As AG said this topic has been beaten to death.
But anyway the Periscope wasn't just used to see 6 o'clock (it wasn't used necessarily to aim the guns as they were fixed) but could be turned forward and used a 'glide bombsight'. This way the 234 could bomb from altitude by entering into a shallow dive.
Also while were are on 'bombsight', the 234 bombsight was automated in that the pilot lined up on a general heading to target and engaged auto pilot. He then rotated the control column out of the way and then looked through the bomb site and locked (marked) the site on the target. The 234 adjusted course via the autopilot and then released the bombs on target automatically.
But as a bomber the 234 wasn't that great. It was mostly used a recce. The only 234 to see any kind of significant service is the 234b.
When operated as a bomber, the Ar-234 could be used in shallow dive attacks, low-level horizontal attacks, or high-altitude horizontal attacks. In shallow dive attacks, the pilot would drop from about 5,000 meters to under 1,500 meters (16,400 to 4,920 feet), aiming the bombs through the periscopic sight that stuck up above the cockpit. In low-level horizontal attack, used only when the target was obscured, the pilot simply flew level and dropped the bombs when it seemed appropriate. Results were not generally very impressive.
High-altitude horizontal attacks were particularly interesting. Since the Ar-234 was a single-seat aircraft, the pilot had to double as the bombardier, and did so with the help of a sophisticated Patin autopilot system. The pilot would fly to within about 30 kilometers (19 miles) of the target, engage the autopilot, swivel the control column out of his way to the right, and then lean over and sight the target through the Lotfe 7K bomb sight. The bomb sight was linked to the autopilot. As long as the pilot held the target in the crosshairs, the autopilot would change the aircraft's heading accordingly, and then the bomb sight would automatically drop the bombs at the right moment.
In principle, the Ar-234B had a pair of fixed rearward-firing 20 millimeter MG-151/20 cannon for protecting its tail, with the pilot sighting the guns through the periscope. Not only did the pilot have to be his own bombardier, he was his own tail gunner as well. However, in practice the guns were not always fitted and were never an important feature of the aircraft. Armor plate was attached to the rear wall of the cockpit to give the pilot a little protection.
Also, if you look at AH's 190s event the A-5 does 415mph or so at FTH. The fastest A series 190 was the A-9, the fastest production 190 was the Dora-9.
If your books tell you other wise burn them.
FYI an F-3 is basically an A-5 made into a fighter-bomber. Both the F-8 and F-9 were faster on the deck.
