Outboard Horizontal Stabilizers Research Articles

Quantitative Prediction of the Idealized Performance of Aircraft wtih Outboard-Horizontal Stabilizers

An outboard-horizontal-stabilizer aircraft configuration is one in which the horizontal and vertical tail surfaces are supported by booms projecting downwind from each wing tip of a monoplane such that these surfaces lie within the upwash and inwash flow generated by each wing tip. The horizontal surfaces project, therefore, outboard of each wing tip, with a vertical surface mounted above each boom. A description is given of the inherent advantage of an outboard-horizontal-stabilizer configuration. A theoretical treatment, closely based on fundamental concepts, is presented that is designed to facilitate the evaluation of the net drag of an outboard-horizontal-stabilizer configuration in terms of the wing-lift coefficient of an equivalent conventional configuration of equal lift. The theoretical treatment is applied to several outboard-horizontal-stabilizer-type configurations to evaluate flight performance in terms of lift/drag versus wing-lift coefficient. These performances are compared with the idealized performances of equivalent conventional configurations. It was found that, depending upon the details of the basis of the comparison, the outboard-horizontal-stabilizer configurations were from 30 to 50 % more efficient in terms of lift/ drag than their conventional alternatives.

Drag Reductions Possible with Aircraft Employing Outboard Horizontal Stabilizers

The potential of using outboard horizontal stabilizers (OHS) to reduce aircraft drag and, hence, improve fuel economy was investigated both experimentally and theoretically. The feasibility of OHS configurations on the basis of the structural stress levels expected was also studied. The overall findings of the survey showed that from simple, low-Reynolds-number wind-tunnel tests at a wing-chord-based Reynolds number of approximately 6 × × 10 4 , and also from theoretical analyses for a higher Reynolds number of 9 × × 10 6 , lift/drag value increases in the region of 30 to 50% for wing and tail surfaces can be expected relative to corresponding values for conventional aircraft. The analytical stress-level work showed that contrary to what, on a first-thought basis, might be expected, there were no major stress problems. Flight tests employing radio-controlled, powered, model aircraft, that is, unmanned aerial vehicles, showed that aircraft of the OHS type were easily controlled in flight and were stable. An examination was made of additional areas that may contribute yet further to the development of the OHS concept.

Swept-Wing Outboard-Horizontal-Stabilizer Aircraft Configuration

The concept of a high-subsonic Mach-number, swept-wing, aircraft configuration with outboard horizontal stabilizers (OHS) was investigated experimentally by means of wind-tunnel tests. Because the wind-tunnel model employed airfoil surfaces with symmetric sections, additional theoretical work was carried out to investigate the influence on OHS flight performance of substituting wings of asymmetric section as often used for so-called supercritical airfoils designed for high-subsonic Mach-number flight. Such airfoils generate significant negative pitching-moment coefficients

Structural Loading of Outbound-Horizontal Stabilizer Aircraft Relative to Comparable Conventional Designs

The objective was to study the aerodynamic and gravitational structural loadings, under steady, level, flight conditions, of aircraft with outboard horizontal-stabilizers (OHS). The aerodynamics of OHS configurations have been studied previously yielding results reported in the literature. The main reasons for interest in OHS configurations are explained briefly. The approach was based on evaluating by analytical means, structural loadings, predominantly, but not exclusively, consisting of wing-root bending moments and wing-root torsional loadings for OHS configurations. The corresponding, complementary, aerodynamic loadings were obtained from previously published data. The main conclusions from the work were that contrary to what might, at first glance, appear to be a problem OHS aircraft configurations do not suffer from excessive structural wing bending moments or torsional loadings relative to conventional designs of equal gross lift and main-plane (wing) aspect ratio nor do they appear to be more prone to flutter.

Case for aircraft with outboard horizontal stabilizers

A description is given of what is believed to be an innovative aircraft configuration in which the horizontal stabilizing surfaces are mounted outboard, and downwind, of the tips of the mainplane. It was shown theoretically that the pitch-control effectiveness of such tail surfaces is, due to their location in the mainplane-generated upwash, greater than that of a corresponding conventional horizontal stabilizer subjected to the mainplane downwash. Wind-tunnel and flow visualization tests were carried out that showed that the divided horizontal stabilizer was also usable as an effective lifting surface to augment the lift of the mainplane. It was found experimentally that the liftidrag ratio of the new configuration can be up to about 30% greater than that of an otherwise comparable conventional configuration. The results of flight tests are reported of large, powered, radio-controlled model aircraft featuring the new configuration. These did not reveal any significant problems with flying qualities. A simplified analysis of structural loading showed that provided the design parameters are chosen correctly, wing bending and torsional loads are fairly comparable with those of conventional aircraft.

Aircraft configurations with outboard horizontal stabilizers

Aircraft configurations with outboard horizontal stabilizers