Jul 31, 2009
The Boeing 787 Dreamliner: Composites on Trial Part II sciencetech” />
Boeing 787-8, Prototype
Photo – Aviation Explorer / Wikipedia
Boeing’s 787 Dreamliner is 80% composite materials by volume and 50% by weight. Rising fuel costs mandate widespread use of composites, but questions about long term structural stability have yet to be resolved. In the second of a three-part series, we assess the Dreamliner in minute detail, while also bringing you news of a dramatic blog post on composite fuselage cracks written by an industry insider.
Boeing 787 / Dreamliner -
Composite materials in aircraft design are now subjected to increasing and skeptical scrutiny. That searchlight is on the Boeing 787 Dreamliner as well as Airbus aircraft. The Dreamliner program began in April, 2004 and there is a large, international, network of parts manufacturers. Boeing’s 777-200ER and 300 ER are sometimes viewed by the press as competition to the Airbus 350, but more often are compared to the Airbus jetliners A340-500HGW and A340-600HGW. Composite fuselage parts account for 9% of a Boeing’s 777 total weight and include the cabin floor and rudder.
Dreamliner Test Bed in action at Rolls Royce. Trent 1000 engines power the 787.
As of the Rollout Ceremony on July 8, 2007, the Boeing 787 had become the fastest selling, wide body airliner in history. 861 Dreamliners had been ordered by 56 customers as of April, 2009. Originally scheduled to enter service in May, 2008, there is now no scheduled maiden flight and service debut might occur sometime in 2010.
Boeing Wide Body, Aircraft Assembly Plant at Everett, Washington / 747, 777, 787
Photo – Maurice King / Flikr
Final assembly of the 787-8 Prototype began May 21, 2007 at Everett Washington USA after the successful manufacture and delivery of major components from partners in several countries. FHI and KHI in Japan contributed the forward fuselage, center wing and center wheel. Each fuselage barrel is made in one piece and the barrel sections are joined end to end to form the fuselage, thereby eliminating the need for the 50,000 fasteners required to build a conventional aluminum fuselage. This composite fuselage also allows for higher cabin pressure during flight.
Boeing 787 / Composite Fuselage Assembly
Photo – markjhandel / Flikr
The Boeing 787 is the first major commercial jet liner to use composite materials for more than 50% of its construction, thereby significantly reducing aircraft weight and fuel costs. Dreamliner materials by weight are: 50% composite, 20% Aluminum, 15% Titanium and 5% steel. The Boeing 787 is 80% composite by volume and contains ~35 tons of carbon composite, made with 23 tons of carbon fiber and reinforced with plastic. Composites are used in fuselage, wings, tail, doors and interior. Aluminum is used for the wing and tail leading edges. Titanium is found mostly in the engines.
Boeing 787 / Computer Modeling
Photo – shearforce / Flikr
An aircraft fuselage built mostly with composite parts may have a reduced capacity to shed the electricity from a lightening strike. John Leahy of Airbus has publicly criticized the use of composites in the 787 fuselage as ‘rushed and ridiculous”. Vince Weldon, a former Boeing senior engineer, has stated that the risks inherent in a composite fuselage have not been fully assessed and that such a fuselage should not be attempted at this time. Weldon specifically referred to the composite fuselage as more shatter prone than aluminum, and if burning after a crash would release highly toxic fumes.
Carbon fiber does not reveal cracks and fatigue as does metal. The Dreamliner fuselage composite may have 1,000 X the electrical resistance of Aluminum, which greatly increases the risk of damage during a lightening strike. Use of a virtual reality simulation of the 787’s manufacturing process to uncover design problems has been criticized.
Boeing has refuted such analysis and explained how the risks described have been taken seriously and attended to with success. Building and testing of composite sections of the 787 fuselage began nearly ten years ago and a great deal of experience has accumulated.
Boeing 787 / Carbon Fibre – Fuselage Section
Photo – Cjboffoli / Wikipedia
There are also other sources of delay in moving the Boeing 787 program forward on schedule. The complexity in delivering a breakthrough, next generation aircraft through production, and then fulfilling multiple orders from airlines around the world should never be underestimated. The story of fuselage fasteners is a good illustration of the challenge.
Construction of composite fuselage section, no sound.
Granted thousands of fasteners have been eliminated with the adoption of a composite fuselage, but thousands are still required. Many of these are aluminum and Alcoa is the supplier. Following 9-11, Alcoa reduced its work force by 40% and was not in a position to adequately fulfill the Boeing contract for Dreamliner fasteners.
As you can imagine, quality standards are stringent. While Alcoa plays catch-up, parts are being delivered to Boeing with temporary fasteners, some of which are everyday hardware store items. These will be removed and replaced, which in turn creates yet another potential problem that has to be inspected. Composite parts are sensitive to clamping pressure and installation force. Those parts that were temporarily held together with low grade fasteners will have to be re-inspected for structural defects after final fastener upgrade. This issue is mission critical to state the obvious.
Walk through Boeing Assembly Plant during last stages of building 787-8 prototype
The Rollout Ceremony for the first Dreamliner 787-8 prototype was held on July 8, 2007. Mitsubishi built the carbon-fiber wings and Alenia Aeronautica in Italy delivered the horizontal stabilizer. American manufacturers of composite parts included Boeing who built the vertical tail fin; and Spirit Aerosystems, manufacturers of the nose and cockpit section that was 42’ (12.8 m) long, 19’ (5.74 m) wide and 21’ (6.4 m) in height. Vought delivered two rear sections. Rolls Royce engines were shipped from the UK on June 7 and June 21, 2007.
Boeing 787–8 / Rollout, July 8, 2007
Photo – markjhandel / Wikipedia
There are three variants of the Boeing 787. The 787-8 is now planned to enter commercial service in 2010 with a typical seating configuration for 210-242 passengers and range of 7650 to 8200 nautical miles (14,200 to 15,200 km). The 787-9 should make its debut in 2013. It has a ‘stretched fuselage’ and will seat 250-290 passengers with a range of 8,000 to 8,500 nm (14,800 to 15,750 km). The 787-3 is a shorter range aircraft with a range of 2500 to 3050 nm (4,650 to 5,650 km) and a 290 passenger configuration. It is designed to compete with, then replace the Airbus A300/Airbus A310 and Boeing’s 757-300/Boeing 767-200 on short regional routes between large cities. Production problems have yet to be completely solved and there is no projected date for its entry into the travel market.
First estimates of entry date for any new commercial aircraft are always extended because the complexities attending assembly, testing and integration of multiple international partners are formidable.
Piaggio p.180 / Composite Fuselage Cracks -
Italy / Piaggio P.180
Photo – 0lorenzo0 / Wikipedia
A dramatic post by ‘Kenavo’ appeared on July 6, 2009 on Securite Aerienne, an aviation security, industry blog whose contributors include pilots, engineers and industry professionals. ‘Kenavo’ describes himself as a former structural engineer – country and corporation not identified – who worked with composites 20 years ago. He left that industry when he realized that composite tensile strength falls off continuously over time. The plastic resin outgasses plasticizer and becomes more brittle with time. Composite part failure – cracks, breakage – can occur without warning. Aircraft frames built from metals have fatigue limits below which strength does not fail.
Now a pilot, ‘Kenavo’ describes that in 2002, his personal aircraft, which was built without composite parts and had logged 10,000 flight hours, had no cracks in the airframe. On one poignant day, ‘Kenavo’’s plane was parked next to a composite Piaggio executive aircraft. The Piaggio with 700 hours of flight time had multiple cracks all over the fuselage that were very visible.
Piaggio Avanti / takeoff and landing
The Piaggio Avanti uses composite parts in the tail, engine nacelles, canards, outboard wing flaps, landing gear doors and tail cone. I cannot determine whether current Piaggio Avanti models are 10% or 40% composite by weight. Regardless, ‘Kenavo’’s report is extremely serious unless the aircraft he observed was a one off ‘lemon’. Is the FAA not releasing the complete story on composite frailty as ‘Kenavo’ claims? Are Boeing and Airbus glossing over composite part weaknesses or have they conquered these long known structural problems? It is impossible for anyone outside these two giant corporations to know with any certainty. This story has many chapters yet to be written.
1, 2, 3, 4, 5