Seventy four miles pedalled in 3hr 54min:the epic story of the Daedalus record flightby John McIntyre; plans and detail draw-ings by Pat Lloyd

MAN’S GREATEST flight, in terms of physical effort,design efficiency and sheer bravado established anincredible record on 23rd April. As an answer to thequestion ‘What’s next?’ the possibility of recreating themythical escape of Daedalus from Crete had first beensuggested, back in May 1984, by John Langford andMark Drela shortly after their Monarch HPA had wonthe œ20,000 first prize in the RAeS organized speedcompetition. Spanning nearly four years the project hadbought together experts in the field of aeronauticalengineering, meteorology, medicine and even classicalliterature - all with one, common hobby -AEROMODELLING.

AchievementThis aeromodelling-based achievement has

reached far beyond the flight itself by pushing forwardunderstanding of the limits of human endurance.Ultimately it could enable construction of high-altitude,long-duration aircraft that may even find application inthe Planetary Sciences - or be flown in the atmosphereof Mars as airborne ‘Martian Rovers’.

Veterans of the MIT Chrysalis and Monarch HPAteams, most of them aeromodellers holding AMANational and FAI International Records, formed thecore of this remarkable team. They set their target,survived disaster as well as success and with more thana little skill reproduced a classic myth with a reality thatmade headlines around the world.

Prototype successThe Daedalus aircraft, unique amongst HPAs in

that the limits. of the pilot/engine were established fromdata collected after endurance tests carried out on aspecially constructed ergometer, is the result of over

two years’ design and construction work. Only after thesuccess of a prototype, the Michelob Light Eagle,sponsored by Anheuser Busch, did the working groupfeel ready to build Daedalus. This accumulated manyhours’ flying time and set a distance record on 22ndJanuary 1987 (when Glen Tremml flew 37.2 miles atEdwards Air Force Base). Nearly three-quarters of amillion dollars - actually $685,000 - was contributed bymajor sponsors NASA, MIT and United Technologies,while many other companies donated valuable equip-ment and support.

Calculation and experimentBut what of the craft itself? Mark Drela, Senior Engi-neer was responsible for aerodynamic design. A pastmember of Chrysalis and Monarch HPA teams andAssistant Professor in the MIT Department of Aeronau-tics at MIT, he devised a computer program accuratelyto predict the effects of laminar separation bubbles onaerofoil performance in order to design efficient wing,propeller and fairing sections. The extremely highaspect ratio wing, meant to operate at a cruise coeffi-cient of lift (CL) of 1.1 uses three different sectionscarefully tailored to the conditions of falling ReynoldsNumber as the plan form tapers from 45in root chord to15in at the tip.

Everything about Daedalus is the result ofcareful calculation and experiment. For example, thefairing housing the drive shaft is asymmetric with asection that tapers with propeller diameter so that it canextract thrust from the twisted slipstream, thus increas-ing overall efficiency.

A flying speed of 15 mph was dictated by theneed to fly against a possible light headwind and stillmake the seventy four mile crossing to Santorini inunder seven hours - the longest daylight period forwhich winds of under three knots could be expected!.Using a single bracing wire to carry some of the liftload from the wing was found optimum for flyingspeeds between 11 and 18 mph (an aircraft with exten-

MAN’S GREATEST FLIGHT

sive wire bracing, such as Gossamer Albatross, canachieve greater endurance and range, but not within aweather ‘window’ that would permit a crossing of theCretan Sea).

The streamlined fuselage, which provides notonly a pilot fairing but vertical area for stability, issuspended from the wing with just two small bolts. Asemi-recumbent cycling position reduced frontal area;ergometer tests showed no disadvantage compared tothe more usual ‘upright’ arrangement.

Power is transmitted to the propeller via carbonfibre drive shafts and special gearboxes built by BobParks, the Senior Engineer responsible for mechanicaldesign. His uncompromising craftsmanship served as aninspiration to the team. The variable pitch propeller,geared to rotate at 1.1/2 times pedal revolutions, iscontrolled through Bowden cable R/C model type‘snakes’ from a small lever so the pilot/engine canmatch output to his pedalling rate. In truth, Daedalus isan REM model - that’s Rudder/ Elevator/Motor! Thereare no ailerons. Rudder alone provides more thanadequate maneuverability during the long, slow flights.The all-flying fin and tailplane are connected to a side-stick at the pilot’s right hand by closed-loop braidedKevlar cables. A foam servo tab, which runs the wholelength of the fin trailing edge, generates a powerfulcantering force to allow ‘hands-off’ flight - a mostimportant consideration, for at the end of a multi-hourflight the pilot, who will be fatigued, may not bethinking clearly at

Tubular secretsThe carbon-fibre epoxy tubes which form the craft’sload-bearing structure are all hand-made by structuralengineers Hal Youngren, Juan Cruz and ClaudiaRanniger using uni-directional CF pre-pregs. Thismaterial is supplied uncured, sandwiched betweenwaxed paper backing sheets. It is cut to size andwrapped around Teflon release-film-coated aluminummandrels. Great care is taken to ensure that the spirallywound carbon fibre plies butt exactly, leaving no gaps.The number of layers, and their angle of application isdetermined by the load to be sustained. For example, in

the main spar (which carries not only the main wingbending loads but some compression and torsion too)the carbon fibre is applied at plus and minus fortydegrees to the tube’s longitudinal axis. On the otherhand, the equivalent angle at the rear spar, which carriesonly tension and compression is ñ 12 degrees.

‘The entire fuselage tips the scales at51b 14ozs...’

Tapered caps are then added to form flanges atthe top and bottom of the spar. The tube is wrapped with‘peel ply’ to leave a rough surface which will aidsubsequent bonding. Finally the whole sandwich istightly bound with heat-shrink tape on a purpose builtmachine.

When enough tubes had been made they weretaken 200 miles to the Sikorsky helicopter plant wherethey were oven-cured at 175ø. At this temperature thealuminum mandrel expands and the heat shrink tapecontracts, thus compacting the carbon fibre. Tubes overone-inch diameter are pulled off their mandrels - anoperation not always without difficulties, as modellersor builders of composite HPAs will be aware! Afterseveral unsuccessful attempts to free one sixteen-foottailboom, involving winches and two university rugbyteams, the trio of tube builders stayed up till 2am toensure no witnesses before fixing one end of themandrel to a concrete bollard and lashing the tailboomitself to the back end of a truck, which was then slowlydriven away... Smaller tubes are etched out with hydro-chloric acid, as usually employed for cleaning swim-ming pools.

To prevent catastrophic buckling of such thinwalled, large diameter tubes, balsa/ Rohacell sandwichbulkheads are fitted at 10in intervals. Tubes are buttedat joints, reinforced with carbon fibre cloth and finallylashed with Kevlar or carbon fibre. The five piece, 112ftmainspar, stressed to 2G, weighs only nineteen pounds -and the entire fuselage structure, which is 26ft long and6ft high, tips the scales at just 51b.14oz!

Ribs and wrappingIn common with other HPA projects, wing ribs are from1/4in thick, 1lb density styrofoam beadboard. Cap stripsof 1/32in basswood are bonded with aliphatic resin;holes around the spars are locally reinforced with 1/16inbalsa sheet.

Remarkably, the leading edge sheeting is hotwire cut - not wrapped - from 1.1/41b density pink foamsold in the States under the trade name Foamular’.Steven Finberg, Senior Engineer in charge of electronicdesign, built a numerically controlled cutter expresslyfor this purpose. This resembled two upended ‘X-Y’plotters bolted to a ply base and connected by nichromewire. IBM donated a PC which can be programmed tocut the complex, tapered wing sheet panels. Result: amost accurate profile which means the lowest drag andrequired power yet achieved in any HPA.

Load testing the Michelob Light Eagle wingusing bottles filled with water.

A pilots eye view of the cockpit.Photo Steve Finberg

Ryan recumbent cycle paces Daedalus ‘A’ over the vast flats of Edwards air force base in California. Significantly,with experienced cyclists the aerodynamic efficiency of the human powered aircraft enables airscrew drive to matchthe effort required for the wheeled bicycle. Photo Steve Finberg

Covering of 0.0005in tensilised Mylar, donatedby Paul MacCready of Gossamer project fame (whokept in close touch with the Daedalus team throughout)is fixed to the wing structure with two sides tape andcontact adhesive. ‘Incredible’ is the only way to de-scribe the empty weight of 69.1/21bs; carefully calcu-lated construction of carbon epoxy being solely respon-sible for this.

Pedal powerThe major difficulty facing HPA builders has alwaysbeen finding athletes who are also qualified pilots. In acomplete reversal for the Daedalus project, five worldclass cyclists were recruited and taught to fly, first inhigh performance gliders and then in a flight simulatorbuilt by Steven Finberg. Training programs werestaggered so that one flier would always be at readiness.Who were the chosen ones?

Kanellos Kanellopoulos is a fourteen-time Greekcycling champion, a graduate of the University ofAthens and a member of the Greek Olympic Cyclingteam. Erik Schmidt and Frank Scioscia are full-timeamateur cyclists from Colorado and Pennsylvaniarespectively; Frank being a member of the US NationalCycling team. Co-ordinator and senior member of theDaedalus pilot team was Glen Tremml from Connecti-cut, an amateur triathlete and licensed sailplane andlight aircraft pilot. Fourth member of the pilot/engineteam was Greg Zack, whose

‘To keep Daedalus flying nearly onekilowatt of waste heat is produced...’

credentials include two years’ participation in nationallevel cycling races in the States.

What problems are faced in translating humanpower for flight? Working as an aero engine, the pilotreaches only about 20% efficiency, which means that ingenerating the 200 watts needed to keep the aircraftflying nearly one kilowatt of waste heat is produced - asmuch as a one-bar electric fire! Preventing overheatingand dehydration thus assume major importance. Most ofthe fuselage facing is covered in reflective, silver Mylarto minimise solar heating, and a large, carefully de-signed air scoop beneath the wing collects the oh-so-important cooling air.

To compensate for fluid loss, five litres of acocktail of a carefully balanced mixture of salts, waterand glucose, formulated by project physiologist Dr.Etham Nadel in association with the Shaklee Corpora-tion who specialise in the manufacture of sports foods,was carried in six plastic ‘lemonade’ bottles. Consump-tion was regulated at one litre/hour!

First wingsFirst flight of Daedalus A was on 2nd December 1987.By the second week in January ’88 twenty-four hours of

air time had been accumulated, including four flights ofover 25 miles each (thus breaking Bryan Allen’s recordof 22 miles, set in 1979) during a three-day period byGreg Zack, Erik Schmidt and Kanellos Kanellopoulos.

Daedalus flew well from the start, its powerrequirement of only 2.9 watts per kilogram of pilot massat 15mph being significantly lower than the equivalentfigure of 3.5 w/kg for Gossamer Albatross for a speedonly two-thirds as much. The specific power require-ment (watts/kg) is the governing requirement forsuccessful human powered flight. As a further compari-son, Gunther Rochelt’s Musculair I needs 220 watts fora pilot weight of 54kg, meaning an endurance-limiting4.2 w/kg requirement.

Daedalus A was badly damaged in a crash on 7thFebruary 1988, caused by a combination of a thermalunder one wing and a stretched rudder cable. Repairswere not completed until the middle of March. In orderto minimise the risk of a further similar crash thedihedral was slightly increased. By February 1988Daedalus B was ready. After testing, both craft (and theMichelob Light Eagle) were taken to McGuire wherethey were loaded into a Greek Air Force C-130 andflown, via Athens, to Heraklion on Crete itself.

There had been no idleness in the precedingweeks. A hangar had to be shipped to Crete and erectedfor the craft’s arrival - a process which took ratherlonger than expected as the crew were at first unable toreconcile the high level of craftsmanship needed forHPA assembly with the rather more basic standardsusually applied to hangar building!

Daedalus B was given a shakedown flight atHeraklion Airport. It seemed as though the whole townbad turned out to watch, for the terminal buildingbalcony was packed as the craft was carried out andrigged with the sea and the barren island of Dia, aboutthree miles offshore, as a backdrop. After a short roll thewheels lifted from the tarmac and Daedalus slowly flewthe length of the runway - a milestone in itself; its firstflight in Crete.

In the event it was to be nearly a month beforethe weather, hotter than expected and dominated bypersistent headwinds, allowed a chance for the Santoriniflight. Three attempts had to be abandoned in the firstweek alone. This frustrating period was spent in makingdetailed improvements to the aeroplanes, and, of course,pilot training continued so that one was always onstand-by. Various unsuccessful attempts were made tocycle up Mount Ida in the centre of the island! Defeat -and buckled wheels - were the result. Nevertheless,besides sightseeing, time was taken up with a usefulseries of seminars covering project-associated topicssuch as Aerofoil Design and Documentary Film Mak-ing.

Readiness...Towards the middle of the third week in April ’88 theevening weather forecasts began to look more hopeful.Northerly winds dropped and the sea became a mill-pond. During Friday the 22nd, Steven Bussolari, Project

The sheer grace of Daedalus ‘A’ in flight at Edw

ards is captured in Mike Sm

ith’s photo where the azure C

alifornian sky emphasises the elegant

ultralight form. From

the first tests over the desert, the team of aerom

odelling engineers had every confidence of making the target flight over the

Aegean sea.

How did it go? - Post flight checks by theflight directors and engineers logged everydetail. At this stage the drive shaft aerody-namic fairing is not fitted. Who played withthe Daedalus name stickers we wonder. (MikeSmith photo.)

Kanellos Kanellopoulos learing to fly beforepiloting Daedalus. (Mike Smith photo.)

Dr. Etham Nadel tests a pilot on the ergometer.(Steve Finberg photo.)

Daedalus pilots, left to right: Greg Zack, FrankScioscia, Glenn Tremml, Erik Schmidt andKanellos Kanellopoulos (Steve Finbergphoto.)

Mark Drela encourages Lois McCallin at thestart of a test flight on Crete. Louis McCallinholds the Woman’s duration and distancerecords, flying 15.44 km in 37 minutes and 38seconds over Rodgers dry lake. (Steve Finbergphoto.)

Approaching the beach at Santorini. (SteveFinberg photo.)

At the point of no return - midway on the 73mile flight, Kanellos Kanellopoulos advisesthe command boat that he’s coasting andconfidant. (John McIntyre photo.)

Meteorologist, was frequently cross examined, andthere was speculation about what might happen at oneAthens newspaper which had run an article stating thatthe team had given up and gone home!

At the 7pm press conference MIT student TimTownsend surprised many by passing round a half-inchlength of carbon fibre tube, announcing that he hadsaved two grams and a little drag by sawing off aredundant bit of the fin. Steven Bussolari, with aid of aweather map that had taken all afternoon to prepare,forecast light, southerly tailwinds on Saturday andSunday. A definite attempt had to be made on themorrow, with Sunday as reserve date, if flight operationhad to be cancelled. John Langford, program Manager,who had initiated the Daedalus project four yearspreviously after leading development of Chrysalis andMonarch craft, explained the rigging of Daedalus sothat no one would walk into a bracing wire in the pre-dawn darkness. The team’s Director of Engineering, HalYoungren, dealt with the ditching and recovery proce-dure (the plan was to dismantle the craft and load it ontoone of the coastguard boats). A quiet supper and earlybed was next for the team after the press had meltedaway.

By 3am the weather boat, out at sea beyond Dia,had reported a one-knot southerly wind. Just what waswanted. At five o’clock we walked down to the harbour.Equipment was stowed and someone went in search ofice cubes for the champagne.

Confidence! Radios on, and crews on boat and atthe field could now communicate. As Daedalus wasrigged under arc lamps it was time for crowdedthoughts. Would this be just a practice? Would the flightbe called off, allowing everyone to return to the XeniaHotel for breakfast and Juan Cruiz’s seminar onDaedalus’ structural design? Or might there be aditching? Pilot fatigue? Supposing the flight wasachieved - what would happen at Santorini? The aimed-for beach at Perissa is small with soft sand and treesbeyond. At a fast, downwind landing might the aircraftbog down, crumpling the wings forward and precipitat-ing the pilot through the windscreen?

The boats drifted half-a-mile offshore in the colddawn land breeze. Radio interrupted - and we heard thatfourteen-times Greek cyclist champ Kanellos was tapedinto the cockpit and spinning the prop to warm up. Outat Santorini the weather station reported a three-knotsoutherly. It was up to Steven Bussolari. His was theresponsibility to ahead or cancel.Came the OK - the flight was on!

...and away!Daedalus was supported, gently, at the wingtips. Asmoke flare’s horizontal trail meant a momentary waitfor a lull - then at 7.06 Kanellos was rolling. Sunflashed on the propeller as daylight appeared under thewheels - an easy take-off despite the pilot’s concernabout the strong tailwind.

To the offshore observers Daedalus grew steadilylarger as it seemed to drift out to sea, chased by

inflatables. Sunlight glanced from those elegant wingsas it swept by, fifty feet up. The flotilla raced out pastDia, throttles wide to keep pace with Daedalus whichwas now making 20 knots over the water thanks to thehealthy tailwind. Kanellos made sure he kept above theturbulent layer next to the surface - doubly sensible, forthe extra height would give the leading inflatable a fewvaluable seconds in which to pick up the line if therewere problems. In this way a water landing could beavoided and Daedalus could be towed to safety for afurther attempt.

In company with Louis Toth from MIT I triedunsuccessfully to count Kanellos’ pedalling rate, orcadence, to get a figure for prop RPM. In fact, the pilotput in an almost constant 80 revs at the pedals to give120 at the airscrew. Kanellos radioed his pulse rate andairspeed every fifteen minutes, allowing careful moni-toring of his fluid consumption to avoid dehydrationand exhaustion.

The wind began to veer west, slowing Daedalusand forcing Kanellos to crab in order to stay on course.Calm conversations passed between the boats and thegroup on Santorini. John Langford in the commandvessel announced the records as they were set; firstcame straight-line distance after 37.2 miles, followed by2 hours, 49 minutes duration at 9.51am. SomehowSteven Finberg had managed to get on board an escort-ing coastguard helicopter. He raced past at wave topheight, filming from the open door. Louis and I sharedan impromptu picnic with our crew on LS 34, duringwhich they were presented with Daedalus sweat shirtsto mark the occasion.

Then came drama. Just after loam a containership was spotted on a collision course with the flotilla.At first contact was unavailing; then the skipper thought

Heraklion to Santorini - seventy four milesaccross the sea of Crete. A UK equivalent wouldbe from London to Peterborough!

he was the victim of a hoax. Once convinced, he made aspectacular about-turn to divert from trouble.

Santorini ahead! On the beach the wind wasgusting at five knots, parallel to the shore. As wepowered ahead to be on site for the landing, Daedalusshimmered over the sea, now far astern and to star-board. Thanks to the local radio station, which hadbroadcast progress reports every half-hour, about 400spectators were ready to welcome Kanellos.

The record!Ashore - and how hot was the black sand after the coolsea wind as we ran to the landing area, already markedwith flares. Then Daedalus curved in as Kanellos triedto head into wind - and the starboard wing folded as thefin went hard over, tumbling the craft ten yards off-shore. Kanellos broke through the Mylar door andswam to the beach where congratulations and cham-pagne were on hand to commemorate a record smashingseventy-four mile crossing in 3hr. 54min, giving anaverage speed 18.5mph.

As Daedalus was pulled ashore the scene was amixture of crash, conference and beach party. There wasno escape for Hal Youngren, the project’s Chief Engi-neer, who was interviewed for TV while he was still inthe water, grasping one end of the shredded wing hewas helping to rescue. He told them; ‘This is easily thecoolest airplane crash I’ve ever seen!’

‘Celebrations continued late into thenight... surely more aeromodellersshare their vision...’

The wreckage was loaded into the waiting trailer,parked at the beach for over a month in readiness. Thenit was time for the Press as John Langford stood atop abeached boat, first with the pilots, then with the rest ofthe team, to spread the words of achievement.

Suddenly the team found themselves alone onthe beach. Hal went to phone Bob Parks, the SeniorEngineer responsible for mechanical design, with thenews. No matter that over in California it was three inthe morning! Juan Cruz, composite structures master-mind, summed up feelings by his comment that withoutthe crash, which underlined the craft’s fragility, it wouldall have seemed too easy. Project Engineer Jean JosephCote added, ‘That wasn’t a crash - that was a happen-ing!’

Much to her credit, the owner of the ElfersinaHotel (where the weather station crew were based)wasn’t in the least ruffled by the sudden invasion ofalmost the entire Daedalus team, disheveled, sunburned,some clutching pieces of aeroplane, and for the mostpart without a Drachma apiece. And imagine everyone’sdelight to find, on the verandah writing postcards, PeterErnst, a Swiss leading builder of human-poweredvehicles. He had spent a month at Santorini waiting to

see Daedalus. Never had he any doubt that it would besuccessful.

Celebrations continued late into the night. It wasafter 2am before the remains of Daedalus were finallycollected from the beach and allowed to slumber outsidethe hotel...

What next?The story does not end there. The Michelob Light Eagleis to return to the USA for more flight tests andDaedalus is assured of display in the SmithsonianInstitute. Then what? Henry Kremer is to sponsor twomore prizes for human-powered flight, as announced inHangar Doors in this issue. The success of a smallgroup of dedicated enthusiasts shows what imaginationand ingenuity can achieve - surely there are moreaeromodellers and engineers who share their vision?

But perhaps the final words should rest withJuan Cruz. After the press had departed, seeminglybemused by an aeroplane crash where everyone washappy, he said: ‘That’s it, folks. You’ve been workingfor three years; you’ve been famous for fifteen minutes- and 1 bet we miss the news!’

Miss the news? Man’s greatest flight? Not achance...

Aeromodellers every where will appreciate the extremeserenity of successful man-powered flight, perfectlyillustrated by this evocative shot of Daedalus duringtrials...

J. McIntyre, drawings by Pat LloydAeromodeller August 1988

Reproduced with permission from Ron Moulton.