Bombsight - lowest altitude

[Yaab]

What was the lowest altitude at which bombardier in level bombers used bombsight like Sperry or Norden to aim bombs? Was there a cutoff point at which pilots started aiming with bomber's nose in a shallow glide?

Also, does LowGnd skill represents aiming with bomber's nose (1000 feet) while Gnd skill represents bombing with bombsight (2000 feet -xx,xxx feet)? Seems LowGnd is only trained and used at 1,000 feet.

[Buckrock]

Without checking sources, I think the early war Nordens and Sperrys had issues beginning below 10,000ft. It appears quite a few medium outfits
in the Pacific made use of the simpler bombsights like the Estoppey for low (and even medium) level bombing. By mid-war though, the latest Norden
variant appears to have been able to cope with altitudes as low as 4000ft.

[geofflambert]

From the Wiki on the Norden:

The new design, the Mark XV, was delivered in production quality in the summer of 1931. In testing it proved to eliminate all of the problems of the earlier Mk. XI design. From 1,200 metres (4,000 ft) altitude the prototype delivered a CEP of 11 metres (35 ft), while even the latest production Mk. XI's were 17 metres (55 ft).[12] At higher altitudes, a series of 80 bomb runs demonstrated a CEP of 23 metres (75 ft).[2] In a test on 7 October 1931, the Mk. XV dropped 50% of its bombs on a static target, the USS Pennsylvania, while a similar aircraft with the Mk. XI had only 20% of its bombs hit.[13]

Moreover, the new system was dramatically simpler to use. After locating the target in the sighting system, the bombardier simply made fine adjustments using two control wheels throughout the bomb run. There was no need for external calculation, lookup tables or pre-run measurements - everything was carried out automatically through an internal wheel-and-disc calculator. The calculator took a short time to settle on a solution, with setups as short as 6 seconds, compared to the 50 needed for the Mk. XI to measure its ground speed.[2] In general, the bomb run needed to be only 30 seconds long.[14]

Operationally this kind of accuracy was rarely achieved, and this from the Wiki:

The Norden operated by mechanically turning the viewpoint so the target remained stationary in the display. The mechanism was designed for the low angular rate encountered at high altitudes, and thus had a relatively low range of operational speeds. The Norden could not rotate the sight fast enough for bombing at low altitude, for instance. Typically this was solved by removing the Norden completely and replacing it with simpler sighting systems.[42]

A good example of its replacement was the refitting of the Doolittle Raiders with a simple iron sight. Designed by Capt. C. Ross Greening, the sight was mounted to the existing pilot direction indicator, allowing the bombardier to make corrections remotely, like the bombsights of an earlier era.[42]

However, the Norden combined two functions, aiming and stabilization. While the former was not useful at low altitudes, the latter could be even more useful, especially if flying in rough air near the surface. This led James "Buck" Dozier to mount a Doolittle-like sight on top of the stabilizer in the place of the sighting head in order to attack German submarines in the Caribbean Sea. This proved extraordinarily useful and was soon used throughout the fleet.[43]

[sic] Apparently by "former" the writer was referring to the Norden and "latter" refers to the iron sight.

[geofflambert]

The USAAF developed a box formation with the planes closer together, increasing their defensive firepower, while only the lead bombardier used the Norden and the rest dropped on his cue. The Navy, for whom the sight was developed, mostly dropped it's use.

[geofflambert]

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[geofflambert]

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[geofflambert]

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[spence]

My father, as a USN pilot who flew PV-1s during the war, was trained to attack ground and naval targets from low altitude. He told me that no bomb-sight was used but rather the pilot aimed the plane using the Mk1 Mod 0 eyeball in a shallow glide to guesstimate when to release his bomb/bombs (individual or multiple release).

In the initial production of the aircraft there was a bombardier position in the nose with some sort of bomb-sight (don't think it was a Norden) but in the field and in later production the bombardier position/crewman was replaced with a "chin-pack" of 3 x .50 cal MGs. The pilot could use the "tracers" from 7 x .50 cal MGs to supplement his guesstimate.

[BBfanboy]

ORIGINAL: Yaab

What was the lowest altitude at which bombardier in level bombers used bombsight like Sperry or Norden to aim bombs? Was there a cutoff point at which pilots started aiming with bomber's nose in a shallow glide?

Also, does LowGnd skill represents aiming with bomber's nose (1000 feet) while Gnd skill represents bombing with bombsight (2000 feet -xx,xxx feet)? Seems LowGnd is only trained and used at 1,000 feet.

When the game first came out the threshold for LowG was 6000 feet. It was changed to 1000 feet in a simplification of the bombing AI that removed Glide Bombing and high altitude dive bombing. I don't know why 1000 feet was chosen for Low G. It may have been to limit the use of LowG to an altitude that Japanese flak had a better chance to hit (because small caliber AA like the 25mm cannot reach 6000 feet).

[Bearcat2]

My father initially flew A-20A's; the Group took out the Norden's in late 42' and put in MarkIX, then they got RAF bombadiers attached to their unit and flew with them until they got US trained bombadiers in the MarkIX. When they went to A20G's, they flew more ground support missions [not close support], they took out the bombsight. When they had a mission to level bomb, they would have the lead A-20A with a bombadier and the rest of the planes would drop on him.
They never used them in actual combat, but in Jan42', they put Mark XIII torpedo's on their A20A's and flew missions out of Fresno, but the the Japanese Navy didn't show up, that was the only time they carried torpedo's.

Level bombing with a bombadier was no lower than 10,000 ft. Ground support\anti-shipping was up to the pilot.