Boeing 787 update and CO2 emissions perspective
(All statements, models and assessments represent the independent opinions and analyses of Lissys. They do not imply any connection with, or approval by the manufacturer or any other organisation.)
An early Piano analysis of the Boeing 787 Dreamliner was given here in 2005 and noted the challenging nature of some targets. In 2008 the first adjustable Piano-X model of the B787 was publicly released here.
Lissys is now making its updated (2011) assessment available as a free download. This model is intended to represent near-EIS (entry into service) levels of performance for the Boeing 787-8 at its increased certification MTOW (502.5k lb). It does not reflect the status of early deliveries to ANA. A free model of the Boeing 767-300ERW is also released in parallel.
As with all Piano-X models, various adjustments are accessible to the user. A default OEW of 266.3k lb is given as a typical operator's empty weight for the B787-8. There has been no obvious necessity, in generating this model with Piano-5, to disturb structural weight factors from settings that yield satisfactory statistical OEW correlations for primarily aluminium aircraft.
For a typical mission carrying 22 metric tonnes over 5000 nm (roughly HND-FRA), the block fuel burn of the B787-8 is calculated to be 50.1 tonnes. This compares to 50.7 tonnes for the B767-300ERW based on nominal performance (no in-service deterioration) and common reserve-rule assumptions that can be accessed via the models. Plots of fuel burn as a function of distance and payload are given below at the same transparent conditions.
Press releases and articles have regularly stated that the Boeing 787 is "20% more fuel efficient than similarly sized airplanes". It is still appropriate to mention that the B787 typically cruises at Mach 0.85 compared to Mach 0.80 for the 767 and provides a wider cabin, higher levels of comfort and pressurisation, and a longer range potential. Manufacturing and maintenance benefits are also claimed. Finally, the B767-300ERW represents a relatively recent version of a mature, well-understood design with fully exploited structural margins.
Comprehensive performance tabulations for the two aircraft can be generated as necessary by running the Piano-X files. Any comments on the accuracy of the model by manufacturer or operators if supplied with all assumptions relevant to comparisons will be appended to Piano-X releases on request.
This reassessment is confined to one aircraft type. Nonetheless, it invites some inferences that are relevant to the ongoing process of defining regulatory standards for CO2 emissions. Specifically:
The need for a common reference and certification tool capable of transparent quantitative comparisons in a public arena;
The need to develop adjustable models that can track the evolution of a design from early claims through to EIS and beyond to maturity;
And the need to account for the complex consequences of technological choices and strategic aircraft-sizing decisions by examining wide-ranging mission scenarios.
The last point in particular precludes the adoption of simplistic CO2 standards based on single-point measurements that summarily dismiss the diversity of payload-distance regimes over which disparate aircraft types compete. In the opinion of Lissys, any coarse CO2 certification measures that suppress these effects will inevitably invite systemic gaming pressures with unpredictable repercussions for both industrial competitiveness and actual global emissions.
The B787-8 is used by ANA in domestic and regional service over distances of 300 to 1200 nm (HND-OKJ, HND-PEK). Such usage is ill-matched to intrinsic design-sizing considerations for this aircraft. For example, when carrying 25 tonnes over 1000 nm the B787-8 burns approximately 10.6 tonnes of fuel (and more for early deliveries with acknowledged performance shortfalls). In contrast, a B757-300W is better sized to carry the same payload over the same distance, burning merely 8.6 tonnes despite its senescence, albeit at economy-class comfort levels (no deterioration, best engine option). The B767-300ERW burns 10.3 tonnes under the same circumstances. The factual significance and operational reality of such (counter-expectational) mission-specific fuel burns can appear negated or reversed through contrived definitions of efficiency metrics based on point conditions.
If you have used Piano-X before, you can click here to download the B787-8 and B767-300ERW models. Extract the individual files from the zip file and drag them into your existing 'pianox-planes' folder, then restart Piano-X.
Piano-X models constitute the best estimates of Lissys and are not endorsed in any way by the manufacturer or operators. Information from publicly-released Piano-X models can be distributed or published freely provided full credit is given to Piano, but may not be sold or used for purposes of commercial gain or reward. It must not be incorporated in any other software, carbon calculator or database without the explicit written permission of Lissys.