A bombsight is a device used by military aircraft to accurately drop bombs. Bombsights are a feature of combat aircraft from World War I on, first found on purpose-designed bomber aircraft, and then moving to fighter-bombers and modern tactical aircraft as these aircraft took up the brunt of the bombing role.
A bombsight has to estimate the path the bomb will take after release from the aircraft. The two primary forces during its fall are gravity and air drag, which make the path of the bomb through the air roughly parabolic. There are additional factors such as changes in air density and wind that may be considered, but these are only a concern for bombs that spend a significant portion of a minute falling through the air. These effects can be minimized by reducing the fall time through low-level bombing or by increasing the speed of the bombs. These effects are combined in the dive bomber. However, low-level bombing also increases the danger to the bomber from ground-based defences, and accurate bombing from higher altitudes has always been desired. This has led to a series of increasingly sophisticated bombsight designs dedicated to high-altitude level bombing.
Since their first application prior to WWI, bombsights have gone though several major revisions. The earliest systems were iron sights that were pre-set to an estimated fall angle. In some cases these consisted of nothing more than a series of nails hammered into a convenient spar, lines drawn on the aircraft, or visual alignments of certain parts of the structure. These were replaced by the earliest custom-designed systems, normally iron sights that could be set based on the aircraft's airspeed and altitude. These early systems were replaced by the vector bombsights, which added the ability to measure and adjust for winds. Vector bombsights were useful for altitudes up to about 3,000 m and speeds up to about 300 km/h. Starting in the 1930s, mechanical computers with the performance needed to "solve" the equations of motion were incorporated into the new tachometric bombsights, the most famous being the Norden. Later in World War II, tachometric bombsights were often combined with radar systems to allow accurate bombing through clouds or at night. When post-war studies demonstrated that bomb accuracy was roughly equal when optically or radar guided, optical bombsights were generally removed and the role passed to dedicated radar bombsights. Finally, especially from the 1960s on, fully computerized bombsights were introduced, which combined the bombing with long-range navigation and mapping.
Modern aircraft do not have a bombsight, per se, instead using highly computerized systems that combine bombing, gunnery, missile fire and navigation into a single head-up display. These systems have the performance to calculate the bomb trajectory in real time as the aircraft manoeuvres, and add the ability to adjust for weather, relative altitude, relative speeds for moving targets, and climb or dive angle. This makes them useful both for level bombing, as in earlier generations, and tactical missions formerly bombed by eye.
n. A device which allows bombs to be accurately dropped from moving aircraft so as to hit a desired target.
The Collaborative International Dictionary
bombsight \bombsight\ n. 1. a sighting device in an aircraft for aiming bombs.
n. a sighting device in an aircraft for aiming bombs
Usage examples of "bombsight".
Sitting there with his knees bracketing the bombsight January dozed, and as he dozed he daydreamed his way out.
The bombsight rose before him, spearing the black sky and blocking some of the hundreds of little cruciform stars.
January leaned forward and put his face in the cool headrest of the bombsight, hoping that its grasp might hold his thoughts as well as his forehead.
January shouted, shielding the bombsight with his body from the eyes of the pilots.
Fitch gave him altimeter readings to dial into the bombsight, Matthews gave him windspeeds.
Already he hung over the bombsight like a drowning man over a life preserver, wiping his eyes with his sleeves while staring down into the aiming viewer.
The group had missed the bridge at Ferrara again for the seventh straight day with the bombsight that could put bombs into a pickle barrel at forty thousand feet, and one whole week had already passed since Colonel Cathcart had volunteered to have his men destroy the bridge in twenty-four hours.
There was nothing he could do until his bombs dropped but look back into the bombsight, where the fine cross-hairs in the lens were glued magnetically over the target exactly where he had placed them, intersecting perfectly deep inside the yard of his block of camouflaged warehouses before the base of the first building.
At last the indices on the bombsight crossed, tripping away the eight 500-pounders one after the other.
Yossarian bent away from the bombsight crookedly to watch the indicator on his left.
He lunged forward over the bombsight to search downward through the plexiglass for some reassuring sign of Orr, who drew flak like a magnet and who had undoubtedly attracted the crack batteries of the whole Hermann Goering Division to Bologna overnight from wherever the hell they had been stationed the day before when Orr was still in Rome.
Bologna straight and level with my head in the bombsight and listen to all that flak pumping away all around me.
He was working from radar reports alone with no fancy computing bombsight to think for him.
Well, I was stretched out over the Norden bombsight and I steadied myself and took my time.
High, cruising over Berlin in your trusty B-52, looking through your Norden bombsight and waiting for just the right moment to push the button.