"Emmanuel Gustin" wrote in message
...
"Jim Doyle" wrote in message
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Not being able to read German - could someone please explain the
principal
workings of the gunsight in the first diagram? (The two concentric
circles
and cross as rear sight, with vane-looking gizmo as foresight - attached
to
the MG15).

Vane sights. In a flexible gun position, gunners must take into
account not only 'lead' on the target but also relative wind.
If the gun is aimed perpendicular to the direction of flight the
bullet will have, relative to the air, a sideways as well as
a forward velocity component, so drag will caused it to fall
behind the line of sight. The size of the effect depends on the
angle and on the speed of the aircraft the gunner is sitting in.

Hence the spring-loaded vane sight. If the gun is pointing aft,
the bead is in line with the barrel. If the gun is pointed sideways,
the vane will be pushed at by the air current, and the bead will
move in the opposite direction, indicating the correction angle.
The larger the rotation of the gun or the speed of the aircraft,
the larger the movement of the bead. A lot of ingenuity went
into the design of such sights during WWI and afterwards, until
most people standardised on reflector sights.

Lead, of course, must still be judged by the gunner from the
distance and the relative speed of the two aircraft, using the
deflection rings.

The Germans continued to use such sights longer than others,
it seems -- but they made relatively little use of gun turrets.
IIRC one US bomber group also used them on the waist gun
positions of B-17s, with good results.

Cheers for that, it all makes sense!

I guess though - no matter what sight adjustments you make - having a sharp,
skilled and determined gunner is what makes the difference. I don't imagine
that in combat you'd be crouched over you gun and squinting through the
sights hoping the drift's correct when the enemy's bearing down on you,
cannons blazing!

Jim Doyle


--
Emmanuel Gustin
Emmanuel dot Gustin @t skynet dot be
Flying Guns Books and Site: http://users.skynet.be/Emmanuel.Gustin/