This paper reports on an experimental investigation where the longitudinal aerodynamic characteristics were determined up to high angles of attack for configurations employing parametric variations in strake span and wing sweep and includes correlations with theory. The investigation included both component and complete configuration studies to provide information for the analysis of interaction effects. Comparisons between strake-wing and high canard-wing configurations demonstrate the strake wing to develop higher lift coefficients than did the canard wing due to enhanced interference effects. Correlations with theory demonstrate the suction analogy to be a useful method for estimating the effects of vortex flow aerodynamics on both component and total forces and moments.

Aerodynamics of Strake-Wing Interactions

An investigation was conducted at Mach numbers of 0.7 and 0.9 to determine the lift interference effect of canard location on wing planforms typical of maneuvering fighter configurations. The canard had an exposed area of 16.0 percent of the wing reference area and was located in the plane of the wing or in a position 18.5 percent of the wing mean geometric chord above the wing plane. In addition, the canard could be located at two longitudinal stations. Two different wing planforms were tested: one with a leading-edge sweep angle of 60 deg and the other with a leading-edge sweep angle of 44 deg. The results indicated that although downwash from the canard reduced the wing lift at angles of attack up to approximately 16 deg, the total lift was substantially greater with the canard on than with the canard off. At angles of attack above 16 deg, the canard delayed the wing stall. Changing canard deflection had essentially no effect on the total lift, since the additional lift generated by the canard deflection was lost on the wing due to an increased downwash at the wing from the canard.

/pdf/canard-wing-lift-interference-related-to-maneuvering-ww708ryjam.pdf

Canard-wing lift interference related to maneuvering aircraft at subsonic speeds

By applying Prandtl's relation for the induced drag of a biplane to typical wing-tail combinations, it can be shown that the minimum induced drag occurs with a positive tail upload. This fact has been overlooked because the reduction in the total induced drag by a tail download was overestimated by using the total downwash of the wing on the tail, while neglecting the downwash produced on the wing by the tail. It is proved that, regardless of the relative size of the tail, the downwash produced by a tail download increases the induced drag of the wing so as to cancel the additional "tail thrust," and keep the mutually induced drag of a wing-tail combination the same as that induced upon the tail alone when it is in the wing's Trefftz-plane. At any finite tail length the bound circulation vortex of the wing produces a downwash that increases the induced drag of a tail upload. However, the circulation vortex system of the tail upload produces an upwash on the wing that results in a "wing thrust" component that cancels the increased drag on the tail so that the total induced drag is a minimum with a positive tail load. In order to facilitate the calculation of the mutually induced drag of typical wing-tail combinations, an explicit relation is derived for the limiting case of a small-span tail at any distance above or below a large-span wing.

Positive Tail Loads for Minimum Induced Drag of Subsonic Aircraft

A generalized wind-tunnel model, typical of highly maneuverable aircraft, was tested in the Langley 8-foot transonic pressure tunnel at Mach numbers from 0.70 to 1.20 to determine the effects of canard location and size on canard-wing interference effects and aerodynamic center shift at transonic speeds. The canards had exposed areas of 16.0 and 28.0 percent of the wing reference area and were located in the chord plane of the wing or in a position 18.5 percent of the wing mean geometric chord above or below the wing chord plane. Two different wing planforms were tested, one with leading-edge sweep of 60 deg and the other 44 deg; both wings had the same reference area and span. The results indicated that the largest benefits in lift and drag were obtained with the canard above the wing chord plane for both wings tested. The low canard configuration for the 60 deg swept wing proved to be more stable and produced a more linear pitching-moment curve than the high and coplanar canard configurations for the subsonic test Mach numbers.

Effect of canard location and size on canard-wing interference and aerodynamic center shift related to maneuvering aircraft at transonic speeds

A generalized wind-tunnel model, with canard and wing planforms typical of highly maneuverable aircraft, was tested in the Langley high-speed 7- by 10-foot tunnel at a Mach number of 0.30. The test was conducted in order to determine the effects of canard sweep and canard dihedral on canard-wing interference at high angles of attack. In general, the effect of canard sweep on lift is small up to an angle of attack of 16 deg. However, for angles of attack greater than 16 deg, an increase in the canard sweep results in an increase in lift developed by the canard when the canard is above or in the wing chord plane. This increased lift results in a lift increase for the total configuration for the canard above the wing chord plane. For the canard in the wing chord plane, the increased canard lift is partially lost by increased interference on the wing.

https://ntrs.nasa.gov/api/citations/19750004860/downloads/19750004860.pdf

The effect of canard leading edge sweep and dihedral angle on the longitudinal and lateral aerodynamic characteristic of a close-coupled canard-wing configuration

The results of a preliminary analytical and experimental study of trim drag characteristics at maneuvering lift coefficients have been summarized. The study included aft-tail configurations at subsonic and supersonic speeds and canard configurations at subsonic speeds. It is shown that the tail load required to minimize trim drag is highly dependent on the wingbody drag-due-to-lift characteristics with examples presented for both the full and zero leading-edge suction cases. For the high drag case (corresponding to zero leading-edge suction), which tends to be typical at high maneuvering lift coefficients and high speeds, rather large uploads on the tail are required to reduce the trim drag problem. The analytical predictions of trim drag characteristics compare well with the experiment for the aft-tail configuration. At supersonic speeds, reductions in down tail load required to trim, obtained by increasing tail volume and thereby allowing a favorable rebalancing of the aircraft, result in relatively large reductions in trim drag for aft-tail configurations. At subsonic speeds, the experimental studies for the canard configuration exhibit considerably higher trim drag than the analytical prediction as a result of canard stall.

LlNWOOD W. McKlNNEY

Papers

Some Trim Drag Considerations for Maneuvering Aircraft