FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1932
1932 - 0360.PDF
FLIGHT, APRIL 15, 1932 costing less in the first place and having lower running costs. Or alternatively, the range could be increased by about 40 per cent. An increase of 30 per cent, in pay load should enable civil aviation to free itself from the unnatural state of partial dependence on a subsidy. In conclusion, Mr. Stieger said that he knew, none better, that the limit in weight reduction had not been reached, and he predicted a wing weight of 1\ per cent, of the all-up weight of the aircraft. He did not expect anyone to believe him, but he was not worrying. He was not yet trying to convince anybody. A Stringer Type of Monospar Wing : Mr. Stieger recom mended this type of construction when the wing area exceeded 800 sq. ft. The Discussion When Mr. Stieger had read his paper the Chairman called upon Mr. McKinnon Wood to open the discussion. Mr. McKinnon Wood said he spoke with a great deal of diffidence, as he had never had the opportunity to make a specialised study of the very complex subject of aircraft structures. In the main he agreed with the lecturer on his remarks about fabric covering, the multi-spar wing, and the need for stiffness. In his view it was not a question of choosing between monospar and multispar, but between the monospar and the two-spar wing. In his lecture some time ago Mr. Farren had shown how torsional stiffness helped to distribute the load between the two spars. Mr. McKinnon Wood sketched two wing sections on the blackboard, one having a rectangular formation single-girder spar located in the region of the centre of pressure, and the other being the Stieger system. Mr. McKinnon Wood said that to him it seemed that the most economical wing of the two would be that in which the spar end elevation included the larger area. Concerning Mr. Stieger's remarks about the trailing edge angle he was a little uncertain what was meant, but assumed that the lecturer was referring to the angle included between upper and lower surface at the trailing edge of the section. He would like to know upon what information the lecturer based his statement that this angle was important in influ encing the stalling characteristics. He personally was under the impression that this angle did not affect the stalling to any very large extent within fairly wide limits. Mr. F. Duncanson (of the Gloster Aircraft Co.) con sidered Mr. Stieger's monospar wing the most important invention in recent years, and recalled that when Mr. Stieger first endeavoured to introduce it he met a great deal of opposition. He was to be congratulated not only on now having proved his case but also on having been able to secure the necessary support elsewhere than in the aircraft industry. The vexed question, monoplane or biplane, no longer existed, he thought, and the only ex ception to that was the biplane for certain military types in which, for other than structural reasons, the biplane arrangement was preferred. He confessed that when the monospar wing was being built for the Fokker F.VII 3-m he was a little doubtful of the adequacy of the torsional strength, but flight tests had proved this to be quite satisfactory. He thought the strength requirements at present in force in this country might not be quite logical, and was inclined to favour the German system of demand ing a deflection of not more than 3J degrees under terminal nose dive conditions. Concerning the slide shown of a single-spar section in which the spar consisted of an I-section beam for taking bending loads and a surrounding circular-section tube to take torsional loads, there were, Mr. Duncanson said, very good scientific reasons why such a spar arrangement was efficient. (A wing of this construction was used by Mr. Duncanson in an article on cantilever wings, published in THE AIRCRAFT ENGINEER Monthly Technical Supplement to FLIGHT on June 27, 1929.—ED.) Mr. Hollis Williams (of the Fairey Aviation Company) said that the lecturer had put him in a slightly awkward position by mentioning the low weight of the monospar cantilever wing, since the head of the company with which he was associated was in the chair that evening and might well be wondering why his (Mr. Fairey's) monoplane wings did not weigh as little. Mr. Stieger appeared to have shot all their preconceived notions to pieces, but on comparing the lecturer's figures with those for a number of Fairey machines he had come to the conclusion that the secondary structure ran away with a great deal of unexpected weight. The company had had large numbers of machines in service for many years in many different localities, and the ques tion of making aircraft robust enough to stand handling always had to be kept in mind. He thought he might put the case by saying that his firm had a millstone of experi ence around its neck. Average figures for Fairey machines showed that their biplane wings weighed a little under 1 lb. per sq. ft., while the monoplane wing weight was a little over 1 lb. Taking it all around, he thought one might say that the monospar wing would save something like £ lb. per sq. ft. He also pointed out that in a military machine liable to be shot at, there was something to be said for redundancy of structural members. Dr. Lachmann (of Handley Page, Ltd.) came to the defence of his compatriot, Mr. Messerschmitt (whose B.F.W. wing construction was somewhat criticised by Mr. Stieger), by pointing out that the B.F.W. tests referred to were carried out to establish experimental proof of a formula which had been evolved for calculating torsional stiffness of a single spar with metal skin over the nose of the wing. The wing actually weighed approximately the same as the Stieger wing, and the nose covering gave the advantage of greater redundancy. Mr. H. J. Pollard (who has been mainly responsible for the Bristol multispar wing) challenged the lecturer on the subject of deflection, claiming that the slide shown gave a grossly exaggerated impression. He did not agree with Mr. Stieger that the stress should be the same in all the spars. It should be uniform over the whole length of each spar, but might differ from spar to spar. One advantage the multispar wing with metal covering had was that there was no rigging to be done, while the covering could be in stainless steel and make the wing impervious to the weather. General Arrangement of Stieger Monospar system of wing Mr. Mettam (of Westland Aircraft Works) claimed that his firm had proved that one could make a strut or wire braced monoplane as free from flutter as a biplane, while the wings weighed no more. He thought it was obvious from the paper (Mr. Stieger having said that the function of the tail was to overcome and control an inefficient wing) that what the lecturer wanted was a " Pterodactyl." The converse was not necessarily true. He agreed that wash out gave but little loss of lift. He would like to know if the task of selecting the torsion bracing wire to be removed was left to someone with a personal grudge against the test pilot! He also would like to know at what speed the machine was dived. (Concluded on page 331.)
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
