BABY TWIN-BOOMERThe Anderson, Greenwood AG-14 was one victim of the great post-war bust.

Locate a need in the marketplaceand fill it with your product. The principleis as old as the art of invention. At theclose of World War II, airplane design-ers saw an obvious need for new lightairplanes to satisfy the flying lust of re-turning military pilots. The automobilewas old news, further stifled by fiveyears of frozen design in which every-thing that rolled off the assembly lineswas olive drab. In the modern era ofpeace and prosperity, everyone wouldfly — a spanking new airplane in everygarage.

Two designers had a head start onthe pack, having come up with theirconcept even before they went off to

by Mark Phelps

Boeing to do their part for the war effort.Their personal airplane was easy to fly,safe and most important, as pleasant away to get from place to place as anycar. It was quiet, smooth and providedan excellent view of the unfolding land-scape. It also looked unusual, a twin-boom pusher with tricycle gear and alow-slung fuselage pod incorporatinglots of glass. Pilot and passenger satside-by-side on a bench seat, steered

on the ground with the control wheeland stopped with a single brake pedaljust like in the family Buick. Yes, it wasmore expensive than a car, all of $4,200Gl dollars, but after the war there wouldbe lots of money for every family. Thisgeneration's historical task had beencompleted at tremendous cost and nowit was time for the survivors to relax andenjoy the good life.

But people were to find that life wasn'tso simple. Even the tragic price paid bya generation did not guarantee peaceand prosperity. To those who designedairplanes, the bitter pill was that theautomobile was indeed alive and well— still first in the hearts of the American

_________________________Jim Koepnick

family. The fallout of the post-war avia-tion bust saw several clever prototypesrelegated to aero-trivia. There were onlyfive of the funny little pushers built andone of them has found its way to theEAA Aviation Museum — a fitting rep-resentative of the promising contendersthat never got a start in the aviationmarketplace. Many of those stillbornairplanes were marvels of engineeringthat simply came along at the wrongtime — a time that had seemed toeveryone to be so right.

It was in 1940 that a young MarvinGreenwood left the Southern AircraftCompany in Texas and joined hisbrother-in-law, Ben Anderson, to form asmall company in Houston. Greenwoodwas an aeronautical engineer with mas-ters' degrees from Rice Institute inTexas and Cal Tech in California. BenAnderson had formed a successful ac-counting firm that is still in businesstoday. The new company was called An-derson, Greenwood Company, or AGCO,and its first project was the AG-11, atwo-place, tandem, low-wing monoplanewith retractable landing gear. Earlyin 1941, however, the military beganrationing aluminum among aircraft pro-ducers and independent aircraft pro-duction became an impractical idea.Besides, the large aircraft manufactur-ers were dangling big salaries in frontof people with aircraft production ex-

perience. Both men joined Boeing inSeattle for the duration of World War IIand Marvin Greenwood became assis-tant chief engineer on the B-29 pro-gram.

After the war, the two men filteredback to Houston and AGCO was rekin-dled at the old Sam Houston Airport.Using their personal funds, the mendeveloped a new light airplane basedon a design philosophy that mightsound familiar today but was a newidea back then. In Document 227 of theInstitute for Aeronautical Sciences,Greenwood laid out the design goals.The machine was to be built aroundenvironmental considerations of the oc-cupants, and the engineering was toserve human needs, not the other way.around. Instead of trying to build anairplane that would fly faster, farther orcheaper, ease of operation and crea-ture comforts filled the front engineeringburners.

Greenwood figured that the onesense out of five that airplanes servedpositively — sight — should be para-mount in the design. Hearing, feel andtouch were all negatively affected byairplane flying (taste remained neutral).The theory — maximize the effect onan occupant's sense of sight while mini-mizing the other three.

It became clear that the noisy, smellyand shaky powerplant belonged well

insulated behind the passenger com-partment where it wasn't blocking theview. Twin booms added a measure ofsafety, disallowing an easy misstep intothe whirling propeller. Simple.

Of course the pusher design was notnew. Besides the Wright Flyer and theearly Curtiss machines, the configura-tion was found on more modernairplanes such as the Stearman-Ham-mond (later the Kaiser-Hammond), theWheelair III and the Republic Seabee.Like the designers of these machines,AGCO faced the difficulties imposed bywing-body interference, cooling and ba-lance. These were some of the en-gineering hurdles to be overcome enroute to the ideal personal airplane.

Wing-body Airflow SeparationWind tunnel tests determined that a

shoulder-high wing was ideal for mini-mal wing-body airflow separation that isintrinsic to the pusher configuration. Italso provided the best visibility. TheModel 14's wing also had the highestaspect ratio (9.6) yet designed for apersonal airplane. The all-metal,monospar wing relied on internal web-bing and its thick airfoil for strength. Anauxilliary spar well aft carried the flapand aileron front hinges.The thick airfoilallowed the engineers to use fewer ribsand lighter-gauge skin for lower weight,while improving stall characteristics —

52 MAY 1988

although at some expense to top speed.Double-opening split flaps were triedbut later discarded in favor of simplersingle-surface flaps because the differ-ence in minimum controllable airspeedproved not enough to warrant the addedcomplexity.

BalanceMounting the engine close to the

center of gravity presents some balanc-ing problems, usually associated withstall behavior. Without that largeamount of weight pulling the nosedown, many textbook aeronautical de-sign principles fly out the window. TheBell P-39 Airacobra with its mid-fuse-lage Allison engine is a good example.

Since the passenger compartmentmust be placed off of the CG, variationsin crew weight necessitate wide limitsof trim excursion and light stick forcesin pitch. In the stall regime, the pusherdesign tends to go into a flat spin. TheModel 14 countered this tendency witha sharp seven-degree dihedral for di-rectional stability. This also allowedplacing the seating centerline closer tothe CG, minimizing the trim problem.Additional dihedral effect was gainedby shaping the wingtips with an upwardslope to the bottom.

The steep dihedral and limitedelevator travel made the Model 14 virtu-ally spinproof. Even when forced into

an incipient spin by a skilled test pilot,the airplane would recover by itself afterone turn, even if the pilot held the con-trols crossed to the stops. Anotherbalancing act consisted of using a four-inch extension shaft on the propeller,allowing the engine to be mounted evencloser to the CG.

CoolingBurying an engine in the aircraft's

"body" (as the fuselage pod was calledon the Model 14) keeps it well out of thebreeze enjoyed by a tractor configu-rated engine arrangement, especiallyduring ground handling. The prototypeModel 14 used rectangular scoopsunder the wings to allow free airflowinto the engine compartment. The pro-peller created enough suction in the en-gine compartment to keep it cool on theground. At first, one cylinder exceededoil and cylinder-head temperature red-lines, so a dedicated blast tube wasadded and cooling presented no furtherproblems in flight or on the ground.

AGCO's Jim Elder was instrumentalin turning concept into aluminum. Thebody was built up from a keel beamwith standard monocoque construction.The twin booms were built with a toppan and sides and bottom made fromone bent up sheet with two W sectionsinside of each lower corner to increasecompression strength. An intercostal

piece with lightening holes was addedat the midpoint of the inside of the boomto increase buckling strength of thesides. The back of the 44-inch-widebench seat folds forward to reveal aspacious baggage compartment capa-ble of holding 240 pounds, but not ac-cessible during flight. In the machinedonated to the EAA, the fire extin-guisher is mounted in the baggagecompartment — not really the best spot.The nosegear steers through the con-trol yoke and a single pedal activatesboth hydraulic brakes. The floor of theModel 14 looks like that of a 1940ssedan with the starter button mountedbetween the two rudder pedals and thebrake pedal mounted to the right.

Only the left boom has a ruddermounted on the vertical fin — and it's asmall rudder at that. Model 14 pilotslearned healthy respect for crosswindsas the steep dihedral required lots ofaileron and, as in the Ercoupe, a quicktransition to neutral before the yoke-linked, steerable nosewheel met theturf. The drill was to make contact withone wheel and make certain that theairplane had quit flying for sure beforecentering the yoke and letting thenosewheel down. The flaps are ac-tuated manually with a two-positionlever between the occupants.

So AGCO had an airplane thatseemed to answer its design philosophy

SPORT AVIATION 53

needs with acceptable trade-offs. Buthow would it fly? Early one Septembermorning in 1947, test pilot Ted Yar-borough took off in the prototype for thefirst time from Sam Houston Airport.His verdict — not a bad airplane but theelevator was too small. Before dusk, ithad been replaced with a larger surfaceand Yarborough had flown a total of fivehours. He pronounced the airplane air-worthy and even checked out Man/inGreenwood on that first day.

Throughout 1948 and 1949 Green-wood quietly flew a concentrated testprogram and made several minor ad-justments to the design. The small aile-rons with steep deflection were re-placed with longer-span surfaces thatfilled the space between flaps andwingtips. The horizontal stabilizer wasmoved from the base to the midpoint ofthe vertical tails. The cooling scoopsunder the wings were replaced with thelatest NACA triangular ducts on the aftfuselage for drag reduction. The au-tomobile-style safety glass windshieldwas replaced with a molded Plexiglasone-piece unit. Engine baffling was im-proved and the airplane was put on adiet, losing several pounds of emptyweight.

Late in 1949, AGCO decided to buildfive pre-production prototypes in the fro-zen design configuration incorporatingall the improvements. The companyalso decided to replace the 85-hp en-gine with a Continental C-90-12FP (re-designed by Continental and desig-nated P for "pusher") and a Hartzellground-adjustable propeller. Boostingthe output from the powerplant and cut-ting down on the empty weight gave theAG-14 acceptable take-off performanceand a good speed range, although mostpilots who have flown the AG-14 wouldhave preferred an increase to 150 hp.

In September 1950, CAA test pilotJohn Paul Jones of the Fort Worth Re-gional Office issued Type Certificate4A1 to the Model 14. The airplanecruised at 110 mph with a top speed ofover 120 mph. Initial climb rate was 700fpm. Once airborne, handling wasdocile and the airplane was comfortableand fun to fly from the quiet, well insu-lated cabin. A pair of controllable freshair vents were situated on either side ofthe nose-mounted landing light. Thevents look like the machine gun fairingson a P-38, the better to scare lesserpilots out of the landing pattern. Entryand exit were easy and dignifiedthrough the car-type door on the rightside of the body. The retail price wasset at $4,200 to $4,500 — or about theprice of a premium 1950 Cadillac.

AGCO had done its work well, pro-ducing a safe, fun airplane that usedthe latest technology. The problem wasin the marketplace. By 1950, there wasvirtually no light airplane market left.

By then the large manufacturers had54 MAY 1988

Above: The AG-14 panel holds justenough for cruising on a sunny day. Notethe car-like appointments.

Left: Only the left vertical fin has a rudder.

Below: Marvin Greenwood (left) and BenAnderson at Oshkosh '86 for the dedlca-tlon of the EAA Museum's AG-14.

all but given up on light aircraft. Repub-lic had dropped the Seabee, Lockheedhad written off John Thorp's Little Dip-per, the North American Navion waslimping along and Grumman's "Kitten"project was figuratively drowned inLong Island Sound. The traditional light-plane manufacturers such as Piper,Aeronca and Cessna had reverted toprewar designs leaving new technologyfor dead. Only the Beech Bonanza de-fied the plague — a modern classic in1946 that survives to this day. Howcould the AG-14 make its way in sucha climate? It couldn't. Fortunately forthe company, though, the governmentgranted it a military contract to keep thedoors open, perhaps as recompensefor another rationing of aluminum duringthe Korean War. In fact, as a directresult of that contract, AGCO went onto become a prime designer and pro-ducer of high-tech valves for the spaceprogram and others — a role in whichthe company continues to prosper.

The five pre-production AG-14s werethe only ones ever built. In 1962 andagain in 1968, licenses to produce theairplane (to be called the "SpaceCoupe") were granted to two com-panies in California, but the licensesboth expired before any productionbegan, although some parts were man-ufactured.

That did not end AGCO's involve-ment in airplane design. In the early1970s, the company purchased Bel-lanca Aircraft as a facility to producethe Aries T-250, an advanced four-place airplane designed by Man/inGreenwood. Timing was again the cul-prit as soaring interest rates (22%prime) doomed the design after aboutfour were built.

The latest In low-drag cooling ducting for1949. Blast tube keeps a hot cylinderwithin redline.

In 1983 another Greenwood design,an ultralight called the Witch, hit themarket — again with little commercialsuccess. The Greenwood Aircraft Com-pany, producer of the Witch, was notdirectly affiliated with AGCO which isnow a wholly owned subsidiary of theKeystone Corporation and employsabout 650 people in Bellaire, Texas.

So where did the five prototypes windup? Obviously one is here in Oshkoshat EAA's Pioneer Airport. The othersare a mystery. The EAA machine,N314AG, was originally N3902K (serialnumber 3) and we don't know muchabout its travels after leaving the Ander-son, Greenwood factory the first time.The faded compass correction card hasa Canadian registration number at thetop of it so perhaps the airplane spentsome time in Canada.

One other AG-14 remains on the FAAregister. N3903K (serial number 4) waspurchased in June 1955 by the Univer-sity of Mississippi Aerophysics Depart-ment which had a military contract for

"Serial

numbers 2

and 5 are also

missing.

— Any clues?'

experiments in boundary layer control(BLC). The airplane spent several yearsas a test bed aircraft and later as ageneral transport airplane. As part ofthe testing, a duct was mounted aroundthe propeller and that modificationalone increased climb performance by200 to 300 fpm, according to Universitytest pilot Glen Bryant. At the conclusionof the test program the airplane wasreturned to its standard configurationand was flown to the EAA Conventionat Rockford in 1961 by MelvinSwarzberg. Pictures of it appear in theOctober 1961 issue of Sport Aviation.Efforts to reach its current registeredowner have not been successful so far.The University subsequently bought asecond AG-14 that it totally reconfi-gured, removing the tail and wings andreplacing them with composite units in-corporating a ducted fan propulsionsystem. The front of the fuselage wasalso extensively modified. This airplanehad increased so dramatically in emptyweight and lost so much lift with the

Open wide! Note the four-inch extensionshaft on the Hartzell ground-adjustablepropeller.

new wing that Bryant says he wouldonly fly it very carefully if at all. Hismethod was to gingerly climb out aftera very long take-off roll, gently turn intothe pattern with a shallow bank andperform his tests quickly in the patternbefore landing as soon as possible.Most of the testing, which involved sev-eral different propeller designs, wasperformed on the ground.

Both airplanes were sold to a brokerin Oklahoma and the restored machine(S/N 4) is still on the FAA register. Thewhereabouts of the highly modifiedairplane (S/N 1) are a mystery, althoughthe University had saved all the originalparts for eventual restoration and theywent with the airplane when it was sold.Serial numbers 2 and 5 are also miss-ing, having last been reported in stor-age in parts unknown. Any clues?

The normal survival rate for an air-craft type is about 50 percent. If 500were built, then 250 will probably sur-vive. The AG-14 seems to be right onthe money for this ratio. Two survivewith one question mark. Of all the freshdesigns to come from the post-war era,this track record is not bad. Boyd Gal-laher, former corporate pilot for the pre-sent Anderson, Greenwood Companyflew the EAA's AG-14 from its last homein Houston at the parent company toOshkosh for donation to the Museum.He made the trip with his wife in oneday with three fuel stops. Like all pilotswho flew the AG-14, he would haveliked a bit more horsepower, especiallyfor take-off and climb, but overall, helikes the little airplane. "It was a verystable and friendly airplane to fly," hesays, "and, oh, what a view! A greatway to see the countryside on a sunnyday." It sounds like the answer to adesigner's dream of the perfect per-sonal airplane.

SPORT AVIATION 55