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Aviation History
1921
1921 - 0315.PDF
MAY 5, 1921 THE AMERICAN JUNKERS S. L-6 COMMERCIAL MONOPLANE Some Official Performance Tests [IN view of the attention wnich is now being paid by designers all over the world to the cantilever type of monoplane, the following American official report on some performance tests made with the American Junkers (Larsen) monoplane may not be without interest, and they appear to indicate that the low position of the wings is not conducive to nice handling, according to reports by the test pilots. The performance is good for the power loading showing that the thick tapered cantilever wing is not necessarily inefficient.—ED.] Official Performance Test—Summary of Results Aeroplane, Junkers S. L-6 ; No. P-145. Type, Commercial. Engine, 185 h.p. B.M.W. engine ; 243 h.p. at 1,445 r.p.m. Propeller, German make. Equipped as passenger machine. Weight (lbs.) :— Empty (including water) -- . . . . Crew Fuel (benzole 50 per cent.; petrol 50 per cent.) . . . . . . .. . . 569 Oil 64 2,317 655 Weight loaded Weight/square foot, 8.64 lbs. Weight/horse power, 14.8 lbs. 3.605 This engine develops 243 h.p. at 1,445 r.p.m. run on a mixture of half benzole and half petrol. Standardaltitude in feet. 0 6,500 . . 10,000 . . 13,200* 15,goof Time, in min. 0 • M-4 •• 27-3 • 48-7 — • Service ceiling. Climb. R/p.m. 1.365 1.365 1.365 1,360 I.35O Rate ft. min. 580 345 215 100 0 t Absolute Speed. M.p.h. 111 • 2 107-2 102-5 95" 1 67 ceiling. R.p.m J.445 1,435 1,420 1.395 1,350 Endurance, full throttle at 10,000 ft. (incl. climb), 7 hours 35 minutes. Minimum speed at sea level (lowest throttle), 52-1 m.p.h. Pilots' Observations The flying qualities of the JL-6 all metal monoplane appear new and different when originally flown by pilots familiar with conventional types, but the same general flying principles applying to all aeroplanes govern the flying of the Junker. An exact co-ordination and proportioning of the amount of the controls is required or the aeroplane will side slip or skid badly. It is extremely sensitive in this respect. The rudder and elevators appear and feel too small. The aeroplane is spirally unstable due to the large fin area toward the tail causing a lifting of the rear of the fuselage in the event of a side-slip. Until familiar with the aeroplane, pilots invariably use too little bottom rudder in making turns. When stalled, both with power and without, the tendency to spin is easily checked, the aeroplane responding readily to the controls. The JL-6 takes off very slowly, especially when heavily loaded. The tail "does not come up until some distance has been travelled. The visibility for the pilot is not good. One side is almost entirely blind, and it is difficult to see over the end of the nose. The fact of flying from one side with the other partially blind has a tendency to cause the pilot to fly with one wing low ; a very bad feature in landing. The aeroplane has an exceedingly long and flat glide. The absence of wires gives the erroneous impression of slow speed in the glide. The pilot must be careful in landing. The JL-6 will suddenly drop a wing when flying speed is lost unless care is used to keep the wings parallel to the ground in the glide. A stall landing is hazardous. The aeroplane has a tendency to ground loop in landing or in taxying in a strong wind. It rolls but a short distance after landing. The landing gear .effectively cushions the landing shock. The position of the controls is unhandy, especially for a pilot of medium stature. The distance from the seat to the pedals is too great to permit of their use in a natural position. Operation of these pedals having one end hinged to floor cramps the ankles and leg muscles. The long reach to the throttle and switch does not permit quick action in emergency. The notched push-rod type of throttle makes delicate use difficult. A standard engine throttle is desirable. A mixture of one-half petrol and one-half benzole gives the best engine resul:s. The radiation surface is ample, even in warm weather. The shutter control is quite inadequate. The oiling system caused no trouble. The maintenance of this aeroplane is, on the whole, very simple, especially in regard to the engine. The mounting gives easy access to spark plugs, distributors, carburettors, etc. The all-metal construction makes a hangar unnecessary for its protection. Back firing of the engine tended to ignite and explode petrol from the carburettor which drained into the fuselage through air intakes having no outlet from the fuselage. Efforts were made, which were apparently successful, to eliminate lire hazard bv installing air intake pipes leading from the pan under the crankcase to the outside of the aeroplane below the engine, thus directing back fires from outside the fuselage. Breakage of dangfious gas lines was prevented by the installation of flexible hose connections. The petrol pump was firmly fastened at the bottom. Holes were cut across the bottom of the fuselage at the bulkhead back of the engine to prevent the collection of petrol and oil in the fuselage. Considering the fire hazard eliminated and that the aero- plane is flown only by good pilots familiar with its flying qualities, the JL-6 should be considered as an extremely important development, being very economical and efficient, having a remarkable performance and presenting features of construction having valuable possibilities. J. A. MACREADY, 1st Lieut., A.S., Test Pilot HAROLD R. HARRIS, 1st Lieut., A.S., Test Pilot IN PARLIAMENT Fleet ServiceVISCOUNT CURZON on April 26 asked the Secretary of State for Air how many flying officers are now serving in the fully-commissioned ships in theFleet; how many in aircraft carriers ; what is the establishment of flying officers in each case ; how many flights from fully-commissioned ships havebeen made since the 1st January, 1921 ; how many flights from aircraft carriers in the same period ; and how many landings have been made onaircraft carriers in the same period ? The Secretary of State for Air : The answer to the first part of the questionis one, and to the second part, twelve. The remainder of the flying officers for work in co-operation with the Fleet are borne on the establishment of theRoyal Air Force Base at Leuchers, the establishment of which for 1021-22 is 51, but this will not be entirely filled until later in the year. In additionto these, there is another squadron engaged in co-operation with the Navy and available for embarkation. If the noble and gallant Lord is interested inthese experiments I will show him full reports which deal with the latter parts of the question. The Air ForceON Report of the resolution passed in Committee of Supply for an additional number of men for the Air Force,Lieut.-Com. Kenworthy, on May s, urged that no case had yet been presented for calling out the Air Force Reserve, and that they ought to bedisbanded at the earliest possible moment. Capt. Guest, Secretary of State for Air, said that the Air Force Reserveconsisted of 250 officers and 5,800 of other ranks. He regretted to say that the current weekly expenditure was as much as £24,500. The Air Forcewas the only force capable of performing two very necessary duties—the carrying of mails to important centres, should the railways not be runningand the road service being unsuitable, or inconvenient, and the carrying of urgent communications should there be anything wrong with the telegraphservice. The Air Force did very important work in guarding Government stores. The risk cf storming an aerodrome and destroying its inflammablestores would be so simple that nothing could be left to chance. Very generous leave was granted to the officers of the Reserve, who were highly skilled mentechnically, in order to enable them to make private arrangements with their employers. Mr. White asked whether special leave meant that a man might return tohis employment and not be called up again unless the situation became very much more serious than at present. Capt. Guest, leplying, said that the terms of leave were practically assuggested by Mr. White. The man was subject to recall should circumstances make it necessary.The resolution was carried by 173 votes against 26. 315
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