The risk all of us in aviation focus on is flying safety, and that is paramount. But there is another major risk to consider, and that is the chance that a new design will not actually be an improvement. That's why evolutionary airplanes have enjoyed such success,and none more so than the Hawker 125 line of business jets that traces its roots back to 1962. Now, with winglets to add range and climb performance, and an advanced Collins Pro Line 21 cockpit, the Hawker 850XP delivers more of what pilots and passengers have loved about the airplane for 44 years, and the improvements are risk free. The Hawker is joining a growing line of jets to sprout winglets, and they all have the same objective - to make the wing behave as though it were longer. In general, the longer the wingspan, the more efficient and lower drag it will be at typical airspeeds. That's why the most efficient of airplanes - gliders - have such long and slender wings. A long wing will climb more quickly and have lower drag at high altitude cruise.
However, as with all things in airplane design, there is a tradeoff when wingspan grows. Each increment of wingspan lengthening increases the bending loads on the wing root, and thus requires more structural strength to carry the loads. The issue is a matter of leverage. For example, if you hold your driver at the end of the grip, it will feel heavy. Pick up the same golf club near the center of the shaft, and it feels lighter. Your hand is absorbing the increased bending moment of the full length of the club shaft.
The increased moment, or leverage, of a longer wing multiplies the loads on the center of the wing, particularly when the effects of turbulence are considered, as they must be. At some point the loads of a long wing would be so great that the center of the wing would need to be far too heavy and thick to be efficient. That's why wings are a compromise between the aerodynamic efficiency of long span and the structural requirements to carry the bending loads.
But properly designed winglets can deliver many of the aerodynamic benefits of greater span with only a fraction of increased strain on the wing structure. The interaction of the winglet with the high-pressure air that flows out from under the wingtip is very complex, but in general, the air behaves as though the wing continued for a greater span. That's one of the reasons the most efficient winglets angle outboard.
Aviation Partners Inc., an aerodynamic design firm specializing in winglets that also created winglets for the Boeing 737 and other jets, turned its attention to the Hawker a few years ago. The people at Raytheon Aircraft, Hawker's parent company, considered making a deal with Aviation Partners, but decided to create their own winglets for new airplanes. Raytheon has experience with winglets on the Beech King Air 350 and also had the opportunity to optimize the Hawker winglet design for new construction airplanes without compromise that may be required to fit them to existing airplanes.
