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Boeing 787 Dreamliner Delayed Again
An anonymous reader writes "It's not just that the Boeing 787 Dreamliner may be unsafe or vulnerable to hacker attacks. At this point, it seems everyone would be happy for it to arrive in any state. The 787's carbon-fiber construction and next-generation technology have pushed back their delivery schedule once again, this time requiring a redesign of the plane's wingbox. Airlines will have to wait 18 more months to get it delivered, which is an extremely serious blow to the credibility of the company and their financial standing, as they would have to pay penalties to the buyers of more than 850 of these planes. And we thought Airbus had problems." Good thing Boeing can still count on its patent portfolio.
The A380 entered service for Singapore Airlines roughly 18 months late, with other airlines suffering between an 18 month and 22 month delay when they start receiving them later this year.
Airbuses delays were almost advantageous to the A380 however, since they were all post first flight and pre EIS (entry into service) - this allowed Airbus to iron out most of the issues a new type has when first put into service, with SQ having only three technical problems with their first three A380s in 6 months, which is a lot lower than other new types.
Boeing, however, are suffering their delays before they have even achieved the first 'power on' milestone in their first aircraft, and they are still relying on an uneventful flight test program to bring the aircraft in under the new schedule. This means that the 787 will probably still be subject to the usual new type issues with its first operators. And thats not even taking into account the possibility of *another* delay - which many in the industry are considering highly likely.
Uh I am a bit fuzzy on the details - used to be an aviation nut - but there is a payoff between fuel used/distance traveled/paying passengers.
Concorde just couldn't ride that fine balance economocally enough.
Then - most countries do not allow supesonic overflights - I remember concorde had to fly subsonic while over land and could only go supersonic while over the ocean on the trans atlantic crossing.
The Concorde was noisy - the engines needed to push a large plane to go that fast are very noisy, no leaky turbofans here - and with airports being so close to cities the overflights over suburban areas were problematic.
There is the issue of the optimum aerodynamic shape - there are basically three wing shapes: Swing wing (think B1 Bomber), works well in subsonic and supersonic flight - it is efficient during both flight profiles, but the mechanics is heavy. Probably the best option for the future.
"Normal" swept wings - not optimal for supersonic flight. Is the optimum configuration for carrying heavy loads long distances.
Delta Wings (Like the Concorde) - great for high speed flight, the Valkyrie bomber used a nice Delta wing design that "rode" the shock wave of supersonic flight at high speed to conserve fuel. It is not an optimum load carrying wing, and is not good for low-speed flight. Delta wings have a poor take-off and landing performance, i.e. it means that it lands and takes off at a high speed, and the landing profile is very "low" meaning it flies low over urban areas when taking off and landing. Also it needs a long runway to take off and land - the larger the plane the longer the runway needed. Whereas a wing for the A380 could be optimised for better performance in this flight envelope and not lose a lot of performance when it is actually airborne, for a delta the line to be walked is much finer.
Thus while the speed of supersonic flight would be great for international travel - plus the coolness factor - and there are technologies available today that were not available to the designers of the Concorde and Valkyrie (composite materials for one) there is still the trade-off of a wide range of flight envelopes (take-off, landing, subsonic flight, supersonic flight), size (the bigger you go the less efficient any design is), fuel use (supersonic flight uses a LOT of fuel - hence impacting plane size which makes the design less efficient and on and on) and then the greenies of course haha that makes large supersonic airlines not economically viable today.
Then also designing a supersonic superjumbo is a lot more expensive than is the case for a subsonic superjumbo. Development time is also much longer due to the newer tech, optimizing the design for all the flight profiles, engine design...
It is just not economically viable. It would actually make more sense to design a passenger liner that would "hop" into space to cross vast distances in the upper stratosphere and then fly down to land like a subsonic jetliner.
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Oh, in addition to my other post, this 18 month delay is not the whole story - Boeing has put back the 787-9 stretch to 2012 (around a 2 year delay from its original EIS date of 2010) and decided to not commit to a schedule for the the 787-3 short range variant, which was supposed to EIS before the -9.
What impact does this have? It drastically reduces the head start Boeing had over Airbuses closest comparable aircraft, the A350-800, from 4 years to 2 years (the A350-800 has an EIS of 2014), meaning suddenly the A350-800 becomes a much more palatable rival. This may cost Boeing sales in the long run.
This delay also pushes back Boeings production schedule a full two years - Boeing now has two years less production slots to sell, which will certainly cost them sales in the medium term.
But the biggest impact this will have is Boeing is not in a position to offer the 787-10 stretch, which airlines have been demanding for about a year now - Airbus will be able to offer a comparable product, the A350-900, in 2013 right after the 787-900 EIS. This will definitely cost Boeing sales.
Airbus on the other hand, are looking likely to deliver the A350 on time and within schedule - they have laid out a schedule which is almost double that which Boeing laid out for the 787 (7 years from industrial launch to EIS for the A350 verses 4 years from industrial launch to EIS for the 787). That padded schedule gives Airbus more breathing space.
When you are talking about near supersonic or supersonic speeds, this is no longer true. http://en.wikipedia.org/wiki/Drag_divergence_Mach_number In fact, drag increases much more rapidly as you approach the speed of sound, but then much more slowly after that point.
Another concern for continued high-speed operation is the engines. Jet engines create thrust by increasing the temperature of the air they ingest, and as the aircraft speeds up, this air increases in temperature before it reaches the engines. The maximum temperature of the exhaust is determined by the materials in the turbine at the rear of the engine, so as the aircraft speeds up the difference in intake and exhaust temperature the engine can extract decreases, and the thrust along with it. Air cooling the turbine area was a key solution, which continued to improve though the 1950s and on to this day.
Intake design is also a major issue. The engine can only ingest subsonic air, so ramps in the intake are used to create shock waves that slow the airflow before it reaches the engine. Doing so removes energy from the airflow, causing drag. The key to reducing this drag was to use multiple small oblique shock waves, but this was difficult because the angle they made inside the intake changed with changes in Mach number. In order to efficiently operate across a range of speeds, the shock waves had to be "tuned." North American had already worked with advanced inlets on the A3J supersonic bomber for the U.S. Navy, which featured multiple ramps which were moved and angled automatically.
An aircraft able to operate for extended periods at supersonic speeds has a potential range advantage over a similar design operating subsonically. Most of the drag an aircraft sees while speeding up to supersonic speeds occurs just below the speed of sound, due to an aerodynamic effect known as wave drag. An aircraft that could fly past this speed saw a significant drag decrease, and could cruise supersonically with improved fuel economy. However, due to the way lift is generated supersonically, the lift-to-drag ratio of the aircraft as a whole drops, leading to lower range, offsetting or overturning this advantage.
The key to having low supersonic drag is to properly shape the overall aircraft to be long and skinny, as close as possible to a "perfect" shape, the von Karman ogive or Sears-Haack body. This has led to almost every supercruising aircraft looking very similar, with a very long and skinny fuselage and large delta wings, cf. SR-71, Concorde, etc. Although not ideal for passenger aircraft, the shaping is quite adaptable for bomber use.
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