{"id":11616,"date":"2017-10-05T00:07:54","date_gmt":"2017-10-05T07:07:54","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=11616"},"modified":"2017-10-15T22:28:38","modified_gmt":"2017-10-16T05:28:38","slug":"david-ullman-flying-on-multiple-tiny-motors","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/david-ullman-flying-on-multiple-tiny-motors\/","title":{"rendered":"David Ullman: Flying on Multiple Tiny Motors"},"content":{"rendered":"

David Ullman, a professor emeritus at Oregon State University, predicted electric flight\u2019s future in articles in 2009* and 2010**.\u00a0 His predictions have come (mostly) true and David is working to fulfill the rest.\u00a0 His background in mechanical and aeronautical engineering provides credibility for his prognostications, and he\u2019s taking practical steps to take electric aviation to a next, very creative level.<\/p>\n

While Uber\u2019s Elevate Summit in Dallas earlier this year focused on big-money players in the vertical aviation world, David and co-creator Vincent H. Homer promoted their paper, \u201cThe IDEAL for Near-VTOL Aircraft.<\/a>\u201d \u00a0IDEAL represents \u201cIntegrated Distributed Electric \u2013 Augmented Lift\u201d flight, using \u201cthrust from distributed electric propulsion to improve the lift and drag performance of the aircraft during takeoff, cruise and landing.\u201d\u00a0 As their paper explains, VTOL flight requires power equal to 1.25 times the weight of the aircraft to ensure secure takeoffs and landings.\u00a0 An IDEAL aircraft would require thrust equaling about one-third of the STOL craft\u2019s weight to provide excellent performance.<\/p>\n

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It doesn’t look much like a four-seat Jabiru, but that’s the donor plane for the DW-1 – the realization of an IDEAL<\/p><\/div>\n

Because so little relative power is necessary, the IDEAL aircraft would have greater range \u201cusing current batteries,\u201d or would be able to reduce battery weight for the same range as that of a comparable VTOL craft.<\/p>\n

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The Ullman wind tunnel in his Independence, Oregon Hangar\/garage.<\/p><\/div>\n

Even better, though, the design can provide management of the lift distribution on the wing, and the 16 to 20 motors David proposes would provide a high level of reliability.\u00a0 When he first saw the design concept last year, your editor was a bit skeptical, but having seen David\u2019s large wind tunnel and well-defined testing techniques, that outlook has been replaced by the attitude that David and Vincent are on to something with great promise.<\/p>\n

Similar but Different<\/strong><\/p>\n

Similar to NASA\u2019s X-57 Maxwell, the DW-1 (real-world version of IDEAL) is a distributed thrust machine, with 16-to-20 small electric ducted fans spread across the front of the wing.\u00a0 The X-57 has tractor (forward-facing) propellers, though, pushing air over the top and bottom surfaces of the wing.\u00a0 DW-1\u2019s propellers are housed in ducted fans blowing only over the top of the wing.<\/p>\n

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Electric ducted fans blow air over only the top of DW-1’s wing<\/p><\/div>\n

According to the presentation on the DW-1, <\/a>the redesigned wing has only 60 square feet compared to the original\u2019s 100.5, and the aspect ratio goes from 9.8 to 15.\u00a0 That would reduce the overall chord of the wing to about two feet, requiring a good low-Reynolds number airfoil, something accommodated by the Riblett 37 A6 18 used in initial wind-tunnel tests.<\/p>\n

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Maxwell visits future DW-1. Mary Maxwell takes in David Ullman’s explanation .about future for rebuilt Jabiru: red and green beard helped David direct traffic at fly-in that day<\/p><\/div>\n

 <\/p>\n

The Jabiru, which David is resuscitating from a wreck, has its six-cylinder Jabiru 3,300 cc engine in place for initial flight testing, which should take place soon.\u00a0 After that, the new wing and distributed power system will take the old wing\u2019s place, and the Jabiru will give way to a newly streamlined nose, which will also make the fuselage a lifting body.<\/p>\n

16 or 20 Tiny Ducted Fans<\/strong><\/p>\n

David has selected an electric ducted fan that in the current design, will populate 16 places across the leading edge of the wing.\u00a0 Each 50-millimeter (almost two-inch) diameter fan can produce 4.2 horsepower and nine pounds of thrust \u2013 67.2 horsepower and 144 pounds of thrust total. \u00a0\u00a0David notes that Airbus\u2019s E-Fan\u2019s two EDFs produced 86 horsepower peak.\u00a0 At $375 each, the little powerhouses total $6,000 and weigh only 21 pounds total (including 11 pounds of 10 AWG wire).\u00a0 Admit that it\u2019s a bit noteworthy that the wiring weighs more than the motors.<\/p>\n

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16 of this two-inch diameter EDFs can produce 144 pounds of thrust<\/p><\/div>\n

Besides the extremely redundant power system, the blowing adds to the lift coefficient for the wing.\u00a0 A plain wing without flaps can take off at 51knots (58.65 mph), and the same wing with 10 degrees of flaps can leave the ground at 44 knots (50.6 mph).\u00a0 30 degrees of split leading-edge flaps yields a 37 knot (42.55 mph) lift off, but David\u2019s ducted wing drops that to 24 knots (27.6 mph) \u2013 ultralight speed.<\/p>\n

Predicting Again<\/strong><\/p>\n

A great deal will depend on available batteries.\u00a0 David keeps an optimistic outlook about that, the chart below detailing current realities and projected, realistic assessments of the near future. \u00a0He sees batteries as evolving rapidly, with an annual rate of improvement in energy density, for instance, of seven to eight percent.\u00a0 Costs are dropping, making future costs even more of an incentive to go electric.\u00a0 DW-1\u2019s 16 motors cost $6,000, but compare that to a $17,000 Rotax 912, which weighs 171 pounds and consumes about $25 per hour in gasoline.<\/p>\n

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We\u2019ll be following up on the DW-1.\u00a0 David\u2019s history as a designer, teacher, and President of EAA Chapter 292 shows that he can organize and carry out significant programs.\u00a0 His progress on what last year was a basket-case Jabiru shows his practical capabilities.\u00a0 This could be a contender at STOL events in the near future.<\/p>\n

Book Review:\u00a0 What Will Your Grandchildren See When They Look Up?<\/strong><\/p>\n

Amazon explains a book edited by David Ullman this way.<\/p>\n

\u201cThis book explores the future of aviation. It was developed by students in a class titled \u201cThe History of Aviation 1800-2200\u201d offered through the Honors College at Oregon State University. The course reviewed the history of atmospheric flight and, in parallel worked with the students to generate a vision of the future, specifically at a time when their grandchildren become aware of objects in the sky – about 2050. The students make predictions about the future of drones, autonomous flight, supersonic passenger flight, the use of new materials and other topics driving the evolution of aviation in the twenty-first century.\u201d<\/p>\n

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Your editor read the first edition, and aside from a few quibbles (former English teacher, you know) found the work of the young people involved to be a great reflection on David\u2019s teaching skills.\u00a0 The second edition, quibble-free, is available for a modest price and is well worth the time of any forward-looking reader.<\/p>\n

*\u201cHear the Hum? An electric airplane may be coming soon to an airport near you.\u201d KITPLANES, November 2009, pp 15-19.<\/em><\/p>\n

**\u201cThe Electric Powered Aircraft: Technical Challenges\u201c, EAA Experimenter, May 2010.<\/em><\/p>\n