VLR B-24 Liberators and the Mid-Atlantic Gap (2 Viewers)

[Geoffrey Sinclair]

Bristol type 142M Blenheim I, to specification 28/35
Bristol type 149 Bolingbroke, started off as a response to specification G.24/35, no aircraft ordered, specification became 10/36 to which the type 152 Beaufort and the Botha were ordered. While specification 11/36 was issued for the interim GR version, the type 149 Bolingbroke, it was to have a 4 person crew, more fuel, more powerful engines, lengthened nose for bomb-aimer/navigator, outer wings made watertight and also the rear fuselage aft of the gun turret, dinghy stowage the port engine nacelle, provision for 8 reconnaissance flares and 2 forced landing flares, space for sea markers and flame floats, station with window for a wireless operator immediately forward of the gun turret. This is what the RAAF and RCAF were interested in, the RAF ordered 134 for itself. Bristol tested the lengthened nose on Blenheim I K7072, the extra fuel in Blenheim I L1222. RAF Bolingbroke order cancelled in December 1937 replaced by Blenheims with as many as possible built to the Blenheim IV standard.

Bristol construction numbers note reuse of Bolingbroke RAF serials
start / end / No / type / Note
8168 / 8301 / 134 / Bolingbroke I / RAF order cancelled L1531 to L1546, L4817 to L4934
8302 / 8379 / 78 / Beaufort I / RAF order 1 L4441 to L4518
8380 / 8849 / 470 / Blenheim I / RAF order 2 but 8814 and 5 Yugoslavia, L1097 to L1546, L4817 to L4834

After the cancellation Bristol used the more powerful engines, extra fuel and lengthened nose in the Type 149 Blenheim IV. The Canadians wanted a home built GR version so they fitted wanted GR features into the Blenheim IV and adapted production to the methods available in Canada in 1938/39 keeping the name Bolingbroke, the most visible differences to the Blenheim IV are the dingy stowage and fuselage window. The first Blenheim IV from Bristol was delivered in January 1939, the first Blenheim IV from Rootes in September 1939, the first Canadian Bolingbroke I in November 1939, the first Blenheim IV from Avro in March 1940. The Blenheim I, Bolingbroke (UK idea), Blenheim IV, Canadian built Bolingbroke I, III, IV are all very related but definitely distinct aircraft. As Blenheim IV appeared Blenheim I released were sent overseas, in early 1940 the start was made converting Battle squadrons to Blenheim.

In chronological order, patrol designs ordered for Coastal Command that made it to some production, 1935 to 1940
Supermarine Scapa, biplane, out of service end 1938
Short Singapore, biplane, some in Singapore late 1941
Saunders-Roe London, biplane, in service until mid 1940.
Supermarine Stranraer, biplane, stayed in service until April 1941
Short Sunderland I, 74 built in 35 months from May 1938, with extra lines production finally hit double figures in April 1942.
Saunders-Roe Lerwick, into service end 1939, significant problems, grounded twice
Bristol Beaufort, problems in 1940 with the engines.
Blackburn Botha, failure
None of the pre war flying boats were built in numbers. As of early 1940 of the 4 new types of longer range aircraft the Lerwick has too many problems, the Sunderland is rare, the Botha a failure and the Beaufort has engine problems.

Historically in September 1939 Coastal Command had 1 Hudson and 9 (including 4 reserve) Anson squadrons
48, Anson from March 1936 to December 1941 (Beaufort June to November 1940), Hudson from September 1941
206 Anson from June 1936 to June 1940, Hudson from March 1940
217 Anson from March 1937 to December 1940, Beaufort from September 1940
220 Anson from August 1936 to December 1939, Hudson from September 1939
269 Anson from December 1936 to June 1940, Hudson from April 1940
500 Anson from March 1939 to April 1941, replaced by Blenheim IV that month
502 Anson from January 1939 to October 1940, Botha August to November 1940, Whitley from September 1940
608 Anson from March 1939 to May 1941, Botha June to November 1940, Blenheim from February 1941
612 Anson June 1939 to January 1941, Whitley from November 1940.

From Bomber Command,
58 Squadron Whitley 6 October 1939, back 14 February 1940
102 Squadron Whitley 1 September 1940, back 10 October
114 Squadron Blenheim 2 March 1941, back 19 July
107 Squadron Blenheim 3 March 1941, back on 11 May
82 Squadron Blenheim 18 April 1941, back on 11 May
21 Squadron Blenheim 27 May 1941, back 14 June, sent again 7 to 21 September
455 Squadron Hampden 20 April 1942
144 Squadron Hampden 21 April 1942
311 Squadron Wellington 28 April 1942
51, 58, 77 Squadrons Whitley 6 May 1942 (77 back 5 October, 51 back 27 October)
304 Squadron Wellington 10 May 1942
405 Squadron Wellington 25 October 1942, back 1 March 1943

From Fighter Command
254 Squadron Blenheim If,IVf 28 January 1940
248 Squadron Blenheim If 24 February 1940
235 Squadron Blenheim If,IVf 27 February 1940
236 Squadron Blenheim If 29 February 1940

Also, to end 1940, 272 squadron Blenheim IVf on 18 November, 252 Squadron Blenheim If,IVf/Beaufighter on 21 November formed in Coastal Command.

The longer the flight the more internal room becomes important for the crew to move about, take a break, etc. the Sunderland was fitted with a galley. Also the recovery time from a 12 hour flight is more than just twice the time for a 6 hour flight. RAF inventory at the start of the war was something like 1,089 Blenheim, 1,014 Battle and 760 Anson. RAF Aircraft performance report, all ranges less 50 minutes allowances,

Anson GR at 8,580 pounds, 500 pounds of bombs, 540 miles/3.5 hours at 154 mph at 5,000 feet (120 gallons fuel)
Anson GR at 9,030 pounds, 500 pounds of bombs, 1,040 miles/8.5 hours at 125 mph at 5,000 feet (180 gallons fuel)
Battle I at 11,711 pounds, 1,500 pounds of bombs, 876 miles/5.95 hours at 148 mph at 15,000 feet (212 gallons fuel)
Blenheim I at 13,100 pounds, 1,000 pounds of bombs, 920 miles/5.57 hours at 165 mph at 15,000 feet (278 gallons fuel)
Blenheim IV at 15,682 pounds, 1,000 pounds of bombs, 1,457 miles/8.55 hours at 170 mph at 15,000 feet (465 gallons fuel)
Hudson I at 19,500 pounds, 900 pounds of bombs, 1,355 miles/8.75 hours
Hudson II at 20,000 pounds, 950 pounds of bombs, 1,380 miles/8.9 hours
Hudson III, IV at 20,000 pounds, 40 pounds of bombs, 1,465 miles/9.45 hours
All Hudson at 155 mph at 15,000 feet with 536 gallons fuel
Botha at 18,450 pounds, 800 pounds of bombs, 1,400 miles/8.24 hours at 170 mph at 15,000 feet (439 gallons fuel)
Beaufort at 18,500 pounds, no bombs, 1,600 miles/9.15 hours at 175 mph at 15,000 feet (510 gallons fuel)

Flying boats at 5,000 feet
London II at 104 mph, 500 pounds of bombs, 1,500 miles/14.4 hours, 862 gallons
Lerwick at 143 mph, 1,250 pounds of bombs, 2,600 miles/18.2 hours, 1,440 gallons
Singapore III at 104 mph, no bombs, 1,235 miles/11.9 hours, 1,254 gallons
Sunderland I at 141 mph, 2,000 pounds bombs, 2,530 miles/17.9 hours, 2,034 gallons
Scapa at 106 mph, no bombs, 1,475 miles/13.9 hours, 616 gallons
Stranraer at 103 mph, 500 pounds bombs, 1,615 miles/15.7 hours, 850 gallons.

Whitley V at 155 mph at 15,000 feet 3,750 pounds of bombs, 1,700 miles/10.95 hours
Wellington Ic at 165 mph at 10,000 feet, 500 pounds of bombs, 2,550 miles/15.5 hours (2,800 pounds of bombs 1,805 miles/10.95 hours)
Stirling I at 175 mph at 10,000 feet, 3,500 pounds of bombs, 2,500 miles/14.3 hours
Halifax I at 190 mph at 15,000 feet, 3,000 pounds of bombs, 2,780 miles/14.65 hours.

Given the many references to Ansons being short ranged it would appear the 180 gallon option was not in regular use. Cancelling Sunderlands and replacing them with Stirlings would be a win, the Anson squadrons held 200 aircraft at the start of the war, there were 497 Blenheim IV built in 1939 and the RAF liked 100% reserves, 138 Hudsons delivered to the RAF March to October 1939, another 6 in December, another 212 during 1940. The RAF had 5 bomber groups in 1939, numbers 1 and 2 expected to go to France as soon as possible, either as army support or closer to strategic targets. The Army would be unimpressed if one or both went to Coastal Command instead.

On 1 January 1942 Coastal Command is reported to have 562 aircraft, rising to 617 a year later. If all its units were at full strength Bomber Command held 832 aircraft on 1 January 1942 (581 serviceable), strength was 746 a year later (547 serviceable)

As usual the numbers in this report differ from others. Operational hours by command, aircraft type and month,

Other is Spitfire, Hurricane and PR types

CC

Beaufighter

Beaufort

Blenheim

Catalina

Fortress

Hampden

Hudson

Liberator

Northrop

Sunderland

Wellington

Whitley

Other

Total

Dec-41​

181​

522​

749​

1,204​

0​

0​

2,843​

174​

75​

539​

106​

891​

0​

7,284​

Jan-42​

149​

250​

407​

740​

0​

0​

2,588​

170​

122​

269​

0​

548​

0​

5,243​

Feb-42​

340​

696​

661​

925​

0​

0​

3,510​

205​

102​

595​

0​

591​

0​

7,625​

Mar-42​

521​

347​

617​

746​

0​

0​

4,341​

66​

282​

850​

0​

1,072​

650​

9,492​

Apr-42​

790​

237​

675​

573​

0​

0​

5,632​

378​

326​

1,323​

0​

1,380​

869​

12,183​

May-42​

698​

619​

435​

790​

137​

107​

6,484​

516​

429​

1,036​

354​

1,465​

886​

13,956​

Jun-42​

718​

65​

391​

346​

68​

40​

5,674​

373​

147​

1,036​

619​

3,224​

669​

13,370​

Jul-42​

718​

3​

265​

475​

186​

491​

5,825​

576​

358​

1,800​

1,719​

3,433​

882​

16,731​

Aug-42​

585​

0​

297​

701​

500​

226​

3,925​

781​

274​

1,695​

2,036​

1,991​

1,464​

14,475​

Sep-42​

853​

0​

514​

1,155​

599​

298​

3,902​

388​

186​

1,623​

2,181​

2,667​

558​

14,924​

Oct-42​

955​

0​

0​

1,026​

1,093​

259​

2,424​

527​

199​

1,259​

1,990​

2,583​

666​

12,981​

Nov-42​

1,272​

0​

0​

2,515​

1,357​

490​

2,682​

901​

81​

2,366​

2,411​

2,693​

672​

17,440​

Dec-42​

913​

0​

0​

1,922​

930​

511​

2,287​

570​

22​

1,972​

2,626​

1,329​

585​

13,667​

Total

8,512​

2,217​

4,262​

11,914​

4,870​

2,422​

49,274​

5,451​

2,528​

15,824​

13,936​

22,976​

7,901​

152,087​

Other is Mitchell, Ventura, Lysander, Mosquito

BC	Halifax	Lancaster	Manchester	Stirling	Hampden	Whitley	Wellington	Blenheim	Boston	Other	Total
Jan-42​	254​	0​	621​	303​	2,952​	1,592​	5,096​	220​	0​	0​	11,038​
Feb-42​	283​	0​	792​	231​	2,393​	1,078​	3,304​	119​	0​	0​	8,200​
Mar-42​	518​	92​	844​	797​	2,427​	1,181​	5,532​	146​	83​	0​	11,620​
Apr-42​	894​	452​	1,015​	1,973​	3,284​	1,505​	11,626​	218​	475​	0​	21,442​
May-42​	1,596​	1,178​	572​	1,659​	1,009​	195​	6,131​	243​	215​	12​	12,810​
Jun-42​	2,854​	2,065​	328​	2,046​	1,302​	333​	8,832​	576​	511​	42​	18,889​
Jul-42​	2,145​	2,809​	0​	1,882​	1,242​	229​	7,491​	435​	411​	124​	16,768​
Aug-42​	1,370​	4,162​	0​	2,095​	800​	273​	5,710​	174​	205​	93​	14,882​
Sep-42​	2,599​	5,049​	0​	2,162​	304​	233​	5,543​	0​	184​	156​	16,230​
Oct-42​	2,709​	5,158​	0​	2,142​	0​	319​	4,841​	0​	181​	327​	15,677​
Nov-42​	3,726​	5,498​	0​	2,224​	0​	794​	3,779​	0​	235​	113​	16,369​
Dec-42​	3,907​	4,633​	0​	1,439​	0​	1,448​	2,065​	0​	149​	347​	13,988​
Total	22,855​	31,096​	4,172​	18,953​	15,713​	9,180​	69,950​	2,131​	2,649​	1,214​	177,913​

The hours of the Coastal Command main anti submarine types, Catalina, Fortress, Hudson, Liberator, Northrop, Sunderland, Wellington, Whitley come to 126,773. Bomber Command hours less Hampden, Blenheim, Boston and other come to 156,206. The data shows Bomber Command was not in a situation where it could lose "a few" units that would then give Coastal Command "a big" boost, Bomber Command was going through about as much spare parts, fuel and crew time as Coastal Command, an X% increase in Coastal Command activity would be around an X% drop in Bomber Command unless there is some reason Coastal Command could obtain more hours per airframe. At the same time Bomber Command was a strong user of the better quality aircraft. As specialist equipment and training increased it was harder to transfer across commands, a 1940 Bomber Command and Coastal Command Wellington and crew would be very similar, not so in 1943.

The pattern of the early U-boat war was as escorts became too strong U-boats moved on and did not return, therefore Coastal Command needs to keep increasing the average range of its aircraft, forcing the U-boats further out. Barrier patrols without radar generally means, like range, the payoff is reducing the U-boat efficiency instead of sinkings. Daylight non radar equipped sorties means their effectiveness depends on the weather and season. The fundamental way to cut shipping losses 1939 to 1942 is more convoys, escorted further out from the European coast, that in turn comes down to number and range of surface and air escorts, sort of chicken and egg, the key to escort effectiveness at spotting U-boats is radar given the average weather and amount of light.

Barrier patrols, decide length of day, visibility, the probability you want a surfaced U-boat will be spotted and know U-boat performance, calculate the numbers required, increase numbers as radar enables night missions. Convoy cover depends on number of convoys and how far out they are covered, again increasing as radar arrives.

End 1940 Coastal Command had 5 Anson, 1 Wellington and 1 Whitley squadrons, Bomber Command had 9 Blenheim, 6 Whitley and 14 plus 2 half Wellington Squadrons, at least move the equipment so Coastal Command no longer uses Ansons by the end of the year, easy to say as the invasion threat will mandate a strong bombing force until October/November. After which upgrades to Coastal Command strength and equipment become easier. End 1941 the 12 squadrons of Hudsons have become the shorter range anti submarine type, Bomber Command has 3 operational squadrons each of Halifax, Stirling, Manchester, 21 Wellington and 5 Whitley, equipment and maybe unit changes can be made but shipping losses wise Coastal Command was not in the main action, probably best to send all 12 Hudson squadrons to the US immediately and decide how many need to be replaced immediately or over time and whether the Hudsons should be replaced as the units return after the US builds up its air patrols.

To fight the first U-boat happy time changes to Coastal Command need to happen probably by the end of March 1940 at the latest, given the 1940 crisis, the drop off in shipping losses in the second half of 1941 removes some of the pressure, the 1942 action is mainly elsewhere and end 1942/early 1943 there is not a lot you can change to take effect before the U-boat defeat in the North Atlantic. As people keep pointing out there is not a simple answer.

 

[WATU]

Blackett used data from the German bombing of Hull to create a model for the effect Bomber Command might be having with its area bombing policy. Applying this to the attacks in Germany in December 1941 he estimated around 400 deaths. They would be mostly random civilians. For that effort Bomber Command lost almost as many trained aircrew plus, of course the aircraft.

Greater Coastal Command effort around threatened convoys would save ships. That cost aircrew and aircraft, as much from weather and accidents as anything else. However it also saved sailors, ships and cargoes.

On balance I think that that the ratio of aircraft reinforcements should have shifted early in 1942 with an increase in the flow to Coastal Command and a decrease in the aircraft to Bomber Command.

 

[nuuumannn]

Everyone concentrates on the Ultra and breaking German codes at Bletchley Park to determine where the U-boats wrre. But have you ever stopped to think about where Bletchley got the messages to decode in the first place?

That work was carried out by the 'Y' Service. A network of radio intercept stations across the UK run by the RN, Army, RAF and the GPO. Many of these sites also had a direction finding function. So even If codes couldn't be broken enough information could be gleaned from direction finding alone to locate, with a fair degree of accuracy but not down to an exact to the mile position, where a U-boat was located. That allowed warnings to be given to escort groups or evasive routing of convoys. That could be done immediately a 'fix' was obtained.

Y service - Wikipedia

en.m.wikipedia.org

As for breaking the KM codes, Bletchley had success from mid-1940. However, it was the introduction of a new Enigma machine with a fourth rotor in combination with a new code that rendered them blind for most of 1942.

But it wasn't just a question of breaking codes and being able to read messages. It was the speed with which it could be done to make the intelligence derived there from useful. Reading within 24 hours was only achieved from about autumn 1943.

Enigma - Allied breaking of Naval Enigma - Technical pages - German U-boats of WWII - Kriegsmarine - uboat.net

The U-boat War in World War Two (Kriegsmarine, 1939-1945) and World War One (Kaiserliche Marine, 1914-1918) and the Allied efforts to counter the threat. Over 40.000 pages on the officers, the boats, technology and the Allied efforts to counter the U-boat threat.

uboat.net

Naval Enigma ciphers - Technical pages - German U-boats of WWII - Kriegsmarine - uboat.net

The U-boat War in World War Two (Kriegsmarine, 1939-1945) and World War One (Kaiserliche Marine, 1914-1918) and the Allied efforts to counter the threat. Over 40.000 pages on the officers, the boats, technology and the Allied efforts to counter the U-boat threat.

uboat.net

Yes, but the Y service intercepted radio signals, to them it was just gibberish. The work done at Bletchley was the meat and potatoes of it. Without them, the intercepted signals may as well have been in Martian. This isn't to diminish the Y service, but to recognise Ultra for what it was.

 

[nuuumannn]

As for breaking the KM codes, Bletchley had success from mid-1940. However, it was the introduction of a new Enigma machine with a fourth rotor in combination with a new code that rendered them blind for most of 1942.

Some of the codes, they gathered important information, but the breakthrough came a year later in 1941 as I mentioned, they certainly were not able to decipher the messages in their entirety back in 1940 (re-read that link you posted, Ewen, it goes into it there). As I mentioned, it wasn't until late 1942 that they were able to determine where the boats were because of the fourth Enigma wheel, which this is the third time I've mentioned it.

 

[WATU]

They were blind from Feb 42 to Dec 42 on the main Atlantic Shark/Triton cipher. They could still read the coastal messages which gave a lot of hints on activity such a departing and returning U-boats along with other minor ciphers. Then you have the shore-based HF/DF tracking to add to the mix. The Submarine Tracking Room did its best while Shark was out but it was much less precise. The interception of messages was still very important. Some messages had standard format so the nature of the content was known. Others had recognisable prefixes or call signs which helped as part of the Traffic Analysis.

 

[MIflyer]

On balance I think that that the ratio of aircraft reinforcements should have shifted early in 1942 with an increase in the flow to Coastal Command and a decrease in the aircraft to Bomber Command.

Well, note that the Hudson was first used as a daylight bomber and that did not work out too well. So they used it as a marine patrol and ASW aircraft and the results seem to have been at least acceptable.

But note that ship attack had a horrific loss rate, the probability of surviving a tour of operations being around 17%, and for two tours it was zero. Switching heavy bombers from night bombing to marine combat use would have been catastrophic in some cases. Obviously, going after U-boats was much less fraught with peril than hitting surface ships.

 

[syscom3]

When the escorts received HF/DF gear, they could home in on the Germans with a lot more accuracy than the shore based units.

 

[Shortround6]

Coastal Command had several different duties/roles.
General maritime recon
Maritime strike
ASW recon/strike.
Others?

Obviously using a Singapore III to attack a Kriegsmarine warship was not going to end well for the Singapore.

As good as the Sunderland was in many ways, basically they didn't have enough of them.
Of Mr Sinclair's list of flying boats only the Sunderland was available in any worthwhile numbers.
London II....38 built, last in May 1938. Number in fall of 1939?
Lerwick........21 built, this was such a failure that several of the last 8 built (with the best engines) were never issued (and this was at the end of 1940) and stored until scrapped.
Singapore III...37 built, last in June of 1937. 19 may have still been in service in Fall of 1939?
Sunderland I, history is known.
Scapa ...........15 built, predecessor of the Stranaer. All retired in 1939 or a few left in training units?
Stranraer......17 built for the RAF starting in Dec 1936 (?). 40 more built in Canada for the RCAF.

Please note that aside from the Lerwick and Sunderland, all of these were fabric covered metal wings and metal hulls. They needed a lot maintenance.
The Lerwick was supposed to be the smaller/cheaper plane (1/2 the weight and 1/2 the wing area) to make up numbers for the more expensive Sunderlands and replace the old biplanes. The Lerwick was first flown in Autumn of 1938 but the original hull, elevators, vertical tail assemblies were all far from satisfactory and many modifications were tried to fix things. Things got better but not enough and while No 209 squadron got some in the Fall of 1940 they were taken out of first line service in May 1941.

Actual numbers of flying boats was nowhere near what was needed once war broke out. Numbers above include planes based in Gibraltar and other places(?).

Americans got very lucky with the PBY. Most of the flying boats that tried to be much faster were still not fast enough to avoid fighters or AA fire. They would up being expensive for what they actually offered. Consolidated own PB2Y Coronado turned out to not have enough extra capability to be worth the extra cost.

 

[WATU]

When the escorts received HF/DF gear, they could home in on the Germans with a lot more accuracy than the shore based units.

True but while shore-based and ship-based HF/DF sets used similar boxes, but with very different aerials, their operational use was quite different.
Shore-based supplied higher level operational information primarily to the OIC who in turn fed Western Approaches Command. This allowed the re-routing of convoys around U-boat patrol lines. Escort groups could be warned of a general threat and direction.
The ship-based set offered a passive tactical sensor for the escort group commander that had a greater range than radar, out to 30 miles. Note that it did not provide range detail and that cross-bearings from two ships were not very accurate. This gave him the ability to send escorts down bearings to suppress and hopefully attack U-boats. It was a vital system and was used to great effect.

 

[MIflyer]

Americans got very lucky with the PBY.

I read of the first delivery of a PBY to the British.

After it landed a visiting reporter said it could not have flown very far because there was not enough oil over the engine cowlings.

When the Americans described the route they had taken the British were silent, because it was obvious to them the Americans were lying. No British aircraft could have flown that route.

When the British asked about the range of the radios the Americans replied that they had been communicating with San Diego during final approach. This also was unbelievable.

The next day the Brits went up in the PBY, participated in another radio contact with San Diego, and saw that the engines did not leak much oil.

At Midway, though, the USN found out that "every type of Japanese aircraft could and did attack the PBY's" including Betty bombers flying out of Wake Island. And the USN noted that the USAAF B-17's were flying right over the IJN fleet, not ducking in and out of clouds like the PBY's. The result was the adoption of the PB4Y-1 and -2 and the PBY being used in areas where enemy air opposition was not likely to be encountered.

 

[RDEAN5809]

Concur that "Blackett's War" is a great read on the topic. A concise summary is in this one on Amazon: https://www.amazon.com/Great-Mariti...ooks&sprefix=ralph+dean,stripbooks,157&sr=1-3

 

[Peter Gunn]

Good points about the PBY but it's first flight was what, 1935? Not bad for a waaay pre-war design that was useful basically to the end of the war.