Heinkel He 71

Heinkel He 71 впервые взлетел весной 1933 года. Он был по существу уменьшенной одноместной версией туристского самолета He 64. На прототипе, первоначально имевшем открытую кабину пилота и мотор Hirth HM60 мощностью 60 л.с. (45 кВт), позднее появился фонарь кабины и мотор Hirth HM4 мощностью 78 л.с. (58 кВт). На этом аэроплане с дополнительным запасом бензина для увеличения дальности полета до 2410 км немецкая летчица Элли Байнхорн совершила ряд полетов над Африкой.

Flight, September 1932

THE NEW HEINKEL HE 64
By EDWIN P. A. HEINZE

   ONE of the financially soundest aeroplane factories in Germany, and one of the busiest, too, is that of Heinkel at Warnemunde, on the shores of the Baltic. Yet this maker is relatively less known to the general public than most of the others, because he neither builds transport planes of a type used in Germany nor, up to the present, small planes such as the clubs and individual owners would purchase. The factory has specialised more in the production of school machines and catapult planes, and has occupied itself most extensively with the design of military planes for foreign powers. Hence it created a sensation when one day news leaked out that Heinkel was entering the light plane field, and that he intended taking part in this year's International Light Plane Competition on the Continent. The fine performance of the German officer Seidemann, with his colleague Witt as observer, in an Argus-powered Heinkel, during the air tour forming part of this competition Heinkel into the limelight of public interest.
   Indeed, the new Heinkel machine appears to be what may be termed a "hit," which is all the more remarkable as this is the first machine of this type developed by the company that was founded in 1922 by Dr. Ernst Heinkel, already then an aircraft engineer of long standing, who for years had been the technical chief of other aeroplane factories in Germany, especially during the War.
   The new Heinkel is a low wing cantilever monoplane built entirely of wood, with a long and slender fuselage of oval section, with which the wing stubs are integrally formed. The single spar wings are of trapezoid contour and are secured by universal joints and lever-operated bolts. The connection is so well worked that the small gap between the wings and stub wings barely measures one millimetre, so a special covering strip is not required. The bolt lever, however, permanently protrudes slightly on the lower wing surface. The maximum chord of the wing at the roots is 2 metres (6.56 ft.), and 0.8 metre (2.62 ft.) at the rounded tips. The wings are set at a dihedral angle of 4 1/2 degrees, and have a span of 9.8 metres (32.15 ft.). The over-all length of the machine, which has two seats arranged one behind the other, is 8.31 m. (27.26 ft.) and the greatest beam (i.e., horizontal diameter) of the fuselage 0.73 m. (2.4 ft.).
   The wings are provided with slow-flying flaps and ailerons extending to and partially completing the rounded wing tips. The leading edge of each wing is additionally equipped with two independent Handley-Page slots covering the whole length of the wing. The outer slats, having the length of the ailerons (1.93 m. or 6.33 ft.), are of the automatic type, while the inner slats are connected with the slow-flying flaps. It is due to these means that the machine, which with the Argus 140/150 h.p. engine has a maximum speed of some 155 m.p.h., can actually fly without loss of altitude at 38.6 m.p.h., as was done, for instance, by Junck and Seidemann during the slow-flying tests at the international meeting above referred to. The wing area of the machine totals 155 sq. ft., including the ailerons, which each has a surface of 5.23 sq. ft.
   The two cockpits are covered by a common, long cellon hood of streamline form, merging at the rear end into the top of the fuselage, which, as all parts offering air resistance, has been most carefully designed. The seats in the cockpits are adjustable for height and leg length. Dual controls are provided, those in the rear being so designed that they can be "switched off" literally instantaneously by a small lever within reach of the front pilot. The stick and pedals then move freely without affecting the plane's steering. This is an excellent feature for schoolwork. The controls can additionally be taken out entirely and replaced and connected within a few seconds. Otherwise the controls are wholly normal. Provision for the inspection of the cables, etc., is made by well-covered apertures in the fuselage.
   The tail surfaces, i.e., stabiliser and elevator, are entirely made of wood and have a long oval form, 9.02 ft. in length and 2.88 ft. deep, the depth of the elevator being 1.34 ft. The area of the stabiliser is 10.37 sq. ft. and that of the elevator 8.63 sq. ft. The stabiliser is adjustable during flight to the extent of +3 and -8 degrees. The rounded rudder fin, which is braced by lateral wires against the stabiliser, has an area of 3.4 sq. ft., and the rudder is of 5 sq. ft.
   The undercarriage is of the divided type, with Palmer brake wheels and combined hydraulical and pneumatic struts. The wheels are not provided with spats.
   As already indicated, the machines are equipped with the new Argus engines of 140/150 h.p. maximum output. These inverted engines are well faired by an aluminium casing, which is easily detachable. A variable pitch propeller of 6.88 ft. diameter is employed (generally set to a pitch of 4.59 ft.). The engine is mounted on a steel tube frame attached to the fire bulkhead in the usual manner. Extensive use is made of rubber for engine suspension, so that vibration is considerably damped. The engine draws its fuel supply by means of two diaphragm pumps from two tanks, one of which is situated immediately behind the fire bulkhead in the fuselage, while the other is arranged in the bulging parts of the fuselage between the first and second seat. The oil tank forms part of the nose of the right stub wing, where it is effectively cooled by the slipstream.
   The machine weighs complete with instruments and ready for flight, but otherwise empty, 990 lb., and will take a load of 660 lb., so the full flying weight comes to 1,650 lb. The wing loading amounts to 10.65 lb. per sq. ft.

Some Editorial Comment

   The description of the Heinkel He.64 by our German correspondent, printed above, gives the main data, etc., of the machine. During the recent visit of the "weekenders" a number of Heinkels were seen and inspected, and a good opportunity to watch their behaviour was afforded. Moreover, on Monday of this week Handley Page, Ltd., arranged a demonstration at Radlett, at which three of the Heinkels were flown. Thus one is able, quite apart from Herr Heinze's description, to form a very good idea of the qualities of the He.64.
   As a piece of workmanship the Heinkel is an outstanding example of German craftsmanship. The finish is such as is rarely seen anywhere, and the machines looked spick and span in spite of their strenuous time in the International Touring Competition.
   Something should be added about the slot mechanism, which is of a more advanced type than has ever been seen on an aircraft in this country. The wings are slotted and "flapped" over their whole span, slots as well as flaps being divided into what may be termed lift and control devices respectively.
   The inner slots, which extend from the wing root to the automatic wing tip slots, are automatic in action, and are so connected to their trailing edge flaps that when the slots open the flaps are pulled down to their full extent. The outer slots are also automatic, and are connected to the aileron flaps in such a way that as the slot opens the aileron drops a few degrees. After that, however, the aileron is free to operate in the normal way without interfering with its slot.
   The lift slots can be locked in the "closed" position, when their associated trailing edge flaps are flush with the wing surface. They cannot, however, be locked in the "open" position, with the flaps down, nor do they have any intermediate position. Either they are fully closed or fully open. To us it appears that this is not the best possible arrangement, and that the automatic operation is of somewhat doubtful value. We believe an improvement would be for the lift slots and their flaps to be manually operated, or at any rate for them to be under the control of the pilot in such a way that any desired intermediate position between fully closed and fully opened could be maintained. In gusty weather there seems to be a tendency for the lift slots to slam about, and one of our photographs actually shows that it is possible for the lift slot on one side to be closed and the other open. We understand that actually Handley Page, Ltd., who designed the slots for the Heinkel machines, desired a torque tube to be incorporated so as to ensure the simultaneous opening and closing of the port and starboard lift slots, but that as wing-folding was an important feature for machines in the International Touring Competition, the Heinkel firm decided to do without this interconnection.
   The Heinkels were flown, during the demonstrations, by the various German pilots, but it was Capt. Cordes, Handley Page's test pilot, who gave far and away the most impressive demonstration. Although he had flown the machine for only about two minutes before, he took off in a nearly vertical "zoom" for the benefit of our photographer, and afterwards flew about quite low down, with the machine at an alarming angle, but definitely showing that even at the largest angles the controls are effective. The demonstration was a credit to the Handley Page slots, but it was also a welcome reminder that Cordes is a pilot of more than average ability.
   In trying to form an opinion of the Heinkel He.64 it is essential that one should remember that the machine was designed specifically with the International Touring Competition in mind, and that the International Touring Competition was designed to produce a useful type of aircraft for the private owner. The Heinkel very nearly achieved its object, but it is doubtful if the International Touring Competition did. As a competition machine, a collector of points for take-off and alighting, the Heinkel is very nearly all that a machine could be. As a private owner's machine it is not yet ideal.
   From the point of view of the pilot, the Heinkel is undoubtedly an interesting machine, but during a short flight we cannot honestly say that we were impressed with its suitability as an aeroplane for the average private owner. It is true that a very low flying speed can be achieved without an undue sinking speed, which is only natural in view of the fully-slotted wing, but it did seem to us that it was necessary to use the engine if the full benefit of the slots was to be obtained. On the glide there was a distinct, and somewhat unpleasant, snatch when the slots opened, and we gather that normally the German pilots do not let the gliding speed fall below a fairly high figure, at which the glide was, as one would expect, very flat. The controls were efficient and reasonably coordinated, although the rudder of the machine we flew was distinctly heavy; this, however, we understand was due to mechanical friction in the hinges. This explanation would appear to be correct, as despite the length of fuselage the amount of control available was by no means excessive. It was definitely greater than that usually provided by German designers, but hardly up to the average English aeroplane. The ailerons were good, giving full control even when all slots were open and one was hanging on the engine, and it was in this manner that the competition landings were made during the Rundflug. Whether or not there is sufficient control without the engine for such short landings to be made in cases of necessity seems to us to be a matter for some doubt. At top speed the machine was comfortable to fly, and the controls were not unduly heavy, but for comfort on long journeys considerably more shoulder and head room would have to be provided for the pilot if it was proposed to sell the machine for private use; this is not, we understand, likely to be the case. The view forward is not so good as one is entitled to expect from an aeroplane with an inverted engine and a fuselage of such narrow cross-section; neither is the wind screen arrangement comfortable except when completely closed.
   The take-off is straightforward, though at the same time the super slotted arrangement would seem to make extra care necessary, as side gusts might well open one slot before the other with possible difficult complications.
   The undercarriage, as at present fitted, is very harsh, but presumably that is entirely due to competition desiderata.
   The Argus 140 was disappointing, being rough without giving one the impression that one had 140 h.p. to play with; and in any case 140 h.p. would seem a lot to pay for this form of two seater, with a performance very little better than British designers obtain with cabin machines giving much greater comfort and seating capacity.
   It can, we think, be said that the Handley Page slot has outstripped the technical development of the aircraft. The Heinkel He.64 will hang in the air at 38 m.p.h. or so, but at a very large angle. To alight at that angle would result in serious damage to the machine, as the tail skid would hit first, and the undercarriage then come down with considerable force, probably resulting in a crash. Consequently the speed at which the machine can safely be put down is considerably higher than the minimum speed at which it can hang in the air (with engine running). So long as that is so, there seems to be little point in all this slottery.
   One demonstration which would have been convincing was not given: a landing with engine stopped. While the engine is running, the combined effect of the slipstream and the upward pull of the airscrew assist materially in making possible the remarkably low speed. With a "dead" engine, and of course no slipstream, the result would probably have been a good deal less impressive.
   Before the fully-slotted aeroplane is a practical proposition, and before it adds materially to the safety of the average private owner, it will be necessary to incorporate not only a variable incidence but also an undercarriage capable of absorbing the shock of a landing at high rate of sinking. And even then, the reversal of controls necessary for flattening out may prove a stumbling block to some pilots.