The Bennett BTC-1

The Bennett was built “outside the box” in two ways, horsepower versus weight and materials advancement.The principal structural material was Duraloid, a plywood impregnated with resin and processed under a patented process. If the Bennett design criteria proved successful the machine could be driven at competitive speeds with less power at lower manufacturing costs. Given the dictionary definition of a plastic, the Bennett was the first truly plastic airplane predating theWindecker by at least twenty five years. The internal fuselage structure of the BTC-1 was one of built-up frames with alignment and load transfer through the medium of routed stringers. The basic frame became the mounting mechanism to which the Duraloid outer skin was bonded. From existing printed and photographic evidence it is not possible to determine the number and disposition of parting lines of the fuselage skin. However, if WilliamHawley Bowlus followed his own standard practice, entire sides from upper to lower center lines would have been molded as one piece. The average thickness of the skin would have been one quarter inch with additional laminations providing attaching footprint surfaces for the internal structure. Given the overall use of Duraloid throughout the airframe components it is reasonable to believe the outer skin to structure bonding was accomplished using the same Bakelite based resin.When the fuselage was fully skinned and mated itwas covered with balloon cloth. The current counterpart of balloon cloth would be glider cloth, a lightweightfabric covering material. In 1936 it would have beeneither cotton or linen doped over the Duraloid skin.The bonding and filling process would have beenaccomplished through the use of clear nitrate dope. Thefilling of the fabric weave would have been accom-plished by mixing extra fine sawdust with the clear dope sanded smooth to the desired finish. This same process was followed throughout the aircraft. Some of the earliest comments on the airplane were on the outstanding finish of the product.With the benefit of over seventy years of hindsight it would appear the interior layout of the fuselage suffered from the same obstruction as some of the earlier Lockheeds. The mass of the main spar and its related hump virtually separated the cockpit from the cabin. This necessitated two different entry doors requiring over-wing access. Portable stairs would have been required for the assistance of female passengers dressed in skirts.

The wing structure of the BTC-1 has been described with arguable technical accuracy. Depending on the textavailable the material selection could vary from allDuraloid to a mixture of that material and untreatedaviation grade plywood. Given Bowlus’s penchant forconsistency and the proof of concept basis for theproduction of the aircraft, the all-Duraloid constructionseems most likely.There is no photographic or descriptive text indicatingthe wing to have been other than a fully monocoquecantilever structure. Available information is generally inagreement that the main spar of the wing was fabricatedas a full span tapered box. To this box spar was attacheda formed leading edge resulting in a full span D-cell.The ribs were bonded to the aft face of the spar andupper and lower wing skins. This method of assemblywould have resulted in a strong, light structure.The flap structure followed the same format as thewing including the covering of the upper and lowersurfaces with the impregnated plywood.Aileron structure varied only in being fabric covered.EmpennageThe vertical fin and horizontal stabilizers were fixedcantilever structures. Their construction followed thesame practices as the wing structure. It was noted thatadditional thickness at the leading edge was added to thestabilizers as protection from rock and foreign objectstrikes brought about by the tail wheel configuration ofthe aircraft.The rudder and elevators were of the same construc-tion but were covered with fabric. Directional and longi-tudinal trim was accomplished through trim tabsadjustable from the cockpit.It should be noted that while Vance Breese was primar-ily referred to as the test pilot he was also acknowledgedas a contributing designer of the Executive. The empen-nage of the BTC-1 was almost certainly a Breese design.When compared with the configurations of the Breese-Dallas, the Vultee model V-1, and the Vultee model 51,which became the BT-13 and 15, the planforms andratios are virtually the same. Breese engineering skillscontributed to all of those designs.PowerplantThe Executive was equipped with two 285 horse-power Jacobs seven cylinder L-5 radial engines.However, many of the performance figures quoted bythe Bennett group were based upon anticipated perfor-mance of the aircraft using Jacobs 300 horsepower L-6engines. Sales information provided also mentions antic-ipated use of the Wright R-760-E Whirlwind of 350horsepower. There is no record of installation of either ofthe larger engine choices.The propellers were two-bladed Hamilton-Standardcontrollable pitch with the published option of constantspeed units of the same manufacturer.The engines were mated to the nacelles through stan-dard practice welded steel tube engine mounts. It isnotable in the era of the use of mild steel such as the 10and 20 series for aircraft structure that the Bennett spec-ifications called out the use of 4130 Chrome-Molybde-num tubing and flat stock for the steel structures. It isreasonable to assume that load bearing members of themount system extended far enough to transfer thetorsion and tension loads into the main wing structure.

The fully retractable main landing gear wasconstructed of welded steel and flat stock structuresproviding for single fork mounting of Goodyear lowpressure tires which took up part of the landing shockloads. The majority of the landing loads were absorbedthrough air-oil struts providing eight inches of travel.Landing loads were carried to the main wing and nacellestructures by welded steel transfer members.Landing gear retraction was hydraulically providedby an engine driven pump with emergency extensionprovided for by gravity and a manually operated handpump in the cockpit.The aircraft was equipped with a full swiveling tailwheel. There is no mention of the auxiliary wheel beingretractable.AccommodationsAs previously mentioned, the cockpit and passengercabin were separated by the passage of the mainwing spar.The cockpit provided seating and controls for two;however, the right hand controls were noted as beingeasily removable, allowing for the substitution of aseventh passenger in lieu of the additional pilot.The passenger cabin provided seating for six in vari-ous configurations.There were provisions for luggage stowage in theaft cabin and in a smaller compartment in the nose ofthe aircraft.DoorsBoth the cockpit and passenger cabin were enteredfrom the upper surface of the wing center section.Access was accomplished through the use of bi-folddoors latched at the bottom. Both doors were equippedwith a center hinge allowing the doors, when opened, tolay folded onto the upper surface of the fuselage.Finish and AppearanceThe aircraft was painted in overall cream with trimlines and number in red. The outstanding feature ofappearance was its smooth skin and excellent finish, avirtual trademark of William Hawley Bowlus.

Bennett BTC-1 General Description

Wing Span . . . . . . . . . . . . . . . . . . . . . . . . 48 ft 2 in

Length . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 ft 6 in .............................................................Height . . . . . . . . . . . . . . . . . . . . . 9 ft 5 in

Wing Area . . . . . . . . . . . . . . . . . . . . . . . . 302 sq ft............................................................Gross Weight . . . . . . . . . .. . . . . . . 6,908 lbs

Useful Load . . . . . . . . . . . . . . . . . . . . . . . 2,392 lbs...........................................................Certificated Maximum Payload ... . . 1,584 lbs

Wing Loading . . . . . . . . . . . . . . . . . . . . . 22.8 lb/sq ft........................................................Power Loading . . . . . . . . . . . . . . . . 11.5 lb/hp

Fuel Capacity . . . . . . . . . . . . . . . . . . . . . 200 gal...............................................................Oil Capacity . . . . . . .. . . . . . . . . . . . 13 gal

Performance*High speed level flight . . . . . . 206 mph @ s/l Cruise speed . .. . . . . 196 mph @ 8,000 ft Rate of climb

. . . . . . . . . . 1,480 ft/min @ s/lService ceiling . . . . . . . . . . . . . . . 22,500 f......tLanding speed . . . . . . . . . . . . . . . 54 mph

Single engine ceiling . . . . . . . . . . 9,000 ft.....Single engine cruise . . . . . . . . . . 145 mph.....Takeoff distance . . . . . . . . . . . . . 750 ft @ s/l

Fuel consumption/cruise . . . . . . . 32.4 gal/hr__________*Manufacturer’s published figures.

From an aricle in Skyway Magazine January 2005 by Fred Maupin