The following U.S. military report on the Luftwaffe Dornier Do 217E bomber was originally published in Tactical and Technical Trends, No. 10, Oct. 22, 1942. [DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

THE GERMAN AIRPLANE WITH AN UMBRELLA Much has been written about the Dornier Do-217E but not until recently have details of its construction been known. As can be seen from the sketch, one of the most interesting features of this twin-engined bomber is the tail dive-brakes. These brakes when closed form a "cigar-like" extension to the tail, causing it to look very much like the rear section of a giant grasshopper. The dive-brakes consist of two pairs of flaps arranged at right angles to each other. In a fully extended position, the upper and lower or main flaps approach a vertical position, while the shorter and narrower horizontal flaps lie immediately behind the trailing edges of the elevators. The rear ends of the dive-brakes are hinged to a threaded collar that rides on a threaded tube. They are centrally supported by four brace rods hinged at both ends. This arrangement produces the effect of an umbrella and has given rise to the expression "umbrella" or "parachute" bomber. Slots and holes along the edges of the flaps act as vents when the plane is in a dive. Upon entering a dive it is possible to set in operation an automatic electrically operated mechanism which turns the threaded tube and causes to travel forward the nut-like device to which the flaps are hinged. This opens the brakes gradually until, at the maximum diving angle of the plane, they are fully extended. After the bombs have been released at the end of the dive, the tail flaps are again closed automatically by the threaded tube rotating in the opposite direction. It is assumed that the tail brake works automatically when the automatic bombsight is engaged and the plane begins its dive, but the pilot may also without the use of the bombsight adjust the dive-brakes by electrical means to any selected diving angle. The entire tail assembly is fastened by means of four removable pins. In an emergency, this tail brake can be jettisoned by the pilot. The airplane is then operated in the normal manner. Recent developments indicate that this brake alone is insufficient in steep dives. In later models of the Do-217E types additional brakes have appeared, mounted on the underside of the wings, inboard of the engines.

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