B-29 & Altitude

[GrauGeist]

In regards to the Tallboy and Grand Slam bombs, it was found in many cases that the bombs falling near the target was sufficient enough to cause damage to the target.

Other Lancaster precision raids - Augsburg and Le Cruesot with the associated attack on Montchanin led by Gibson.

The raid on Augsburg in April of 1942 was hardly precision, of the few Lancasters that got through and completed rheir bombing run, minimal damage was inflicted for the cost of the mission. Aside from several of the bombs not detonating, quite a few missed their mark.

In the Le Crusat raid of October 1942, the strike was successful against the factory's main building, but many bombs fell short, hitting residences.

 

[gjs238]

I think a couple of Lancaster Squadrons would disagree with you there.

617 & 9 Squadrons?

 

[Shortround6]

In the Le Crusat raid of October 1942, the strike was successful against the factory's main building, but many bombs fell short, hitting residences.

And.
"The main attack was made on the factory from a height of 4,000 feet; a small formation of six aircraft attacked the transformer and switching station from 500 feet."

From: Operation Robinson hits Le Creusot works - WWII Today

While done by heavy bombers it certainly wasn't done from medium or high altitudes.

 

[Shortround6]

We have two problems or questions here and they revolve around the definition of precision.

As in "is it precision bombing if one bomb in ten hits the intended target/aiming point vs one bomb in a hundred (or one in a thousand?)"
And "what is the size of the intended target/aiming point?" A lot easier to be precise when the target is around a 1/4 mile wide and over a 1/2 mile long.
Modern day Marshaling yard. WW II were smaller.

Vrs a bridge or particular building.

Add in what was considered a hit? Had to be inside the target area or close enough to do damage to the target? The latter adds 20-100yds around the target. Not counting broken windows.

 

[stona]

617 & 9 Squadrons?

No. 617 Squadron used the SABS bomb sight and accuracy improved greatly with an average radial error of 170 yards being recorded over the period of June to August 1944 and improved to 125 yards in the period of February 1945 to March 1945.
No. 9 Squadron still used the Mk XIV bomb sight and in the period of February to March 1945 achieved and average error of 195 yards.
They typically bombed from 10000-12000ft during this period, though very late in the war they bombed from even lower altitude.

Given those errors for RAF 'precision' bombing, which is by far the most accurate for any strategic bombing force, what amounts to precision depends very much on how you define it.

Cheers

Steve

 

[pbehn]

There is a scale of accuracy going from hitting individual targets like the Tirpitz or the Shellhus at one end to bombing the wrong city or even a neutral country on the other.

 

[stona]

I'm not sure Operation Carthage is a good example, Despite the heroics of the aircrew and the successful bombing of the Shellhus by seven (or eight) aircraft, several bombed the crash site of Kleboe and Hall's aircraft, unfortunately a school. The bombing was accurate, but in the wrong place. The killing of 86 children (and 16 adults) here was obviously not intended, but is an illustration of the difficulties of these special operations. They also often led to unsupportable losses in the attacking squadrons.
In any case such raids are in no way representative of the so called precision bombing by the USAAF strategic bomber forces, which, for the most part, was anything but precise. At least the RAF didn't even pretend to be so.
Cheers
Steve

 

[Zipper730]

I should hope so!

Tell me about it! According to the B-29 flight-manual, stall speed at full-load (140,000 pounds) is 145 mph, which is a little under 240 mph at 35,000 feet.

Between 12,000ft and 18,000ft I believe.

I thought they flew higher, since they removed the mid-upper gunner, and fitted the aircraft with the merlins that had the twin-stage superchargers.

Both propellers and wings have the same problems with air density. Propellers work by accelerating a mass of air to a higher speed and directing it rearward in relation to the aircraft. If the air at altitude"X" is 1/2 the mass/weight per cubic ft as sea level air a prop of a given diameter and pitch will only have 1/2 the thrust. Somewhat simplified but you get the idea.

It does seem that, considering the aircraft does often go faster as it goes higher, the propeller produces more thrust than the wings do drag.

Ceilings for formation flying (and small formations at that) were several thousand feet below service ceilings and combat ceilings were even lower.

So the planes on the inside of the turn don't stall out

 

[wuzak]

I thought they flew higher, since they removed the mid-upper gunner, and fitted the aircraft with the merlins that had the twin-stage superchargers.

I'd have to check when I got home, but they only removed the upper turret for the Grand Slam. The Tallboy was within the Lancaster's standard lift capabilities.

Only a few Lancasters were fitted with 2 stage Merlins. These were the B.VI, of which only 9 were built, according to Wiki. Mostly used for the PFF.

 

[Zipper730]

I'd have to check when I got home, but they only removed the upper turret for the Grand Slam. The Tallboy was within the Lancaster's standard lift capabilities.

Oh, okay: I thought for the Tirpitz mission they took them off

Only a few Lancasters were fitted with 2 stage Merlins. These were the B.VI, of which only 9 were built, according to Wiki. Mostly used for the PFF.

Why were they needed for the Pathfinders? They usually flew low...

 

[wuzak]

Why were they needed for the Pathfinders? They usually flew low...

Pathfinders also used Oboe, which had longer range if you flew higher.

 

[wuzak]

Oh, okay: I thought for the Tirpitz mission they took them off

They may have done for the Tirpitz mission, as it was a long range mission.

 

[fahrens]

Just finished an long and interesting discussion with a B-29 Flight Engineer who served from Guam during WWII. The major reason for the low altitude was engine cooling issues that didn't get resolved for the majority of the aircraft until the last months of the war. He had almost daily briefings from a team of Boeing - PW engineers on the "proper" settings for the cooling vents during takeoff, cruse, and attack. The engine nacelle, framing, mountings, and ducting were often conflicting the air flow. Since the magnesium parts were critically cooled, staying low keep the denser air cooling the engine. The climb to bombing altitude was a long slow climb to get the last bit of dense air before the combat rating. He had the "fun" experience of bailing out of three birds, and crashing two others due to engine fires, and isn't bashful about expressing his views on the engines. He was called back for the Korean War, also served in B-29s and was happy to see the engine issues were things of the past.

 

[GrauGeist]

...He had almost daily briefings from a team of Boeing - PW engineers on the "proper" settings for the cooling vents during takeoff, cruse, and attack...

Did he perhaps mean "Wright engineers"?
Because the B-29's engines were Wright R-3350 radials

 

[Zipper730]

Pathfinders also used Oboe, which had longer range if you flew higher.

You mean like line-of-sight?

They may have done for the Tirpitz mission, as it was a long range mission.

Makes enough sense

 

[wuzak]

You mean like line-of-sight?

Yes.

There were experiments with Oboe repeater aircraft (Wellingtons IIRC), but they weren't used operationally.

 

[Zipper730]

Yes.

But didn't the Oboe aircraft drop to low altitudes in some cases towards the target area to set-up flare marking?

That sounds like it would put you under the line of sight, though the higher altitudes would allow a greater cruise-speed and range which could be useful.

There were experiments with Oboe repeater aircraft (Wellingtons IIRC), but they weren't used operationally.

What's an Oboe repeater? Do you mean like a relay?

 

[wuzak]

But didn't the Oboe aircraft drop to low altitudes in some cases towards the target area to set-up flare marking?

I believe low level marking was visual.

Often it would be done after the initial marking using Oboe.

What's an Oboe repeater? Do you mean like a relay?

Yes, exactly that.

An aircraft would act as a relay for the signal. Trials were conducted with a Wellington as the relay aircraft, but the system was not used operationally.

 

[Zipper730]

I believe low level marking was visual.

Often it would be done after the initial marking using Oboe.

Okay, I got it.

Yes, exactly that.

An aircraft would act as a relay for the signal. Trials were conducted with a Wellington as the relay aircraft, but the system was not used operationally.

Didn't LORAN provide the long-range need?

 

[wuzak]

Okay, I got it.

Didn't LORAN provide the long-range need?

I don't think so.

The British also used Gee and Gee-H. LORAN was a development of Gee.

LORAN, short for long range navigation, was a hyperbolicradio navigation system developed in the United States during World War II. It was similar to the UK's Gee system but operated at lower frequencies in order to provide improved range up to 1,500 miles (2,400 km) with accuracy of tens of miles. It was first used for ship convoys crossing the Atlantic Ocean, and then by long-range patrol aircraft, but found its main use on the ships and aircraft operating in the Pacific theatre.

LORAN - Wikipedia, the free encyclopedia

Gee was used as a bombing aid, but later was mainly used for navigation.
Gee (navigation) - Wikipedia, the free encyclopedia

Gee-H was used as a bombing aid.
Gee-H (navigation) - Wikipedia, the free encyclopedia

They also used H2S (radar) - Wikipedia, the free encyclopedia which didn't require the use of ground stations, so its range wasn't restricted by the equipment.