Re: Bomber Command failure at Urft Dam.
 

H2S in 1944 was not what we would call a precision targeting device today. It allowed Bomber Command to find larger cities, but nothing as small as a single dam. Target markers dropped using H2S often had errors of up to a mile, but at the time that was a big improvement over the errors of tens of miles using purely visual methods early in the war.

It was more a navigation aid than a bomb sight. Postwar refinements allowed developed versions of H2S to be used as a bomb sight, as in the runway bombing in the Falklands.

All the pictures of 617 Lancasters I can find on the web do not show an H2S fairing.

Re: Bomber Command failure at Urft Dam.
 

Thanks Kutscha, Nick and Bill for providing evidence that neither H2S nor GEE were accurate enough for 617 Squadron.

That leaves Oboe and GEE-H, both of which gave an error radius of 110 metres at 400 kms (120 yards at 250 miles), said to be as good as optical gunsights.
Is there any evidence, I wonder, that 617 Squadron used either Oboe or Gee-H when dropping Tallboys on targets obscured by cloud?

By the way, and not off-topic, 2TAF was at that time experimenting with using one of their four AMES Type 25 convoys for controlling blind bombing by Bombphoons.

In July 1944 the RAF had formed and begun training the first MRCP (Mobile Radar Control Post), which was a Modified SCR.584. It was shipped to Erp in Holland in October and used for the first time to direct (not control) Typhoons on November 11 in the attack on Venraij when the MRCP put 6 aircraft of 247 Squadron on the target which however they missed. But on the same day 5 aircraft of 137 Squadron were directed to a battery 5 miles SE of Goch and claimed the destruction of 2 guns. The month's trial with 83 Group had shown that the MRCP had some small benefit in directing pilots in conditions of poor visibility, but was limited by short range. The MRCP was then transferred to 84 Group for experiments in blind bombing.
Its mean error of 350 yards indicated that its best application with Tactical Air Force Fighter Bomber groups was the blind level bombing of targets such as villages containing concentrations of enemy troops in forward areas behind the enemy lines, under conditions when visual attack by fighter-bombers was impossible. Although bombs dropped with this accuracy were of some effect, it in no way replaced the value of bombing by fighter-bombers under good visual conditions, when an accuracy possibly as good as 20 yards was obtained. Since the bombs dropped by fighter-bombers were of relatively small size, the value of their bombing depended to a great extent on a high degree of accuracy which was possible only when the bombing was visual, and was rarely achieved even then.
Richard Hough of 197 Squadron in 'One Boy's War', described being controlled by an MRCP while bombing with his Bombphoon;
"Some scientist, who became very unpopular with us, had invented a form of blind bombing, straight and level, by radar. We felt very foolish flying in loose formation above 10/10th cloud and in blazing sun all pressing the bomb tit together when a distant voice over the R/T ordered us to do so. We were told the bombing was highly accurate. 'If we're going to have a wizard prang, I like to see it,' someone complained."
The effective range of the Type 25 Convoy was increased with the introduction of the American Microwave Early Warning Set (AMES) Type 70 Radar to 83 Group at Erp in Holland in early February 1945. A second Type 70 was built for 84 Group but was not operational at the end of hostilities.

Re: Bomber Command failure at Urft Dam.
 

For those interested, here are contemporary photos of the Urft and Schwammanauel dams together with a map of their location.
Tony

Re: Bomber Command failure at Urft Dam.
 

Hi Tony,

You have not included one of the more obvious possibilities - simply, that the winter weather, which severely restricted bombing by the Allies in December 1944 and January 1945, is a likely explanation for the lack of bombs dropped on the dams. No air force is in the habit of expending a large effort to send a force of bombers to the target only not to bomb unless there are very good reasons.

I would suggest that you find and read the relevant RAF BC Group reports and RAF BC Group and Squadron Operational Record Books in AIR 14 at TNA in order to establish the reasons you seek (8 Group would be a good place to start). The other reasons you have stated are conjecture (unless you find memos from Harris or other BC Commanders directly supporting your hypothesis). Another Bomber Command file worthy of checking is AIR 14/1436, which specifically concerns operations against the Roer and Urft River Dams in the period between October-December 1944.

As to a pinpoint attack by 617 and 9 Squadrons (which were part of Cochrane's 5 Group) with Tallboys; besides any target and resource allocation issues decided at a higher level, reasonably good visibility and other factors such as wind speeds within accepted parameters would be needed in the target area at normal operational height in order to visually bomb the dams using the SABS bomb sight, which, I might add, was a complicated piece of machinery that required a very well-trained and skilled crew to operate with any accuracy, and a long run in to the target before release. Reading the 617 ORB entries in the link provided earlier in this thread bares these points out, and it is obvious from the ORBs that the crews tried repeatedly in well less than ideal conditions to conduct successful bomb runs.

The Tallboy Lancasters could not be equipped with H2S and, anyway, I doubt that any existing blind bombing aid in use at that time could guarrantee the level of accuracy required for the Tallboys to be effective against the dams (i.e. to justify the expenditure of such a valuable commodity as a Tallboy - this is conjucture, further checking of RAF BC files would be needed to exactly establish any Tallboy targeting criteria). It would seem highly unlikely that conventional bombs would have done anything more than pockmark the dams.

Cheers

RodM

Re: Bomber Command failure at Urft Dam.
 

Hi Rod,

You are quite right. I did not originally include the possibility that weather could have explained the RAF failure at the Urft Dam, for the reasons given; the existence of H2S, Oboe, GEE-H and the blind bombing experiments undertaken by 2TAF (admittedly two months later in February/March 1945). I assumed that by December 1944, BC could operate in 10/10th cloud at least within Oboe range. I now know differently.

But it remains difficult to believe that BC should have accepted a bombsight like SABS requiring a long visual run. The adoption of the Norden bombsight by the USAAF could be explained by their clear US skies; they were certainly shocked by European conditions when they eventually arrived. The gales over Lincolnshire referred to in the 617 ORB were another matter since they made take-off by fully laden bombers hazardous.
I t is now known that weather stymied 617 and 9 Squadrons' attacks on the Roer dams. That is a fact, and my thanks to those who provided the evidence.
I will also look at the references in TNA that you have kindly provided.

I came at this matter through the pages of Courtney Hodge's diary, in which he recorded doubts that BC had bombed based on the lack of results. Hodges was GOC 1 US Army, and since air-ground cooperation was organised at army level, he would have been fully briefed by BC. During the time of the bombing, his troops were a maximum 3 miles from the dams.

The question of sabotage by Harris cannot be dismissed as unobvious. It was strongly suspected at the time by Portal. On November 1, 1944 Harris wrote to Portal; “In the past eighteen months, BC has virtually destroyed forty-five of the sixty leading German cities....Are we going to abandon this vast task?” Portal replied; “I have, I must confess, wondered at times whether the magnetism of the remaining German cities has not in the past tended as much to deflect our bombers from their primary objects (transportation, oil, dams) as the tactical or weather difficulties (in attacking oil refineries) which you describe”. You will recall that Harris was told he could fall back onto city bombing whenever weather made the primary targets impracticable. So Harris had a vested interest in calling the weather bad. Harris never hesitated in ordering city raids. “I was against putting everything into oil. It was using a sledgehammer to crack a nut”. He threatened to resign, and Portal gave in, at least to the extent of listing as targets, Berlin, Dresden, and Chemnitz, which sealed Dresden's fate.
So you had Harris advocating city destruction, Portal advocating oil attacks, and Sinclair wanting troop support such as the Roer dam destruction. So my question whether internal Air Ministry feuding had anything to do with the failure at the Urft Dam was, I hope you will agree, not far-fetched, even if it turned out to be a non-starter.

Tony

Re: Bomber Command failure at Urft Dam.
 

post #3

Re: Bomber Command failure at Urft Dam.
 

Yes, Hodges mentioned bad weather.
BC reported bombing in spite of bad weather but without results.
H2S, Oboe, GEE-H and radar-control are weather independent.
At that point in the thread it had not been established that BC's technique for dam destruction required a long clear run-up. That came up later.
And even now the thread has not established that even in clear weather, and with a direct hit, BC could destroy a high-walled or concrete-filled earth dam since they had abandoned the proven (for high-walled dams) bouncing bomb and focused on Tallboys.
I suspect they needed Grand Slam to breach the Schwammenauel.

Tony

Re: Bomber Command failure at Urft Dam.
 

"But it remains difficult to believe that BC should have accepted a bombsight like SABS requiring a long visual run. "

You could perhaps explain the operation of any alternative? The design and creation of any bombsight is a specialised task, the SABS was the best available at the time. Precision targeting is a difficult task, there were no lasers or GPS in 1944. One of the prime requirements is that the aircraft be absolutely steady and dead on the right course, and this is not an instantaneous achievement.

Re: Bomber Command failure at Urft Dam.
 

Graham.
Let's define the required accuracy.

"Tallboy and Grand Slam required to be dropped within 150 yards of the target from 20,000 ft.
617 Sqn with SABS achieved 170 yards over the period June-August 1944, improving to 125 yards in February-March 1945."
source: http://www.geocities.com/skidaddy20000/Air-Bomber.html

"Oboe was extremely accurate, with an error radius of about 110 meters (120 yards) at a range of 400 kilometers (250 miles), about as good as optical bombsights."
source: http://en.wikipedia.org/wiki/Oboe_%28navigation%29

I understand that Oboe was not a bombsight. The effect of wind and speed and length of drop would have to be computed separately, but was well within the technical capabilities of the time (SABS and Norden).

Furthermore by December 1944 there would have been time to set up Oboe cat and mouse sites in Holland and France to extend Oboe coverage well beyond Berlin at 20,000 ft.
It is not clear whether in December 1944, 617 Sqn had achieved the required accuracy.

Tony

Re: Bomber Command failure at Urft Dam.
 

It should be noted that all these bomb sights require accurate knowledge of the winds at all levels through which the bomb is to drop. Our met people simply did not have the means, I know special flights were made to determine target area winds, but for the accuracy required and the drop height, too much data was necessary.
Also visibility of the target, NW Europe winter weather does not help much.