Unconventional Aircraft Concepts

UNCONVENTIONAL AIRCRAFT CONCEPTS

Editors: F.J. Sterk E. Torenbeek - ...

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Fig.42. EFSW - CFT. Sc & ST deflections.

Obviously many combinations are possible. The idea here is to optimise LID without causing an adverse effect on the wing root flow. At cruise type CL therefore a negative or small Sc may pro vide a better LID. At higher CL the favourable effect of the canard on the wing root flow is needed and +SC will be accompanied by +Sr

103

b. LE & TE De'lices on CF

Figure 43 shows results of an "ad-hoc" approach to extend the CL - cr characteristics of the CF combination with simple extended chord LE and TE flaps. The flap deflections are not optimised for this exercise. The effect of the LE flap on the CL and Cm characteristics is particularly significant and the linear part is maintained to CL near l .I. As expected, the flap incurrs a drag increase for low CL below 0.8, but LID is considerably improved at higher CL" The TE flap gave an improvement of 0.53 to raise the CLmax to 1.62. The envelope of LID curves can therefore be extended beyond a CL of 0.92 obtained with the LE flap.

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Fig.47. EFSW - F & CF, LID impravement due ta Wing Fences. e. A and AT Cambinatians (EASW Series)

The effect of tailplane and its defIection óT (-5°, 0°, +5°) is depicted in Fig.48. CL and Cm "breaks" from Iinearity occur near CL

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followed by a sharp stalI. Maximum LID of 17.5 for the wing-body occurs at CL = 0.57. With the tailplane, the maximum value of LID depends on óT but it occurs near CL 0.62.

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.:Fig.48. EASW - AT, ST de/leetion. /. Winglets on AT The effect of winglets (with swept-back LE) on the AT combination is shown in Fig.49. At low CL the winglets produce a penalty in LID. At higher lift leads to ab out 3% gain in LID. The stalling

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high CL there is a penalty again as the winglets may encourage tip stal!. ."

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