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Newsletter 13
Summer 2006
Updated on 25May2006
Published by the Hawker Association
for the Members.
Contents Hawker Association

Contents
Editorial
Aviation Heritage Project
Camm Bust for RAF Club
Correction
Crescent Wing More
Crescent Wing Even More
Harrier News
Hawk - First Delivery
Hawk News
Joe Turner
Members
People News
Programme
RAF Harrier Story
Sopwith Catalogue
Test Flying the Hunter
Ties
Tripartite Squadron
Walter John Biggs
Wartime Project Office
 
Harry Fraser-Mitchell has more to say and comments on the above piece...
 
I believe that (Kosin's comments re wing attachment points and the undercarriage) supports the point I made which is that the sweeping forward of the outer panels of the Arado wing was allied to CG considerations.
 
The AR234 wing tested in the wind tunnel had sweeps of approx. 32, 24 and 17 deg from the apex outwards and corresponding thickness:chord ratios of 10.5, 10.5, 10 and 9 %. The Victor wing in its earliest form had sweeps of 50, 40 and 30 deg and t:c ratios of 16, 12, 10 and 9 % linked to this to keep the Mcrit constant across the span. I do not think that the Arado wing had this linkage and I believe this constitutes a major difference between the two layouts. Another difference is that the Victor wing had an intake at the root whereas the Arado had podded engines. The shape of the intersection at the Victor fuselage was also helpful in maintaining isobar sweep right up to the wing root.
 
And Even More on Crescent Wing

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Let us now consider what influence knowledge of the Arado work may have had on the thinking of HP's Chief Aerodynamicist at the time, Godfrey Lee. In a letter to Dietrich Kuchemann he wrote: "The real start of the Victor design was a visit in the autumn of 1945 to...Gottingen and Volkenrode by an MAP fact-finding team in which the Handley Page representative was the writer. It was here that the concept of swept wings as a means of enabling an aircraft with a reasonably thick wing to fly at high subsonic speeds without drag rise first became clearly understood." He goes on to say "...led to the need to have both high sweep and moderately high aspect ratio...For us combining high sweep and high aspect ratio gave rise to the tip stall problem. The so-called 'crescent wing' was evolved to deal with this difficulty."
 
Editor's note. For brevity I paraphrase Harry's letter here...Lee established that the main reason for the problem was outward drift of the boundary layer towards the tip, basically due to the action of a flow obliquely entering a region where suction reduces to the rear which causes the flow to try to turn in a direction parallel to the swept isobars. He proposed three solutions but settled on: "reduce the outflow at the tips by reducing the obliquity of the isobars for the outer part of the wing, and this clearly suggests a progressive reduction in sweepback from the centreline to tip."
 
Harry also says that that he has May-June 1946 correspondence between Lee and Lachman, Head of HP Research engaged in translating and analysing German reports. A letter to Lee included a sketch of the Arado wing and a sketch of his own idea of a 'crescent' planform.
 
Thus, says Harry, we can establish that the Arado work was known about; but was the idea adopted from Arado's work?  
 
He believes not, from the sort of  analysis in HP reports and HP's own work in the low speed wind tunnel. In a letter to Lachman in June Lee says of his wing; "It is rather like the Arado planform." Thus Harry believes that Lee arrived at his conclusions for reducing wing outboard sweep quite independently of Arado, and when their work was pointed out by Lachmann he used it to support his contentions. To say that HP's ideas of how to ameliorate the low speed behaviour of swept wings owed anything to, and certainly not the "adoption" of, Kosin's ideas is, Harry believes, far from the truth and gives less than justice to the originator of the Victor wing helped, as he always maintained, by others in the firm and in the UK research establishments.