I have trawled back through the airliners.net archives to find a Northwest article on their selection of the A330.
All in all it's a very interesting article....
It does much to dispel the misguided "always go for the biggest, heaviest, longest-range" sentiment that pervades airliners.net discussions about fleet choice.
Perspective on NW's Recent Selection of the A330 of 777
By Tim Campbell, Managing Director- Performance Analysis
From On Course, Northwest Flight Operations Magazine May/June 2001
The January February issue of On Course contained an article by Capt. Jeff Carlson that outlined the details of Northwest's multibillion-dollar investment in new aircraft. A large component of this order includes 24 PW4168A-powered A330-300s. Numerous questions have arisen since the announcement of this order, specifically why the A330 was selected instead of the 777.
This article will address these questions by summarising our assessment of the performance characteristics of the A330 relative to the 777 and how this information was used in the final evaluation of these two aircraft.
The competition between the 777 and A330 was for a new aircraft that would replace our DC-10-30s on dedicated transatlantic missions.
Perhaps the most important performance-related aspect of this aircraft evaluation was finding the best match between aircraft payload-range capability and forecasted payload demand. We were seeking an aircraft that efficiently meets our projected requirements. As shown in the graphs, the A330 most optimally meets our payload requirements in the Atlantic. This payload capability, when coupled with operating costs and projected market requirements (demand) for both passenger and cargo traffic, offers the highest earnings potential.
The match between capability and market requirements is important because it is inefficient to operate aircraft with excess capability. Our evaluation clearly shows that the 777-200ER aircraft has significantly more payload-range capability than the A330-300.
The additional range capability could be helpful if the same aircraft were also flown across the Pacific. However this possible dual mission capability was determined to be impractical because Pacific aircraft require a much greater share of World Business Class seats than Atlantic aircraft. Furthermore, the Pratt powered 777-200ER could not fly many critical Pacific missions with full passenger load, and most missions required weight limits on cargo.
This is not necessarily apparent if one looks from the generic marketing material from Boeing because the range of the 777-200, evaluated with Northwest rules and interiors, is approximately 1,100 miles less than advertised.
The 777 can carry more seats than the A330 although the A330 already carries 29 more seats than our current DC-10-30s. The optimal 777-200 configuration we modelled had 27 more seats than the A330-300 (329-302) and 56 seats more than the DC-10-30 (329-273). However, these additional seats were economy seats that typically would be filled with lower yielding passengers.
The 777 has the same empty weight for all available MTOW's (580,000-656,000 lbs). Northwest requires only the lowest weight for nearly all markets, roughly comparable to the A330. The net result to Northwest is that the 777 is more than 41,000 pounds heavier than the A330 yet provides minimal additional revenue capacity.
The heavier weight of the 777 translates directly into a fuel burn penalty. On a typical 3,500 nm mission, the A330 burns approximately 28% less fuel than a DC-10-30; accounting for its higher seating capacity, it burns 35% less on a per seat basis. The much heavier 777 burns approximately 16% more fuel than the A330 on a per trip basis, and 6% more on a per seat basis.
Questions have arisen about the cruise speed of the A330, largely due to issues surrounding the cruise speed of the A340. NW
intends to operate the A330 at a cruise speed of Mach 0.82. This speed corresponds to the aircraft's LRC (long range cruise) Mach number for most gross weight/altitude combinations. While the published cruise speed of the A340 is Mach 0.82, our analysis substantiates the experience of line pilots that certain operators fly slower to avoid excessive fuel burn. Airbus has implicitly recognised the cruise speed issue with the "first generation" A340's by redesigning the wing on the A340-500 and -600.
757/767 DC10-30 A330 777/747-200
Cruise speed .80 .82 .82 .84
As shown in the table, the A33's cruise speed is slower than the 777, but it is consistent with our DC-10-30 and faster than other aircraft operating across the Atlantic. The cruise speed differences between the 777 and A330 equates to a trip length difference of approximately 10 minutes on a typical Atlantic mission. It may be interesting to note that Northwest negotiated stringent, comprehensive contractual commitments from Airbus to ensure the A330 will meet our performance expectations both at the time of deliver and for several years thereafter. This is a requirement we make of airframe/engine manufacturers, including Boeing. The performance level of the new 757-300's has a similar level of protection. Our agreement with Airbus also provides us with mission flexibility we could not achieve with Boeing. The Airbus agreement is structured to allow us to take delivery of other members of the A330 family if our requirements change over time. A shorter member of the A330 family, the A330-200, has 257 seats in the Northwest configuration. It has approximately 900 nm more range than the A330-300. This added flexibility to tailor capacity to market requirements not offered by the 777 since Boeing was unwilling to formally offer a smaller, lower priced version of the 777.
In summary, the excess capacity of the 777 leads to operating economics inferior to the A330. This situation is further degraded when the notably higher purchase price of the 777 is factored into the analysis. The marginal improvement in revenue the 777's size offers simply cannot overcome its increased operating and ownership costs. Our Atlantic replacement decision does not mean that the 777 will be excluded from future aircraft competitions. The longer-range version of the 777-200 and 777-300 will be evaluated against the A340-500 and A340-600 when we begin the 747-200-replacement analysis.
Atlantic Range requirements for NW
- The range capability of the A330 family is a better match for NW
requirements than the 777-200ER
-Markets with capability to carry 302 pax, plus at least 20,000 lbs. cargo in both directions: BOS
Pacific Range Requirements for NW
- The range capability of the PW4090 powered 777-20ER is insufficient to be considered as a suitable replacement for the Pacific
Original thread (Credit to XFSUgimpLB41X for posting this originally)