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Raisbeck Continues to Confront Drag Queens
Well, not exactly. But James Raisbeck's latest drag reduction project
involves a full-fledged attack on the steep, transonic drag rise
incurred by Learjet 30-series aircraft at high-speed cruise. Raisbeck
Engineering (Booth 2501; Static 22) has a 30-year involvement with
the Learjet, including development of Mark II and Mark IV wing leading
edge modifications for 20- and 30-series Learjets, later wrapped
into Century III and Soft Flite wing designs, according to the firm.
Most recently, Raisbeck developed the Learjet aft luggage locker,
a factory standard option on Learjet 31A aircraft. Prior to development
of the locker, lack of an external baggage compartment was one of
the aircraft's most notable shortcomings.
Now Raisbeck has access to the latest CFD software, enabling the
firm to develop a new generation of wing systems using the latest
computer tools, Raisbeck told Show News on Monday evening.
En route to NBAA in a Learjet 35, Raisbeck spent most of the time
collecting base-line drag polar data. There are many opportunities
to reduce drag on the vintage 20- and 30-series Learjets, according
to Nate Lachendro, Raisbeck's lead aero wizard. "Quite candidly,
there has been apparently no significant drag reduction on these
aircraft in four decades, save the addition of winglets to the
Learjet 31," Lachendro commented. Raisbeck echoed those comments.
Raisbeck's new initiative will focus on developing a wing-to-body
fairing for 30-series Learjets. Learjet fitted such a fairing
to Model 55 and 60 aircraft, but didn't bother with earlier models.
Preliminary aero tests by Raisbeck indicate that lack of such
a fairing contributes to a local Mach number approaching 1.6 a
few inches aft of the leading edge of the wing, close to the fuselage,
while the Learjet 35 cruises at 0.81 IMN. If a properly contoured
wing-to-body fairing can be developed, it could reduce overall
drag by 10% at high-speed cruise. But Raisbeck Engineering won't
stop there. Lachendro is also looking at drag reduction modifications
of the engine nacelles, pylons and wing trailing edges. For more
information, visit www.raisbeck.com or call (206) 723-2000.
By Fred George
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