Bronzavia D 30 bombsight

The Bronzavia D 30 was fitted aboard the LeO.451 and DB-7 bombers.

Read the manual (in French)

Study the pictures (partly translated)


The Bronzavia D 30 seems to be a rather simple targeting system, more sophisticated than the Blenheim's but less than complex systems like the famous Norden sight. That is to say the bombardier is still dependant on the pilot to fly the aircraft over the target. Some LeO.451s were eventually fitted with a more sophisticated system, including a gyroscopic stabilized bomb sight coupled to the plane's autopilot - but only after the Armistice.

Bombsight description:

The Bronzavia D 30 bombsight is partly externally mounted on the DB-7, its lower part being outside the glass nose. When planes are parked on the ground this equipment is protected by some piece of cloth or leather. Actually the Bronzavia sight was designed for larger aircraft and it is not that surprising that the DB-7 does not have as much room in the bombardier's position as the LeO.451. This is visible on some of those DB-7 pics .

The D 30 has the form of a periscope and can rotate around the vertical axis. It is linked to a target heading indicator (the "repetiteur type 11", or "indicateur de Cap" ) that is mounted on the pilot's instrument panel. All bombardment parameters are input via knobs on the upper part of the sight.

The "repetiteur type 11" seems to be fitted on the DB-7 immediately under the pilot's directional gyro. (Indeed, it is also fitted near the directional gyro aboard the LeO.451 as this page shows ) It does not show on the DB-7 manufacturer's pic (because, exactly like the gunsight, this equipment was fitted by the Armée de l'air, not by Douglas), but it is (barely) visible on this photograph of an operational DB-7's cockpit . Notice the horizontal thing immediately left of the yoke axis, and the wire hanging from it.

Aside from a complex bombardment data parameter entry, the bombardier interacts with the bombsight using the following controls: Bombing procedure:

After various settings/calibration procedures (tediously explained in pages 1-5 of the manual), the bombardier guides the pilot above the target as explained in page 6-7 of the manual. Here's how:

He locates the target in his sight, looking beyond the bombardement angle via the exploration button, and if needed by rotating the sight in direction. At the same time, the angle of rotation is indicated to the pilot on the "repetiteur Bronzavia type 11" indicator. The pilot uses this information to correct the aircraft's heading until it is aligned on the target. There is probably no need for vocal interaction between the crew members at this point.

If important corrections in heading are needed, the bombardier rotates the sight with the crank while depressing the pedal. If only fine corrections are needed, he only modifies the indicated target heading without turning the sight by using the crank without depressing the pedal. When the target appears on the sight reticule's vertical line, the heading is correct.

When the view pitch angle is in 10-15° range of the bombardment angle, the bombardier switches to "bombardment mode". When the target is in the center of the cross the bombs are released.

Various questions (now with answers):

Question 1: Does the bombardier manually rotate the sight to keep the target aligned, or is the sight somehow automatically rotated - perhaps via a synchronization with the directional gyro? Notice it is the same Sperry directional gyro on the LeO as on the DB-7 (or a license-built copy).
 The sight is manually rotated, either my the main handle on the left, or by the the little crank on the front right. However, there is a calibration procedure with the directional gyro (page 6 of the manual), so the target heading indicator certainly gives accurate heading corrections.
Question 2: How exactly are input the bombardment parameters on the sight - at least there are altitude, aircraft speed, perhaps wind or slip? 
The parameter input is very complex: wind speed, wind direction, aircraft ground speed, aircraft ground heading, height relative to the ground, bomb ballistic parameters ("traînage", whatever that means).
Question 3: what are exactly the optical characteristics of the periscope, we need at the very least the magnification (if any) and the field of view
from a SHAA document (I don't have the document reference right now though)
Question 4: are the bombs manually released by the bombardier using the sight's reticule, or is there a more sophisticated system? What is the use of the stopwatch on the bombsight?
The bombs are manually released. The stopwatch is used for speed measurement and calibration procedures (via angular speed of an observed spot on the ground).
Question 5: what is the interaction, if any, with the aircraft's autopilot?
None.
Question 6: how does the reticule aspect change as the bombardment parameters are input?
The manual does not say, however it is unclear anything at all changes.