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Middle River Aerostructure Systems

World-Leading Manufacturer of Nacelle Systems

Acquired from GE Aviation in early 2019, Middle River Aircraft Structures (MRAS) is a world-leading manufacturer of thrust reversers, engine nacelle components and specialised aerostructures. MRAS also has a composites centre of excellence with decades of in-house expertise and extensive production resources for lightweight materials across a full range of aviation applications.

Located in Maryland’s Chesapeake Bay near Baltimore and operating in a 1.7-million sq ft facility, MRAS has designed, built and equipped civil and military aircraft for over 90 years.



Middle River Aerostructure Systems (MRAS) has taken an important role in one of the most rapid production ramp-ups in civil aviation history, significantly expanding its manufacturing capabilities to build thrust reverser and nacelle components for Airbus A320neo jetliners powered by CFM International LEAP-1A engines.

Working as a partner to Safran Nacelles – the French-based Tier-1 supplier for LEAP-1A nacelles – MRAS’ responsibility includes the thrust reverser’s transcowl and cascades (both produced with composite materials), the thrust reverser actuation system, and engine build-up hardware associated with integrating the nacelle to the LEAP-1A powerplant.

This involved the acquisition of an automated fiber placement system for composite layup, along with expanding the company’s composite preparation area, and installing additional autoclaves for the processing of composite parts. Among the state-of-the-art machines brought into service at MRAS are two route & trim centers and two 6-axis drilling centers used to create the millions of holes for acoustic treatment on the transcowl inner walls.

Additionally, MRAS expanded its non-destructive testing capability for composite structures and instituted lean manufacturing processes for its transcowl production.

MRAS manages the supply chain for the other components it integrates into the LEAP-1A nacelle, ensuring the company achieves the targeted production rates, which are projected to exceed 500 units from 2018.


Through its Nexcelle joint venture with Safran Nacelles, Middle River Aerostructure Systems (MRAS) has a key role in the nacelle system for CFM International’s LEAP-1C turbofan engine, which powers the COMAC C919 jetliner.

The LEAP-1C is the first truly integrated propulsion system (IPS) in its thrust category, and MRAS contributes its design, development and production expertise in realising the IPS advantages – including optimised weight, improved operational efficiency and facilitated maintenance.

MRAS responsibility on the LEAP-1C involves the nacelle’s inlet, fan cowls, inner fixed structure and engine mounts. The MRAS-designed single-piece aluminum inlet lip is the largest of its kind to enter production on a large commercial jet engine – contributing to the nacelle’s low-drag front end, improving airflow and lower noise levels.

The fan cowl module is designed at the GE China Technology Center (CTC) in Shanghai under Middle River Aircraft Systems responsibility, underscoring MRAS’ international reach and benefitting from the global resources of its GE Aviation parent company.

MRAS has personnel located at a facility adjacent to the C919 final assembly line near Shanghai Pudong Airport, ensuring continuous on-site support for LEAP-1C nacelle build-up and podding with the engine, and its team members also support the jetliner’s flight test activities at two other locations elsewhere in China.


Middle River Aerostructure Systems (MRAS) has the lead role for the nacelle system on GE Aviation’s Passport turbofan engine, working with its industrial partner Safran Nacelles in their Nexcelle joint venture.

The Passport powers Bombardier’s Global 7500 business aircraft and is business aviation’s first truly integrated propulsion system (IPS), resulting from the Nexcelle joint venture’s close working relationship with GE Aviation as the powerplant manufacturer.

Features of the nacelle components supplied by MRAS include an extensive use of composites for reduced weight – including the large two-piece fan cowl doors that facilitate access to the engine for inspection and maintenance, along with a 360-degree single-piece extended inner barrel that integrates advanced acoustic protection for lower engine noise levels.

Other MRAS supplied components of the Passport nacelle are its one-piece aluminum inlet lip for reduced aerodynamic drag; and an innovative anti-ice system that utilizes the directed flow nozzle concept.


Middle River Aerostructure Systems’ (MRAS) thrust reverser on GE Aviation’s GEnx-2B engine for the Boeing 747-8 jetliner incorporates MRAS’ core competencies in advanced composite materials design and analysis, as well as close tolerance, complex nacelle assembly. This results in a highly-reliable, lightweight and acoustically-efficient nacelle system.

Design features include a one-piece single cure, graphite-epoxy inner fixed structure – the first of its kind for MRAS – improving upon three-piece metallic and precured BMI structures from previous-generation thrust reverser designs. The resulting concept significantly reduces weight, the amount of attachment hardware needed and allows for greater ease of field reparability for a lower overall cost of ownership.

This cascade-style thrust reverser has a single-piece translating sleeve manufactured by MRAS using a one stage co-cured design that reduces autoclave cycles resulting in lower overall production cost.

Contributing to the GEnx’s superior acoustic and vibratory performance are the double degree of freedom Nomex honeycomb core and perforated facesheets, along with aft end serrations (chevrons) giving the cowling its unique appearance.

Extremely close-tolerance internal and external flow surfaces, coupled with tightly controlled internal and external steps and gaps, serve to minimize drag thus resulting in optimal fuel efficiency from the nacelle.


Nacelle components built by Middle River Aerostructure Systems (MRAS) are in widespread use on GE Aviation CF34 turbofan engines, which power E190/E195 regional aircraft from Brazil’s Embraer and are now beginning service with a new market entrant: the COMAC ARJ21, one of China’s first jetliners built to international civil aviation regulatory standards.

On the CF34-10E version, MRAS produces the cascade-type thrust reverser and provides spare parts aftermarket support for the engine’s use with twin-engine E190/E195s. More than 600 of these Embraer “E-Jets” are in operation with carriers around the world.

MRAS has wider responsibilities for the CF34-10A variant, producing this engine’s thrust reverser and fan cowl, along with oversight for the nacelle inlet. Following the ARJ21’s initial airline service entry in 2015, MRAS is beginning to ramp up the production rate for its CF34-10A components, joining GE Aviation in a long-term strategy of being present in China’s civil aircraft marketplace.


General Electric’s CF6 has earned its reputation as the cornerstone turbofan engine for widebody aircraft, and Middle River Aerostructure Systems provides the thrust reverser for numerous uses of this workhorse powerplant.

The MRAS-built cascade-type thrust reverser has a metallic inner-fixed structure and a composite translating sleeve.

Jetliner applications of the CF6 with MRAS’ thrust reverser systems are the twin-engine Boeing 767 (powered by the CF6-80C2), and the Airbus A330 (the CF6-80E1 version).

Military CF6 variants equipped with MRAS thrust reversers are the CF6-L1F for Lockheed-Martin’s C-5 Galaxy four-engine heavyweight airlifter, and the CF6-80K1F on Kawasaki’s C-2 twin-engine military transport aircraft.


From engine nacelle components to secondary aerostructures of all sizes, Middle River Aircraft Systems offers its expertise in assisting the start-up of new product lines, reengineering legacy programs, and taking on overflow production capacity.

MRAS can serve as the extension of a partner’s development and integrated product teams – bringing its proven design and engineering resources, manufacturing engineering skills and materials expertise. These capabilities are based on MRAS’ decades of collaborative experience with leading aerospace industry aircraft and helicopter manufacturers, enabling the company to deliver both build-to-spec and build-to print-solutions.

For production and overflow capacity, MRAS offers full-service manufacturing in its 1.7-million sq. ft. facility on 180 acres northeast of Baltimore, Maryland, with access to road, rail and air transportation infrastructure.

The company’s competence is demonstrated by its current role in the P-3 Orion’s Mid-Life Upgrade (MLU) program, replacing fatigue-critical structural components to enable an additional 15,000-plus flight hours for this Lockheed Martin maritime patrol aircraft. MRAS plays a key role in the low-risk, cost-effective service life extension program by building new-production horizontal stabilisers, leading edge assemblies, and longeron assemblies for the P-3.

In response to the MLU project’s needs, MRAS undertook a digital industrialisation of decades-old 2D drawings and Mylar drafting film, while also fully digitising and retooling the longeron assemblies, and retooling the leading-edge layup dies. Additionally, MRAS redefined the horizontal stabiliser assembly’s manufacturing philosophy – significantly increasing producibility when compared to the legacy tooling approach.

Other MRAS aerostructures programs have included the production of airframe components for the Boeing Chinook and Apache military helicopters (involving reverse-engineering and the extensive digitalization of 2D drawings and Mylar drafting film for a modernised industrialisation process), and the manufacture of composite upper deck fairings and the main rotor pylon for Sikorsky S92 medium-lift helicopters (retooling for low-rate production with the support of MRAS manufacturing engineers).

The company’s engineering services and manufacturing capacity also was utilised for production of the large metallic antenna structure that equips the Boeing 737 Wedgetail airborne early warning and control (AEW&C) aircraft.