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The Pursuit of Maximum Lift

The Pursuit of Maximum Lift Aircraft Engineering VOL XXVII No 311 JANUARY 1955 down to a span to chord ratio of unity; which has what is perhaps its corollary that wings of circular plan form have particularly high ITHOUT perhaps bringing out any very new points M R maximum lift. In parenthesis, we would like here to interpose the NONWEILER'S survey of the available data on the maximum remark that we, and so possibly others, find it constantly necessary lift of symmetrical wings does serve to emphasize to remind ourselves that it is only maximum lift that is being con­ certain features which may not always be fully appreciated. The sidered, whereas other equally important matters have to be taken paper, which was issued in March 1954 as a Note of the College of into account, when selecting a wing section and shape. This strictly Aeronautics, does not, of course, profess to include the results of limited consideration repeatedly tends to have the effect of producing any original investigations but is none the less, we feel, worth what at first sight seems surprising, though not in fact illogical, introducing to a wider circle of readers than it would reach in its results. original form. Conversely, in the case of moderately thick unswept wings reduc­ tion of aspect ratio reduces the maximum lift until a certain ratio, Principal Data of about 1½, is reached when a sudden recovery occurs, again to be One of the impressions that strikes us is the very noticeable followed by a fall. Indeed at low aspect ratios the maximum lift variation in the amount of data that appears to be available, and of thick wings is, M R NONWEILLER notes, not greatly in excess of that therefore of the investigating work done, on various aspects of the for flat plate sections. What is the explanation of this phenomenon subject. The major part of it seems to be on the general subject of the is not clear. two geometrical characteristics of the ratio of maximum thickness to chord and nose radius. The effect of camber as a separate element Flaps cannot be satisfactorily isolated since the two geometrical charac­ In view of the considerable number of years over which they have teristics of thickness and nose ratio necessarily affect, for instance, been in use it is rather surprising to find that the amount of data on the position of maximum camber. It can however be deduced from high lift aids is comparatively small. Perhaps this is the explanation the evidence that a forward position of the maximum camber' is of the very remarkable variety of flaps and slots of all sorts and kinds, advantageous; this surely only confirms what was known to, and fitted in almost every conceivable position, that is to be found in practised by, our forefather pioneers though admittedly a position modern aeroplanes. It has, to our mind, been one of the most within 15 per cent of the chord from the nose is considerably more noticeable features of design in the last few years. One has long felt forward than they put it. that they cannot all of them be right and we feel that to a consider­ able extent designers are in many instances following an individual New Considerations 'hunch' rather than any scientifically justified line of thought. We A comforting reflection in view of present-day developments in feel that the section on high lift aids in this paper to a large extent aerofoils is that thin sections are hardly affected adversely at all by, confirms this view. There is even, so we learn, a lack of data on the and indeed may derive benefit from, roughness—with the reservation effect of aspect ratio on the maximum lift increments due to flaps— that may or may not be significant that this is only stated to be so far a matter which we would have thought would have received ample as maximum lift is concerned. We should like to know, on the other attention long ere this. hand, whether this is equally true in regard to drag. It hardly seems An interesting point raised by the author is the apparent advantage that this can be the case. over other forms of flap of what he calls the external aerofoil and A comparatively new point brought out by the author is the front auxiliary. This is a completely separate auxiliary aerofoil beneficial effect of increasing the thickness of the trailing edge— mounted in tandem with and immediately, respectively, behind or again, from the point of view of maximum lift alone as it may have in front of the main wing. In the former case when deflected it opens other obvious undeniable effects. There is, however, the warning a gap, rather than a slot, though performing some of the same that it is not enough to achieve this increased thickness merely by functions. It has the advantage over the flap that it can also be used cutting off the section at a certain point along the chord as this may as a control, the author claims. The front auxiliary he suggests well have the effect of changing the whole basic characteristics of might well be a fixed, rather than moving, surface. We gather that the aerofoil. some research into the properties of these two devices has been carried out by the N.A.C.A., but so far as we can remember neither Effect of Shape has been actually incorporated in an aeroplane. They are, of course, quite different from the JUNKERS auxiliary wing and the YOUNGMAN On the question of plan form, aspect ratio reduction generally flap. improves the maximum lift of thin sharp-nosed unswept wings even http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

The Pursuit of Maximum Lift

Aircraft Engineering and Aerospace Technology , Volume 27 (1): 1 – Jan 1, 1955

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb032509
Publisher site
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Abstract

Aircraft Engineering VOL XXVII No 311 JANUARY 1955 down to a span to chord ratio of unity; which has what is perhaps its corollary that wings of circular plan form have particularly high ITHOUT perhaps bringing out any very new points M R maximum lift. In parenthesis, we would like here to interpose the NONWEILER'S survey of the available data on the maximum remark that we, and so possibly others, find it constantly necessary lift of symmetrical wings does serve to emphasize to remind ourselves that it is only maximum lift that is being con­ certain features which may not always be fully appreciated. The sidered, whereas other equally important matters have to be taken paper, which was issued in March 1954 as a Note of the College of into account, when selecting a wing section and shape. This strictly Aeronautics, does not, of course, profess to include the results of limited consideration repeatedly tends to have the effect of producing any original investigations but is none the less, we feel, worth what at first sight seems surprising, though not in fact illogical, introducing to a wider circle of readers than it would reach in its results. original form. Conversely, in the case of moderately thick unswept wings reduc­ tion of aspect ratio reduces the maximum lift until a certain ratio, Principal Data of about 1½, is reached when a sudden recovery occurs, again to be One of the impressions that strikes us is the very noticeable followed by a fall. Indeed at low aspect ratios the maximum lift variation in the amount of data that appears to be available, and of thick wings is, M R NONWEILLER notes, not greatly in excess of that therefore of the investigating work done, on various aspects of the for flat plate sections. What is the explanation of this phenomenon subject. The major part of it seems to be on the general subject of the is not clear. two geometrical characteristics of the ratio of maximum thickness to chord and nose radius. The effect of camber as a separate element Flaps cannot be satisfactorily isolated since the two geometrical charac­ In view of the considerable number of years over which they have teristics of thickness and nose ratio necessarily affect, for instance, been in use it is rather surprising to find that the amount of data on the position of maximum camber. It can however be deduced from high lift aids is comparatively small. Perhaps this is the explanation the evidence that a forward position of the maximum camber' is of the very remarkable variety of flaps and slots of all sorts and kinds, advantageous; this surely only confirms what was known to, and fitted in almost every conceivable position, that is to be found in practised by, our forefather pioneers though admittedly a position modern aeroplanes. It has, to our mind, been one of the most within 15 per cent of the chord from the nose is considerably more noticeable features of design in the last few years. One has long felt forward than they put it. that they cannot all of them be right and we feel that to a consider­ able extent designers are in many instances following an individual New Considerations 'hunch' rather than any scientifically justified line of thought. We A comforting reflection in view of present-day developments in feel that the section on high lift aids in this paper to a large extent aerofoils is that thin sections are hardly affected adversely at all by, confirms this view. There is even, so we learn, a lack of data on the and indeed may derive benefit from, roughness—with the reservation effect of aspect ratio on the maximum lift increments due to flaps— that may or may not be significant that this is only stated to be so far a matter which we would have thought would have received ample as maximum lift is concerned. We should like to know, on the other attention long ere this. hand, whether this is equally true in regard to drag. It hardly seems An interesting point raised by the author is the apparent advantage that this can be the case. over other forms of flap of what he calls the external aerofoil and A comparatively new point brought out by the author is the front auxiliary. This is a completely separate auxiliary aerofoil beneficial effect of increasing the thickness of the trailing edge— mounted in tandem with and immediately, respectively, behind or again, from the point of view of maximum lift alone as it may have in front of the main wing. In the former case when deflected it opens other obvious undeniable effects. There is, however, the warning a gap, rather than a slot, though performing some of the same that it is not enough to achieve this increased thickness merely by functions. It has the advantage over the flap that it can also be used cutting off the section at a certain point along the chord as this may as a control, the author claims. The front auxiliary he suggests well have the effect of changing the whole basic characteristics of might well be a fixed, rather than moving, surface. We gather that the aerofoil. some research into the properties of these two devices has been carried out by the N.A.C.A., but so far as we can remember neither Effect of Shape has been actually incorporated in an aeroplane. They are, of course, quite different from the JUNKERS auxiliary wing and the YOUNGMAN On the question of plan form, aspect ratio reduction generally flap. improves the maximum lift of thin sharp-nosed unswept wings even

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: Jan 1, 1955

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