Raisbeck Learjet Newsletter

RADIAL Vol. 1, No. 4, August 2006 ZR LITE Performance System: Vortilons help stall characteristics

ne of the lessons the ZR LITE program reinforced here at thus causing separation and a sudden loss of lift, i.e. stall. ORaisbeck Engineering is minor changes can lead to significant By re-energizing the airflow over the wing at high angles of results. ZR LITE’s vortilons could well be the poster child for this attack vortilons delay the airflow separation that causes stall. philosophical concept. Much has been done to improve the stall The vortilons also work with existing segments of the wing to characteristics of Learjets over the years and ZR LITE presents improve stall characteristics. For example, the inboard pair of another important step forward in the 35/36 series vortilons are placed halfway between the stall strip wing. The four vortilons are aerodynamically and the stall fence. The existing stall fence is positioned on the leading edge of the wing there to insure the inboard section of the to greatly improve the Learjet’s stall wing stalls first, thereby allowing the characteristics. outboard section to continue creating When an aircraft has poor stall lift. This gives the pilot control of characteristics or poor low speed the ailerons longer into the stall. The handling there are many solutions that inboard vortilons performs as a second may exist, ranging from redesigned stall fence. They shed a vortex of high leading edges to the incorporation energy air, which in turn helps prevent of stick shakers and pushers. Two of the air separation that occurs inboard the more simple and effective solutions from spreading out to the ailerons. In are vortilons and vortex generators. addition, the outboard pair of vortilons Both vortilons and vortex generators create are positioned directly in front of the ailerons, disturbances in the air flowing over the wing. They which helps keep the air attached to the ailerons re-energize the airflow, which delays the onset of stall. Vortex further into the stall. The results are an aircraft that requires generators, because they are typically located on upper surface significantly less pilot workload during an impending stall which of the wing, create drag. Vortilons, on the other hand, are in turn allows the recovery to be very straightforward. positioned on the lower surface of the leading edge, thus they The shape and position of vortilons is not an exact science only effect the airflow at the high and requires a significant amount angles of attack encountered The results are an aircraft that requires of flight-testing and knowledge to during a stall. Vortilons have no significantly less pilot workload during be precise in their location. Our performance deterioration in all an impending stall. engineers and pilots designed and other phases of flight. tested many vortilon geometries To understand how the vortilons help an aircraft’s stall and locations while performing hundreds of stalls in order to characteristics, one first must understand why an aircraft stalls. arrive at the ideal configuration forZR LITE. As you can see, small As the air flowing over the upper surface of the wing gets further changes can indeed lead to big results. The Raisbeck ZR LITE is aft, it slows down and loses energy causing the boundary layer living proof. to get thicker. During a stall, as the angle of attack increases the boundary layer continues to grow and lose more and more energy. If the angle of attack gets great enough the air on the upper Scott Keefe surface of the wing will lose the energy it needs to stay attached Marketing Manager, Learjet Performance Systems Raisbeck Learjet Newsletter RADIAL Vol. 1, No. 4, August 2006 ZR LITE – A pilot’s point of view

ood pilots are sometimes hard to find. And Gsome of the best are found in the left seat of the celebrated Learjet. As the chief pilot of Arizona-based Wheels Up Aviation, Prits Tailor certainly qualifies as one of the finest. Having logged over 5,000 hours of total time in Learjets, he has certainly become an expert over the years. Tailor’s opinion of the Learjet is better than ever since installing the ZR LITE on 35A-318 early this year. Time savings alone has made this performance system a must for their operations. The Learjet 35 already offers a combination of speed and range at a cost that leaves its competition in its wake. When Tailor heard that he could reduce his operating costs further and takeoff with more weight by installing the new ZR LITE Performance System, he jumped at the opportunity. He is thrilled with his new performance capabilities and his fuel savings are money in the a longer take-off roll than available runway using flaps 8° and bank. wouldn’t meet the second segment climb gradient if using flaps Tailor is as impressed with the ZR LITE results today as he 20°. was on his first flight from Seattle to Wichita. The departure “Something had to give and, of course, it would not be offloading passengers. It would be a reduction in fuel witha pit stop an hour into flight,” Tailor said. “The flaps 14° setting “I wouldn’t have believed it if I hadn’t allows us to carry a certain number of passengers with more fuel experienced it myself.” and still have a good warm fuzzy feeling after rotation. To be Prits Tailor, Chief Pilot, 35A-318 honest, I’ve used flaps 14° on every takeoff since the ZR LITE was installed.” conditions from BFI were ISA +10 with a takeoff weight of 16,500 Already a fantastic combination of performance and value, lbs. Tailor couldn’t believe he didn’t have to step climb to achieve adding ZR LITE to your Learjet maximizes its potential. The FL 430 and easily attained a cruise Mach of .76. After realizing new flaps 14° takeoff position allows hundreds of more pounds his Learjet’s new capabilities, Tailor’s exact words were, “I’ll be in takeoff weight from the limiting airports Tailor frequents. damned. I wouldn’t have believed it if I hadn’t experienced it By increasing the overall operational flexibility of the Learjet, myself.” Raisbeck Performance Systems make both the plane and pilot Prits has been logging 90 hours a month since ZR LITE was look better. Just ask Prits or any other Raisbeck-equipped Learjet installed and most of his legs are from limiting runways. The pilot! The owner also wins as the ZR LITE is an investment with a runway conditions are too short, too hot, high in altitude or a strong ROI. ZR LITE — strong performance and ROI. combination of all three as is the case from Deer Valley, Arizona. Under these limiting conditions, Tailor explained that neither the flaps 8° nor flaps 20° takeoff setting would work with his desired fuel load and number of people on board. The plane would need

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