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23 FEBRUARY 2015
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The words are by Captain Bob Colvin and reproduced with thanks from Aviation Week & Space Technology.
"As a pilot for US Airways, I always believed there had to be a better way for single-aisle aircraft to fly long distances. I used to fly the Airbus A321 from Philadelphia (PHL) to Los Angeles (LAX) and San Francisco (SFO), but even with two auxiliary centre tanks, the A321's advertised range of 3,000 nm (2,400 nm useful range) limited it to only transcontinental flights. I also flew the Boeing 757 from Brussels (BRU) to PHL many times, taking off with a full load of fuel, passengers and cargo at maximum take-off weight every time.
But from BRU the 757 just barely has the range to complete this leg from the western edge of Europe with minimal reserves. Even though the 757 range is 4,100 nm with winglets, the true useful range is about 20% less (3,280 nm) when flying westbound against headwinds.
My solution would be for Airbus to build a truly long-range aircraft in the A320 family. The European airframer just announced an A321LR that Aviation Week called “a Boeing 757 replacement.” Its advertised range of 4,000 nm is indeed in 757 territory. (See BTN 19 January)
But we need something with longer legs. The “A322,” as I call my concept, would have a minimum range of 5,000 (4,000 useful) nm. That would open up many new, thin international routes to most of Europe, from US airline hubs in Minneapolis-St. Paul, Chicago, Louisville, Charlotte, Atlanta, Washington, PHL, New York JFK and Newark, Boston, etc. This would make the A322 much more versatile for the airlines, rather than restricting their thin-route transatlantic flights to those from the west coast of Europe to the northeastern US.
A few years ago, I thought about a possible 757 replacement that international passengers would find more comfortable. My idea then was an updated A310neo, with an A330cockpit, or a similarly updated Boeing 767. But at the time there was not much interest in a small widebody aircraft with larger engines than the 757 to fill the void at Airbus and Boeing. In the intervening years, this size gap has only spread as larger widebody jets have been built and the A310 and 767 have been discontinued.
That sparked a new idea. I studied what physical traits made the 757 so successful. Most important, it has plenty of power and wing area to lift a heavy load, with enough range to cross the Atlantic. The small wing is the downfall of the current A321, as it was optimized for the A319 and A320, not a long-range A321 that has reached its limits of growth.
Look first at the power of the 757—87,000 lb. of thrust total with its 255,000-lb. gross takeoff weight. This equates to a power loading of 2.93 lb. per pound of thrust. The current A321 gross takeoff weight is 206,000 lb. With its 66,000-lb.-thrust total, that works out to 3.12 lb. per pound of thrust for normal takeoff performance, or about 10% more than the 757.
Until recently, there were no new engine choices in the higher-thrust range that would be required for this proposed long-range A322. However, this is no longer true. The Pratt & Whitney PurePower PW1140G geared turbofan is now the solution for an efficient 40,000-lb.-thrust turbine. The fan and turbine both turn at optimum speeds, due to the planetary gearing between them, creating a 15% savings in fuel.
With two engines, my proposed long-range A322 would have 80,000 lb. total thrust. With the 757 power loading of 2.93 lb., it would have a 234,500 lb. maximum gross takeoff weight. This would only be required for improved performance at short, hot and high airports for true 757 performance. The gross take-off weight for normal airport takeoffs could then be easily raised 10% to 258,000 lb. This would allow a much higher payload for additional fuel or revenue.
Next, the 757’s 255,000-lb. gross takeoff weight with its large 1,951-sq.-ft. wing, equates to a low wing loading of only 130.7 lb./sq. ft. The A321’s 206,000-lb. gross takeoff weight with 1,320 sq. ft. of wing area, equates to a high wing loading of 156.1 lb./sq. ft., which limits any large increase in weight. This is already about 20% more weight per square foot of wing area than for the 757. The new wing area required to carry the 234,500-lb. gross weight, divided by the 757’s 130.7 lb./sq. ft. wing loading equates to a 1,794-sq.-ft. wing area, which requires at least a 36% larger wing to hold the required fuel. It might have to be even bigger, though, as a bigger A322 wing might be needed to carry the 77,000 lb. of fuel that I envision.
A newly designed long-range-cruise wing would be required; possibly a scaled-down A330neo wing with sharklets would improve performance 5%. The larger wing centre section will add a few more rows of seats, and almost double the standard A321 fuel capacity to 74,000 lb. Doing away with any auxiliary centre tanks (ACTs) would add capacity for two LD3-46 cargo containers, bumping up the capacity to 10 containers from eight. (The latest Airbus A321neo proposal requires three ACTs to fly only 4,000 nm.)
Additional fuel could be stored in a stabilizer trim tank (3,000 lb.), like the A330 fuel system, to maintain efficient aft centre-of-gravity during cruise. Longer-range flights of 6,000 (4,800 useful) nm would be possible with optional ACTs. Airline hubs in Seattle, Salt Lake City, Memphis, Dallas-Fort Worth, Miami, etc., could then have direct flights to most of Europe using the long-range A322. Double-axle-boogie landing gear would be required to spread out the weight and improve braking. This is already a standard option on the A320 series and is used mainly on unimproved landing strips in India by A320 operators.
With the new, larger wing, a stretched A323 version, similar to the 757-300 also could be developed easily. Its payload and range would probably be just enough to cross the Atlantic, like the current 757. But it would be perfect to fly US coast-to-coast routes and to Hawaii, or for the luxurious JFK – LAX transcontinental flights on the American Airlines A321TC: one-third 1+1 first-class seating; one-third 2+2 in business class; and one third 3+3 in coach.
Airbus and Boeing both have tour groups and airlines in Europe and Asia that require a high-density, 295-seat, one-class aircraft like this. The current A321neo proposal fits nicely between the current A321 and this proposed A322. Using my specifications, the A322 would provide a true Airbus replacement for the 1,050 757s and fill the large void at Airbus and Boeing between narrow and widebody aircraft. This is the long-range 757 replacement airlines have been demanding. The question is, who will build it, Airbus or Boeing?"
Based in Philadelphia, Captain Colvin flies the 737, 757, 767, A320 and A330 for US Airways/American Airlines.
Simon Finn, London
No one would build it because (i) most 757 are not needed for transatlantic use so the market is much smaller than Colvin suggests; (ii) the costs of the new wing could not be justified for the market that exists; (iii) An "A322" would bleed market away from A330neo/787 sales. (iv) An "A322" would not have sufficiently flexible operating costs to be efficient on shorter routes where most NB operations take place!