[SLASHDOT] Airplanes in a Gist

US Air Force Selects Boeing 747-8 To Replace Air Force One

http://yro.slashdot.org/comments.pl?sid=6862945&cid=48935743

Re:Not going to disappear quickly.... (Score:4, Interesting)

by Solandri (704621) on Thursday January 29, 2015 @07:22PM (#48935743) 

Even if Boeing stopped building 747 variants tomorrow, they'd be around for ages. They're the mainstay for long-haul travel, and dwindling sales probably are more related to market saturation - as in, there are enough in the air now to meet current demand - than any inherent shortcoming in the design.

An individual airframe is typically retired before 100,000 pressurization cycles. This is a limitation of the aluminum used to make the skin, which unlike other ferrous metals does not have a fatigue limit [wikipedia.org]. In other words, aluminum always grows weaker with use. As you get closer to 100,000 cycles, you increase the odds of a catastrophic fatigue failure [wikipedia.org] where the aluminum literally unzips like plastic shrinkwrap after you've cut a notch in it. (Aloha 243 had nearly 90,000 cycles due to its short-duration island-hopping history.) 

The 747 is typically used on long-haul overseas flights lasting 10+ hours. This drastically reduces the rate at which airlines can rack up pressurization cycles. Even if one were flown 2x a day every day, it would take over 130 years to reach 100,000 cycles. By comparison, a 737 used for the 40-minute LAX to Las Vegas route may fly 10x a day and reach 100,000 cycles in a little over 25 years. This is why 747s are hanging around - their skins simply have less wear and tear on them despite being in service for more years and logging more flight hours than other planes. 

The 747-8 was always a bit dodgy. When Boeing made the original 747, they weren't planning to make it with a partial second deck. It was supposed to be a stepping stone to future models with a full second deck (designing the 747 nearly bankrupted the company). Boeing pitched the full two-decker model to the airlines for decades but could never get enough interest to justify actually building it. Then Airbus came with its "who cares if we'll sell enough to make money, our governments will pay for it if it doesn't so let's build it" A380, and Boeing threw together the 747-8 as a possible alternative. 

The slow rate of A380 sales (nearly 10 years old, 318 orders, 147 deliveries) seems to substantiate Boeing's marketing research that there just wasn't sufficient demand (yet) for such a large plane. By comparison, the 747-400 had 465 deliveries in its first 10 years. The 747-8 has 119 orders, 83 deliveries in the same timeframe as the A380. As you state, in the 400-525 passenger category, the market is pretty well-saturated by older 747s which are still airworthy.

I suspect that there are more refinements to come - it's just too useful an airframe to discard. It may take Boeing a bit to roll in some of the working dreamliner tech but it seems reasonable that they'd try to do that when time and demand permit.

In terms of airline operating economics, the number of passenger per flight nearly always has a larger magnitude of effect than efficiency gains for new technology. For an airline you are almost always nearly best-off flying a plane with slightly more capacity than the number of passengers. Airbus tried to claim the A380 would be so efficient this wouldn't matter, and you could fly a 747-sized number of passengers on a A380 for cheaper than a 747. I was very skeptical, and the fact that airlines aren't tripping over themselves to replace their old 747s with A380s is a pretty good indication that it's still cheaper to fly a 747 for 747-sized passenger capacities. 

The next place to watch is to see if Airbus will roll out a twin-engine competitor to the 777 (maybe a longer A350-1000?). Airbus' competitor to the 777 had been the A340 (both are in the 300-450 passenger range). But the A340 is a 4-engine plane which uses much more fuel. Consequently, the 777 beat the A340 into a bloody pulp in the market. The 777 has had 1827 orders in 20 years, vs 379 orders for the A340 in 20 years. Right now, that's the gap in Airbus' lineup 

A320 = 100-200 passengers.

A330/A350 = 250-370 passengers.

* A340 = 300-420 (retired in 2011)

A380 = 500-625 passengers. 

That leaves a gap between 370-500 passengers which is currently being filled by the 777 and legacy 747s. Airbus claims you can configure the A380 for as few as 407 passengers, but no sane airline is gonna do that when they can configure the exact same plane for 500-650. I suspect they're holding off on a 777 competitor in hopes of directing more sales to the A380, but such sales inevitably end up going to the 777. In contrast, Boeing's lineup tightly covers all passenger capacities pretty well right now: 

737 = 100-200 passengers

787 = 240-360 passengers

777 = 315-450 passengers

747 = 467-525 passengers