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.