The year 2012 has proved moresignificant in the race for the AHSIgor I. Sikorsky Human Powered

Helicopter prize than any year since itsinception in 1980. Maryland has madeleaps and bounds with their flights ofthe Gamera II, and two new competitorshave entered the race from Canada andCalifornia, respectively. Team AeroVelo isfresh off success with a human-poweredornithopter, and the Neil Saiki-led NTSWorks team has strived to haveachieved both the first and the finalsuccessful flights in the AHS humanpowered helicopter competition.

Gamera Breaking Records

As described in the July/August2012 Vertiflite, the University ofMaryland unveiled their Gamera II

aircraft and flew it over the course ofseveral weeks in June. This aircraft set anNAA-certified record of 49.9 seconds offlight endurance, piloted by KyleGluesenkamp. In late August, Marylandwas back testing with a new vehicle,now called Gamera II XR (for “extendedradius”), with all new rotor blades andtransmission system enhancements.

Each step of the way, from Gamera Ito Gamera II and Gamera II XR,significant improvements have beenmade to the vehicle. This was in no smallpart due to the guidance and supportgiven by the Aerospace Engineering

department at the UMD Glenn L. MartinSchool of Engineering. Ph.D. studentWilliam Staruk said that at every stageof the competition they knew that itwas potentially the last chance theywould get to fly. However, each time

34 VERTIFLITE November/December 2012

The University of Maryland’s Gamera II has reached a height of 9.4 ft (2.9 m) in the AHS Human Powered Helicopter Competition. The AHS banner canbe seen in the background. Photo by Andrew Rivers, Essential Eye Photographics.

Human Powered HelicoptersRise Higher

By Benjamin Hein and Mike Hirschberg

Seconds after this photo was taken, Gamera II broke up in flight. Fortunately no one was injured.Ph.D. student Elizabeth Weiner’s fingertip is 7 ft 2 inches (2.2 m) high. Photo by Earl Zubkoff,Essential Eye Photographics.

flight attempts were undertaken andsuch significant improvements inaltitude and duration were made, that itwas virtually impossible for studentsand faculty to say “no” to continuedresearch and development of theGamera vehicle.

What was the recipe for the latestround of record breaking flights?Science and cycling. The Maryland teamhas continued improvements in thedrivetrain and optimization of thevehicle for the power-to-weight ratio ofthe pilot-vehicle-system, zeroing in on140 lb (63.5 kg) individuals. These pilotsare capable of generatingapproximately 8 Watts/kg, or animpressive 510 Watts (0.68 hp) for 60seconds.

The basic foundation of the Gameraaircraft family began with testing ofisolated rotor systems. This gaveMaryland the insight into basic designchanges to the rotors to minimize thepower required for a large, low-Reynoldsnumber rotor in extreme ground effect.The research surveyed different low-Reairfoils in order to find a combination ofhigh stiffness and good performance fortheir rotor blades. The team has alsoconducted extensive research onseveral factors of human powergeneration that culminated in therefined hand-foot crank system on allthe Gamera aircraft. This research set thestage for a string of success over thepast two years. Further improvementswere made to the Gamera II, for theAugust flights, based on extensivecalculation, testing and refinedmanufacturing processes.

For the Gamera II, Maryland studentsrevisited their multi-disciplinaryoptimization of airfoil and bladestructure. These efforts have yielded in alighter, stiffer and longer rotor blade. Asindicated in Maryland’s publishedpapers, the first flights in June ofGamera featured a rotor radius of 6.5 m(11.5 ft). However, the second round oftesting included a major diameterincrease to 7.2 m (23.6 ft). With theincreasing size of the rotor system, theGamera vehicle gained roughly 12 lb(5.4 kg) between the June and AugustGamera II vehicles. These designchanges predicted a net benefit for pilotworkload: a 12% reduction in the powerrequired to hover.

Maryland’s engineering effort hasobviously paid off. After only a fewflights, the vehicle hover endurance wasincreased dramatically to 65 seconds.Following the endurance expansionflights, the team quickly moved on tobreaking altitude records, culminating ina not-yet official altitude of over 9 ft.Measurements showed the pilot’s seatwas at 9.4 ft, while the vehicle wasrolling slightly so that one of thelanding posts might have been slightlylower. The longest flights so far havebeen held by student pilots Colin Goreand Kyle Gluesenkamp. The altituderecord has been captured by HenryEnerson. AHS members were on-site towitness the event. Unfortunately, thevehicle sustained significant damagefrom several hard landings; fortunately,no one was hurt.

As of October, these are the pilotstatistics for Gamera II flights, courtesyof Ph.D. candidate Ben Berry:

Colin Gore: totals of 39 flights, 903seconds and 8.6 ft (2.6 m)maximum altitude. The pilot of theunofficial 65 second enduranceflight.

Kyle Gluesenkamp: 24 flights, 673seconds, 7 ft (2.1 m) max. Kyleholds the official record of 49.9seconds from June. Kyle alsoperformed a 70 second tetheredflight in early August, the longestflight to date.

Henry Enerson: 21 flights, 405seconds, >9 ft max. Henry’s bestendurance flight is 55 seconds.

Dennis Bodewits: 13 flights, 259seconds, 2.5 ft (0.8 m) max.

Maryland student Judy Wexler wasthe sole pilot who achieved flight withGamera I. During 2011, she had made atotal of 6 flights totaling 37.8 seconds inthe air, reaching a maximum altitude ofabout 12 inches (0.3 m).

While they have nearly the rightcombination flight parameters to winthe prize, it will take further refinementsto simultaneously achieve the 3 maltitude and 60 sec endurance flight. Todate, the team has accomplished all thiswithout a control system. As a result,drift remains the major challenge forthe Maryland team. With both the handsand feet employed by the pilot, it will betricky for the Gamera team to develop acontrol system that allows the pilot tocontrol the vehicle. Maryland has goneback to the drawing-board and plans tofly again in November. The rotorcraftand human powered vehiclecommunity must wait for follow-onflight testing to see the next round ofupgrades to Gamera.

Atlas First Flight

Most followers will know thatanother serious team hasentered the fray to compete for

the AHS Igor I. Sikorsky HPHC prize.AeroVelo (“flying bike”) is led by twoindividuals, carried by a team ofvolunteers, engineers and others, andsupported by friends and family. Theteam also has a long list of supportersthat have donated hardware and moneyto their cause, including through afundraising campaign throughKickstarter.com.

Unlike most other human-poweredhelicopter teams, AeroVelo’s pilot ToddReichert is also one of its chiefengineers. Cameron Robertson is theother chief engineer, an indispensableasset when Todd is piloting the aircraft.With many lessons learned from theirsuccessful design, build and flight of ahuman-powered ornithopter AeroVeloexemplifies a tightly knit, efficient teamof engineers and mechanics. In 2011,the AeroVelo team also smashed the

Vol. 58, No. 6 35

Neil Shah and Jiho Yeom are part of the rotorfabrication team. Seven additional spareblades were stockpiled next to them.

collegiate human-powered bicyclespeed record, achieving 72.6 mph (116.9km/hr).

Like the Nihon University Yuri I testedin the 1990s and the University ofMaryland Gamera, AeroVelo is workingon a quad-rotor HPH. AeroVelo’s vehiclehas been appropriately named Atlas, asits dimensions are impressive. Each rotoris 20.4 m (66.9 ft) in diameter, with amaximum dimension of 58 m (190 ft) ona diagonal. Their circular spars are bothimpossibly long and at the same timeunexpectedly light. The blades have anon-linear taper that arguably give therotor an enhanced efficiency over thosewith linearly tapered blades. Theairframe system is also an incrediblylight carbon tube and polymer linetruss. Todd pedals on a heavily modifiedCervelo carbon bike frame suspendedwith the same polymer at the center ofthe truss. The transmission is driven bypolymer line to four custom Kevlar-wound spoke wheels at the center ofeach rotor.

The AeroVelo engineers alsoconducted extensive analysis on theirdesign. A multi-disciplinary optimizationof structural weight, geometry, andaerodynamic performance wasconducted with many design variables.Cameron indicated that a lifting-lineand wake model was used to study therotor aerodynamics with details of theroot and tip flow considered in their

design. At 120 lb (54.4 kb), the Atlas isnearly in line with Gamera I’s emptyweight. Ultimately, the power requiredby the pilot to hover is a combination ofweight and disk loading, as well asmechanical and aerodynamic efficiency.Based on measurements from the foot-only pedal system, Todd hasdemonstrated an incredible 770 Watts(1 hp) of power output for over oneminute, which is theoretically enough to

meet the endurance specification of thecompetition.

Testing of AeroVelo’s Atlas HPH wasconducted inside the Ontario SoccerCentre in late August/early September.At the end of each flight day, however,the entire aircraft was disassembled andstored in their trailer around back. Thisfeat was accomplished in as few as 20minutes, when flights went late into theafternoon. The Gamera is similarlydesigned for modular deconstruction, apainful compromise for vehicles sosensitive to the performance-weight-strength balance.

The AeroVelo team has dared tothink big, and the results speak forthemselves. After a few days of shakingout their design, the Atlas flew for anestimated 15 seconds. This statistic putsthe Atlas in the top three teams ofunofficial endurance records in thehistory of human-powered helicopterflight. The first being University ofMaryland, with its current record of 65seconds. To put this in perspective, thesecond best endurance time by anyHPH team was the Nihon Universityflight of the Yuri I at 24 sec (unofficial).This achievement only occurred afteryears of research and development, andin the second round of testing. However,credit must be given to the Japanese

36 VERTIFLITE November/December 2012

AeroVelo’s Atlas is the largest human powered helicopter to have ever flown and the first one inCanada. AHS photo.

AeroVelo rotor blade. The taper is not an illusion of the perspective. The wingtip canard is a controlsurface connected to levels on the handlebars of the bike. Photo by the author.

team for laying the groundwork for thesuccess of teams to follow. Similarly, theofficial flight endurance during the firstround of testing for the Maryland – withGamera I – was 11.4 sec.

AeroVelo does have one distinctadvantage over the competition at thispoint in time. Their vehicle hasamenities for a mechanical differentialpitch and roll system. The rotor bladeshave a variable pitch flap, integratedinto a canard style wing-tip. This systemis expected to enable the aircraft to stayinside a 10 m by 10 m (32.8 ft) squarebox when significant heights areachieved. While this team has also hadtheir fair share of mechanical failuresand fixes on the vehicle, AHS anticipatesanother round of testing in thefollowing months, with likely asignificant improvement inperformance.

Upturn First Flight andPassing of the Torch

The other major news in the race towin the AHS Sikorsky prize, alsodescribed in the July/August

Vertiflite, was the first flight of theUpturn. The aircraft and pilot RobertPasco achieved an impressive unofficial10 sec flight, at 2 ft (0.6 m) of altitude on

June 24, 2012. The flight was terminatedwhen he became exhausted and theaircraft was caught by a safety lineattached to the ceiling above. Roberthad competed in a bicycle race earlier inthe day in addition to three other flightattempts.

Neal Saiki had been part of the 1989student team at California StatePolytechnic University (Cal Poly) in SanLuis Obispo, California that built the firsthuman powered helicopters to lift offthe ground, culminating in “Da Vinci IV”– it flew for a record 8.6 seconds and aheight of 8 inches (20 cm). Saiki’s teamhad achieved the first successful flightin the AHS Sikorsky Competition andhoped than the Upturn would alsocapture the AHS HPH Prize. However,NTS Works has now turned its focusback to its core business. Nonetheless,the company has generously donatedthe Upturn to the California PolytechnicState University (Cal Poly) in San LuisObispo, California for continueddevelopment, so Saiki’s Upturn may stillachieve that goal. Under the guidance

of Prof. Kurt Colvin, the new team hasbegun to consider the tremendouschallenges of the AHS competition andapproaches to tackle them. The uniquepropeller-driven Upturn promises toshow even better endurance in thefuture in the hands of the university. Itwill be interesting to see if they can getthe weight out, increase efficiencyand/or increase their diameter to beatthe quad-rotors to the prize.

2012 – The Year of the HPH

Three human powered vehicleteams have flown in the past year,and the boundary of human-

powered VTOL flight has been pushedbeyond the 60 second mark. But evenwith the incredible advancements seenin human powered helicoptertechnology in the past year, thechallenge of the AHS Igor I. SikorskyHuman Powered Helicopter prize stillremains unclaimed after 32 years.However, unlike years past, it is safe tosay that it will not stay that way forever.

Vol. 58, No. 6 37

Todd Reichert (left) and Cameron Robertsonare both the brains, and Reichert is the brawnin AeroVelo’s human powered vehicle efforts.The team has made extensive use of polymerline for strength, rigidity and even for controllines. AHS photo.

During one of several late August tests, Atlas takes flight. Aeroelasticity, trimming the four rotorsystems and gyroscopic precession were all interesting challenges. AHS photo.

Upturn in the air with pilot Robert Pasco.

38 VERTIFLITE November/December 2012

Significant ChallengesRemain

Much as in the early years of thedevelopment of thecombustion-powered

helicopter, weight and control remainsignificant challenges to human-powered helicopters. With the harshlimitation on power-available to thevehicle by a single human for 60seconds, the HPH designers must refinetheir designs even further to eliminateweight, while maintaining stiffness andstrength. In hover, conventionalhelicopters are driven by inducedpower, which is a function of weight androtor disk area. If you consult helicopterperformance references, you will findthat the relationship is more stronglyweighted by weight than disk area. Sodesigners must find and expand thelimit of practical rotor radius, while

maintaining or even lowering thevehicle weight, which is the morepowerful parameter when it comes topower-required-to-hover. As we haveseen from the historical designsolutions, this limit is governed byblades stiffness, airframe strength andthe size of the facility in which it can betested.

The spirit of the competition is todesign, build and fly a vehicle poweredand controlled purely by a human.Governing the use of controls is stronglylimited by the regulation of stored-energy. Past committee chairs wereconsulted during negotiations withactive HPH teams as to whether storedbattery power is permissible. It wasconcluded that use of chemical energywould violate the spirit of the rules, asthey were originally written. Whileclarifications to the rules allow the useof batteries, in systems not contributing

to the rotor system power available,these will be prohibited followingAugust 2013. If needed, competitors willhave to find a way to generate electricalpower derived from the human pilot.

It was fairly obvious from videofootage of Gamera’s flights that anysmall disturbance leads to uncontrolleddrift, especially as the vehicle gainedaltitude. Credit must go to the AeroVeloteam for pioneering a unique system tocontrol the vehicle’s pitch and rollduring flight without the use ofbatteries. Similarly, systems are beingdeveloped for Gamera and Upturn tocontrol the vehicles’ attitude. It isunlikely that the 10 x10 m flightenvelope can be maintained without acontrol system. AHS looks forward toseeing how novel systems can beemployed to add the final leg of the trioof core regulations.

About the Authors

Ben Hein is a senior engineer atSikorsky Aircraft Corporation,currently investigating active rotor

technology. Ben holds patents inhelicopter design and rotor systemdesign. He has been the AHS Igor I.Sikorsky Human Powered HelicopterCommittee chair since May 2012.

Mike Hirschberg is the ExecutiveDirector of AHS International.

Cal Poly has taken over the Upturn. An organization meeting was held in September. Cal PolyPhoto.

Vehicle Da Vinci III / IV Yuri I Gamera I Gamera II Gamera II XR Upturn Atlas

Team Cal Poly U. Nihon U. U. Maryland U. Maryland U. Maryland NTS Works AeroVelo RotorType

(# Blades/Rotor) Single MR,

Propeller (2) Quadrotor (2) Quadrotor (2) Quadrotor (2) Quadrotor (2)

Single MR, Propeller (4)

Quadrotor (2)

First flight Dec 1989 Dec 1993 May 2011 June 2012 Aug 2012 Jun 2012 Aug 2012 Rotor diameter 100 ft / 30.5 m 33 ft / 10 m 42.6 ft / 13 m 42.6 ft / 13 m 47.2 ft / 14.4 m 85 ft / 25.9 m 66.9 ft / 20.4 m Max dimension 100 ft / 30.5 m ~ 80 ft / 24.5 m 105 ft / 32 m 105 ft / 32 m 115 ft / 35 m 85 ft / 25.9 m 190 ft / 58 m Empty weight 97 lb / 44 kg 83 lb / 38 kg 106 lb / 48 kg 76 lb / 34 kg 82 lb / 37 kg 95 lb / 43 kg 120 lb / 54.4 kg

Max endurance 8.6 sec 19.46 sec 11.4 sec 50 sec 65 sec 10 sec 15 sec Max altitude 8 in / 20 cm 8 in / 20 cm 1 ft / 30 cm 3.5 ft / 1.1 m 9 ft / 2.7 m 2 ft / 0.6 m 1.6 ft / 0.5 m

n/a = not available

Successful Human Powered Helicopters in the AHS HPH Competition

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