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Aviation History
1927
1927 - 0504.PDF
JULY 7, 1927 and the other on Wednesday of last week, the three German pilots who made up crew and passengers being Herren Lusser, technical director of the Klemm Light 'Plane Works of Sindelnngen, Lorzer, who took part in the Rundflug on a Daimler machine, and Siebel, pilot and member of the firm. At the demonstration at Croydon, Herr Lusser did most of the flying, and showed up the machine to best advantage, although water in the carburettor interfered somewhat with the exhibition. The machine left the ground after an incredibly short run (there was a fairly strong wind blowing at the time), and climbed very well. Immelmann turns were carried out repeatedly, as well as some of the tightest loops we have ever seen, the machine apparently losing no height in the loops. The loops seemed to be of a diameter very little more than about twice the length of the machine, and vertical turns were equally short. Certainly the machine was, obviously, both controllable and manoeuvrable. Flat glides and steep glides were made, and on landing the machine pulled up after a run of a couple of dozen feet or so. Doubt- less what helps to make the machines so controllable is the type of double aileron fitted. This was described in FLIGHT at the time of the Rundflug, but it may be as well to recall here that the aileron consists of an ordinary trailing-edge flap to which is coupled a pivoted wing tip. Whether or not the wing tip is slightly overbalanced so as to form a sort of horn balance for the trailing-edge flap is not known. It could be so made, although it need not be, all according to where its centre of pivoting is in relation to its centre of pressure. That the combination is efficient seems obvious. Even during stalls the machine appeared to require very little aileron control, nor did it seem to have any tendency to go into a spin. During the afternoon several passengers were taken up, among them being that flying enthusiast Lady Bailey, who went up with Herr Lusser and took control of the machine. In spite of the gusty wind and the light wing loading, the L.20 seems to be very steady in the air. We gather that the two machines are likely to remain in this country for some little time, and it is to be hoped that they will pay a visit to some of our light 'plane clubs, such visits being most valuable in promoting good feeling among light 'plane enthusiasts in the two countries. Before dealing with the L.20 machine, a few words con- cerning its constructors may be of interest. Originally the Sindelnngen works where the L20 machines were built was a branch of the Mercedes-Daimler Co. The designer of the machines is Herr Klemm, who is still associated with the Mercedes firm, although a new company has now been formed, entirely independent of the main firm, under the name Klemm Light 'Plane Works, Sindelnngen. Of the new firm Herr Lusser, one of the pilots who visited Croydon, is technical director. Piloted by Herr Lusser, one of the L20 monoplanes has recently made a flight from Sindelnngen via Hamburg to Scandinavia and back to SindeLnngen via Berlin. This machine, we were informed, has actually covered something like 10,000 km. (6,000 miles) since the beginning of May without the engine being overhauled. At Croydon it looked little the worse for its mileage. The Klemm-Daimler L20 is, as already stated, a low-wing monoplane, of the pure cantilever tvpe. The construction is along orthodox lines, with wood playing a predominant part. The wings are covered with plywood, and are detach- able at the fuselage from a fixed wing root. They do not fold, so that the operation of dismantling takes rather long accord- ing to British ideas. The undercarriage is of the divided type, the telescopic member running to the wing root, with the shock absorbers partly housed inside the wing. The Mercedes engine is a flat twin air cooled, of 885 c.c. capacity. It is neatly cowled in, and even the inner portion of the propeller is practically free of interference. A high compression ratio is employed (7 to 1) and normally the fuel used is a mixture of 60 per cent, benzol and 40 per cent petrol. The reduction gear (ratio 3 to 1) which has been incorporated, has considerable effect on the performance of the machine. The maximum permissible speed of the engine is 3,000 r p.m., so that airscrew speed never exceeds 1,000 r.p.m. Consequentlv the propeller efficiency, especially during taking off and climbing, is uncommonly good. Doubt- less this fact is largely responsible for the " strong " riving of the machine, without any impression of being under powered. In point of fact, it seems likely that at the minimum power required nearly 50 per cent, of the engine power is in reserve. Detail performance figures are not available, but we under- stand that the top speed is in the neighbourhood of i'Jli km. h. (74-5 m.p.h.), while the machine cruises at 1(K) llll km. h. (62-67 m.p.h.). The actual stalling speed is not definitely known, but at Croydon the machine floated alum; at certainly less than 20 ni.p.h. against the wind. Stalled descents along a steeply inclined flight path seem quite feasible on this machine, without any signs of loss of control. The main data of the Klemm-Daimler L20 are: Wins; span, 13 m. (42 ft. 7 in.) ; wing area, 20 sq. m. (215 sq. ft.) ; weight empty, 265 kg. (583 lb.) ; fuel for four hours, 25 k<;. (55 1b.) ; useful load, 160 kg. (352 lb.) ; total loaded weight, 450 k»'. (990 lb.) ; wing loading, 4-6 lb./sq. ft. ; power load- ing (on 20 h.p.), 49-5 Ib.'h.p. Actually the engine must develop considerably more than 20 h.p., but even assuming 30 h.p., the power loading is still very high (33 lb. 'h.p.). The reason for the amazing efficiency of the L20 is net far to seek. The ratio -'. . . - is no less than 1 -84, so that the\\ eight induced drag is very small. Thus at the cruising speed of 65 m.p.h. the ratio of lift over induced drag is no less than 62-25, which gives an induced drag of only 16 lb., correspond- ing to a propeller horse-power of 2-87 only. The cruisint; speed, with the wing loading of 4-6 lb. sq. ft., corresponds to a lift coefficient of 0-2 about. It seems likely that trie profile drag coefficient is not more than 0 005, which would give a profile drag at cruising speed of about 23 lb., or a total wing drag of 39 lb. This would correspond to a thrust horse-power of 6-8, or at 75 per cent, efficiency 9 b.h p. The speed corresponding to minimum power required would probably be lower so that one may assume that the maximum power reserve is not likely to be less than 50 per cent, of the total, and is probably more. It may be of interest to recall briefly the characteristics of the Beardmore " Wee Bee I " monoplane which won the Daily Mail light 'plane competition. The weight empty of that machine was more than 100 lb. less than that of the L20, being 462 lb. The total loaded weight was 837 lb.,anil the wing area 187 sq. ft. The ratio was very nearly theweight same as that of the L20. The wing loading of the two machines is also very nearly the same. The Bristol 'Cherub ' engine of the "Wee Bee" was of 1,100 ex. capacity but direct drive was used. Finally, it may be men- tioned that the L20 sells in Germany for 8,400 marks (about /420). LIGHT 'PLANE CLUBS London Aeroplane Club, Stag Lane, Edgware. Sec, H. E. Perrin, |3, Clifford Street, London, W.I. | Bristol and Wessex Aeroplane Club, Yate, Gloucester. Sec, C, S. |Clarke, Channel Road, Walton Park, Clevedon, Somerset. j Hampshire Aeroplane Club, Hamble, Southampton. Sec, Maj. Ross jWhite, Hamble, Southampton. I Lancashire Aero Club, Woodford, Lanes. Sec, C. J. Wood, Oakneld,Dukinfield, near Manchester. Midland Aero Club, Castle Bromwich, Birmingham. Sec, Maj. GilbertDennison, 22, Villa Road, Handsworth, Birmingham. Sewcastle-upon-Tyne Aero Club, Cramlington, Northumberland. Sec, A. H. Bell, c/o The Club. Norfolk and Norwich Aero Club, Mousehold, Norwich. Sec, H. u- Bennett, 5, Opk Street, Norwich. The Scottish Aero Club Movement, 101, St. Vincent Street, Glasgow. Sec.: Harry W. Smith. ,•Suffolk Aeroplane Club, Ipswich.—Secretary. Courtney N. Wen""- " HaicldeH," Stowmarket, Suffolk. , v Yorkshire Aeroplane Club, Sherburn-in-Elmet, Yorks. Sec, J- • Barnes, 39, Swan Arcade, Bradford. LONDON AEROPLANE CLUB THE total flying time for the week ending 2nd inst. was 18 hrs. 55 ruinsFlying was suspended Friday and Saturday owing to the R.A.F. Display rehearsals. Pilot instructors : Capt. F. G. M. Sparks, Capt. S. L. F. St Barbe. '—• -^ jj Richardson, Col. O'Meara, Miss O'Brien, A. S. Mulder, Miss Spooiier, J. Vcasey, R. Drysdale Smith, H. M. Samuelson, Dr. Cooper. s,n,,mont, Solo Flying :-Squad.-Lcader M. E. A. Wright, Major K. M. r>e.. H. Craig, A. R. Ogston, W. Hay, C. H. Swan, N. Jones, J. <-• K V Wiht L M S Vl M L B A F Wallace
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