Balloon barrages equipped with steel cables, which are used to protect
industrial and military areas in the British Isles, and used to some extent in
Egypt, present formidable obstacles to German fighters and bombers. These
barrages are both fixed and mobile, and are capable of effective operation at
considerable altitudes. In numerous instances, they have damaged the wings or
fuselage to such an extent as to cause the enemy planes to crash or force-land
on British territory. Avoidance of these barrages can be effected by flying over
them, but this reduces the accuracy of level bombing. There are other means
of avoiding balloon cables.
To cope with the situation, the Germans have developed knife-edge cutters
called Kutonase which are fitted to the leading edge of the wings, and
sometimes around the nose of the fuselage. They are made of steel, and the
blade is suitably faired.
|LEADING EDGE OF DORNIER WING, FITTED WITH KUTONASE|
Three different types of Kutonase have been examined and tested. On
the Ju-88 it was applied to a standard wing, the cutter
having a hardened edge, covered with a thin sheet of duralumin forming
the wing leading edge.
On the Dornier 217E, the wing in front of the spar had been specifically
designed to take the cutter. The general design is similar to that on
the Ju-88, but the cutter is of rolled steel instead of being fabricated, while
the adverse effect of the fairing on the cutting is minimized by the insertion
of a strip of thinner material along the fairing immediately over the cutting edge.
The Kutonase found on a Heinkel 111 was of an overshoe type, designed to
be fitted to aircraft already in service, the complete unit being held in position
by straps anchored to the front spar, and covered with doped fabric. In this
case, the only material interposed between the cutter and the cable was doped
fabric, but the advantage of this is probably decreased by the additional stiffness
provided by the turned-in edges of the metal fairing. The cutter plate and
mounting were similar to those on the Ju-88.
It is believed that the Kutonase on the Dornier 217E provides complete
protection against heavy balloon cables at speeds over 200 mph but is effective
against light barrage wire only at a considerably higher speed. Although the
type used on the He-111 is just as efficient as that used on the Dornier 217E, the
former plane is not so well protected on account of its lower maximum and
cruising speeds. The Kutonase of the Ju-88 appears to provide little or
no protection in normal flight, but might be effective at the speeds obtained
after pulling out of a steep dive.