Heinkel HD 39
1-2 seat aircraft designed for transport of newspapers
Length 10,0 m, height 3,7 m, span 14,8 m, wing area 51,0 m2
Empty 1250 kg, crew 170 kg, fuel 230 kg, pay load 400 kg, flying weight 2050 kg, wing loading 39 kg/m2, power loading 8,8 kg/hp
Speed 160 - 170 km/h, landing speed 72 km/h, climb to 1000 m 7 min., range 800 km
Bz 1.  HD 39 entered service in April 1926 by the Ullstein-Verlag and remained in Service until 1931, when
distribution of B.Z. by air was taken over by Deutsche Luft Hansa. Shown at the  Luftfahrt-Sammlung in Berlin-
Die ersten 100 000 km eines Zeitungs-Transport-Flugzeuges.
Am 29. März hat ein im täglichen Luftdienst eines großen Berliner Verlages
Hegendes Heinkel-Zeitungstransport-Flugzeiig seinen 100000 Kilometer
gelegt. Diese außerordentliche Leistung, die ohne Unterbrechung und
nennenswerte Störung vollbracht wurde und die deshalb als bahnbrechend
für den Eildienst-Lastentransport der Zukunft angesehen werden darf,
verdient um so höhere
Anerkennung, als es sich hier um den ersten Versuch einer Privatfirma
ihre Leistungsfähigkeit und Rentabilität durch Einstellung eigener Flugzeuge
erhöhen. Nach den mit dem Heinkel-Hugzeug gemachten Erfahrungen hat
Versuch die Erwartungen nicht nur voll erfüllt, sondern sogar weit übertreffen.
Taglich und auf die Minute übernahm dieses Flugzeug im Zentralflughafen
Tempelhof seine schwere Zeitungslast, brachte sie in kürzester Zeit nach oft
entlegenen Provinzstädten und kehrte ebenso pünktlich zum Flughafen
zurück. Auf diese Weise wurden in bisher 11 Monaten Flugdienst insgesamt
85 400 kg Zeitungen, das sind ca. 1308200 Exemplare, befördert und hierbei
- wie schon erwähnt - insgesamt 100000 Flugkilometer zurückgelegt. Es
ist dies auf seinem Gebiet eine Weltrekordleistung, die wiederum einen
überzeugenden Beweis für die hohe Leistung und Betriebssicherheit nicht nur
des Flugzeuges, sondern auch des eingebauten BMW IV-Motors darstellt. Hinzugefügt sei noch, daß dieses Heinkel-Flugzeug, Typ H.D.39, als normaler Doppeldecker gebaut ist und eine Normal-Nutzlast von 400 kg mit einer Horizontalgeschwindigkeit von 166 km/Std. zu befördern vermag.
The Heinkel H.D.39 is a further development of the postal airplane H.D.27, which has long been successfully used in airmail service in other countries (than Germany) both day and night.    It has, however, been adapted, by a series of changes in detail, to the special purpose of carrying newspapers. These changes meet the requirements of easy loading and unloading, optional release of newspaper packages by the pilot, and ability to land without danger even on poor ground.    It is a strongly staggered biplane.   The longerons and bulkheads of the fuselage are American spruce and are covered with plywood.    The fuselage is very roomy so as to receive the special equipment.    Its interior is readily accessible through manholes for the inspection of the control cables.   All openings,  through which water or dirt might enter the fuselage, are tightly closed.
The rear portion of the fuselage lies close to the ground, in order to afford convenient access.   It is entered through a door near the middle. From here a passage leads forward by the
right of the pilot's seat to the freight room at the center of gravity of the airplane, where the releasing device is located.
Both the passage and the freight room are well lighted with win-
The two seats are abreast, with the pilot's seat on the left. Due to the elevated position of the seat and the strong stagger, an excellent field of view is obtained    The view is still further improved by the fact that the cabane is not attached, as customary, to the upper fuselage girders, but rests on special supports which lead to the lower fuselage longeron  This makes it narrower, so that both the pilot and his companion can easily see past it.   The pilot's seat is adjustable.   All levers are within easy reach and the instruments are easily readable. The seat for the pilot's companion can be folded against the right outer wall, so as to leave the way open to the freight room. The control stick is replaced by a steering wheel, which tires the pilot less on a long flight.   The rudder is operated by pedals, which are placed so that the feet can rest in them comfortably.   All the steering controls can be readily inspected by the companion during flight. Careful attention was given to a convenient arrangement of the equipment

1   All the necessary navigating instruments, as also the ones for controlling the engine, namely, altimeter, speedometer, fuel gauge, revolution counter, oil-pressure gauge, clock and cooling-water thermometer.   All the instruments are readily readable from either seat.

2.   Loading and releasing devices.   The packages to be forwarded and dropped are suspended in a special freight room near the center of gravity of the airplane.    There are ten suspension points for ten packages with a maximum weight of 50 kg (110 lb.) each.    These packages are distributed on three supports in such a way that four hang on the right, four on the left and two in the middle.    Even when completely loaded, one can enter the room and inspect the separate suspension points, the entrance being over a slide door in the floor, which can be easily opened and closed from the pilots seat.   The three supports are connected with one another by a system of transverse tubes, which facilitate the loading of the magazine.   The packages are lifted by hook and tackle through the opening in the floor and conducted to their respective suspension points.

The suspension and releasing device consists of a system of longitudinal tubes provided with small slots.    The individual releasing hooks, while leaded, rest on these tubes. The packages are released by the pilot with the aid of a hand lever. The supporting tubes for the hooks slide longitudinally under the action of the lever, so that the individual slots come one after another under the suspension hooks.   Each hook drops through the corresponding slot and releases one of the packages.-   It is so arranged that only one package can drop at a time.    By shifting a special device, it is possible to. select the support from which it is desired to drop the package-    It is especially noteworthy that the pilot himself, in case he is unaccompanied, can operate the releasing device and can select the desired support. It is moreover possible for bis companion, to rearrange the packages during flight.
The motive power is supplied by the well-known 230 HP- BMW. IV water-cooled engine.    It rests on a steel tubing support , which is secured'by four steel bolts, to suitable .fittings on the fuselage struts.    This support carries the whole cooling system and all the engine accessories.   This manner of fastening has proved satisfactory in all our recent productions and is now exclusively employed by us   The whole power plant can be re- moved in a very short time and be replaced by another. Furthermore, it can be transferred altogether to the test bench, in order to give it a thorough test before installing or after overhauling.   The hood is so constructed as to render all parts of the engine easily accessible.   The engine is separated from the rest of the fuselage by a fireproof steel bulkhead.    A fire cock is inserted, in order to enable the instantaneous shutting off of the fuel supply, in case of fire in the carburetor. The fuel is contained in two easily removable tanks in the upper wing and flows to the carburetor under the influence of gravity alone.    This eliminates all compressed-air pipes or fuel pumps and the accompanying; disturbances and insures the continuous flow cf the fuel.
In order to render the various pipes easily distinguishable, they are painted as follows  water pipes  green; oil pipes, brown; fuel pipes, red; air pipes and dynamic-pressure gauge, blue.   The fuel gauges are plainly visible on the under side of the wing, there being one for each fuel tank.   All overflow pipes load into the outside air, in order to prevent the collecting of fuel in the fuselage.
The upper and lower wings are divided.   The spars are box girders and consist of spruce flanges with plywood webs- The stagger of the wing is such that the rear spar of the upper wing is vertically over the front spar of the lower wing. The plane thus produced is braced by cross wires.   This arrangement has the advantage of fewer wires and,  in combination with the N-struts, produces a statically perfect cell.   The lift wire is double.   The antilift. wire is single.    The struts are streamlined.
Instead of inside bracing and for the sake of lightness and. ease of repair,  the under side of the wings, between the spars is covered with plywood, which absorbs the thrust stresses. The leading edge of the wings is covered with plywood, in order to maintain a more favorable profile.   The wings are secured by bolts to the cabane and to the lower fuselage longerons.
The vertical tail fin is wood and is joined directly to the fuselage- The horizontal fin or stabilizer is adjustable during flight by a hand wheel within easy reach of the pilot. The rudder and elevator are balanced in the usual manner, in order to make the steering easier.    Banking is accomplished by .means of two large specially constructed ailerons in the upper wing, which are very efficient and easily operated.
The landing gear differs considerably from the usual form. In order not to interfere with the dropping of the packages, it has no continuous axle.   This also facilitates loading through the bottom of the fuselage.   The landing gear consists of two entirely separate parts.   The track.gouge ia very large, in order to insure a safe landing on uneven ground-   Each half of the landing gear consists cf two streamlined struts hinged to the bottem fuselage longeron and a third strut, containing a shock absorber, flexibly attached to the upper fuselage longeron The shock absorber itself consists of rubber cords and is contained in a streamlined housing in the upper part cf the third strut.
In order to facilitate ground maneuvering, the tail skid can be turned by the pedals along with the rudder, a device which has been successfully employed  on a number of our airplanes. The airplane takes off quickly, climbs well and has .an extremely low landing speed-    It is so constructed that even long flights in bad weather do not fatigue the pilot.
From "Flugsport,11 May 1, 1926, pp. 167-172.
Fig 1    Top: the wing structure.    There is no internal wing bracing.    The bottom and the leading edge of the wing are covered with plywood.    This absorbs the thrust stresses and maintains the profile, especially of the leading edge.    On the left there is an empty space for one of the fuel tanks.    Only-gravity tanks in the wings are used, which eliminate all pumps with their accompanying troubles and assure a continuous flow of fuel.
Bottom.: the fuselage structure.    The rear half of the fuselage is covered with plywood, as also the vertical fin.    In the bulkheads there are holes for the passage of the control wires.
Fig:. 3.    Upper left.    The pilot's, seat is on the left, of the roomy fuselage.    Its elevated position affords an excellent view.    The levers on the left wall are painted with different colors,  in order to make it easier to distinguish them. They are the throttle lever, ignition lever and fuel-control lever. The elevator and ailerons are operated by a hand wheel. The grease cup for the water pump is within easy reach on the left wall.    On the right, a Bosch starter and an inclinometer are visible.    
Upper right.   The instrument board has the following apparatus:    at the extreme left, the switch for throwing the engine on and off; near and above it, the oil-pressure gauge; to the right of the latter, a revolution counter; next on the right, a speedometer; above the latter, an altimeter; still higher, a knob for regulating the water cooling; immediately above the inclinometer, a small clock.   The large hand wheel on the right serves to adjust the horizontal stabilizer during flight. The lever in the upper right-hand corner of the instrument board operates the releasing device.   By means of it, the pilot can. select during flight the package he wishes to release!
Lower left. The device for releasing the newspaper packages. The latter hang by .loops, as shown in the picture, and are distributed on three tubes: four on the right, four on the left  and two on the middle tube.    The releasing device consists of a system of longitudinal tubes which are provided with small slots. The releasing hooks, on which the loops of tho packages are suspended, rest on these tubes.    Lower right.   The removable steel tubing engine support.
Heinkel Zeitungstransportflugzeuge.
Das Flugzeug H D39 hat vor einiger Zeit seinen 100000ten Flug-kilometer ohne Störung zurückgelegt (siehe Flugsport Heft 8, S. 160). Nachdem sich das Baumuster, wie vorstehender Erfolg zeigt, sehr gut bewährt hat, beabsichtigt Heinkel. denselben weiterzuentwickeln. In aller Kürze wird daher ein neuer Zeitungstransport-Typ im Flugbetrieb erscheinen, der statt bisher 230 PS nunmehr 500 PS hat und bei 4 Stunden Flugzeit eine Zeitungslast von 1000 kg trauen wird.
Die vorstehende Abbildung läßt die Raumeinteilung der HD 39 erkennen. Vorn befinden sich in den Abwurfvorrichtungen Zeitungspakete. Dahinter ein weiterer Raum für Passagiere, Zeitungen oder Fracht. Für den Ueberseetranspoit wird diese Maschine in verhältnismäßig kleinen Kisten verpackt. Für die internationalen Interessenten dürften diese Kistenmaße, welche aus obenstehender Abbildung hervorgehen, nützlich sein.