Winglet Wonder

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 Jo Clark, founder of Aviation Partners, stand as a legend all of his own, in an industry populated by remarkable, talented people. He shares his winglet odyssey in a way only he could

The most basic aerodynamic understanding of how wings produce lift reveals that air flows faster across their upper surface than it does their underside. Physics dictates that an area of low pressure is created above, with higher pressure below; depending on individual interpretation, the low pressure then ‘sucks’ the wing upwards, or the high pressure ‘pushes’ it, either way, the product is known as resultant lift.

​It’s typical of aviation that wing function, a most fundamental requirement, comes with compromise. At the wing tip, high-pressure air naturally tends to ‘spill’ upwards into the lower pressure region above, the two airflows mingling into a violent spiral, or vortex, that creates significant drag. Reduce or eliminate these tip vortices and there are considerable savings in fuel burn and noticeable improvements in aircraft performance to be had. This was the basic premise upon which Joe Clark founded Aviation Partners, Inc (API) with Dennis Washington, in 1991, embarking upon a remarkable winglet story.

​EVA caught up with Clark at API’s impressive NBAA booth, where he was quick to emphasise that the winglet idea actually belonged to NASA aerodynamicist Richard Whitcomb. The issue of tip vortices had long been recognised and vertical endplates suggested as a solution, but during the 1970s, Whitcomb refined the idea, explaining: “It is a little wing. That’s why I call them winglets”.

​Clark had an impressive aviation career behind him even before the winglet idea hit, including time with Raisbeck Engineering and as a Learjet sales executive. He explains: “I’d seen the gamut of modification and was also involved in starting Horizon Airlines in the late 1970s, which we later sold to Alaska. Then Dennis Washington, a Gulfstream II owner and friend of mine, called me and asked if I could put winglets on it. I said: ‘What would you want to do that for?’ He said he wanted to make it look like a GIII and he thought it might perform a little better.

​“So I looked into it. I gathered a group of retirees from Boeing and Lockheed, my ‘dream team’, all of them in their 70s, and between us we decided to do a study. We reckoned it would cost $5,000 or $10,000 to see if we could put GIII winglets on a GII, and deduced it’d be a real problem. I went to Al Paulson at Gulfstream and asked if he’d sell us the data and he agreed, but reckoned it wasn’t a very good idea.”

​One of Clark’s septuagenarian team thought different. “Dr Bernie Gratzer had worked as chief aerodynamicist in Boeing’s wind tunnels. Now retired, he was lecturing as a university professor. He didn’t think wind tunnels accurately predicted the size or shape of a winglet. Bernie had a new design for something he called a ‘Blended Winglet’, which he thought would be really effective.” Gratzer obtained a patent for his Blended Winglet, later assigning it to API.

​Washington wasn’t immediately impressed by the idea so Clark, a man not to be dissuaded from pursuing what he considers a good idea, had some Blended Winglet images made up. “When I showed him he said: ‘That’s pretty cool!’ So I suggested we form a company and put Blended Winglets on a Gulfstream.

​“I went back to my friend Allen Paulson, who I’d bought a Learjet from when I was younger, and asked to buy the data to put the winglets on the GII. He said, ‘That’d be like putting hubcaps on a Cadillac,’ but I told him we thought they’d work well. We equipped the GII with sophisticated instrumentation an

d flew it without the winglets, then used a fibreglass boat shop to build two winglets. We flew the same points in the sky and got a 7.5% drag reduction – and it looked really cool too!

​“That launched us. We certified the GII and did about 80% of the fleet, giving the airplane another 200 miles of range. More importantly, the buyer’s perception was one of having a whole new aircraft because they looked so different. Most people bought them for the looks and were shocked at the performance.”

Second Phase

Today, API is perhaps most readily associated with the Boeing 737 BBJ and the commercial airliners on which the platform is based. The connection with Boeing grew out of what Clark calls API’s second phase. “Borge Boeskov, head of product design and later president at Boeing Business Jets, came to see me one day. He told me they had two people buying BBJs and they wanted them to look more like business jets. He knew our winglets looked cool, but he was dubious about how effective they’d be. His idea was for us to design a set simply for the looks, but I did a study and came back a month later promising around 6.5% drag reduction.

​“Boeing said they knew that was impossible, so I offered to build the winglets at our cost if they’d provide an airplane to fly them on – this was for the 737‑800, before it was certified. We built the winglets, but still didn’t have an airplane for them, so I placed them in a hangar, on stands at 737 wingtip height and about 120ft apart, then showed them to the Boeing execs. They thought they looked great and Borge called about a month later and said, ‘I think we have you an airplane’. The president of Hapag-Lloyd was coming over from Europe. He’d launched the 737‑800 and Borge told me: ‘We’d like you to come and meet him, but we want you to keep your mouth shut!’

​“Sitting next to him in the meeting he asked me who I was. I said, ‘I’m the winglet guy,’ and he said, ‘Tell me about it’. I said, ‘I’d like to but…’ Instead of telling him, we went down to the hangar. He walked around the winglets three times and reckoned they were a work of art. He said he’d provide an aircraft and, if they worked, he’d put them on his next 60 Boeings. We flew them, got exactly the performance we said and surprised the guys at Boeing. That’s how the 737 programme got started. Soon we had our first big order, from Southwest, for 550 ship sets. The rest is history – we’ve done over 7,000 airplanes since and,” he says, looking up at the rapidly winding counter above the booth, “saved the world 7.75 billion gallons of fuel so far.”

​More recently, API ‘reinvented itself’, according to Clark, creating the Split Scimitar winglet. “It gives you another 2.5%,” he says, “and the ‘splits’ are proving popular for both BBJs and airliners.”

​With API Blended Winglets available for retrofit on Hawker and Dassault Falcon business jets, Boeing 767s, older 737 BBJs and other types, and offered as line fit on new 737s and many Falcons, they’re now a common sight. “We’re in the Aviation partners Boeing joint venture for the BBJ and customers can buy them direct from Boeing or from us; about 97% of owners take them. On the Falcon, Dassault said they’d fit our winglets if we could reduce drag by 5% at Mach 0.8. We did, so they fit them, but at normal cruising speed we reduce drag by 7.5%, giving some models an extra 300 miles range.”

​Take a moment to study API’s products carefully, especially the Split Scimitar design, and they take on a unique, artistic form of their own, a fact not lost on Joe Clark. “They’re beautiful, stunning. They look like jewellery. And it’s the real deal, with all the engineering and LED lighting built in. They have carbon spars and carbon graphite skins, with metal fittings and aluminium leading edges for birdstrike protection.” He admits that the highly polished leading edges also look cool.

​“I tickle myself every time I look at one because they make the airplane look so elegant. The look’s important. You never get a second chance to make a first impression and I want our customers to be impressed. We used to ship our GII winglets in boxes printed in the same colour Tiffany used. They’re not cheap, but they pay for themselves in 18 months or two years and they’re very, very high quality.

​“It’s been an interesting story. We’re a small company and dealing with the big boys hasn’t been easy. It’s like you’re a mosquito around an elephant; one swish of its tail in the wrong direction and you’re dead! I’ve done a lot of ducking and diving! Now we’re looking at some new technologies on a Spiroid Winglet design. We could use a split spiroid on some of the bigger airplanes, to increase performance, but fuel is cheap at the moment and the airlines don’t see such an advantage in winglets. But there’s still so much fuel to be saved and we’ll keep coming up with new ideas, just like we did when I hired my original dream team.”