Large Aircraft Modifications

To talk about modifications and upgrades to large transport category aircraft, AMT visited Aviation Technical Services (ATS), a large MRO provider located at Paine Field in Everett, WA. ATS provides MRO services primarily for Boeing narrow and widebody...


In the October 2010 issue of AMT magazine the subject of performance upgrades to business and corporate use aircraft was discussed with one of the manufacturers of this type of aircraft. The article described some of the reasons why owners upgrade aircraft and their potential impact to future maintenance.

Similar to their smaller siblings, large transport category aircraft operated by airlines often undergo the same types of upgrades and modifications such as interior refurbishment, installation of passenger convenience items, and modifications to gain greater performance.

To talk about modifications and upgrades to large transport category aircraft, AMT visited Aviation Technical Services (ATS), a large MRO provider located at Paine Field in Everett, WA. ATS provides MRO services primarily for Boeing narrow and widebody aircraft. Two very different types of modifications were used as examples to discuss the more important issues of project planning and relationship building between the customer, the suppliers, and the MRO provider.

Winglet installations

You can’t pass by any commercial airport these days without noticing how many aircraft have large wingtip devices on the ends of their wings. Aircraft are delivered from the factory with these efficiency gaining devices while others are retrofit installations. One company that supplies these devices for Boeing aircraft is Aviation Partners Boeing (APB). APB is a joint venture between Aviation Partners Inc. and the Boeing Company.

APB engineered and obtained a supplemental type certificate (STC) for its devices and supplies an STC kit which includes the winglet, hardware and parts, instructions, and the associated workcards. The airline or customer either hires the services of an MRO provider, or if able they accomplish the installation themselves. APB supplies these kits for installation on several of the Boeing 737 family of aircraft, the Boeing 757-200 and -300, and the Boeing 767-300ER. They are also available for installation on new production Boeing 737 aircraft. Many MRO providers and airlines have experience installing the APB blended winglets including ATS. ATS accomplished the first Boeing 737 prototype APB blended winglet installation.

ATS explains some of the details of the installation on the Hawaiian Airlines Boeing 767-300ER, and the discussion rapidly turned toward the importance of early planning for any new large-scale project. Installation of these devices requires several structural modifications to the outboard section of the wing.

A 14-foot section of the original upper and lower wing-skins is removed to accommodate the addition of new structure. Two new internal stringers are installed on both the upper and lower wing skins the length of the wing requiring full access to the inside of both wings. Several new ribs and other new structures are installed near the outboard section of the wing. Large fixtures and tooling are involved for location and alignment throughout the project. Eventually all wing modifications are accomplished and the winglets are bolted onto the end of the wings.

Sounds simple; we know it’s not. Mike Beck, director of business development, shares, “Our experience with any large scale modification is it takes up to three aircraft to achieve what we call a steady-state. At that point we’re down the learning curve, technicians and engineering staff have a routine, working relationships are established, and the project moves efficiently. A lot of work goes into properly planning a project like this.”

David Keimig, director of operations, shares, “As with most large projects, technical deviations sometimes surface for a variety of reasons during the project. With this project they are managed by our engineering group working directly with the airline customer and the APB engineering groups. This is where the early relationship building comes into the project.”

In-flight entertainment systems (IFE)

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