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NASA F-16XL laminar-flow tests will aid HSCT effort

NASA EXPECTS TO begin, a year-long laminar-flow flight-test programme, on a Lockheed F-16XL by October, in support of US industry efforts to build a next-generation high-speed commercial transport (HSCT).

The work follows delivery of a new laminar-flow panel to the agency's Dryden Flight Research Center at Edwards AFB, California, late in January. The testing is part of NASA's high-speed-research (HSR) programme.

The 2.4 x 7m titanium glove, developed for about $14 million by Boeing, McDonnell Douglas and Rockwell, contains more than 3 billion laser-drilled holes in the active - or suction - section.

The glove is being fitted to the left wing of NASA's second F-16XL, XL-2, and covers more than double the surface area of a previous active-laminar-flow panel tested on the XL-1. It is expected to develop laminar flow across 50-60% of the local chord. The surface-contour details have been developed from data collected during tests of an instrumented, passive glove previously mounted on the XL-2.

NASA F-16XL laminar-flow research manager Marta Bohn-Meyer says that the next nine months will be spent on integration activity to prepare for flight tests and will involve some major modifications in external appearance. The first five to ten flights will cover flight-envelope clearance as well as qualification of the suction device - a Boeing 707 turbo-compressor modified to run at higher RPMs.

"The first laminar-flow demonstrations won't be until one month after first flight," says Bohn-Meyer, who expects that between 45 and 60 flights will be made throughout the test programme.

The glove is designed to optimise suction levels and to validate design tools for the HSCT, which may include active laminar-flow control techniques. The glove is fitted with a suction-distribution control system to vary the area and intensity on suction in flight.

Meanwhile, sister aircraft XL-1 is undergoing a supersonic-boom probe experiment with a NASA Lockheed SR-71. The tests involve using the XL-1 as a probe to fly in the wake of the SR-71 and examine the boundary of the supersonic-boom shock wave.

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