IRKUT MC-21 analysis, Part 2

Transcription

1 IRKUT MC-21 analysis, Part 2 By Bjorn Fehrm Introduction Feb. 24, 2016,. Leeham Co: Two weeks ago we started our analysis of the new Russian single aisle aircraft, United Aircraft s Irkut MC-21. We looked at key design features and compared these to the Airbus A320. We also analyzed the passenger capacity where we found that the model which will start flight testing, the MC , has a capacity between the A320 and the A321. The closest aircraft in capacity and performance in the MC-21 lineup versus the competition would be the MC and A320neo. We have therefore decided to do our efficiency analysis between these variants. Summary: The MC-21 has a wider fuselage than the A320. This is a positive as it allows passengers to pass each other in the aisle of the cabin. The drawback of the wider fuselage is a bit higher aircraft drag. Coupled with a lower wing aspect ratio, the lighter MC-21 cannot open a fuel consumption advantage over the A320neo, despite being a more modern design. Discussion In the initial analysis we found that the MC-21 is no copy of an existing Western aircraft. It has chosen its own technical solutions. The fuselage has a slightly larger cross section than the A320, something that allows a wider aisle, Figure 1.

2 Figure 1. MC-21 cross section with standard economy seating. Source: Leeham Co. Irkut has aimed for an aisle where passengers can pass each other and squeeze past a serving trolley. With equal seating width, the aisle will be 24 inches wide instead of the normal 19 inches. The area of the cabin that seems less well thought out is the emergency exit concept. In the seat capacity between 140 to 180 passengers, the preferred exit configuration has converged towards two entry/exit door pairs front and rear, complemented with single or double overwing exits dependent on passenger capacity. The design drawings of the MC and -300 show that the -200 will be a three door pair layout with the second door pair behind the wing and that the -300 variant introduces a fourth door pair ahead of the wing. It might be that the certification authorities and airlines that participate in the development of the MC-21 prefer such configurations. Emergency exit configurations which allow the higher seating densities now being introduced for Western aircraft is something that can be introduced later in the project.

3 We don t have the empty weights for the MC-21 variants. We therefore let our aircraft model estimate the likely empty weights based on aircraft dimensions and construction principles, Figure 2.

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5 Figure 2. Data and efficiency for A320neo and MC-21. Source: Leeham Co. With the MC-21 dimensions, wetted areas/weights and the data for the Pratt & Whitney engine, it is possible to make a first estimate of the fuel consumption for the MC-21. It consumes fuel in the same ballpark as an A320neo. The difference of 0.8% one can ignore, the modeling is done with estimated data for several parameters. How come that the more modern aircraft does not have an advantage over the older A320neo? The aircraft share the same engine, in this case, the Pratt & Whitney GTF 1100G series, so there is no difference there. The MC-21 is somewhat lighter but the A320neo wing has a higher aspect ratio thanks to its sharklets. Further, the larger fuselage diameter of the MC-21 results in higher fuselage pressure drag. With the dominant drag, which is generated by the aircraft s wetted areas, being practically the same, the similarity in the aircraft s fuel consumption is not surprising. We have not tried to go further and compare the Cash Operating Costs of the aircraft. Too little is known about things like MC-21 maintenance concept and support network to make that possible. Next step In the next article, we will take a deeper look at the Aviadvigatel PD-14. The PD-14 will be an alternative engine to the Pratt & Whitney PW1128G for the MC-21. The PD-14 is the first new Russian turbofan in over 30 years. A number of turbofan technologies that previously were shared inside the Soviet Union, and especially with Ukraine, now have been re-developed inside the Russian Federation. The PD-14 is therefore a very important project for the rebirth of the Russian aeronautical industry.