indicated as the most commonly used approach method for crosswind. When using this technique, your actions should be quick. You approach the aircraft by pointing the nose of the aircraft against the wind, keeping the wing line in the horizon, thus compensating for drift in the wind. Before touching it, you must align the plane in a strip using the rudder and immediately touch the strip to avoid slipping from the center line. If your actions are not fast enough, then you will immediately hear the screeching sound of rubber on your chassis.
The slip method is based on creating a roll against the wind and using the rudder in the opposite direction, obstructing the turn, thus counteracting the drift in the wind. This position should be maintained until the runway wheel touches the windward side. Use the rudder to maintain the trajectory of movement in the air and along the lane.
You should be extremely careful ...
... when landing on an airplane with a tail wheel in a gusty crosswind. Since the center of gravity on these types of aircraft is located behind the main landing gear, they are unstable in the direction on the ground. This means that an unexpected reversal may occur, the so-called "compass". This can be especially critical after touching the strip and losing speed, when the effectiveness of the rudder decreases. You will have to deflect the rudder to the entire angle of rotation, at this moment its effectiveness may suddenly increase sharply, and if you react too slowly, it will surely turn around at a fairly high speed.
Learn SOPs, remember control values and configurations, practice with an instructor in strong crosswind conditions. You may never be famous for your perfect landings, but if you learn to fly in a stormy, gusty wind, you will be a cut above the many other pilots and will be able to provide a much safer flight.
Catch the goat
So you think that you have already landed safely, when you suddenly discover that you are already 3 meters above the strip, and you can’t understand what exactly happened? You just "caught a goat." And this happened because: (1) your landing speed was too high, and you simply bounced off the runway, (2) the descent speed was high, you did not respond quickly enough, or, possibly, both variants of the situation.
So what to do now? Two ways out of this situation are proposed:
a) Urgent go to the second round. Immediately increase power to maximum, begin to climb and get ready for the second approach. Perhaps this will be the safest scenario, rather than trying to land the plane on the remaining runway.
b) Add a little gas at the highest point from the rebound - enough to avoid loss of airspeed and allow the aircraft to drop to the landing strip with a sufficient supply of lift in order to work out the landing correctly a second time. If you need to change the pitch of the screw, set it small. Whatever you do, do everything smoothly so as not to fail the second attempt. Just hold the power settings to create an air cushion when you descend. If you start to pull the elevator in an attempt to catch the next moment of contact, then you will easily catch the second goat. And then again, and again, until you lose airspeed or reach the end of the runway.
Practice your “goat” landing under the supervision of a good instructor to hone your skills and easily get out of this situation.
Translation of Thomas A. Horne. Translated by Maxim Shlyapnikov.