he fastest aircraft tested thusfar in the CAFE Foundation and EAA Aircraft Perfor- mance Report program, the Glasair III is a high perfor- mance design. The prototype first flew in 1986. It was de- signed in the mid 1980’s by Tom Hamilton, Ted Setzer, Bob Gavinsky and others at Stoddard Hamilton Aircraft, Inc., the kit manufacturer. Lyle Powell also offered sig- nificant input in the design. An all-composite, kit-built, low-wing aircraft, the Glasair III uses tri-cycle retractable landing gear and a 300 horse- power Lycoming IO-540-K engine. Originally flown with a 23.3 foot wingspan, a later factory option offered wingtip extensions giving a 27 foot wingspan. Bill Stamm, an in- dependent supplier, offered alternative wingtip extensions for a 25.8 foot span. These latter were adopted by Bob Herendeen for his airshow aer- obatic version of the aircraft in order to enhance its climb and tight turning abilities. The Glasair III kit includes pre-molded fuselage skins, wing skins, spars, cowling and empennage made of fiberglass and Derakane vinyl ester resin. It also contains complete hard- ware for the entire aircraft structure including controls, fasteners, weldments, landing gear system, engine mount, windshield, etc. Stoddard Hamilton Aircraft receives high praise from their builders for their technical support. They provide a well planned, detailed Construction Manual and thorough Pilot’s Operating Handbook with the kit for each aircraft. A PERFECT CANDIDATE Chuck Hautamaki’s Glasair III, N313CH, was selected for flight testing because of its lightweight, stock, plans-built airframe with an unmodified Glasair III BY BRIEN A. SEELEY, C.J. STEPHENS AND THE CAFE BOARD Sponsored and Funded by the Experimental Aircraft Association and the Federal Aviation Administration AIRCRAFT PERFORMANCE REPORT T TRIAVIATHON TROPHY CAFE FOUNDATION PRESIDENT Brien Seeley VICE PRESIDENT Larry Ford TREASURER C.J. Stephens SECRETARY Daniel Wayman TEST PILOT C.J. Stephens DIRECTORS Crandon Elmer Otis Holt Jack Norris Stephen Williams Ed Vetter Cris Hawkins CHALLENGE TROPHY
Transcript
he fastest aircrafttested thusfar in theCAFE Foundation andEAA Aircraft Perfor-
mance Report program, theGlasair III is a high perfor-mance design. The prototypefirst flew in 1986. It was de-signed in the mid 1980’s byTom Hamilton, Ted Setzer,Bob Gavinsky and others atStoddard Hamilton Aircraft,Inc., the kit manufacturer.Lyle Powell also offered sig-nificant input in the design.
An all-composite, kit-built,low-wing aircraft, the GlasairIII uses tri-cycle retractablelanding gear and a 300 horse-power Lycoming IO-540-Kengine.
Originally flown with a23.3 foot wingspan, a laterfactory option offered wingtipextensions giving a 27 footwingspan. Bill Stamm, an in-dependent supplier, offeredalternative wingtip extensionsfor a 25.8 foot span. Theselatter were adopted by BobHerendeen for his airshow aer-obatic version of the aircraftin order to enhance its climband tight turning abilities.
The Glasair III kit includespre-molded fuselage skins,wing skins, spars, cowling andempennage made of fiberglassand Derakane vinyl ester resin.It also contains complete hard-ware for the entire aircraft
structure including controls,fasteners, weldments, landinggear system, engine mount,windshield, etc.
Stoddard Hamilton Aircraftreceives high praise from theirbuilders for their technicalsupport. They provide a wellplanned, detailed ConstructionManual and thorough Pilot’sOperating Handbook with thekit for each aircraft.
A PERFECT CANDIDATE
Chuck Hautamaki’s GlasairIII, N313CH, was selected forflight testing because of itslightweight, stock, plans-builtairframe with an unmodified
Glasair IIIBY BRIEN A. SEELEY, C.J. STEPHENS AND THE CAFE BOARD
Sp o n s o re d a n d Fu n d e d by t h e E x p e r i m e n t a l A i rc r a f t A s s o c i a t i o na n d t h e Fe d e r a l Av i a t i o n Ad m i n i s t r a t i o n
AIRCRAFT PERFORMANCE REPORT
T
TRIAVIATHONTROPHY
CAFEFOUNDATION
PRESIDENTBrien Seeley
VICEPRESIDENTLarry Ford
TREASURERC.J. Stephens
SECRETARYDaniel Wayman
TEST PILOTC.J. Stephens
DIRECTORSCrandon Elmer
Otis HoltJack Norris
Stephen WilliamsEd Vetter
Cris Hawkins
CHALLENGE TROPHY
engine. It also was skillfully built tobe straight and very smooth. Its en-gine had only 130 hours since overhauland had recently shown 78/80 com-pression on all cylinders. Ted Setzerand Tim Johnson of Stoddard Hamil-ton Aircraft, Inc., concurred with theselection of this privately owned air-craft and assisted in this report byproviding engineering data about thedesign.
The equipment list of N313CH in-cluded a King Kx-155 navcom, KingKT-76 transponder, intercom, VisionMicro engine instruments, and an 18lb automatic engine fire extinguishersystem.
Chuck acquired his Glasair III kitsecond hand from its original pur-chaser, Clark Pollard, an AmericanAirlines pilot from San Mateo. Hebuilt it in his basement in Minnesota.He received excellent technical sup-port from Stoddard Hamilton Aircraft,after paying a nominal transfer fee.“They treated me very very well.” Hebuilt the III in his basement, alone, ex-cept for some help with the wingclosure, engine overhaul and sewing ofupholstery.
When Stoddard Hamilton changedto a graphite stabilizer on the GlasairIII to achieve more flutter margin,they sent out new stabilizers to theirbuilders at no charge. Chuck said,“SH also lightened up their parts sub-stantially shortly after I got my kit, byimproving the bagging process.”
This aircraft had only 3 smallchanges from the plans; a slightlysmaller induction air inlet, a slight re-contouring of the landing gear doors,and the use of a f ixed rather than ad-justable cowl exit size.
After making the necessary flighttest preparations, Chuck and his son,David, flew his Glasair III to the CAFEFoundation’s test facility in Santa Rosafrom his home base in Loveland, Col-orado.
Chuck's Glasair was built with boththe standard 23.3' wingspan. He alsobuilt a set of longer wingtips whichgive a 27' span. Each long wingtipweighed 10.9 lb. Each short wingtipweighed 2.1 lb. The design of thelonger wing tip makes it possible to in-crease the fuel capacity by putting 2.5gallons of fuel in each tip, but Chuckchose to leave them dry. Not havingfuel in the tips makes changing themquite simple, a 20 minute job. The
Cost of kit, no engine, prop, avionics, paintPlans sold to dateNumber completedEstimated hours to build, from prefab kitsPrototype first flew, dateNormal empty weight, with IO-540 Lyc.Design gross weight, with IO-540 Lyc.Recommended engine(s)Advice to builders:
WingspanWing chord, root/tip, short wingWing area, short/longWing loading, 2400 lb/88 sq ft or 2500/97.2Power loading, 2400 lb/300 hp short wingSpan loading, short/longAirfoil, main wingAirfoil, design lift coefficientAirfoil, thickness to chord ratio
Aspect ratio, span2/ sq ft wing areaWing incidenceThrust line incidence, crankshaftWing dihedralWing taper ratio, root/tip, short wingWing twist or washoutWing sweepSteeringLanding gearHorizontal stab: span/areaHorizontal stabilator chord, root/tipElevator: total span/areaElevator chord: root/tipVertical stabilizer: span/area incl. rudderVertical stabilizer chord: averageRudder: average span/areaRudder chord: bottom/ topAilerons: span/average chord, eachFlaps: span/chord, eachTail incidenceTotal lengthHeight, static with full fuelMinimum turning circleMain gear trackWheelbase, nosewheel to main gearAcceleration LimitsAIRSPEEDS PER OWNER’S P.O.H., IAS
Never exceed, VneManeuvering, VaBest rate of climb, VyBest angle of climb, VxStall, clean, 23.3’ span, 2120 lb GW, VsStall, dirty, 23.3’ span, 2400 lb, GW, VsoStalls, 27’ span Flap Speed, full 45°, VfGear operation/extended, Vge
DESIGNER’S INFORMATION
CAFE FOUNDATION DATA, N313 CH
KIT SUPPLIERStoddard Hamilton Aircraft Corportation, Inc.
18701 58th Ave. NortheastArlington, WA. 98223.
360-435-8533 FAX: 360-435-9525
OWNER/BUILDER N313CHChuck Hautamaki, EAA # 154839
6425 W 35th St.Loveland, CO. 80538
970-203-0037 FAX: 970-203-0071
$36,980320120
20001986
1625 lb2400 lb/2500 lb with long wing
Lyc. IO-540-K1G5D, 37° left rear inductionKeep it light, stick to the plans, join a
builder group and read the factorynewsletter updates.
23 ft 3.5 in/27 ft 50.5 in/ 33” at tip joint
88 sq ft/97.23 sq ft27.27 lb/sq ft /25.7 lb/sq ft
8 lb/hp103 lb/ft /95.6 lb/ft
LS (1) 0413 root, tip.04
13%6.67 short, 7.64 with long tips
+2.3°0°
6°, (3° per side)53.84 in/33 in = 0.61
0°0°
differential braking, toe brakeselectro-hydraulic retractable, tricycle
104 in/16.25 sq ft28/17 in
104 in/ 5.69 sq ft9.75/6.0 in
51.5 in/ 11.4 sq ft31.75 in
51.5 in 6.1 sq ft23/11.25 in42/6.87 in
69/9 in0°
21 ft 4 in7 ft 10.5 in
na10 ft 2 in
see Sample c.g.’s+3.8/-1.0 at gross weight, +6/-4.0 at 2120 lb
291/335 kt/ mph174.5/201 kt/ mph
113/130 kt/ mph87/100 kt/mph
7478
6 mph less than 23.3’ span121.5/140 kt/mph121.5/140 kt/mph
16% increase in wing span promisedto provide some interesting compar-isons in the flying qualities andperformance. Thus, this report actu-ally covers the flying qualities andperformance of two different aircraftwith distinct personalities.
All of the tests were performed in atotal of 6 flights during 2 days, No-vember 9 and 10, 1996. All flightswere made with pilot and 1 crew mem-ber/flight engineer, excepting the finalflight which was performed solo withreduced fuel and long wingspan.
The data presented here are derivedfrom recordings using CAFE baro-graph #3 and pitot probe #2. TheLycoming power chart for the IO-540-K engine was used to derive the powersettings. The fuel flow readings weremade using the Vision Micro gauge onthe aircraft’s instrument panel, and itwas known to be fairly accurate. Theintense testing schedule did not allowequipping the aircraft with the CAFEFoundation’s fuel flow recording sys-tem for these tests and fuel flowreadings were not available during thetest of the short wingspan.
Jack Norris and Andy Bauer made acomputation of the climb rate decre-ment caused by the barograph’s wingdrag and showed it to impose a climbrate penalty of less than 1%.
GLASAIR III
SUBJECTIVE REPORTby
C. J. STEPHENS
Am I lucky.... Or What?
As test pilot for the CAFE founda-tion these past f ive years I have hadopportunity to fly many different air-planes. This experience has enabledme to learn what I like and don’t likeabout various features of aircraft de-signs. A lot of that preference is due to
C.J. Stephens collecting flight data in the shortwing version.
The CAFE team: Above, l-r, back row, Otis Holt and C.J. Stephens (in cockpit), DavidHautamaki, Chuck Hautamaki, Ed Vetter; front row, Brien Seeley, Cris Hawkins, LarryFord, Steve Williams.
Below: The last minute confirmation that the flight data collection is recording correctly.
personal taste but over time one learnshow his “ideal” airplane would be de-signed and equipped.
I was ecstatic when I learned thatthe next airplane to be tested by theCAFE foundation would be a GlasairIII. Not only had I heard many goodthings about the kit manufacturer andthe aircraft’s performance, but I justhappened to start building a GA III onthe 4th of July this year. What an op-portunity it would be to do a completehandling and performance evaluationwhile in the early stages of buildingmy own Glasair III. I hoped that theone presented for evaluation would bea good one that was built close to theplans specification.
This next part proves beyond adoubt that I am extremely lucky. Notonly was this Glasair III built without
any builder design changes but thequality of construction was superb.From the first look at the plane to thelast, as Chuck Hautamaki flew it backto its home in Colorado, it was a feastfor the eyes; a work of art. On myinitial introduction to N313CH wordslike “perfection”, and “masterpiece”kept running through my mind. It wasthe smoothest, shiniest and best look-ing aircraft I had seen, inside and out.This one should become the benchmark of quality to which all buildersshould strive to attain.
THE CHALLENGE
The test plan was to use the f irstday for preparation and the followingtwo days for actual flying. The planincluded evaluating the handling quali-
ties with forward and aft center ofgravity in both long and short wingconf igurations, then installing theCAFE barographs and measuring a va-riety of performance data on each ofthe two wingspans. Considering thelimited time available and the twowing lengths it was to be a busy andchallenging time for our small band ofvolunteers.
ARRIVAL
The plane landed at the CAFE testfacility in the long wing configurationcarrying the short wing tips in the bag-gage compartment.
The first operation after arrival wasto completely de-fuel the airplane toobtain an exact empty weight. Themain fuel tank is in the wing forwardof the spar, with a additional 5 gallonheader tank forward of the instrumentpanel. The exact weight and center ofgravity (c.g.) was determined using thein-floor electronic CAFE scales. Nor-mally we would establish a c.g. of 15%aft of the forward limit for the mostforward measurements, however, evenwith Otis Holt (right seat) carrying 20lbs of lead in his flight suit anklepocket and all of the baggage com-partment ballast in the most forwardlocation, we could only obtain a c.g.48% aft of the forward limit. Duringflight the c.g. normally migrates aftdue to the entire fuel supply being lo-cated forward of the spar.
The main tank is continuous fromwingtip to wingtip and connected inthe center to act as one fuel tank. Thereare several baffling ribs throughout thetank with drain/vent holes to allow thefuel to travel to the center pick-uppoint. Refueling is a slow process re-quiring filling one side then the otherand back again to top off the first side.The fuel fills into the various cavitiesslowly and care must be used to insurea full fuel load is obtained.
The design could also use a bettermethod of grounding the aircraft dur-ing refueling. It has always botheredme a little to connect a static groundwire to the main gear of a f iberglassairplane expecting to get good enoughconductivity to prevent a spark at therefueling point.
During my initial conference withthe owner, I asked many questionsabout flying his plane and reviewedsome important numbers for use in
flight. The information in the POHprovided by Stoddard Hamilton wasexcellent and provided valuable infor-mation for the flight preparation.
PREFLIGHT
Checking the oil and sumping thefuel was easy with the ports providedin the natural places. These small in-spection holes, however, allowed littleaccess to other components for de-tailed preflight inspection of the enginecompartment and other areas of inter-est.
Entry into the cockpit was accom-plished by stepping up onto the backof the wing. As can be seen in thephotos, the plane stands high on itsmain gear and requires a large step toget up onto the wing without steppingdirectly on the flap. This maneuver re-quires a little more than normal agilityand leg strength. Due the high shineand waxed surface, standing on thewing without sliding off was difficultat times.
Note: Another Glasair III, built byLyle Powell, features a nifty little stepon the right side, below the entrance,which retracts by vacuum when the en-gine is started.
About the only way to enter thecockpit is to step on the seat, sit on theseat back and then slip into the seatedposition. The seat back is very sturdyand the procedure is easy after youhave done it the first time. The cockpitis roomy when compared to manyhomebuilts. I measured the instrumentpanel width to be 43” then walked overto a nearby Mooney for comparisonand found it to be 41”.
I was very pleased with the generalphilosophy of construction of this testairplane. It was clean, well organizedand simple. I think we all can learn alittle from that concept. The seats weremade of quality leather with fabric in-serts and the head liner wasUltrasuede. The interior was finishedin soft gray tones which seemed to en-hance the spacious, comfortablefeeling. The seat cushions were madeof a f irm foam which proved to bevery comfortable. The leg wells wereroomy enough to not be constrictingand the good leg support made longflights very relaxing.
The instrument panel was beautifuland well laid out for VFR flying.Across the top of the panel was a hori-
SPECIFICATIONSEmpty weight, gross wt.,, 27’ spanPayload, full fuelUseful loadENGINE:
PROPELLER:MakeMaterialDiameterProp extension, lengthProp ground clearance, full fuelSpinner diameter
Electrical systemFuel systemFuel typeFuel capacity, by CAFE scalesFuel unusableBraking systemFlight control systemHydraulic systemTire size, main/tailCABIN DIMENSIONS:
SeatsCabin entryWidth at hipsWidth at shouldersHeight, seat to headlinerBaggage capacity, rear cabinBaggage door sizeLift over height to baggage areaStep-up height to wing T.E.
Approved maneuvers:
CENTER OF GRAVITY:Range, % MACRange, in. from datumEmpty weight c.g., by CAFEFrom datum locationMain landing gear moment armNosewheel moment armFuel moment arms front/rearCrew moment arm
1646.4 lb/2500 lb with oil510.5 lb853.6 lb
Lycoming, IO-540-K1G5-D, dual mag300 BHP, +5% and -2%
2000 hr2700 RPM29.5 in Hg
NA500˚ F
55-95 psi, 115 psi on startup245° F
18-55 psi, 12 psi for idlena
Bendix RSA-10ED1 fuel injection, rear inlet3.25 sq in
1.75” O.D. ss, 3 into 1 each side, 3.5” O.D. outlet12 qt. 15W-50
Bendix Dual Mag, large coil2 pitot inlets, downdraft
56 sq in (stock cowl)30 sq in, fixed, no cowl flap
13 inPrestolite: alternator, standard large starter
1 header tank in forward fuselage, 1 tank in wing100 or 100LL octane5.4 + 51.8 = 57.2 gal
2 ozCleveland discs
direct push-pull rods aileron+ elev, rud by cableElectro-hydraulic landing gear actuation
5.00-5 (10 PR)/ Lamb 11.00x4.00-5 (8 PR)
2gull wing doors each side
41.5 in39.75 in34.5 in100 lb
16x37 in opening above seatback51.5 in30.5 in
aerobatics with 23.3’ span at 2120 lb: (rolls, loops,Immelman’s, Cuban eights, but no intentional
spins or snap maneuvers).10-28.5 %MAC
79.65-87.88 in79.77 in
60 in fwd of cowl to firewall joint95.75 in35.5 in
65.75/81.35 in108.75 in
GLASAIR III, N313CHEstimated Cost: $ 57,000 total cost including materials, engine, prop, inte-
rior, instruments and radios.Hours to build: 2300 incl. 1400 airframe, 300 engine, 600 for finish work.
Completion date: June 1993
zontal row of five Vision Micro engineinstruments. The second and third in-struments from the left were theManifold pressure and RPM. Sincethose two instruments are referred toso frequently I feel they should standout more and not be buried in a row ofother similar instruments of lesser im-portance. It is a matter of balancingfunction and asthetics. If the panelwere to be set up for IFR flying I feelthat the flight instruments would needto be moved up more to the line of vi-
Above: Chuck Hautamaki helped the CAFE team ready his aircraft for testing.Below: Larry Ford, r, serves a hearty breakfast to the dawn flight test crew.
Owner ChuckHautamaki, l, and CAFEtest pilot C.J. Stephens
ABOUT THE OWNER
Chuck Hautamaki was born inHancock, Michigan and became interest-ed in flying as a child as he observed theadventures of the Apollo Astronauts.He took flying lessons while studyingaerospace engineering at University ofMinnesota. He later switched tomechanical engineering, in which he iscurrently working on his doctorate.
His f irst flight was in a PiperCherokee 140. He never owned any air-craft except homebuilts. He has onlymissed Oshkosh once in the last 16years.
His first homebuilt was a 950 lb, 160hp, 230 mph Glasair taildragger whichhe completed in June, 1983. He enjoyedits rough field capability.
He moved to Idaho a few years ago towork with Dan Denny on the ThunderMustang project in Boise, using his skillsin finite element analysis and graphitestructural design. Then he returned toMinnesota, where many of his familylive, to complete his graduate work.Meanwhile, his wife, Bonnie, who has aMasters of Industrial Engineering, foundgood position working for HewlettPackard in Loveland, CO. Chuck movedto Loveland just this year.
He has been married to Bonnie for 17years and has 2 children, 11 year oldAndrea and 9 year old David.
“I flight plan for a 250 mph average.I haven’t had a G meter, though I thinkI’ve pulled about 3.5 G’s on some highspeed passes.” Chuck explains that DanDenny’s Glasair III, with high compres-sion pistons, porting and electronic igni-tion is quite a bit faster than his.
Future plans: Chuck plans to keepthis aircraft and maintain it in its pristinecondition. “I might look at some numer-ical studies to see if a different airfoilwould benefit this airplane. I’ve done alittle bit of engineering work forStoddard Hamilton in the past. If Idesigned a homebuilt I’d shoot for about230 mph cruise with 200 hp and 4 seats.”
sion rather than having the engine in-struments along the top. The radiostack was kept basic with one nicenav/comm and a transponder using ablind altitude encoder. All of the in-stalled electronic equipment workedflawlessly throughout the flight test-ing.
A simple tow bar was provided forground handling and worked very well.The plane was light enough that oneperson can easily move it about on theconcrete ramp.
TAXIING
The Lycoming IO-540 sprang to lifeand idled beautifully after a brief primeusing the electric fuel pump. A firstimpression is that this is a big engine(300 hp) for such a small airplane andit gives off a beefy sound. The stockexhaust system was installed using nomuffler. The noise level inside thecockpit however seemed quite normaland comfortable.
Very little power was needed to startthe Glasair moving quickly down thetaxiway. Directional control is accom-plished using light braking with the toebrakes. Brake pedals were only in-stalled on the left side, although thefactory makes an optional set availablefor installation on the right side.
No cowl flaps were installed, how-ever the oil temperature and the CHTremained exactly at the desired read-ings on all flights even during thesustained high performance climbs.There was no heat cuff installed forcabin heating or defog operation. Evenwhile flying at altitudes of over 10,000’the cabin remained warm enough prob-ably due to engine heat and the oilcooler discharge air being directly infront of the cabin vent (right side) airintake. There was no outlet for any de-fog system, but a slight foggingproblem encountered on the groundwas quickly cured by opening an entrydoor momentarily.
The gull wing cockpit entry doorswere large, with a very simple and ef-fective pin locking mechanism and gasstruts to hold them open. With the en-gine running the prop wash seemed toblow the doors around quite a bit. Forthat reason it seemed best to keep thedoor closed while taxing. On an windyday it would be even more importantto taxi with entry doors closed to pre-vent damage to the door hinges. The
fuselage sits level during ground oper-ations which provides an excellentfield of view.
The pre-takeoff procedures werewell sequenced and logical using thelaminated checklist provided by thebuilder. The flaps stay full up andlocked, or full down and locked but thetwo intermediate positions stay in po-sition only if there is an air load againstthem. This is due to the way the lock-ing device works on the manual flaphandle located on the center console.The normal takeoff procedure is to usethe f irst notch of flaps. Therefore,when awaiting takeoff clearance theflaps will sometimes increase to ahigher setting. Prior to taking off itmay be necessary to reset the flaps totheir proper position. A more secureflap detent would be desirable to pre-clude possible takeoffs with the flapsin the wrong position.
The only provision for re-trimming
the plane from the cockpit was theelectric pitch trim switch located onthe center console at about the beltloop height. Having it located theremade it awkward to operate. Therewas no pitch trim indicator installed;however by looking back at the eleva-tor counterbalance horn the trim couldbe easily set prior to takeoff.
TAKEOFF
After a quick mental review of thePOH procedures and flight parametersit was time to get airborne for a look atthe flying qualities. I had been advisedthat lift off should occur at about 90MPH IAS with the long wings. Chuckhad also cautioned me about the possi-bility of trapping the main landinggear out if I delayed the gear retractiontoo long or climbed too shallowly atfirst. With the rapid acceleration andthe relatively slow gear retraction it is
The Glasair III sits tall and nearlylevel on its oleo strut landing gear.
necessary to control the airspeed untilall of the landing gear indicators showfull retraction.
Liftoff occurred abruptly upon rota-tion at 90 MPH as expected. Gearretraction was normal and since thespeed was building rapidly a slightlysteeper climb was used to maintainless than 120 MPH until all three lightswere out. Although during the f irstflight the landing gear retracted nor-mally, on one subsequent flight I didmanage to trap the right main in theunlocked position. This situation wasfurther compounded because the threered gear unlock lights are partially hid-den behind the throttle knob and noteasily seen from the left seat.
During the short-winged flights,takeoff occurred at 96 MPH and theairplane climbed in a more noticeablynose high pitch attitude. As indicatedby the tabulated data, the rate of climbsuffers during a climb when flyingwith the short wings.
STATIC LONGITUDINAL STABILITY
The airplane was trimmed to levelflight at Va (201 MPH). Then, usingthe CAFE hand-held stick force gauge,I measured the pitch stick force at each10 MPH increment of airspeed changeover the entire level flight speed enve-lope without re-trimming. This stickforce gradient gives an indication ofthe aircraft’s tendency to return to thetrimmed airspeed. A flat stick force
gradient (low stick forces) makes theplane harder for a pilot to fly sincethere is low control force feedback.This becomes even more important inan airplane such as the Glasair III dueto the high airspeeds normally experi-enced where after even a brief periodof distraction the aircraft will quicklyend up considerably off airspeed andaltitude. The test was repeated at themost forward as well as at the most aftcenter of gravity locations that couldbe reasonably obtained. Measure-ments were made flying with both longand short wings (see graph ).
My opinion is that all f igures ob-tained show that the Glasair has anexcellent stick force gradient. There isa gradual and steady build up of stickforce as the airspeed is changed awayfrom the trimmed speed. Even in themost aft configuration tested, the air-craft showed ample force. The graphshows the full results for comparison.
DYNAMIC LONGITUDINAL STABILITY
Short period damping characteris-tics were evaluated at 6,000’ at140,170, and 200 MPH IAS in theforward and aft c.g. configuration, us-ing f irst the long and then the shortwings. Both stick-fixed and stick-freesituations were compared. The stickwas held in neutral position during thestick-fixed and released during stick-free. The results were vir tuallydeadbeat during all evaluations. Excel-lent natural stability certainly adds tothe Glasair III’s beautiful handling
quality.Dutch roll oscillations were excited
by synchronizing pitch/roll/yaw inputstogether. The damping was immediatewith no evidence of Dutch roll ten-dency when the test was performedusing both wing tip conf igurations.Yaw damping was positive althoughusually two overshoot cycles occurredafter rudder release.
MANEUVERING STABILITY
Stick forces were measured vs gforces with the aircraft trimmed forlevel flight. The tests were conductedat 6,000’ at Va (200 MPH) and in land-ing configuration at 1.3Vs (117 MPH).Measurements were made at both theforward and aft c.g. positions. Aswould be expected, the aft c.g. pro-duced lighter stick forces. The rate ofstick force increase was linear withample stick force present at the maxi-
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ROLL RATES
Roll rates were measured by timingthe bank change from the video record-ing made during each flight. Thechange was measured from a 60 de-gree banking turn in one direction to a60 degree bank in the opposite direc-tion in approximately level flight. Fullstick throw was used with no compen-sation made for the time it takes toaccelerate to the roll rate; therefore theactual sustained roll rate would be inexcess of that reported. Remember thefuel is carried in the wings and wewere performing the roll rate evalua-tions with a nearly full fuel load andwith both seats occupied. The compar-isons were accomplished with similarfuel loads on each flight.
SPIRAL STABILITY
Several tests were performed to ex-plore the natural stability about theroll axis. First the plane wastrimmed to level 30 degree bankturns and released. The times re-quired for the plane to eitherincrease, or decrease, the bank by15 degrees was measured. In allcases the airplane displayed a slight(approximately 1 degree/sec) ten-dency to roll to the left. Thisseemed to be caused by an out-of-trim condition. The only cockpittrim available was pitch trim. I be-lieve that, if the out-of-trimcondition had been corrected, theplane would have remained in acontinuous rate turn, exhibitingneutral spiral stability. The testwas performed at both 200 & 117
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1 1.5 2 2.5 3
Ele
vato
r S
tick
For
ce, l
bs.
Load in G's
Ο GIII, 27' span, fwdc.g.
∇ GIII, 27' span, aftc.g.
Χ GIII, 23.3' span,mid c.g.
F F.8L @ 27% MAC
T-18 @ 21% MAC
Maneuvering stability, 117 mph IASgear and flaps down
Ο
Ο
Ο
∇
∇
∇0
1
2
3
4
5
6
7
1 1.5 2
Ele
vato
r S
tick
For
ce, l
bs.
Load in G's
Ο GIII, 27' span, fwdc.g.
∇ GIII, 27' span, aftc.g.
MPH.
ROLL DUE TO YAW
A test was performed maintaininglevel flight at 130 & 200 MPH IASwith 1/2 rudder displacement, measur-ing the stick force required to hold thebank constant at a bank required tohold a constant heading. The exhibiteddihedral effect should become morepronounced with slower airspeed or in-creased Angle of Attack. See tablebelow.
could be leveled from a 30 degreebank with the use of the rudder alone.In both directions at 160 MPH it waspossible to level the wings althoughduring the right turn the recovery oc-curred more quickly, probably due tothe torque of the engine and the slightout-of-rig condition.
STALLS
This Glasair III had small stall stripsinstalled on the leading edge of thewing near the root. During stall explo-ration I followed the advice containedin the POH by insuring that I hadplenty of altitude, (8000'), before at-tempting stalls. I also mentallyreviewed the suggested spin recovery
technique should an unintentional spinbe encountered. Throughout the sixflights I had the opportunity to per-form many stalls with both winglengths and with varying c.g. loca-tions. Every stall and recoveryappeared to be exactly the same withthe exception of one situation. The ex-ception occurred, on one of the laterflights, with the heavy barograph in-stalled directly in front of the air flowof the aileron. In this situation as theairspeed was reduced, the aileron andrudder required to hold level flight in-creased so much that, just prior to stall,it became necessary to use full rudderand about 1/2 aileron. These abnormalinputs were caused by the installedCAFE test equipment. Even with this
23.3' span, 2366.2 lb
Vmax/6000
75%/8000
65%/8000
55%/8000
Vmax12000
55%/12000
Vy/12000
27' span, 2389.5 lb
Vmax/6000
Vy/6000
Vx/6000
Vmax/8000
55%/8000
65%/8000
75%/8000
Vmax/12000
55%/12000
Vy/12000
SOLO/27' span
Vmax/6000
2328.1
2342.4
2339.2
2334.3
2301.7
2296.8
2291.4
2389.5
2366.4
2349.6
2345.8
2303.6
2297.5
2290.2
2289.0
2329.7
2322.3
2313.6
2261.8
243.9
223.6
213.0
196.0
214.0
194.2
143.0
243.4
146.7
110.8
235.6
196.7
215.9
220.9
215.2
196.2
144.5
246.9
266.6
252.4
240.3
221.0
257.1
233.0
171.5
266.0
161.0
122.2
265.8
221.8
244.0
249.0
258.3
235.4
173.7
269.6
3797.9
5894.3
5896.7
5948.1
10075.0
10077.0
10317.0
3864.1
4610.3
4955.5
5892.2
6073.5
6113.1
5915.1
9935.7
10052.0
10440.0
3885.0
79.5
72.3
71.6
69.9
53.7
52.4
47.0
78.1
67.8
65.9
71.7
67.8
69.1
70.2
55.5
53.0
47.0
77.2
5973
8086
8041
7999
12030
11953
11915
5971
6247
6546
8042
8025
8153
7983
11974
11960
12065
5936
25.8
21.9
21.9
21.8
20.2
18.0
17.7
25.8
16.1
13.8
23.8
22.3
22.3
21.5
20.2
20.6
14.5
25.8
2700
2608
2280
1995
2700
2260
1870
2700
1900
1900
2700
2000
2280
2600
2700
2070
1915
2700
23.7
8.2
7.0
20.0
19.0
15.0
8.3
21.9
253.0
211.8
184.9
153.2
207.2
149.6
110.2
262.7
102.5
87.5
243.2
151.9
189.7
204.1
206.9
159.3
103.8
261.9
84.3
70.6
61.6
51.0
69.0
49.8
36.7
87.5
34.1
29.1
81.0
50.6
63.2
68.0
68.9
53.0
34.6
87.3
281.8
267.0
254.1
232.9
273.3
248.2
177.4
280.5
165.9
124.1
281.5
234.0
258.3
263.4
274.8
250.2
180.3
285.0
Glasair IIIGlasair III
N313CH N313CH
airspeedsairspeeds
correctedcorrected
for dragfor drag
due to thedue to the
barographbarograph
ModeMode A/CA/CWeightWeight
IASIASbarobaro
TASTASbarobaro
Pres.Pres.alt.alt. OAT °FOAT °F Dens.Dens.
alt.alt. M.P.M.P. RPMRPM GphGph BHPBHP %Power%Power Speed, mphSpeed, mphFlight Data
23.3' span
9500-10,500
27' span
9500-10,500
2500-3500
SOLO/27' span
2500-3500
2318.0
2338.0
2370.0
2268.0
156.7
149.0
150.0
150.0
179.0
172.0
159.0
159.0
1162.4
1257.5
1797.9
2078.2
Glasair IIIGlasair III
N313CH N313CH
rate of climbrate of climb
at full powerat full power
on aon a
standard daystandard day
at theat the
altitudesaltitudes
shownshown
Altitude STDAltitude STD A/CA/CWeightWeight
IASIASbarobaro
TASTASbarobaro
Rate ofRate ofclimb,climb,
fpmfpmFlight Data
23.3' span
15
8
8
27' span
4
6
7
7
2400
2500
2500
2400
2400
1800
1800
209
208
255
210
283
145
110
245
241
282
231
298
163
na
1000
1806
2975
2700
4050
1197
1050
Glasair IIIGlasair III
N313CH N313CH
rate of descentrate of descent
at powerat power
shownshown
M.P.M.P. RPMRPM IASIASbarobaro
TASTASbarobaro
Rate ofRate ofdescent,descent,
fpm fpmFlight Data
large amount of control input the stalland recovery characteristics were quitesimilar to the other stalls.
All of the stalls observed reactedwith very little airframe buffet or no-ticeable sounds until about 1 MPHprior to the stall. Then one very no-ticeable shudder would take place andthe stall would occur. At the stall theleft wing would always drop about 20degrees and the nose would pitch downnoticeably but not uncomfortably. Ifeel the slight out-of-rig condition mayhave been the cause of the left wingdrop. In every case the recovery wasinstantaneous and positive followingthe slight forward repositioning of thestick. Altitude loss was minimal andno secondary stalls occurred duringany recovery. It should be noted thatall stalls were preceded with a slow de-celeration of less that 1 MPH persecond.
Accelerated stalls were explored upto an airspeed of 110 MPH with all ofthe same characteristics being dis-played. A pronounced nose highattitude was required to maintain levelflight during approaches to the stall inthe short wing configuration.
DESCENTS
Various types of descent prof ileswere explored and reported. (Seetable). It certainly was impressive tosee rates of descent near 4.000 fpmand true airspeeds in excess of 300MPH.
LANDINGS
I was very interested in evaluatingthe approach and landings of the Gla-sair III since this high performanceairplane has on occasions given a fewpilots some difficulties. Field of view
letting down and entering the pattern isgood. Any blind spots can be elimi-nated through mild banking. The planeis noticeably faster than most air-planes in its class and planning the letdown is a must or you will arrive at theairport either too high or too fast.
The landing gear speed is 140 MPHwhich seems adequate for most situa-tions The airplane is clean and doesnot want to loose speed easily until thegear and flaps are extended. This isanother reason to plan the descentcarefully. Chuck explained that it wasrecommended to fully extend the flapsimmediately after the gear extensionon down wind. However, I felt thatcreated a large drag change and neces-sitated a major power input to maintainlevel flight. My preference was to ex-tend only 1/3 flaps right after the gearextension, then extend the remainingflaps just prior to starting the baseturn.
A pattern of 115 MPH IAS workswell with a target speed across thefence of 100 MPH. Accurate controlof the airspeed is necessary. This air-plane has high performance andrequires good discipline to fly it safely.On f inal it is extremely easy to holdthe airspeed to the exact number that istargeted for approach and touchdown.It has excellent power response whenacceleration is needed and ample dragwhen deceleration is needed. With ac-curate control of the power and pitchon final the airplane will touch downprecisely where desired.
An important item is to not “pulloff ” the power and expect the airplaneto float to a landing. It shows its highspirited, high performance lineage andmust be flown completely throughoutthe landing. It is not a difficult proce-dure but if you are not used to landingthis way it will require some practice.
The cockpit sensation gives thefeeling that the airspeed is quite highduring landing. Normally during myexperience a landing roll of about3,000’ seemed to be the standard al-though shorter rolls could be attainedwith heavier braking. The stiff landinggear leaves no doubt when the landingoccurred.
LONG WING/SHORT WING
A burning question that seems to beomnipresent is "How do the differentwings lengths compare?" The most
noticeable differences are the greaterclimb rate with the long wings and themore nose high attitude at slow speedswith the short wings. At altitudesabove 8000', the long wing seems towin out as far as speed is concerned.As would be expected, the roll ratesare faster with the short wings in-stalled. The short wing f its into asmaller hangar space.
The landing speed with the shortwing is faster requiring greater runwaylength. Due to the Glasair III’s highwing loading, the margin for pilot er-ror during an engine-out approach tolanding would be extremely small.The longer wing configuration wouldimprove the emergency landing prob-lem by reducing the landing speedslightly.
Is it worth the effort to own bothwing lengths? Considering that the in-terchangeable wing tip construction isactually a minimal amount of effort itis probably something that is worth do-ing.
CONCLUSIONS
The Glasair III is a f ine airplanewith excellent flying qualities. It is notan airplane that is meant for the lowtime or inattentive pilot. The speedsand performance are outstanding Thebuilder who keeps his airplane lightand simple is bound to be rewardedwith excellent performance.
Every effort has been made to obtainthe most accurate information possi-ble. The data are presented as mea-sured and are subject to errors from avariety of sources. Any reproduction,sale, republication, or other use of thewhole or any part of this report with-out the consent of the ExperimentalAircraft Association and the CAFEFoundation is strictly prohibited.Reprints of this report may beobtained by writing to: SportAviation, EAA Aviation Center, 3000Poberezny Road, Oshkosh, WI.54903-3086.
ACKNOWLEDGEMENTS
This work was supported in part byFAA Research Grant Number 95-G-037. The CAFE Foundation grateful-ly acknowledges the assistance ofAnne Seeley, Daniel Vetter, EAAChapter 124, the Sonoma CountyAirport FAA Control Tower Staff, andthe engineering departments at Avco-Lycoming and Hartzell Propellers.
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