Mystery 737 Winglet Test


EcoDemonstrator flies by Mt Ranier (Boeing/John Parker)

Boeing’s 737 EcoDemonstrator was quietly delivered to its owner American Airlines on Nov 20, marking the formal end of its short but successful career as a flying testbed for far-reaching technologies that may not be seen in service for years to come. Now simply 737-823 N897NN, the aircraft has already blended anonymously into American’s vast fleet but for a few months this year was a special machine. Packed with an assortment of near to far-term technologies aimed at improving efficiency and safety while reducing noise and fuel burn, the EcoDemonstrator also represented a new way of testing for Boeing.

Modified winglet on test (Joe Walker)

Virtually everything tested on the aircraft was openly discussed by Boeing and American which even allowed AW&ST to ‘embed’ with the flight team for a weekend of testing in September. However, there was at least one proprietary technology tested towards the tail end of the program in October – the purpose of which remains something of a mystery. The test of what appeared to be a drag reducing skin treatment was focused on the upper two-thirds of the starboard winglet. The left winglet remained in standard configuration. Boeing declines to discuss the details although photographs indicate a possible form of boundary layer modification.

Fuel cell in lower aft cargo hold (Boeing)

I’ve had several requests to show images of some of the other technologies tested on the EcoDemonstrator which, in 2013, will be followed by a second EcoDemonstrator program involving a 787. The final choice of airframe is still being decided but chances are it will be ZA004, one of the original Rolls-Royce powered test fleet. One large scale technology test, which partially drove the need for an aircraft with a cargo big enough to hold the experimental set up, was of a fuel cell developed with IHI. Regenerative fuel cells work much like rechargeable batteries and could power some electrical systems independently of engine-driven generators, says Boeing. This would reduce the load of the aircraft’s onboard electrical supply allowing for smaller, lighter generation systems which, in turn, could reduce overall weight, fuel burn and emissions.   

iPads in the flightdeck (Boeing)

Here Boeing New Airplane Product Development chief pilot Mike Carriker shows one of the iPads flown on the 737 as part of numerous tests. These ranged from evaluation of Jeppessen Advanced Research’s tablet application for its ability to optimize strategic flight planning, to viewing graphical weather, uploading new flight plans enroute and hosting the Boeing-developed iQRH, an iPad hosted electronic version of the pilot’s 737 quick reference handbook. The iPads were also tested as possible display screens for cabin and flight deck door security cameras.

Variable area nozzles (top) installed on CFM56-7B and (bottom) in open and closed modes (Boeing)


Tests were also conducted on a variable area fan nozzle (VAFN), developed for the aft end of the 737-800’s CFM56-7B engine with the assistance of CFM. The VAFN is designed to adjust the exit area of the fan duct which, in current commercial high bypass engines, is a fixed nozzle. The concept, which has been adopted for the Pratt & Whitney PW1100G-powered Airbus A320NEO, is designed to improve fan efficiency during take-off, climb and descent and is expected to provide noise benefits. For the CFM56-7B, which was not designed for a VAFN, the unit was fixed, and there are no plans to retrofit the device nor use it on the Leap-1B for the MAX.

Adaptive Trailing Edge (Guy Norris)

The ATE was tested for its potential for cutting drag and redistributing pressure loads. Modifications included the addition of a fixed wedge simulating a mini split flap on the trailing edges of the inboard and outboard flaps. Making the first real steps towards a morphing wing, a moving mini flap was also flown. The modified section, which occupied only 3% of the chord at end of the wing, was 68 inch long and could be actuated to a range of positions from 60 deg down to 30 deg up.

American cockpit check list (Guy Norris), and (below) graphic of device (NASA)


American’s latest aircraft still include the company-specified electromechanical checklist for landing and take-off.

..and finally, here’s a video describing the EcoDemonstrator..


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