Norden bombsight

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Slasher
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Norden bombsight

#1 Post by Slasher » Mon Dec 02, 2019 6:22 am

This useful vid managed to clear up certain aspects I couldn’t understand about its principles of operation.





But what made it superior to say that of the RAF? Was it its automatic trail distance calculation or gyroscopics somehow? 🤔
http://www.youtube.com/watch?v=24m-V2f9-sY

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Re: Norden bombsight

#2 Post by ian16th » Mon Dec 02, 2019 8:39 am

Where's PN when you need him?
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Re: Norden bombsight

#3 Post by Pontius Navigator » Mon Dec 02, 2019 8:43 am

Slasher, I think it was both. Not used the RAF bomb sight but it was pretty Heath Robinson with bar and wires etc and I think the variables were all calculated and pre set.

The later RAF one was modelled on the Norden. We used the T(ype)4. Once I was at a school reunion in Cumberland and in the garden of the public. Was a T3 computer.

If course the Norden was no more accurate on operations than anything else. The big problem is the wind at height is what it is based on and the wind below is what affects the bomb. Get that wind wrong by 36 kts and and a time of bomb fall of 30seconds and you have a 600 yard error.

Best results, stick bombing flying into a steady air mass. Safest flying downwind balls out. Worst dropping in a jet stream cross wind.

In training, 4,000 feet, 180 kts, after a wind finding run, you could get less than 20 feet error. My results were somewhat greater 😀

Get back when I watch the film.

L

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Re: Norden bombsight

#4 Post by Pontius Navigator » Mon Dec 02, 2019 8:44 am

ian16th wrote:
Mon Dec 02, 2019 8:39 am
Where's PN when you need him?
I was typing.

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Re: Norden bombsight

#5 Post by ian16th » Mon Dec 02, 2019 9:03 am

Pontius Navigator wrote:
Mon Dec 02, 2019 8:44 am
ian16th wrote:
Mon Dec 02, 2019 8:39 am
Where's PN when you need him?
I was typing.
The right man for the job :-bd
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I improve with wine :YMPARTY:

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Re: Norden bombsight

#6 Post by Undried Plum » Mon Dec 02, 2019 10:23 am


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Re: Norden bombsight

#7 Post by izod tester » Mon Dec 02, 2019 10:49 am

After 1942, the RAF generally used the Mk XIV bombsight which was designed on the same vector principles as the Norden and used a gyro stabilised sight glass so the aircraft could manoeuvre whilst the bomb aimer could keep the target in sight. It did not have the ability to connect to the aircraft autopilot or to auto release like the Norden which the Americans considered important. 617 Sqn used a more complicated sight, the Stabilised Automatic Bomb Sight which was considered to be a precision sight. However, comparison between 617 Sqn and 9 Sqn (who used the Mk XIV) during practice for the Tirpitz raids showed little difference between the the two squadrons accuracy. A good article on RAF bomb sights in WW2 is http://www.lancaster-archive.com/bc_maiorbombsights.htm.

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Re: Norden bombsight

#8 Post by Fox3WheresMyBanana » Mon Dec 02, 2019 12:00 pm

Get that wind wrong by 36 kts and and a time of bomb fall of 30seconds and you have a 600 yard error.
Conversely, drop from 150 feet and you can use a nail blu-tacked to the coaming as a bombsight ;)))

At the end of TWU, the QWIs revealed that, if all the allowable errors* in all the elements happened to add up in one direction, you could have a perfect pickle picture and a 500' bomb. It was therefore always somewhat down to luck.

Low bomb drops and sheer luck are of course the explanation for my weapons scores.

*Including stuff like bomb fin straightness and release charge size

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Re: Norden bombsight

#9 Post by Pontius Navigator » Mon Dec 02, 2019 2:04 pm

Fox 35 was a PFF Sqn and at the end of the war their CMPI was 400 yards. I don't know whether they dropped there markers at anything lower than 20,000. That was pretty good with the kit they had.

A Bomber Command research branch paper, mid-60s, estimated that training scores could be degraded to 175%. A typical 400 yards bomb might be 700 yards. In training scores from an evasive bomb run might be 1,000 yards so a wartime 1,750 was not unexpected.

'Experienced' crews would cheat, flying at .82 m, around 40k, into wind, and roll out a few miles earlier. A standards ride at .86, 45k and to the SOP roll out one minute from release was all together more sporty.

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Re: Norden bombsight

#10 Post by Fox3WheresMyBanana » Mon Dec 02, 2019 3:40 pm

Thank goodness for nukes, eh? ;)))
For comparison, from low level laydown and dive, my average on TWU was 63 foot, with 93 foot as the worst. The Hawk bombsight was manual, in that one dialed in the weapon and wind, then had to manually hold the height off the altimeter (150ft) and speed off the ASI (400kts, both head down, only the bombsight line was in the HUD), and pickle manually when the impact point in the HUD was over the target. Daytime and not being shot at, of course, and the wind was pretty much dead on since one got it from the range tower.
The Mosquitos mainly did the low level raiding in WW2, and their bombing was very precise, the prison raids for example.
No substitute really for GICASI - Get In Close And Smash It!

One notes that the Argie pilots were often cited for their bravery in ultralow flying during the Falklands war, but in fact many of their bombs failed to arm because they flew too low, and it does of course take a lot more bravery to fly higher, 150ft or above, and in a straight line whilst being shot at, in order for the bombs to arm and have a good chance of hitting the target and exploding.

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Re: Norden bombsight

#11 Post by om15 » Tue Dec 03, 2019 4:53 pm

Slasher, I found this one slightly better,

Alcohol doesn't solve any problems, but then again neither does milk.

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Re: Norden bombsight

#12 Post by Slasher » Thu Dec 05, 2019 6:05 am

Thanks mate. That clears up some holes in the first vid.
http://www.youtube.com/watch?v=24m-V2f9-sY

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Re: Norden bombsight

#13 Post by ian16th » Thu Dec 05, 2019 9:00 am

One thing that this thread has highlighted, is that we don't have an Instrument Fitter amongst us.
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Re: Norden bombsight

#14 Post by Slasher » Thu Dec 05, 2019 9:31 am

A bit of a difficult thread I know, but I think I have finally got the sight worked out. What I didn’t know from om’s vid was that the Norden automatically released the bombs. I thought it was still up to the bombardier to do it ultimately. Was the sight always auto or the bombardier merely backed it up manually at the same time to ensure a release?

The only bomb deliveries I’ve ever done is low level flour bombing out of a DH82 (4 times) and once out of a C150.

I have another question moreso to the sight’s application for targets of large size and area, but that’s in conjunction with a formation enquiry as well which I’ll post tomorrow.
http://www.youtube.com/watch?v=24m-V2f9-sY

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Re: Norden bombsight

#15 Post by Pontius Navigator » Thu Dec 05, 2019 9:47 am

Slasher, still not got around to watching the vid yet, I will when I have finished all the little jobs.

Now in the Vulcan we had the T4 visual sight. The bomb aimer, aka plotter, could steer the aircraft but bomb release was not automatic as there was no feedback loop. I will know more after the vid. However on bomb release, the radar bombing computer was fully automatic. It would open the bomb doors and 10 seconds later the bomb. However, and this is relevant, there might have been light battle damage affecting the release circuits or a bomb bay Jack might have been damaged so it was deemed prudent to open the bomb doors early and when the computer sent the bomb release signal the Captain, copilot, nav radar, and later the nav plotter, would all press their manual release buttons. Belt, braces and boot laces.

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Re: Norden bombsight

#16 Post by Fox3WheresMyBanana » Thu Dec 05, 2019 12:32 pm

light battle damage affecting the release circuits or a bomb bay Jack might have been damaged
One of my favourite movie sequences (over two clips)
Stay on the bomb run, boys. I'm gonna get them bomb doors open if it harelips everybody on Bear Creek!


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Re: Norden bombsight

#17 Post by Pontius Navigator » Thu Dec 05, 2019 1:03 pm

Fox, exactly, apart from the fact we could not get into the bomb bay.

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Re: Norden bombsight

#18 Post by Fox3WheresMyBanana » Thu Dec 05, 2019 1:12 pm

Did the guys know enough about the systems to pull panels off and poke things?
I recall an ex-Gannet looker talking about thumping certain bits to get the hamsters moving again, and the wet crew of Nimrods would occasionally do similar stuff.

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Re: Norden bombsight

#19 Post by Pontius Navigator » Thu Dec 05, 2019 4:51 pm

Fox, Vulcan s? Yes.

The AEO carried a book almost twice the size of the planning document. Essentially a Vulcan workshop manual. When the Vulcan crew bailed out over Yorkshire there was a search for the AEOs nav bag at that volume was valuable.

We knew where all the appropriate fuses were located. The wiring of the NBS was amazing to assist fault an analysis. Failure of equipment lights pointed directly to specific fuses. The CU595 (radar control panel on left of the radar scope) the Indicator 301 (radar display) dial lights and the CU585 (NBC control) all pointed to different fuses. The Nav Panel (above the 585) had a multifunction switch that could display test information as well as TAS, G/S, Distance to run etc. We used to carry spare crystals for the H2S and could do box changes with the crew chief is away on a ranger.

In training,if we were in a 'classification' sortie with our 'constituted' crew were were committed to complete any bombing run declared in the auth sheets. This included any failure whatever including loss of radar picture. The logic was that in war you would go with what you had. In contrast, today if you cannot guarantee to hit the target there is no point in risking the aircraft to no effect.

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Re: Norden bombsight

#20 Post by Pontius Navigator » Thu Dec 05, 2019 4:56 pm

Our T series bombing computers were nothing like the Norden. The Burden is a true tachometric bomb sight. Placing the cross hairs on a spot on the ground before the initial point (IP) the bomb aimer could track the spot and the computer could calculate drift and ground speed. On the bombing run, putting the cross hairs on the target, only small corrections need be made.

Now the RAF bombsight s including the No XIV and the T4 were not like this. I think the reason the Norden was not adopted was the need to maintain a very steady track to the target and the need to identify the target early on.

Now, talking of the T4. In the V-bombers it could be used as a fixed sighting head or using the computer. The computer was fed with drift, ground speed, air speed, altitude, ballistics etc and would calculate the release point sight angle. As a fixed head the bomb aimer would use a large (about 9 inch) black whiz wheel to work out the data. This would be set manually on the T4 computer and would display the RP sight angle, but this was not continuously computed.

The bomb run line and release line were displayed from a collimated head on to a gyro stabilised glass. It would show as an illuminated sword. Fly the sword through the target, press the release button as the cross reached the target. The bomb aimer could steer the aircraft using a rotary bank control or by conning the pilot in the traditional way 'left left, steady, right '.

As the aircraft banked, say 10 degrees the sight glass would move 5 degrees. The weak link was the linkage between gyro and glass.

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