The Revolutionary Boeing 787 Dreamliner and its Implications for Aircraft Maintenance

The Boeing 787 Dreamliner,  developed by Boeing Commercial Airplanes, is a long-range, wide-body, twin-engine jet airline, intended as a follow-on to the Boeing 767.  Boeing 787 Dreamliner aircraft maintenance is expected to be significantly easier than with the Boeing 767, in part because of the use of carbon fiber composites and additionally because of designed interchangeability of its engines  (either Rolls-Royce Trent 1000 or GEnx ).  Only now, after years of delay, is the 787 starting to be deployed in significant numbers, after a late August, 2011 certification from the FAA.  The 787 is the first production carbon fiber composite airliner, with the fuselage assembled in one-piece composite fiber barrel sections,  instead of the usual multiple aluminum sheets and typically 50,000 or so rivet fasteners, used on existing aircraft.   The 787 Dreamliner is composed of

  • 50% composites
  • 20% aluminum
  • 15% titanium
  • 15% other materials

Specifically, carbon fiber reinforced plastic  (CFRP) is the primary composite for the majority of the 787’s structure, with titanium graphite composites additionally integrated into the 787 Dreamliner’s wings.  In contrast, the Boeing 777 has 50% aluminum and only 12% composites. The composite structure of the 787 enables larger windows, lower cabin pressurization and overall higher cabin humidity. Regarding composite repairs, in the publication Boeing 787 from the Ground Up, it is concluded:

 

Boeing 787 Roll-out

Boeing 787 Roll-out. Credit: Yasobara, Wikipedia

 

“In addition to using a robust structural design in damage-prone areas, such as passenger and cargo doors, the 787 has been designed from the start with the capability to be repaired in exactly the same manner that airlines would repair an airplane today — with bolted repairs. The ability to perform bolted repairs in composite structure is service-proven on the 777 and offers comparable repair times and skills as employed on metallic airplanes. (By design, bolted repairs in composite structure can be permanent and damage tolerant, just as they can be on a metal structure.)

Also,

“Improved and expanded monitoring, advanced onboard maintenance systems, and e-enabling technologies make real‑time ground-based monitoring possible. This will aid in troubleshooting the 787. Airplane systems information and fully integrated support products will help maintenance and engineering organizations quickly isolate failed components and reduce return-to-service times. Boeing expects the 787 to show a reduction in NFF removals of 58 percent compared to the 767, reducing yet another major cost driver for 787 operators.”

 

CFRP Expected to Dramatically Lower Maintenance Labor Costs

Corrosion and fatigue in a structure add significantly to the unscheduled maintenance burden of an airline.  Historically, unscheduled maintenance frequently doubles  the total labor hours expended during a maintenance check.  With the expanded use of composites and titanium, combined with getting smarter about the usage of aluminum,  Boeing expects the 787 to have much lower unscheduled maintenance labor costs than a more conventional metallic airframe.  In addition to using a robust structural design in damage-prone areas,  such as passenger and cargo doors, the 787 was designed from the start with the capability of being repaired as if the airplane had a conventional aluminum construction — with bolted repairs. The ability to perform bolted repairs in composite structures is proven on the Boeing 777 and, on a composite, comparable repair times and skills are required, as on metallic airplanes.

In summary, the reduced risk of corrosion and fatigue associated with composites combined with the composite repair techniques  lowers overall maintenance costs and maximizes airline revenue by keeping airplanes flying as much as possible.

In addition to longer intervals between scheduled maintenance checks, the 787 program projects that the labor hours content of maintenance costs will be reduced by 20 percent on a per-airplane check basis and total scheduled labor hours will be reduced by 60 percent over the life of the airplane.

In order to fully understand the revolutionary innovations in the Boeing 787 Dreamliner,  I found it instructive to view the following video of a Boeing 787 assembly,  provided by Boeing and the Seattle Times. Here you can see the global outsourcing of major components.

In addition to carbon fiber composites in the fuselage, the 787 wings are also composites.  One is led to ask, How strong are the carbon fiber composite wings? On March 28, 2010, loads were applied to the 787 test unit to replicate 150 percent of the most extreme forces the airplane is ever expected to experience while in service. The wings were flexed upward by approximately 25 feet during the test and the fuselage was pressurized to 150 percent of its maximum normal operating condition. At 150 percent of maximum, the wings remained stable. Only at conditions exceeding this threshold did the wings fail. Below is the actual test performed in 2010.

Boeing’s 787 GoldCare Program

Carbon fiber, unlike metal, does not visibly show cracks and fatigue, prompting concerns about the safety risks of wide-spread use of the material on an airplane.  Boeing has responded to these safety concerns by noting that composites have been used on wings and other passenger aircraft parts for many years without incident, and that special defect detection procedures will be instituted for the 787 to detect any potential hidden damage. In 2006, Boeing launched the 787 GoldCare program.  This is an optional, comprehensive life-cycle management service whereby aircraft in the program are routinely monitored and repaired as needed. This is the first program of its kind from Boeing. Post-sale buyer protection programs are not new, but have usually been offered by third party service centers. Boeing is also designing and testing composite hardware so that inspections become mainly visual. This reduces the need for ultrasonic and other non-visual inspection methods, saving time and money.

Boeing 787 Dreamliner aircraft maintenance

Disassembled Boeing 787 composite fuselage section

Implications for Aircraft Mechanics

I have three conclusions regarding this revolutionary new 787 aircraft from Boeing:

  1. aircraft manufacturers are making real progress in lowering fuel costs by using CFRP to reduce overall aircraft weight
  2. maintenance costs are expected to be lower due to the extensive use of CFRP in the airframe and wings
  3. Similarly to  major jet engine manufacturers, Boeing is moving in the direction of vendor-focused real-time monitoring of their aircraft, rather than the traditional airframe maintenance burden placed on the carriers.

As noted in a prior post on the Rolls-Royce proactive jet engine monitoring program, industry trends are forcing airlines to save on fuel costs and labor costs.  With the introduction of the 787,  a revolutionary, innovative aircraft program is intended to improve Boeing 787 Dreamliner aircraft maintenance.   In addition to 20% fuel economy savings with respect to the 767, the Dreamliner breaks the mold when it comes to usage of carbon fiber composites for the airframe.  The next time you get a chance to perform some carbon fiber composite bonding repairs in aircraft mechanic school,  pay close attention,  as the trend away from aluminum usage in aircraft may become permanent. Boeing 787 Dreamliner aircraft maintenance is a first look at some important future changes in aircraft maintenance.

by Steve Adams

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