About aerodynamics: Interview with the creators of the Superjet

The authors of the site superjet.wikidot.com there was a very interesting opportunity to talk to one of those who participated in the creation of SSJ-100, Deputy Chief Designer of the aerodynamics GSS Alessandro Viktorovich Dolotovskim and he kindly agreed to answer our questions.

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  • BigThree.png

Here it is the most representative of the photograph on the right and left of the Ivashechkin.

Tell us about the project and the characteristics of the aircraft, about as intended and what happened.

We make a little history. The project — the first company — the new. Usually, when there is such a combination, one of the prominent project is waiting. Ironically, when, as you know, we have been working with Boeing, and the guys with Boeing (and these guys were gray-haired old engineering staff that made the program 737, 767 and 777) have told us that it «Big challenge» (large call) to organize in the open field of a new player. In addition, it was a challenge not only for us but also for the French, our partner in the engine, because Snecma had no experience in the development of civil engine as INTEGRATOR. And in fact, was organized two companies, GSS and PowerJet, and there are two new products, aircraft and engine. In this case, not even the motor, and the power plant, because it includes the nacelle and all units within the sample.

And as said Boeing guys, if you can make a plane at a level that is already a big step forward, because it is not important for you to build an outstanding aircraft, and learn how to build these planes. Actually this route was EADS, when launched Airbus A300 program, which was far from competitors, especially in economics.

But here we had an advantage over other start-up companies. We still live and work in the great air power called Russia. And we have a strong foundation in the face of aviation research centers with unique competencies, especially in the development of aerodynamics and aircraft design and engine. I of course mean TsAGI and SibNII GA. I will only speak about those centers that are associated with my competence, ie aerodynamics.

Therefore, we have the opportunity to invest in a project flavor, using the experience of our research centers. This peculiarity consists in the fact that we are, in terms of aerodynamics, made wide-bodied aircraft with features like single-aisle. Here we rely on almost a century of experience building airplanes in Russia and the Soviet Union

Further, as I understand it, and we’ll talk about the plane.

But first digress. He read in a publication, to be honest? the exact name I can not remember, was a report from Farnborough, which rezanula phrase, such as "standing next to a very high elongation wing Boeing 787 and suddenly felt a particularly scanty looks small wing Superdzheta." And in fact, our wing in their geometrical parameters is almost the same as Boeing. Our wing also made of modern materials and has superkonfiguratsiyu. Aspect ratio at B-787 just over 11, and we have 10. Way and that, and another — a record figure in its class. Here we rely on almost a century of experience building airplanes in Russia and the Soviet Union.

But back to the topic. The task was to get the plane to the level of comfort comparable to the 320th Airbus family. This implies a large diameter fuselage as comfort — this is, above all, the physical size. And thus the level of aerodynamic efficiency level had to be not lower, and even higher than 190 Embraer, which has a diameter less than the fuselage.

And basically it happened.

In fact, we now have a machine whose specific fuselage diameter of about 30% more than the Embraer and more than Bombardier, while we glide higher than the Embraer half a unit (we have about 16.5 at Embraer in District 16), and slightly worse than the CRJ. But that’s because the CRJ fuselage of a small diameter for a large wingspan.

All this has been achieved through our cooperation with the TsAGI. Due to what this has been achieved?
Wing, which we designed together with TsAGI scores of critical profiles are optimized in a special way. For this we used was developed in TsAGI in the 80 years of the special software calculation of flow of the full configuration (ie 3D, taking into account all elements of the airframe). The development of this method is TSAGI since the mid 70’s and perfected by now. This system allows to optimize profiling by any number of sections of the support given by the designer, taking into account a set of requirements, not only aerodynamic, but the layout and technology. Usually the wing, when assembled, is formed when the geometry of the wing, the first place put aerodynamics, the second is the smoothness of geometry, and then it starts to fit the layout. The method that is developed TsAGI, takes into account all of these requirements and at the same time, by varying the weights in the optimization, do this or that claim priority. And another advantage of this method is the optimization of supercritical profile in terms of the time pulling the supercritical wave of the crisis at a given level of Su, ie the reduction due to local control rate of acceleration on the surface profile.

And as a result, we were able to do quite a thick wing thickness on the side of the rib about 15%, moderate sweep and narrow, with an extension of up to 10 units, a record for a regional aircraft class, optimized for flight at Mach = 0.78 … 0.79 in implementation Kmah about 90%.
Simple passenger feels it when the plane climbs easily, easily dispersed at high altitudes up to Mach numbers of 0.8-0.81. Most of the cruise, we carry out at these speeds.

The tricky point, the absence of the wave of the crisis on the surface of the wing and airframe — this means reducing acoustic noise and stress and, of course, the wave resistance. We, together with TsAGI spent a lot of time optimizing the local aerodynamics: the mechanisms flap fairings, fairing wing-body junction, form the nose and tail of the fuselage, wing tips, pylon, etc. All in all we were doing probably about three years. Searches calculations … Regarding the basic geometry we pretty much have changed, for example, have completely redesigned the geometry of fuselage fairing (2006), because they understood that we have the area of supersonic acceleration, and found a very nice solution. Raising his midsection in one area, we have reduced the local flow velocity at the junction of the wing to the fuselage and thus closer to the theoretical maximum aircraft known "among the people", as a rule areas.

That is, you closer to civil aircraft fighter?

More precisely, the optimal high-speed transonic aircraft. But we still have other ideas, which we will develop further. And for that, we will continue to use methods of numerical simulation of flow (Free translation of the Russian term for CFD, Computation of Flow Dynamic). This technique allows visualization of sound and supersonic flow field velocity and pressure flow over the surface of the airframe on a three-dimensional model on a computer screen. It allows you to tenfold increase the amount of research and, most importantly, there is a sense of intuitive understanding of what to do with the layout. And you begin to feel the physics of the process. Previously, flow visualization on the full arrangement was made only in the wind tunnel, and then on short periods of time, or on the flat, ie 2D design models.

For the calculations we use different software products: both domestic and foreign (eg, widespread package Fluent). Using these techniques, in particular, has allowed us to optimize the shape of pylons. It was yet another «Big chall
enge».

The layout purely because of a long nacelle (she’s our plane goes pretty deep in the sand) zone interface MSU, joint nozzle and wing forms a sort of a Laval nozzle. And in order to Mach 0.81 on here do not have the supersonic zones to a maximum operating Mach number = 0.81, we have optimized the shape of the rear pylon in the area of the narrow neck and around her, and so we were able to remove the Mach 0.2 on the local velocity and thereby remove the supersonic and from this zone. Also, in the initial configuration (may remember, it was a bit like the A320) at the head of the fuselage was supersonic jump, and to clean it up, we "ironed" airplane "muzzle". As a result of all the activities on the aircraft when flying at Mach 0.81 supersonic zones we do not only appear in the 0.86-0.88M.

But when it comes to aerodynamics, it is necessary to tell that we have optimized the aerodynamic configuration of aircraft not only by the speed at high values of the Mach numbers, but at high angles of attack, which is the minimum speed. What was done in the interest of safety for our plane.

Current certification requirements, especially in the modern interpretation, simply flip the traditional for our country’s attitude toward the behavior of aircraft at high angles of attack and stall. It is interesting to compare even the Russian and the English term of the condition. That which we call a "stall" in English is called «stall». If we look in the dictionary, we find that the basic meaning of the word — to install, to stop, ie no connection between the stall and fall does not exist. This term means that the speed of the aircraft "set" in its fall and can not decrease more. From the standpoint of aerodynamics, it appears obvious. By increasing the angle of attack, we can only achieve a certain value absolutely maximum lifting force on the wing develops stall such intensity that the vacuum drop in the upper surface of the wing becomes larger than the inlet pressure on the lower surface thereof, ie increase the lift stops. If we take the characteristics obtained for the aircraft model in wind tunnel1, we can easily determine this rate, by the ratio of Su, the wing area and the velocity head.

In terms of flight dynamics, this is not so simple. In case of flow separation on the wing of the aircraft vary sustainability performance and manageability across all channels. In aircraft with swept wings this process is exacerbated by the passage of the flow along the console, which provokes the gap in the end portion of the wing, resulting in stalling the wing was a real scourge of aircraft with swept wings first, and the second generation. Separately it is a loss of directional stability and the consequent movement in the channel yaw plane, also provoking stall the wing, especially for aircraft with swept wings and a positive cross V. This is not a complete list of the problems of flight dynamics, which in many existing (especially old airplanes) can not provide the values obtained in the wind tunnel at the maximum angle of attack flight.

To solve this problem, the whole complex of measures in the formation of aerodynamic configuration, and, as a rule, these measures are mutually contradictory. For example, to improve the aerodynamic qualities necessary to increase the load on the end section of the wing, and the disruption of the flow begins just loaded with more sections. That is, If we are fighting for the quality of blood pressure must be "shipping" section of the terminal, and if for good stall characteristics — that the root. It is important to ensure that a reasonable compromise is not lost in the cruiser, but without spoiling the characteristics of the airplane. Also, do not forget that modern aircraft are not allowed to lose stability and control in icing conditions, but it is a separate big story, especially given our hefty range of CG (width range of 24% of the MAR is a lot, especially for the old Soviet aircraft).

To ensure the necessary level of bearing properties of the wing during takeoff and landing, we have developed and implemented a relatively simple but very effective mechanization of the wing slat and flap odnoschelevogo Fowler. This has allowed us to provide the speed of approach within 140 knots (260 km / h), despite the relatively high wing loading. In addition, the mechanization, by minimizing the number of slots and tilt angles at takeoff, has allowed us to get a supply of local noise 15 EPNLDb relatively ICAO Chapter 3 or 5 EPNLDb relative to the fourth. The corresponding figures in this class now have only V717 (nee MD90) and EMB-190, despite the fact that these aircraft thrust to MTOW is 10% higher than the RRJ-95 and lower wing loading.

Why did we manage to get the angle of the trajectory is not worse than the competition? Due to the fact that mechanization, we have developed, provides a very high level of aerodynamic efficiency during takeoff, and landing configurations, too. The level Sumax (About 2.6 in the landing configuration) is similar to that previously obtained on swept wings only dvuschelevyh flaps. Here, "played" and the extension of the wing and the selected geometry of mechanization.

In order to put our plane on a very short, high-speed aircraft for category C band at 1700 meters (remember, this is the actual length of the path of 1700/1.67 — 450 = 567m), we applied not only high-carbon brakes, but also developed spoilers. We have 3 pairs of the wing sections of the spoilers and 2 pairs of sections of the brake flaps. Because of this, we are on the run presses the plane to the runway very decent negative lift force. As a result of deceleration under braking on the run on a dry runway we got more than an average of 0.42 on run, from touching to stop, and that without the use of reverse thrust! Similar figures we have and with the rejected takeoff. For comparison, the previous generation of aircraft brakes provide deceleration of 0.3, ie more than 30%.

A separate topic of conversation deserves our remote control system, which incorporates the experience of almost all of our aviation industry, including even the "Buran". http://superjet.wikidot.com/wiki:dolotovsky

 

Question: Dear Engineer! With AN-148, in general, more or less clear.
I do not give rest to your words about the superiority of the Erj-190/195. I can not understand by what is this possible?
CF34-10E7 83,7 kN of thrust
SaM146-1s18 — 72,67 kN
The difference is almost 15%! The difference in fuel consumption of 100% load at the first few more. The ratio is approximately: 3120kg / h for CF34 against 3030kg / h However, the selection of the power of 30%, and apparently this is exactly the load on the engine in cruise flight, the difference is compared to values 853kg / h against 856kg / h At idle, with 7% PTO have 313kg / h against 360kg / h
It is regrettable, but we have to recognize the superiority of the characteristics of the U.S. over the Franco-Russian engine.
With all due respect to the Russian engineers aerodynamics, I do not think it was possible to reduce this advantage to create a glider. And given the narrower fuselage Embraer, I think it’s just impossible.
Weight choose this difference also failed. To achieve equality of VSL should be 1.5-2.0 tons lighter.
And time for all about all quite a bit left. Not far off the appearance of a Canadian MRJ engine, and there to remotorization Embraer business can reach. Oh, hard times are coming. In this case, Embraer has already removed all market cream. Optimism is online?

 Igor Sobolev: I can not compare to each other "American" and "Franco-Russian" engines, at the appropriate professional level, to speculate a little about the actual aircraft. Although the desig
ner of the department of general types (like Eugene Kovalenko) would do it competently, but still try. As has been said, the design of aircraft — is a solid ball of compromises, from the overall design (or vysokoplan nizkoplan) and ending with the selection of a huge number of different parameters — passenger capacity, take-off weight, area, extent, narrowing and lengthening of the wing, and lengthening the fuselage midsection, Square shoulder and GO IN, as well as the relation of all these parameters together — thrust-weight ratio, the specific load on the wing, etc. etc. The task of the designer, well, "playing" these parameters to find a "middle ground" to improving one characteristic of the aircraft, not to degrade others.

The aerodynamic characteristics of the aircraft depends on many parameters, and not only the middle section of the fuselage, wing profile or elongation. Of great importance is the choice of this parameter, as the area of the wing, to be exact — the relationship of weight to the aircraft wing area, ie specific load on the wing. After all, the wing not only creates a lifting force required for the flight, but also makes a major contribution to the drag force. If you compare between a TB-3 with Pe-2 or La-5 with I-15, you’ll notice that a faster machines characterized by a high wing loading. This is particularly evident when looking at the "absolutely clean" interceptors like the F-104 or Su-9. The fact that the large wings are only during takeoff and landing to reduce the landing distance, and in cruising GP could be satisfied very tiny wings. "Playing" specific load on the wing, can affect many technical flight characteristics of the aircraft. I propose to compare the sun on this parameter:
AN-158 — Gvzl / Skr = 43700/87.3 = 500.6 kg/m2
SRJ-900 — Gvzl / Skr = 36500/68.6 = 532.1 kg/m2
EmB-190 — Gvzl / Skr = 50300/92.5 = 543.8 kg/m2
SSJ-100 — Gvzl / Skr = 45880/77.0 = 595.8 kg/m2
As you can see, SSJ has the greatest load on the wing among classmates, but thanks to the rest of the layout decisions, we can not afford it, not losing in VPH. Compare the distance run and run:
AN-158 — 1900 / …
SRJ-900 — 1780/1600m
EmB-190 — 1890/1260m
SSJ-100 — 1803 / …
I have already written about the fact that the geometry of the fuselage is very strongly influenced by the distance run and run. In order to get off the ground, the plane had to accelerate to the speed at which the lift-off weight exceeds his. A lift-off speed can reduce or increase the size of the wing, or by using a more efficient (and therefore more complex) of the wing, or creating a large angle of attack. Due to the arrangement number 2 3, SSJ fuselage length of 29.9 m, and y and EmB CRJ (2 +2), with the same capacity, it is 36.2 m As a result, to prevent the tail landing on the runway surface, more competitors limited by the pitch angle at takeoff and landing. And because after lifting the front support and up to separation, the angle of attack of the wing is the pitch angle + angle of the aircraft wing, thanks to the combination of geometrical parameters (length of the fuselage, landing gear, and their relative position), the gap between SSJ going to pitch angles (and attack) 2-3 degrees more than the EmB / CRJ / NA. Due to this, despite the greater the load on the wing, SSJ is not inferior, and vice versa — outperforms the competition in distance run and run.

But, in flight at cruise, a higher specific load on the wing, reducing resistance, fly at high Mach numbers and levels, plus everything — gives a gain in the cost of fuel. I gave a detailed description of these arguments in support of the main thesis is that in the process of designing an airplane, only a long and careful consideration of a large number of different and often conflicting parameters (aerodynamic, geometric, technological, etc.) can achieve in the end defined characteristics.

If I have missed any or nuances in his account, then please correct me Eugene Kovalenko from the point of view of the designer.

As can be seen from the comparison of a single class of aircraft, and the same dimension, the laws of aerodynamics play a very important, but not only these laws, everything is determined. If aircraft designed exclusively "pure" of aerodynamics, we would have seen a section of the fuselage with a pencil and wings of infinite span (there is such a thing in aerodynamics, like an infinite line in geometry). All the same, fiddle in any department plays KB common species, which assembles the car, taking into account the various interests — aerodynamics, engine specialists, businessmen, etc. As a result, it was found they kompomissy it possible to obtain the desired "face" of the liner.

Eugene N. Kovalenko

First, take-off thrust, she was, as ordered in the TK. As regards the SaM-a, on the stand, he and 8 tons showed no problems.
As for the mode of MG, it is not critical. In the initial phase margin stability does not hurt, and then we’ll see. In contrast to the CF34, SaM146 still does not have much experience of operating, so this caution is understandable.
From this somehow does not imply a significant superiority over CF34 SaM146. The SaM146 has fully complied with all the features built into it.

About weight airframe compared to the ERJ-190.

Even RRJ-95LR (about RRJ-95B — say it) — it is easier than any modification of the ERJ-190.
And it is based on actual weights of our LR! Those same three tons, of which there were so many tantrums.
On the ERJ-195 does not make sense to compare — it is a different modification.

By the way, Embraer had the advantage in all versions is not less than ours — and nothing, the world took it without hysteria. And in the LTH almost nothing is lost.

But back to the fuselage. Maybe it will seem strange to people who are on the aerodynamics, but the resistance is determined by the fuselage wetted area of the fuselage and a little envy from his midsection (within reasonable limits).
According to the analysis made in the GHS at the stage of preliminary design, 4-row arrangement is advantageous for the dimension of seats to 70-75 seats above — it is second on the wetted surface of the 5-row layout. And this means inferior to her on the resistance and weight-lifting weight — too. I’m not talking about a high level of comfort 5-row layout, both for passengers and crew.

I do not take in the comparison series aircraft CRJ. They appeared as established on the basis of business jets, which do not need a big trunk. And if America — this is no great loss, then the vast Russian and CIS countries have been cases when the luggage had to send (and send now!) After another aircraft. In other words, again with the new section of the fuselage regionalniki nobody does.

However, the advantage of the wider may be offset losses at its junction with the wing. Cause — as compared with a narrow-body part has a relatively busy wing fuselage — more and correspondingly higher losses in circulation of the wing. In other words, the above inductance.
It took a lot of work of our aerodynamics, together with specialists of TsAGI to minimize these losses by a special geometry ventral fairing. Result — there, glide higher than the Embraer.

As a consequence of all this, RRJ and fuel efficiency is higher than Embraer, although not as good as we would like it. But there is "room to grow."

As you can see, dear FRAM, your initial assumptions are not true, and therefore not true, and your conclusions. I think this — great merit of our opponents are not always honest.

And about the advantages of 5-row layout for the passengers and crew discuss how some other time. I had the opportunity to fly and ERJ-175, and CRJ-200. So there is information for comparison with our car …

I fully support  Igor Alexandrovich. He is right in his argument. After all, an increase in the specific
load on the wing is a way to reduce the total wetted surface and the possibility of flying on a cruiser modes close to the maximum aerodynamics. This is especially important when the ceiling is not limited to aircraft aerodynamics and powered aircraft at these altitudes, and the "ceiling" KSKV or ATC restrictions.

Forgot to add (affects night). Well selected ventral fairing significantly reduces the resistance of the interference of the wing to the fuselage. What is perhaps more important.

You write, "optimism is present!

And that’s the main thing! Good luck to all of you!

Question: "4-row seats arrangement is advantageous for the dimension of 70-75 seats above — it is second on the wetted surface of the 5-row layout. Which means inferior to her on the resistance and weight-lifting weight — too."

To this thesis was understandable — the shorter and thicker fuselage against the long and thin (vs. Sausage Sausages :)) more headroom and less than the length of the beam, which allows you to trim and set the fuselage longitudinal "Wieners" thinner and, accordingly, it is easier. It’s a simple sopromat. In "sardelke" is more effective naddutaya paneling. It’s a simple stoymeh. It is time.

Short fuselage pozvolyatet have shorter chassis and therefore more easy assembly while maintaining the same contact the tail of the fifth (if any :)), or if equal to the "sausage" can improve the adjustment gear TOLC1 due to the large angle of separation. This two. http://superjet.wikidot.com/wiki:wing-load

 

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