Superjet 100 LR – logical refinement
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From the very start of Russian Regional Jet (RRJ) project (now known as Sukhoi Superjet 100 (SSJ100)) in 2011 it was much sought after by mass media and was the subject of wide speculation among the members of aviation community.

The interest in the project is understandable and primarily can be attributed to the high priority of the project set by the government and its significant state and financial support. In spite of the fact that Superjet was dominating the press lately, journalists have undeservingly overlooked one big event. This refers to completion of the assembly of the first Superjet 100-95LR (hereafter referred to as LR) and start of its flight testing. The LR suffix stands for Long Range. I would like to admit that SSJ 100 LR is the logical refinement of the project.

Indeed, the increase of the jet’s maximum take-off weight by 3.57 tons while (as experts assured) keeping the same weight of the airplane affords an opportunity to take more fuel and significantly increase the aircraft’s range (over 4000 km with a full payload). It’s worth noting that according to some authors the payload/range capability is not the strong point of the jet’s Basic version. In late February I had an opportunity to have a conversation with a high-skilled specialist, who was taking part in development of LR version. We have tried to put aside the matters related to the quality of project management and problems connected with the jet’s initial operation by Aeroflot and devoted the most part of the conversation to advantages of the LR version. First of all, he told me about the status of this work:

— The first prototype of Sukhoi Superjet 100-95LR (95032) performed its maiden flight on February, 12th 2013. It was delivered to Zhukovsky on February, 15th. The vehicle has arrived at Gromov Flight Research Institute in accordance with the schedule of preparation for the flight testing. At present it is undergoing preparation for supplementary certification testing, which precedes delivery of the aircraft to the customer. Currently the vehicle is able to undergo tests with a weight of 45.88 tons (this is the weight of certified Basic version). The supplementary certification testing is required in order to confirm the possibility of operating the jet with a maximum take-off weight of 49.45 tons, which is one of the key differences between LR and B (Basic) versions.

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The jet will have the same appearance as the previous version. Its wing has been strengthened and its take-off weight has been increased, however, the jet’s aerodynamics remained the same. In future all the vehicles will have the same design. This also refers to landing gear – the same one installed on the Basic version. The capacity of fuel tanks has also remained the same – 12690 kg of kerosene (density - 0,803).

— There was a report saying that LR will possibly be fitted with winglets. Is it so?

— No. The implementation of winglets is being discussed separately; this matter is not connected with LR. Both LR and B versions may offer winglets as an option. Of course LR (especially the business aviation version) will benefit the most from installation of winglets because of the jet’s range.

- The jet will be powered by SaM146 engine?

- The LR version will be powered by higher trust version of the engine. In fact it is the same engine, but its take-off thrust will be increased by 5%.

- A representative of NPO Saturn said at Dvigateli 2012 show that the guaranteed life of SaM146 engine is 2500 cycles. Has this figure changed ever since?

- The engine manufacturers sign contracts on warranty maintenance of the engines directly with the airlines.

- Can you, please, compare Superjet with Bombardier CSeries?

- Even if we consider the smallest member of CSeries Family - CS100 with a take-off weight of 58 tons and a capacity of 110 seats, we may see that the Canadian aircraft is larger. It is not a rival for Superjet. Our jet may accommodate 98 passengers in a single-class configuration with a seat pitch of 32 inches. The Basic and LR versions have the same cabin. In one word, CSeries is larger and has higher take-off weight, it has longer range and higher capacity.

- How much is the difference between the fuel flow rate claimed by the Canadian airframer – 1.8 tons, and the same indicator of Superjet?

- It’s not much. At present we have a fuel flow rate of about 1.75 tons.

- According to the Transport Clearing House the average fuel flow rate of Aeroflot’s SSJ100B fleet was 2296 kg per hour in 2011. However, the figures provided by the source essentially differ upward from the parameters claimed by the manufacturers (in particular, the fuel flow rate of Tu-204 is 3688 kg, while the airframer specified 3180 kg). Can you give a comment on the matter?

- According to our calculations, if we divide the amount of consumed fuel by the flight time we will obtain about 1,75 - 1,8 tons. As for 2.2 tons – I can’t even imagine where these figures come from!

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- Managers of Bombardier provided data related to the fuel flow rate of the following regional aircraft: CRJ700 - 1,45 tons, CRJ900 - 1,6 tons, CRJ1000 - 1,74 tons per hour. Share your thoughts with us, please.

- If this refers to the cruising flight at the design altitude alone than we have almost the same figure as the one specified for CRJ1000. I would rather compare our jet to our closest rival - Embraer E-190. Superjet’s fuel flow rate is lower by 2% as compared to E-190. E-190 has a fuel flow rate of about 1.8 tons, more precisely - 1,782. In comparison with E-190 our average block-fuel consumption is lower by 2% and it is even lower at cruise. The block-fuel includes taxiing, takeoff and landing approach.

- It is planned to increase the annual output of Komsomolsk-on-Amur Aviation Plant to 60 SSJs. How many Superjet LR aircraft will be manufactured annually? What will the price of LR version be?

- You’d better ask marketing specialists responsible for elaboration of commercial proposals about the prices of B and LR versions. The output will depend on the customers. By the way we already have some customers. We must deliver the first jet to Gazpromavia in 2013.

- You are talking about the jet ferried to Zhukovsky?

- No, the airline will take delivery of the next aircraft. The above-mentioned vehicle will remain with us and will be used for winglets testing. It is a special jet, because it is the first one with the strengthened wing intended for increased take-off weight. That is why it will be used for further testing".

- Will the weight of the airframe increase for LR version?

- Yes, it will. But we have a weight-saving program, which must compensate the increase of LR’s weight. At present the program is being implemented. And this refers not only to airframe, we are also studying the weight of different aircraft systems supplied by Russian and foreign companies.

- The wing area will remain at 84 square meters?

- All the geometry, including wing, will remain the same. The fact is that the design has been certified and we cannot modify it. If we make any changes, than these are “major changes”. For example, now we are increasing take-off weight and strengthening the wing without changing materials – these are also “major changes”. As a result the supplemental type certificate is required.

-You are talking about the certification by AR IAC, and what about EASA?

- The same procedure. First we receive supplemental type certificate from AR IAC and then it will be validated by EASA.

- Can EASA ask to perform additional flights and tests?

- Yes, it can. At first we provide the same documentation for validation. We will submit the results of flights, take-off and landing characteristics and the results of structural tests. We do not expect anything extraordinary from EASA.

- But EASA may ask you to perform additional flights in case its inspector will have any doubts or consider the submitted data to be insufficient.

- Yes, it’s possible. Generally they may ask to perform additional tests at their site.

- It is most likely that you will perform all the required flights in Russia, receive the supplemental type certificate and then apply to EASA?

- Yes. We will deliver the first LRs to Russian customers and so we need to obtain the permission of our national aviation authorities first. And then we may start working with international organizations.

- It was reported that the first LR will be delivered in 2014…

- No, we must deliver the first jet in 2013.

- Can you pull it off?

- Yes, we can! The assembly of first jet intended for the customer (95033) and preparation for the testing of first prototype have already been started despite the fact that the start of this work was scheduled for March. We are working on aircraft performance in March and April, and then – on noise footprint in April and May. We must complete the elaboration of test report in late May and receive the supplemental type certificate by MAKS-2013.

- When will the prototype with an increased take-off weight start performing flights?

- We believe that it will start performing flights in April or May.

- According to the information available, the total weight of the composite elements of the airframe is about 1 ton. Will the share of composite components be increased?

- The following components of Superjet are made of composites: high-lift devices, rudder and elevator, aerodynamic fairing of wing-to-fuselage joint and landing gear doors. In addition, there are some radar-transparent fairings. As for the share of composites… The share of airframe in the total operational empty weight is about 80%. About half of this weight is accounted for equipment – engines, aircraft systems. And only a part of this half may be accounted for composites. However, some components of the powerplant are also made of composites. The case is that engine nacelle is a part of the powerplant and the nacelles are made of composites. The increase of shares of composite components will require a great amount of certification testing.

- As far as I remember, there were reports in 2011 about a program for decreasing the fuel burn of SaM146 engine by 4% and the weight of the powerplant. Several billion roubles have been allocated from the federal budget for implementation of the program and for expansion of Saturn’s production facilities. Have the engine manufacturer managed to succeed?

- First of all let’s clear up the details: Russian-French joint-venture PowerJet is responsible for SaM146 engine. The program for reduction of the engine weight is being implemented in accordance with the schedule. During the regular meeting the engine manufacturers have confirmed the parameters related to weight reduction planned for 2012 – the goals have been achieved. At present they have presented the work program for 2013-2015. The serial engines meet the requirements of performance specification in terms of specific fuel consumption. Everything is under control. First of all, every engine undergoes its own acceptance testing at the manufacturer’s site; its thrust is calibrated and its rating curve is obtained. After acceptance the engine is delivered to Komsomolsk-on-Amur plant and we measure the fuel burn of the aircraft in the network of acceptance testing program. We assess the engine’s propulsion performance and rating curve in accordance with the agreed procedure. Then we confirm that the assembled and installed powerplant meets the requirements of performance specification. At present we have no issues with the engine manufacturer in terms of fuel burn; all the engines meet the specification.

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There are test engines installed on the aircraft prototypes – they have a higher fuel burn. And the much-debated excessive fuel burn was registered on these prototypes. First of all this is due to usage of experimental engines – they have been equipped with an instrumentation package (some elements were installed in the air flow duct). Moreover, these engines have been used for high-angle-of-attack-angle tests and evaluation of runway performance. During these tests over 100 engine cutoffs have been performed with subsequent switch to the takeoff mode. Therefore by the start of evaluation of the rating curve these engines had a flying time in cycles equivalent to 5 or maybe even 10 years of operation. All the serial engines powering the delivered aircraft have the same rating curve and their parameters are much better as compared to the test engines.

- Which airlines besides Gazpromavia are expecting the delivery of LR?

- Interjet (Mexico), which will soon start taking deliveries from Superjet International, will not acquire LR for sure, because it makes no sense for the carrier. The airline is operating its fleet under conditions of high-altitude and hot climate. The parameters of the powerplant during take-off from the airports of Mexico City and Toluca allow the all-up weight of less than 46 tons. In other words, Interjet will operate only Basic version of the jet. Comlux (Switzerland) is the launch customer of Sukhoi Business Jet (SBJ) derived from LR. Possibly, the jet number 95032, which will start undergoing tests soon, will be fitted with the VIP cabin. The next aircraft number 95033 is intended for Gazpromavia. The case is that the aircraft must be fitted with the interior and seats, its systems must be checked and the jet must be painted prior to the delivery. These works usually take a total of 2-3 months. The test aircraft ferried to Zhukovsky is the so-called “green” aircraft without interior. While the aircraft number 95033 will be originally fitted with the interior.

- Besides strengthening the airframe, will any systems of LR be modified?

- Negative: all the basic systems will remain the same without any changes. In theory, the materials used in the interior solutions may be replaced in order to reduce the weight. The corresponding work is under way. This work is connected with the change of a supplier of seats; new seats should be lighter than the ones installed in the Aeroflot’s aircraft. We stick to the concept of high comfort. Our seats are lighter and we have also specified requirements in the area of passenger comfort. The seats made by B/E Aerospace are old but they have been modified for SSJ100. The width of the seat, dimensions of pillows and other details have been discussed. Actually the weight of existing seats may also be reduced; such versions of the seats already exist. In particular, one Russian airline has ordered the modified seats.

- When you approach Superjet it seems like it resembles Airbus aircraft in some way: both jets have the same livery and great appearance. But you see the difference once you enter the jet’s cabin. Why does Superjet have so depressing grey interior? There are no air cooling valves with individual adjustments. The seats seem to be borrowed from the 20-years old Boeing aircraft: the trimming is made of dark-blue fabrics and the pillows seem to be worn-out. Other aircraft of the airline are equipped with advanced leather seats by Rеcaro (earlier - Aeroseat), and only Superjets are fitted with seats by B/E Aerospace …

- I disagree. I have to travel a lot by aircraft and I assure you that many carriers have even worse seats. Aeroflot ordered the trimming made of fabrics for Superjets, while its Airbus aircraft are fitted with leather seats. We use the colour scheme and materials ordered by Aeroflot. You also noted that there are no air cooling valves with individual adjustments for each passenger. Yakutia’s SSJs are equipped with this feature. Aeroflot’s jets will also have this option in «Aeroflot Full» configuration. The absence of the feature on the jets in «Aeroflot Lite» configuration is the decision of the carrier. Individual air conditioning is the option assuming installation of the special valve on the overhead panel above the passenger’s head. The configuration of pipelines does not depend on the option – the air is flowing through the panels anyway. All the serial jets have the same configuration of air-pressure lines, the admission of the air to the valves exists and installation of the valves is included in the list of available options. One carrier has ordered the option, while another one has not.

- The range of LR is nearing Airbus A320 and Boeing 737NG. Will LR be able to find customers at US market? Will it be able to perform flights from US East Coast to the West coast?

- First of all let’s talk about range. The LR has a range of 4,1-4,5 thousand kilometres (2213-2429 nautical miles) depending on the cabin configuration and options. The range of the aircraft seating 98 passengers is 4100 km. If we take a detailed look at the US East-West coast flights, we will see that the required range is over 3000 nautical miles or over 5560 km. Airbus A319 and Boeing 737-700HGW/900ER have a range of 3200 nautical miles and more (with a full payload), thus these jets are able to perform flights from US East Coast to West coast. However, there is no point in having such range for our jet, because it is intended for increasing frequencies on short-haul and medium-haul routes. The same work was being performed by Yak-42 and Tu-134 aircraft in USSR. We are glad to note that Aeroflot started to operate its Superjets correctly this year. And the results are evident. Recently Aeroflot reported about the increase of passenger traffic. If we take a look at the statistics, we will see that among other things the growth of passenger traffic is caused by operating Superjets on short-haul routes, which have been ineffective before. The good trends and dynamic growth was recorded on many routes. At first they use Superjet for 2 or 3 months on such a route and passengers get used to the regular flight performed by Aeroflot on the route. The flight satisfies them in terms of price and quality of service. The passenger traffic increases. For example, at first only 35-40 tickets were sold, 2 or 3 months later – 50-60 tickets and later they start operating A319 or A320 aircraft on the route, because the passenger traffic has increased significantly and there are enough passengers for single-aisle jet. Our aircraft performs evening and night flights often in order to maintain the flight frequency. So, the jet intended for maintaining the flight frequencies does not require the range, which allows performing "coast to coast" flights.

- Which airlines will benefit the most from operating LR instead of SSJ100-95B?

- It is a great question for marketing specialists! I believe that the airlines having routes with a length of over 3000 km will benefit. And the carriers having high capacity aircraft, if the passenger load factor varies from season to season significantly. Sometimes representatives of such airlines talk about “winter aircraft” or “out-of-season aircraft”. It is best to use Superjet for increasing flight frequencies during peak season and for optimization of route network and costs during off-season period. The route network of Gazpromavia includes over 400 destinations and LR makes sense for this carrier.

- Speaking of Moscow airlines, which flights will they be able to perform using SSJ100-95LR?

- Taking into account the jet’s payload-range capabilities, it covers the whole Europe and almost half of Asia. In fact many popular routes may be serviced by the Basic version. As for flights to Europe, Armavia performed flights from Yerevan to Barcelona with 50 or 60 passengers on-board; the length of this route is about 3550 km. Maximum duration of flight performed by Armavia’s Superjet was 5 hours 50 minutes. Besides Barcelona, Armavia performed flights to Marseille and Madrid, however, the payload was not full because of the demand. Of course, LR will look better on flights to the Eastern part of our country: the flight distance to Novosibirsk is about 3000 km and to Krasnoyarsk — 3350 km. We are talking about flights with a full payload. If the payload is lower, LR may even perform flights to Irkutsk (4200 km). One of the state customer’s requirements is performance of flight to Irkutsk with 20 passengers on-board. We must implement the corresponding contract over the next two years and deliver the aircraft. It turns out that the jet having a take-off weight of 45.88 tons meets this requirement, in other words, the Basic version also meets the customer’s requirement. However, the take-off weight is not so important. The major restriction is the volume of fuel tanks. SBJ aircraft derived from SSJ100-95LR will be equipped with additional fuel tanks located in the cargo compartments and its range will be over 7000 km. This is the requirement of SBJ’s launch customer — Comlux: they want to perform flights from Paris to USA.

- There were some reports about upgraded Flight Management System (FMS), when will Sukhoi start installing it on serial jets?

- The first jet in «Aeroflot Full» configuration equipped with upgraded FMS will be delivered to the customer in April. Generally every new version of avionics includes a number of updates. And our avionics is manufactured using state-of-the-art Integrated Module Avionics technology (IMA). It has an open architecture and it is upgraded easily, including FMS. Every new version includes some additional functions of FMS. The changes are divided into packages. The software on already operated jets is replaced in accordance with a service bulletin. The implementation of service bulletins is a common practice. This is the operator’s responsibility. It assumes carrying out some work, for example, replacement of parts or software, and involvement of specialists carrying out this work. This is up to the airline: a service bulletin is not mandatory in terms of flight safety. However, it stands to mention that there are some mandatory bulletins. These are bulletins issued in the network of new airworthiness directives or bulletins aimed at provision of service life. And there are also optional bulletins aimed at improvement of the design.

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- Airbus А380 aircraft owned by Singapore Airlines are fitted with light composite seats made by Kanagawa (Japan) providing significant weight reduction. Are you interested in such solutions? How many companies are manufacturing such seats?

- There are several manufacturers of light seats at the global market, but their products are rather expensive. With regard to SSJ100 a kit of 100 composite seats may reduce the jet’s weight by 400 kg. Materials used during manufacturing of the seat’s frame, pillows and trimming influence the total weight of the seats. Leather seats are heavier than the ones trimmed with fabrics, but they are more durable. For example, Armavia ordered leather seats, which were heavier than the ones ordered by Aeroflot. Additional options like pouches and folding tables also influence the total weight. You may reduce the weight of every seat by optimizing all these things. If the seat does not have a folding back then its weight will decrease by 1 kg.

The key problem of companies offering the seats is customization of them for each aircraft type. It depends on the seat layout and distance between the rails intended for installation of the seat. Even a standard block of three seats is installed in different ways on different aircraft. You need to carry out tests, including qualification tests. The manufacturer of the seats is responsible for this and the tests are carried out using rails provided by the customer. We deliver our rails to B/E Aerospace (the serial jets are equipped with B/E Aerospace seats). If we find another supplier – we will deliver the rails to them for carrying out overload tests (with an overload of 16g). The aviation authorities demand that the seat must withstand the overload of 16g and stay in place. The tests are required in order to prove the conformity to this requirement. The customer pays for customization of the seats for his aircraft type. You must pay twice: for qualification testing and for purchased seats. These are additional costs and not a lot of customers are ready to bear them.

- It is known that Interjet ordered the jets fitted with an Italian interior and seats by Pininfarina. Why did they abandon B/E Aerospace products?

- I’d rather not discuss the choice of the airline and criticize the products of our suppliers. But I must admit that Pininfarina is only responsible for design of interior and development of seats; Alenia Aermacchi is the manufacturer. It cooperates with different enterprises, which supply components and parts.

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- Vedomosti reported earlier with reference to Aeroflot that the fuel burn of Superjet is higher than the specified value. How does that fact influence the competitive capability of the jet?

- The matter of defining the competitive capability may only be discussed as a whole. There are aircraft, which have better fuel burn but lower sales. For example, Boeing 737 Classic. It has lower fuel burn than 737 Next Generation (by several percent) and Airbus А320. But the jet is not in demand and its production has been ceased. I can give another example connecting the competitive capability with the fuel burn. The fuel burn of CRJ aircraft is much lower as compared to E-jets, but the demand for Canadian jets is lower. And now mass-media reports that Superjet has high fuel burn…By the way, our closest rival – Embraer E-190 has a higher fuel burn.

- What are other advantages of SSJ100 over E-190?

- First of all – comfortable cabin. We believe that this factor helped Embraer gain advantage over Bombardier and now we are using the same factor to gain advantage over Embraer. Since I have to perform a lot of business trips I can compare the liners. Some flights are performed by CRJ/BAe-146/E-jet. My personal opinion: CRJ 700/900 and Embraer E-190/195 are viewed by the passengers as an “overgrown regional aircraft”. The centre aisle separates two blocks of seats (two seats in each block), the jets have low cabin roof and low level of overhead bins. All these things leave an impression of a “regional aircraft”, however, the capacity of E-195 is close to the single-aisle liners. But the cabin of E-195 does not come near the cabin of Airbus A320 or Boeing 737. And the Superjet is often compared with these liners, especially A320. This comparison may seem strange, but it comes naturally from the passengers! You can’t say the same about CRJ or E-jets.

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But let’s continue discussing the advantages of SSJ over E-jet. Superjet has lower noise level than Embraer, one of the lowest ones in its class. However, the claimed noise levels of Superjet and Embraer aircraft are the same, because we have carried out tests using the base model in order to meet the completion dates. We have claimed a reasonable and conservative noise level, which granted us the comfortable completion of certification tests. We hope that our parameters will be “improved” during testing of LR. In spite of increasing the take-off weight, the noise footprint will remain the same: the uprated engine allows raising the climb path after separation from the runway.

Our overhead bins are larger. Our passengers do not complain about problems with placing their cabin baggage. Embraer in its own turn stated that a standard suitcase, classified as the cabin baggage, fits in the overhead bin. Indeed, some leather and textile suitcases fit in their overhead bin, but the “standard” metal ones often do not fit and leave the lid open!

Our jet also has more spacious baggage compartment as compared to Embraer. We have a very high specific volume of the baggage compartment per seat. Spacious baggage compartment leaves open the possibility of earning additional money by transporting additional cargo. The loaders have no problems working in the baggage compartment of our jet.

The aircraft’s degree of automation is very high. Its equipment has almost the same functions as the one installed on advanced long-haul aircraft. As for the functions intended for provision of flight safety, we are on the same level as Airbus A380 and Boeing 787. Embraer declared that the avionics and control system will be replaced in the network of upgrading program. We believe that this fact is another testament to our dominance. In the press-release issued by Embraer there is a term "Open loop fly-by-wire system". After reading this we laughed hard, because this term with regard to a system without mechanical backup system means the disconnected command loop! That was funny.

We remind you that the first certified fly-by-wire system without mechanical backup system is the one installed on the Superjet. Of course we have a side stick, which will not be used even on upgraded E-jets. They want to keep the type-rating for the pilots; that is why they will continue using the control wheel. Trying to keep the type-rating, the specialists of Embraer say that they will significantly upgrade the FMS. They want to switch to the fully-digital fly-by-wire system without mechanical backup system. The functionality of the new system remains to be seen. I think that they will try to catch up with us. The SSJ100’s fly-by-wire system is even more advanced than the one installed on А380. We will keep this high level and increase it during further development of our aircraft.

- Do you see any advantages in terms of the powerplant?

- At present SaM146 is in fact the best engine in its class. It demonstrates great rating curve in spite of having a moderate bypass ratio. The jet and its engine are optimized for cruise flight at speeds of about 0,78 Mach. At that SaM146 has much lower Mach sensitivity than some engines with higher bypass ratio. Thrust is the sum of input and output pulse. The diameter of SaM146 is smaller than the diameter of engines with bypass ration of 5 or 6 (CFM-56) or 6-7 (large engines manufactured by CFM International), that is why the impact of the input pulse on the engine’s thrust is lower. In fact the impact of Mach number is also lower. This fact provides advantage in terms of climb rate. Superjet demonstrates great climbing performance at speeds and altitudes close to the cruise mode. It is better than the parameters demonstrated by aircraft powered with engines with higher bypass ratio.

- Can LR with a full payload climb straight to 12 km?

- We have a straight climb path without any horizontal sections. Our jet always climbs to its recommended ceiling at temperatures up to +15 Celsius degrees. However, 12 km is not the optimal altitude for the jet - it is too high for LR with a full payload! There is a term: flight in accordance with corrected weight. The weight is equilibrated to pressure. Corrected weight is the weight equilibrated to conditions of flight at zero altitude with a lift force coefficient Cy corresponding to the optimal consumption per kilometre. The first case: the thrust of two engines is sufficient for climbing to the altitude corresponding to the optimal fuel burn. The second case – the thrust is insufficient, then you have to make a “horizontal section” and after that continue climbing.

- Sometimes in different data sheets the cruise speed of SSJ100 varies from 0,78, to 0,81-0,82 Mach. Which value is correct?

- The maximum cruise speed is М=0,81, and the optimum cruise speed is М=0,78. Superjet is optimized for cruising at the speed of М=0,78 and altitude of 11km. This is the design point for us and engine manufacturer. We are talking about long range cruise. And there is also the maximum speed cruise (the corresponding Mach is М=0,81). Since the jet has a high-speed high-aspect-ratio wing we may switch from М=0,78 to М=0,81 with a slight increase of fuel consumption per kilometre. In fact it is another advantage over E-jet. Our aerodynamic configuration is well-optimized, that is why Superjet’s sensitivity to change of flight modes with respect to the design point is lower. The change of cruising level by 1524-1829 meters causes the increase of fuel burn by less than 3%. As for Embraer, the same change of the cruising level causes the increase of fuel burn by half. That’s because the Brazilian jet is powered by CF34-10 engines with a high bypass ratio and it also has a very large wing. Important nuance: TsAGI has optimized the wing for us, while the wing of E-jet was designed by the specialists of Embraer (to be more exact they cooperated with TsAGI and performed tests in TsAGI’s wind tunnels). As a result we have a wing airfoil intended for higher speed. You may trace it using documents like Airport Planning Manual. As for E-190, the line with a speed of М=0,78 is separated from the line called «Optimum Mach», and the М=0,81 line is located below. In case of SSJ the «Optimum Mach» and M=0,78 lines are in close agreement and M=0,81 line gives a slight change of range (taking into account the fuel reserves, we may say that the range remains almost the same).

One day I saw an article containing information on block-fuel consumption of different aircraft. I was surprised by the values specified for Е- 190: the jet’s block-fuel consumption was 3100 kg (+15% as compared to SSJ) with a range of 926,5 km, while the larger A319 had the block-fuel consumption of 3300 kg. I found out that these are the average indicators provided by the airlines and obtained during real flights. This information reflects the problem of Embraer – flight operations officers often navigate the regional aircraft to lower flight levels. They are navigated to FL330, FL320 (the flight altitude is 10058 meters and 9753 meters respectively). It happens so that the pilot is late to climb to the cruise altitude or there is a transition between air traffic control areas. It is increasing the fuel burn of E-190 significantly. The optimal echelons for E-190 and SSJ 100 (in terms of fuel savings) are FL390 and FL370 (11847 m and 11227 m). Due to non-optimized wing and the wing aerofoil intended for lower speeds the decrease of flight altitude by 914-1524 meters dramatically increases the fuel burn of E-190. The same story was with Yak-42. It has even larger wing. Aeroflot’s crews performing domestic flights often get lower echelons. But it is not so important for Superjet because the decrease of flight altitude does not make so significant impact on the jet’s fuel burn due to the aircraft’s successful aerodynamic configuration.

Vladimir Karnozov

27 Dec 2013 21:14


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