CARISI - PRODUCT DESIGN ||PAGE 1 of 3|
|PREPARED Vincent Carisi||8/21/54||REPORT NO. CB-1|
|TITLE: Summary Report - Structural Study - Burnelli Loadmaster
1. Scope of Study
1.1 Study was made on the basis of production drawings and physical inspection of the aircraft as well as from personal familiarity with the configuration extending over the past 15 years or more.
1.2 This report is a summary of findings which will be exposed in a more detailed manner in a subsequent final report.
2. General Configuration
2.1 Unlike the "conventional" aircraft, where aerodynamic advancement is usually brought about at the cost of increased structural complication, this aircraft depends for its performance on the very principles which simplify its structure.
2.1.1 The lifting body (which replaces the conventional fuselage) is of airfoil cross-section, generating spanwise in a straight line. Thus both upper and lower surfaces are of single curvature. Any transverse section is rectangular.
2.1.2 The pilot's nacelle, while embodying compound curvature, is non-structural.
Tail booms are conventional box-beam structures with rounded fairings at top and bottom edges.
2.1.3 Tail booms are conventional box-beam structures with rounded fairings at top and bottom edges.
2.1.4 Tail surfaces are conventional.
2.1.5 Outer wing panels are of conventional configuration. However, since the body contributes to the total lift, they are much smaller in area than would be the wing panels of a conventional airplane of equivalent payload and power. Since the transverse bending moments are very low compared to those of a dead-weight fuselage aircraft, substantial economies are effected in structural weight.
2.1.6 Landing gear design is the simplest possible single hinge type. Its installation is highly simplified by the uncomplicated and extremely rigid nature of the body structure to which it attaches.
2.1.7 Engine installation utilises standard "package" nacelle units which are very simply attached to the body structure.
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3.1 Lofting for parts fabrication and assembly tooling is greatly simplified by the virtual absence of compound curvatures.
3.1.1 Pre-drilling of attachment and "assembly -pick-up" holes can more accurately be accomplished in flat layout.
3.1.2 Brackets and attachment fittings for installation of fixed equipment, because of the regular shapes of the volumes into which they must fit, are simply designed and easily developed to flat pattern for brake-bending. Location of plumbing and electrical lines is similarly simplified.
3.1.3 The number of die-line templates necessary is very small, since the need for hydropress forming is limited to the wing and tail nose-ribs.
3.2 Jigs and fixtures for assembly are fewer and simpler.
3.2.1 A great number of sub-assemblies can be effected without jigs by using the coordinated-hole method of assembly. (see 3.1.1)
3.2.2 Geodetic points for major assembly fixtures are easily located because of the regular shape of the envelope. Jig structure is, by the same token, simplified.
3.3 Amount and capacity of capital equipment necessary is smaller than for conventional configurations.
3.3.1 Since formed parts are limited in number and small in size, hydropresses of large capacity are not required. (see 3.1.2)
22.214.171.124 Much of the work normally done by hydro-forming can be done on standard tinsmiths' equipment. (see 3.1.2)
3.3.2 Heat-treating equipment necessary is of comparatively small capacity and low operation cost.
3.3.3 Large stretch-press for skin forming are unnecessary. The need for stretch forming is limited to the skins for the lower body corners and the upper and lower tail-boom fairings (2.1.3). It might be possible, with a small amount of redesign, to eliminate this need entirely.
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3.4 Labor manhours are reduced, and average level of skill required is lower.
3.4.1 Costly straightening after heat-treatment is cut to a minimum.
3.4.2 Trimming after forming is at a minimum.
3.4.3 Components laid-out as in 3.1.1 are easily shear-cut or routed to final dimensions.
3.4.4 Attachment holes can be stack-drilled from simple flat templates on the radial-arm drill.
3.4.5 Holes in small components can be gang-pierced with standard piercing punch set-ups in the press-brake.
4.1 Lofting this configuration can be accomplished at 1/3 the cost for a conventional configuration.
4.2 Capital equipment needs are half those necessary for building a conventional airplane.
4.3 Manhour requirements are less than half of requirements for a conventional structure.
4.4 It should be pointed out that the above conclusions are made on a "per pound of airframe" basis. The CBY-3 has a lower empty weight than any current aircraft of equivalent capacity.
5. Personal Qualifications
5.1 The above study was made on the basis of 22 years of various experience as aircraft mechanic, factory superintendent, design engineer, project engineer and design consultant.