Bomb sights for light bombers.

[davebender]

The A-36 discussion has gotten me wondering what bomb sights were employed by other WWII era light bombers.

Ju-87, Ju-88, Me-210, Me-410.
…..Stuvi 5. A purpose built dive bomber sight for these purpose built dive bombers. Everything I have read suggests it was state of the art during WWII.

USN SBD.
IJN Val.
…..These purpose built dive bombers employed a telescopic bomb site. Superficially both bomb sites appear similar mounted on top of the instrument panel and extending through the windscreen.

USN SB2C
IJN Judy
…..Did these late war naval dive bombers have an improved bomb sight?

Me-109 ground attack variants.
Fw-190F Fw-190G
? Did these light bombers have a bomb sight?

A-36 dive bomber.
Apparently none. However that sounds incredible as the A-36 was supposed to be a bomber.

P-38 ground attack variants.
P-40 ground attack variants.
P-47 ground attack variants.
P-51 ground attack variants.
F6F ground attack variants.
F4U ground attack variants.
? What sight was employed when dropping bombs?

Hurricane ground attack variants.
Typhoon
Tempest
Mosquito light bomber variants.
Beaufighter bomber variants.
? What sight was employed when dropping bombs?

A-20 light bomber.
A-26 light bomber.
? Did they use the Norden sight?

Soviet Pe-2 dive bomber.
?

Soviet Il-2 light bomber.
? What sight was employed when dropping bombs?

 

[barney]

I can answer the question for the P-51D - no bomb sight except the K-14 gunnery sight had range marks for rockets.

A P-51D could carry anywhere from a 100 to a 1000 pound bomb under each wing. However, carrying 2 1000 pound bombs restricted the aircraft to straight and level. First select Both or Train on the rocket control panel. Then switch left and right to arm. If Both is selected pressing the button on top of the stick dropped both bombs. Selecting Train dropped one bomb each time the button was pressed. In case of an electrical failure the bombs could be dropped mechanically by way of two levers in the cockpit but could not be armed.

The only other information I found was that when vertical avoid side slipping when bombing or a bomb could go into the propeller.

 

[Siegfried]

The standard mid-late war british bombsight, the Mk.XIV (known as the T.1 when made in the USA by Sperry) could level bomb with only a 10 second straight run required. It could also glide/slide/shallow dive bomb down to 5000ft.

It was fitted to the Mosquito as well as the Lancaster. Unlike the Lotfe 7 or Norden it could not track the ground and calculate wind drift, that had to be entered manually, but it did allow manouvering as well as shallow glide bombing.

I believe the standard German fighter Revi gun sight had a second adjustable cross hairs bar; the pilot adjusted this according to an ofset angle determined by the expected release speed, altitude, dive angle etc. He aimed at the target, pulled up and released when the second recticle crossed the target. This is probably the way Me 109s attacked and sank/damaged the cruiser HMS Fiji.

Spitfires when bombing just aimed with their gun sight at a 45 degree dive, pulled up, counted to 8 and released. (Sptfire versus the V weapons Osprey books).

Low level bombing was purely intuition AFAIKT.

 

[Airframes]

The Mosquito normally used the Coarse Setting bomb sight, although the MkXIV was used by Pathfinder aircraft for precision marking.
Typhoon, Beaufighter, Spit etc, employed the normal gunsight, with the pilot allowing a few degrees left of centre, depending on angle of attack.
Contrary to popular belief, giro sights such as the MkIX, XIV etc, were not widely deployed, as they were only effective above a certain height, that is, approximately 12,000 feet plus, which was above the average altitude for light, or strike, bombers like the Mossie, and ground attack aircraft such a the Typhoon.

 

[davebender]

Revi gun sight had a second adjustable cross hairs bar; the pilot adjusted this according to an ofset angle determined by the expected release speed, altitude, dive angle etc. He aimed at the target, pulled up and released when the second recticle crossed the target

How did accuracy compare to purpose built bomb sights such as the Stuvi 5?

 

[Siegfried]

The Stuvi was far more accurate, a proper solution; the revi was just a broad guide. There is a article on Finnish use of the Stuvi 5B on Ju 88A4 by Jukka?. A good crew could get two bombs within 20ft close enough to knock out tanks in a 22 degree dive starting at 8000ft and pulling out at 5000ft.

The pilot of a German aircraft was expected to do mental calculations, know the dimensions of of wing spans and targets sizes to estimate range using the recticle. The recticle gave a stedomentric guage of range, but there was no adjusting it to get a readout.

AFAIKT Stuvi required the target to be lined up on release so it required a snub nose aircraft (eg Me 410), nose plexiglass eg Ju 88 or alternative a steep dive (ju 87)

This is why the TSA-2D was so important. It would have allowed long nosed aircraft such as Do 335, FW 190, Ta 152 and Me 262 (which did see some service) to accuratly deliver bombs from tree top up to 3000m and of course the Ar 234 as well. It also would have allowed bombing through cloud base. I suspect use of EGON (Oboe Like) blind bombing day or night was more important in european conditions at other times, for that a level bombsight is not required. Fighters would be able to do most of the Luftwaffes bombing work; bombers were getting unaffordbable and inopperable.

 

[parsifal]

My understanding is that mosquitos used a range of bomsights, starting with the Mk VII "wimperia" and moving up to the Mk IXs and Mk XIVs. Mossies also were fitted with US sights, Norden and Sperry of various marks.

Whilst the Mk VII was really only ever used for training in the Mosquito (because of speed limits I think) I was unaware that Pathfinders only used the Mk XIV.

British Bombsights were as a generalization simpler than the US types, and could not compute certain external effects. I am unaware of any serious disadvantages arising from this. There was an advantage arising from this simplicity....they were easier to use, and easier to train bombardiers how to use them....

 

[Edgar Brooks]

RAF fighters used their standard gunsights, plus a lot of skill and practice, since, once the bombs had gone, they reverted to being fighters. Tempests never carried rockets or bombs before the end of the war, and, although I stand to be corrected, I'm doubtful about the Beaufighter carrying bombs as well. The Spitfire V (early) IX would have used the GM2 MkII*, while the Typhoon started with the same sight, but rocket-firers went over to the IIL, which could be adjusted, to allow for rocket-drop, then returned to normal use. Low-back Spitfire XVIs were fitted with the gyro gunsight IID.

 

[gorizont]

IJN late-war dive-bombers used improved gun-bomb sights - Type 2 and Type 3 1"Gou" Gunsight Model 1 (the latter differed by its collimator opposite to optical tube of the previous and its improved calculation unit).
You can find their pictures at ŽË@"š@Æ@€@Ší for instance.

Their difference from earlier Type 1 gun|bomb sights (used in Val's) is that with those sights used a separate calculation unit (as far as remember it called "inclinometer"). The radio operator/gunner input data (drift, speed and angle of dive) into it and by linkage it turned a mirrow in the sight to shift a mark (reticle) image according the calculated corrections. But I don't know if it worked in shallow dive about 20-25 degree.

For horizontal bombing from the late 1942 they prefered to use collimator bombsights with vectoring calculation mechanism. It allow to obtain more accuracy (comparing for example with Norden) while bombing from low level and middle level flights (usually from 100 meters up to 1000 meters, not higher than 2 km).
Usually they were used on two-engine bombers but something of this kind was planned to be installed on Tenzans from 1944.

All the US fighter bombers used through the whole war just a conventional gunsight Mk8 - as a SB2C Beast. As far as I know they were in this area left behind by even Japanese.
Only at the end of war for the F4U-4 there was designed a bombing system for toss-bombing but I'm not sure it was really installed before Japanese capitulation.
But for US pilots such equipment played not so importent role as for Japaneses and Germans - USA had an opportunity to train their pilots and bombardiers more properly and had such an advantage as "bigger battalions" - more dropped bombs gave an icreased chance to hit the target.

For Soviet aviation - Il2 hase a standart collimator gun - bomb sight PBP-1B - which name usually decoded as "the sight which beats a pilot just once but hurt" - because at forced landings the pilots striked their heads against it not seldom and often - to death). So from 1942 those sights were often uninstalled and pilots aimed through mark on the cocpit front window and mark at aircraft cowling.
And there weren't any special sighting device for horizontal bombing.

I don't remember which sight was used for dive-bombing in Pe-2 but I'm sure that all the corrections (drift etc) were calculated by pilot just mentally (a drift figure were calculated - mentally too - by a navigator and transferred by interlink phone to a pilot).

 

[davebender]

Did any of the RAF standard fighter gunsights contain rudimentary bombing capability similiar to the German Revi gunsight?

Do we have historical accuracy data for the Fw-190F/Fw-190G and Typhoon when dropping bombs?

 

[gjs238]

It would be interesting to see a comparison of USN/USMC vs USAAC dive bombing equipment, procedures, and results.
I ASSume that USAAC A-24's and A-25's had the naval sights installed?

 

[mudpuppy]

This is an interesting discussion and I've enjoyed reading (learning) so far. I wish i had information other than a vague recollection of instructions, somewhere, for WWII fighetr pilots in a ground attack role. It may have been some of the pilots manuals posted here in the past.

I did find this one interesting site on the development of targeting computers (early analog computers) as bomb-sights. But it appears the earliest examples here would still have been for the larger birds:
Glenn's Computer Museum

Regards, Derek

 

[Siegfried]

Mechanical analog computation sounds mysterious and difficult but it was really:
1 Numbers are represented by shaft rotations.
2 Two sets of variables can be added or subtracted via a differential gearbox as on a car.
3 A variable can be multiplied by a constant via a step up or step down gearbox
4 Two variables can be multiplied/divided by converting to logarithems using cams (spiral if neccesarry), adding/subtracting via differntials and then converting back via anti-log cams.
5 Tracking servo motors were often used to lighten loads and facilitate interronection of shafts. In the case of early US Mk7 director several men simply read out the dials of intermediate calculations and then used 'follow the dial' to re-enter. For instance the initial calculation that converted angular to cartesian co-ordinates.

Trigonmetric and ballistic data can be encoded onto cams: usually 3 dimensional cams which can be rotated and sliden along.

These were cast to shape and then fine ground.

Integration could be performed via something called a "Faraday Disk Integrator"

Differentiation (to get a speed) was usually in the form of adjusting a small variable speed electric motor: the speed of the motor or postion of the adjusting dial then gave the speed or 'rate' of the object.

The technology used in the Norden had long been used in naval guns and FLAK artillery predictors albeit in bulkier form.

To get a firing solution and fuse setting time an officer would make an initial estimate, this would be fed into the predictor which then automatically made several further estimates by repeatedly clutching in the flight time of the shell.

 

[Siegfried]

British Bombsights were as a generalization simpler than the US types, and could not compute certain external effects. I am unaware of any serious disadvantages arising from this. There was an advantage arising from this simplicity....they were easier to use, and easier to train bombardiers how to use them....

The method of employ of the Norden was to adjust variable speed drives which then tracked a fixed object (or moving ship) on the ground. This then allowed calculation of the wind drift of the bomber (or shift of the target) and therefore and automatic calculation of the offset required, which was then automatically entered into the system. The Bombardier made adjustments to the tracking motor and the correction could be passed straight into the autopilot. The Norden required at least a 30 second straight run.

The German Lotfe 7 and British SABS II worked the same way.

However the M.XIV one had to enter the wind drift or target motion manually from either an estimate or meterological aircraft etc.

However it had other advantages, it required only a 10 second steady run up, allowed a lot of manouvering in the start of the runup. It also allowed shallow dive bombing which the Norden (nor Lotfe) could; of course the Luftwaffe had the specialised Stuvi 5B for realy dive bombing.

There were a few other Luftwaffe sights around, something called a BZA (bomb ziel automat) it was used on fairly shallow attacks eg Ar 234.

 

[gorizont]

USAAF results for usage of dive - bombers?
They abandoned usage of A-24 and A-25 and completely shifted to fighter-bombers as an addition to horizontal bombers.
There is about nothing to compare with USN practice and results in dive-bombing.

As far as I know USAAC A-24's and A-25's indeed had the naval sights installed. Moreover Navy Mk.8 reflectoe sights were used on P-47's and rary P-51's so there were no need to replace them on Sharks and late Banshe's by any army airforce sight.

 

[gorizont]

The method of employ of the Norden was to adjust variable speed drives which then tracked a fixed object (or moving ship) on the ground. This then allowed calculation of the wind drift of the bomber (or shift of the target) and therefore and automatic calculation of the offset required, which was then automatically entered into the system. The Bombardier made adjustments to the tracking motor and the correction could be passed straight into the autopilot. The Norden required at least a 30 second straight run.

The German Lotfe 7 and British SABS II worked the same way.

However the M.XIV one had to enter the wind drift or target motion manually from either an estimate or meterological aircraft etc.

During WWII in bombsights were used mainly three principals of calculations. I'm not sure that I use here correct name - it's a direct translation from Russian/ So the first is "base-measurement calculations" - at Japanese early war bombsights as used on Kates for example. The second is "vector - measurement calculation" used first time by GB at WWI. At WWII it used in their sights mainly by Japanese - their were more accurate while bombing at low level flight and took less time to complete aiming but was less accurate while bombing from high level flight.
The third is "synchronous measurement calculation" and used in Norden, Lofte ans SABS. Their main drawback was that the synchronious calculation mode worked at a level not less than 900-1000 meters.

of course the Luftwaffe had the specialised Stuvi 5B for realy dive bombing.

There were a few other Luftwaffe sights around, something called a BZA (bomb ziel automat) it was used on fairly shallow attacks eg Ar 234.

As far as I know BZA was a computing unit for Stuvi 5. It was used only multiengined bombers and automaticaly produced corrections after the data(speed, drift angle of dive etc) had been input into BZA. On a panel of Stuvi 5 was a switch with two positions - "BZA" and "Hand-" as far as I remember. At Ju-87's data was to input manually.

 

[gorizont]

It's interesting that GB and USA used on their single-engined torpedo-bombers more sophisticated torpedo sights (their called them "directors") than Japanese (Germans hadn't got single-engined torpedo-bombers at all in exception of experimental ones) but their bomber-sights for dive - bombing were much more simpler (just ordinary reflector sights) and based exceptionally on mental calculations of the pilots. Even on post-war Skyraiders.

 

[Siegfried]

Thanks gorizont. This is obviously a subject you have interest in. The term "tachimetric" sometimes spelled "tachymetric" is often used meaning 'speed measuring' with reference to some computing bombsights as well as FLAK predictors or directors.
There was a soviet/russian bombsight used of this kind as well, from 1942 or so I believe?

Primitive computing guns sights measured angular rate (from a rate gyro or generator) and added an offset in consideration of projectile flight time. More advanced systems converted to cartesian coordinates. I ammagine it was the same with bombsights.

 

[gorizont]

Thanks gorizont. This is obviously a subject you have interest in. The term "tachimetric" sometimes spelled "tachymetric" is often used meaning 'speed measuring' with reference to some computing bombsights as well as FLAK predictors or directors.
There was a soviet/russian bombsight used of this kind as well, from 1942 or so I believe?

Primitive computing guns sights measured angular rate (from a rate gyro or generator) and added an offset in consideration of projectile flight time. More advanced systems converted to cartesian coordinates. I ammagine it was the same with bombsights.

Not fully corrected to my point of view. As far as I know the first method of calculations what I meant ("base calculatiuons") was much more simpler. While aiming a bombardier measured by countewise clock the time of flight along a path named "base". In the sight there was a part which was an analog of that path (a segment). The calculations were based on ratio between this path and projected path to the target (which calculated with adjustments of the angle of line of sight to the target compared with the angle of the line of sight to the end of the path from the point of start of time estimation etc) so roughly it was based of proportional measurements of the line dimension (not the angular) and time.
The early war German bomb sights were of that design.

All the WWII lead-computing gun sights were of a tachimetric (angular measurements by gyroscops) design but not the all bomb-sights a fortiori fire control systems.
For example US navy GFCS Mk.37 is often mentioned as fully tachimetric, but it was a linear one and the only thing that created an affinity between it and tachimetric systems that Mk.37 had an input from stabilsing gyro which measured just yaw pitch and roll of the own ship not a parameters of a target.

About russian bomb-sights: up to the middle of the war most of the bombers used for level bombing bombsight OPB-1 ("optical sight for bombing mark 1") in many different modifications. The mods were of the same method of functioning but differed by a rate of automatization of input and calculations.
Прицел - Wiki
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It was much simpler than Norden. It is about similar to Japanese Navy Type 90.

There was a bit more sophisticated OPB-2 but had a limited usage ( File:
File: ). It was about of a similar design as japanese Type-1 (improved Type 90) as I guess.
There were night bomb sights NSPB -4 and -7/
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In 1941 our engineers designed PS-1 -for level bombing but it had a limited usage through the war.
File:
It was of the same method of calculations as Norden or Lofte or Sperry. But it had only limited usage. I don't exactly know why but guess that the reason was the difficulties in manufacturing such a complicated piece of equipment for the war years. Maybe it was of flawed design as in the middle of the war they were removed from Pe-8 and was changed for OPB-2 and NSPB-4.
I found notes that it was used only on Tu-2 and some Pe-8 and Er-2.

For dive-bombing during the war there was just PBP-1 in many modes slightly differed in disign and mainly (I suppose) by their reticles.
It was a simple reflector sight/
File:
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It was used on Pe-2, Tu-2, Il-2, and Yak and La fighters.

There was also a primitive PNB-2 for low-level bombing.
File:

 

[davebender]

Spring 1944. Savio River bridges in Italy.
P-47. No flak. 50% hit within 180 feet of target. 30 bombs required for 1 hit.
P-47. Medium flak. 50% within 300 feet. 84 bombs required for 1 hit.
P-47. Heavy flak. 50% within 420 feet. 164 bombs required for 1 hit.

Sending an entire P-47 Fighter-Bomber Group to score a single bomb hit on a bridge or other such target is crazy. Why didn't we provide them with a proper bomb sight so they could put the P-47s heavy bomb load (sometimes 2 x 1,000 lb) on target?