New horizontal stabilator provides substantial savings to F-22 program

Lockheed Martin estimates that it will save the F-22 program $1 million per aircraft shipset of two with a new horizontal stabilator design.

Lockheed Martin has developed a new horizontal stabilator design for the F-22 Raptor that will save the program an estimated $1 million per aircraft shipset of two. Stabilators are the large, left- and right-hand wing-like aerodynamic control structures horizontally mounted to the F-22's tail. They work either together or independently to control the Raptor's pitch, roll, and yaw movements. Unlike stabilizers, which have both a fixed and a moving surface, the entire horizontal stabilator moves as a single unit to reposition the aircraft in the air.

"The development and implementation of the stabilator's new design and manufacturing process is part of the F-22 program's ongoing product improvement initiative," said Bob Rearden, Lockheed Martin Aeronautics Co. Vice President and F-22 Program General Manager. "The savings incurred through this initiative will help contain the F-22's cost." Currently, the U.S. Air Force has an F-22 acquisition goal of 339 aircraft.

Lockheed Martin's new stabilator design involves mechanically fastening composite materials around a central shaft rather than bonding the materials under high pressure and heat in an autoclave. The new design also incorporates removable edges, which will make the stabilators easier to maintain or repair in the field. The manufacturing process associated with the new design will shave approximately 30 lb from each stabilator and reduce its build time by approximately 25%.

Lockheed Martin has selected Vought Aircraft Industries of Dallas, TX, to build the new stabilator. Under the terms of the $40-million contract, Vought will begin manufacturing the new stabilators early next year and produce 85 shipsets through 2007. Raptor 4040, the fortieth aircraft off the assembly line, will be the last F-22 equipped with the original stabilators. The first F-22 equipped with Vought-built stabilators will be Raptor 4041, which is slated for delivery to Langley Air Force Base, VA.

The F-22 Raptor, the world's first stealthy air dominance fighter, is built by Lockheed Martin Aeronautics in partnership with Boeing. The Raptor is powered by Pratt & Whitney engines and is made from parts and subsystems provided by approximately 1200 subcontractors and suppliers in 46 states.

The Raptor will replace the venerable F-15 Eagle as a front-line fighter jet starting in 2005.

- Frank Bokulich

MTU, the Engine Alliance, and the A380

German-based engine manufacturer MTU, the third largest partner in the GP7000 engine program, has established shared Web portals and databases to ensure effective communications between the companies. The GP7000 is led by the GE-Pratt & Whitney Engine Alliance and is being developed for the Airbus A380. MTU's share in the GP7000 program is put at 22.5%. It says it expects to be responsible for development, production and final assembly of the engine's low-pressure turbine and turbine center frame together with the production of high-pressure turbine blades and disks. The GP7000 builds on the PW4000 low-spool and GE90 core technology with an infusion of several new technologies.

The GP7000's core first ran in March 2000, with the test phase concluding in May 2000. The December 2000 launch of the A380 program lent new impetus to the GP7000, as manifested by a number of modifications made to it, such as a larger fan tip diameter, swept fan blades, and an additional stage for both the low-pressure compressor and the high-pressure turbine.

The first complete engine is scheduled to run in the first half of 2004 with certification in July 2005, and the first GP7000 powering the A380 is to make its maiden flight in January 2006. The other engine option for the Airbus A380 is the Rolls-Royce Trent 900.

- Stuart Birch

BAE Systems' programs and projects

BAE Systems has become a member of a specialist team that includes Westland Helicopters, FHL, and the UK Ministry of Defence, which will develop a digital flight control computer as part of the Helicopters Electric Actuation Technology (HEAT) program. The project involves the replacement of conventional power hydraulic systems, which are used for aircraft control, with all-electric systems. The HEAT program will be demonstrated on the EH101 helicopter. A development contract has been signed with AgustaWestland. According to BAE Systems, the program will bring fly-by-wire (FBW) technology to helicopters, boosting performance by offering increased range or payload, enhanced handling, lower cost of ownership, and improved reliability and safety. BAE Systems has been a pioneer in FBW system development, with units operating on the Eurofighter Typhoon and the Boeing 777.

BAE Systems has also been selected by Lockheed Martin to provide assistance in the support of the Joint Strike Fighter (JSF) program. It will be involved in support of avionics to assist Lockheed Martin's Autonomic Logistics Integrated Team during the system development and demonstration phase of the program. The UK company will also develop the JSF's Active Inceptor Subsystem (AIS). It comprises the pilot's sidestick and throttle control units. The technology was successfully proven during the JSF concept demonstration phase. According to BAE Systems, AIS is an "integral part" of the JSF vehicle management system designed to provide pilots with "unsurpassed" carefree handling qualities. BAE is understood to be looking at possible applications of the technology to helicopters, tiltrotors, and commercial aircraft. BAE systems is now involved in a wide variety of technologies being applied to the JSF including weapons systems design, development, manufacture and support, and the design and integration of the aft fuselage, horizontal and vertical tails, and the wing-fold mechanism of the aircraft carrier variant.

Meanwhile, IPA1, the first production Eurofighter based at BAE Systems' Warton facility in northwest England, completed five further flights in the 10 days following its maiden flight. All have been for production flight acceptance testing. Turnaround between flights was down to about 45 minutes. Following the flights, the aircraft was prepared for the fitment of upgraded avionics, installation of flight refuelling probe, and the start of tests including ground resonance and electromagnetic compatibility. Initial high-speed wind tunnel tests of the Typhoon's conformal fuel tank design have been successfully completed. Tank capacity is 1500 L. The work has been carried out by GKN Engage and BAE Systems. A four-partner project (UK, Germany, Italy, and Spain), emphasis has been placed on reducing cost of ownership of the swing-wing Typhoon, of which 620 have been ordered.

- Stuart Birch

Fighting fire with tin

A cone calorimeter measures heat release and smoke emission.

The development of fire-resistant materials for use in airliner cabins to prevent injuries in post-crash situations is a problem that has faced the aerospace industry for decades. Such materials must have several properties other than fire resistance, including wear longevity, acceptable aesthetics, and passenger comfort, often for extended periods. Now tin-based flame-resistant treatments are being considered for textiles used in aircraft. A feasibility study has recently been conducted by Tin Technology, an organization that represents major tin producers, smelters, and consuming industries. Aim of the study was to identify an environmentally acceptable tin-based flame-resistant treatment that complies with aircraft cabin flammability and smoke emissions specifications and which is both economically viable and practical to use.

Smoke emissions are a particular problem in an enclosed area, and it is this which often reduces passenger survival rate in an emergency. According to Tin Technology, full-size experiments using an aircraft fuselage have demonstrated that the upholstery materials used in passenger seats influence the development of fire. Therefore, all textiles that are used in aircraft cabins are given strict flammability requirements by the regulating authorities. Currently, the materials used for aircraft seats are made of wool or wool-nylon blends as these have higher levels of flame retardancy than other conventional materials. To improve the flame retardancy of these materials, they are treated with potassium hexafluorozirconate (PFZ).

Dr. Paul Cusack, Research Manager of the Chemical Technology Group of Tin Technology, said: "There is a clear demand for new flame-resistant treatments to be identified which are more environmentally friendly than the current zirconium-based PFZ treatment." He added that there is also a need to find a treatment that exhibits lower heat release characteristics combined with reduced emissions of smoke and toxic gases.

The UK Department of Trade and Industry (DTI) under its Civil Aircraft Research and Technology Demonstration (CARAD) program, funded the Tin Technology feasibility study, which was conducted over a period of three months. The consortium partners included Britax Aircraft Interiors and Replin Fabrics (both companies providing the materials) plus Keeling & Walker, who provided the tin-oxide sols. A total of 20 experimental tin-based flame-resistant treatments were applied to a wool-nylon blended fabric, a material that is currently used commercially. Using laboratory fire-test procedures, the treated fabrics were assessed and the performance compared against the commercial PFZ treated fabric samples.

According to Tin Technology, the study suggests that some of the tin-based treatments match or even outperform PFZ, in particular colloids based on tin phosphate, tin tartrate, and zinc hexachlorostannate + tartaric acid. The main benefits of these tin-based treatments include lower smoke emission and reduced levels of carbon monoxide. The next stages of the study involve addressing issues that include cost-benefit analysis of the tin treatments compared with PFZ; durability of the tin treatments to standard laundering/dry cleaning procedures; and effects of the tin treatments on textile strength.

"From the feasibility study it is clear that there is considerable potential for the tin-based technologies to be used commercially in aircraft, provided they are competitive with existing treatments," said Andrew Spiller, Technical Manager at Keeling & Walker. "New legislation could also positively influence the future of these tin-based materials."

Tin Technology is now discussing with the DTI possible funding of a further feasibility study on the potential of using tin-based fire retardants in plastics used in aircraft interiors, including wall panels, overhead baggage compartments, and food trays.

- Stuart Birch