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Lancaster BII - why less performance?


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A quick scan of Google seems to show that Bristol were keen on Turbochargers much more so than RR who had a quick look and decided it wasn't for them. About the time Bristol were struggling with large scale production of sleeve valves the turbo seemed to get forgotten about. I wonder if supercharger design had been pushed down the priority list because turbos are going to be the next big thing.

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3 hours ago, AltcarBoB said:

fundamental design flaw or Bristol just needed to tweak one aspect of the design.

Moving away from the OP, but just thinking about this, did Bristol develop a 2-stage supercharger? 2-speed yes. 2-stage I think not. Air cooled engines do have the problem of the size of an air cooled intercooler something which RR did achieve having the benefit of water cooling and a smaller intercooler package. With this limitation I can see why Bristol had the interest in turbocharging. 

 

 

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Hello Ray

Bristol did developed two-stage supercharged engines, but these were experimental types only. Pre-war Pegasus PE.6S powered Bristol 138A, which set a new altitude world record in 1937. In his book British piston aero-engines and their aircraft (Airlife) Alec Lumsden describes it as a hybrid, with a fully supercharged single stage and an extra second-stage supercharger. It required quite a large intercooler. Both Hercules VIII and XVTM had a second-stage supercharger added more or less in the same vein as PE.6S. Again, Lumsden calls both two-stage Hercules types hybrids. These engines were installed in Folland 43/37 and Wellington V.

I checked Martin Middlebrook's book and the Halifax in question belonged to 76 Sqn and she actually reached 26.000 and not 27.000 ft during the raid. Still, that was more than enough to keep the plane and her crew above the reach of Luftwaffe defences. Cheers

Jure

Edited by Jure Miljevic
incorrect Hercules XIVTM designation changed to XVTM
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7 hours ago, Jure Miljevic said:

Hello Ray

Bristol did developed two-stage supercharged engines, but these were experimental types only. Pre-war Pegasus PE.6S powered Bristol 138A, which set a new altitude world record in 1937. In his book British piston aero-engines and their aircraft (Airlife) Alec Lumsden describes it as a hybrid, with a fully supercharged single stage and an extra second-stage supercharger. It required quite a large intercooler. Both Hercules VIII and XVTM had a second-stage supercharger added more or less in the same vein as PE.6S. Again, Lumsden calls both two-stage Hercules types hybrids. These engines were installed in Folland 43/37 and Wellington V.

I checked Martin Middlebrook's book and the Halifax in question belonged to 76 Sqn and she actually reached 26.000 and not 27.000 ft during the raid. Still, that was more than enough to keep the plane and her crew above the reach of Luftwaffe defences. Cheers

Jure

 

I was just going to mention the Bristol 138. It popped into my head late last night and I was going to ask about it. I also have Lunsden's book and should have re-read that bit.

 

 

 

Chris

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Doesn't the set up of the Bristol 138 qualify more as an auxiliary supercharger rather than a two stage design. The Pegasus had its normal supercharger plus a shaft driven blower mounted on the bulkhead.

 

Semantics I know 😂

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12 hours ago, AltcarBoB said:

Doesn't the set up of the Bristol 138 qualify more as an auxiliary supercharger rather than a two stage design. The Pegasus had its normal supercharger plus a shaft driven blower mounted on the bulkhead.

 

Semantics I know 😂

Yes semantics. It was still a two-stage supercharger.  The difference being that with the Bristol 138 you needed to add a separate blower housing with ductwork to a very bulky air-to-air heat exchanger between the stages. The brilliance of the Merlin 2-stage supercharger was a very compact package using water cooling between the first and second stage integral to the supercharger housing itself before the cooling water left to provide some additional cooling as an aftercooler for the air before it entered the carburettors like so: 

 

spitfire supercharger

Source: apologies some where from the internet and I did did not record where.  

 

Pratt & Whitney, of course did develop successful  two stage superchargers as used in the F4F, F6F and F4U with compact air-to-air heat exchangers. Why Bristol did not go down that path must be answered somewhere, but I have not seen it, yet.  Even the Centaurus did not go to two-stage.  There would be an interesting story in this that some day I hope to read.  

 

My belief is that when comparing Bristol and Rolls Royce, Bristol did not have the benefit of Stanley Hooker's input on supercharger design until much later when Hooker left Rolls Royce and joined Bristol with priorities then turning to jet engines. I think this cannot be understated. Hives, Hooker and the Rolls Royce team certainly provided a great solution without the need for significant change to the Spitfire or the development of a new aircraft to take advantage of this design.

 

If there was a British commitment to develop a multi-altitude fighter around an air cooled radial as pushed by the US Navy it might of been different. Then the air-air intercooling package could of been best designed into the total aircraft system.

 

In all, still a simplistic view, it would be good to get into the depths of the engine design to see what other limitations may of been at play comparing Bristol air cooled sleeve valve radials to the liquid cooled poppet valve Rolls-Royce inlines. 

 

Getting back to OP.  You can see with Rolls Royce supercharger development, they were able to take a lesser power engine at ground level and make it perform at high altitude. 

 

Ray

 

 

 

 

 

 

 

 

 

 

 

   

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I have only spoken with one veteran (Flight Engineer) who flew both Merlin and Hercules 'engined' Lancasters - in fact he was shot down in a B-II. He told me the B-II was a rocket ship at low level, great speed and climb performance even at MAUW. It lost power at altitude due to the supercharger settings, and after the B-I/III supercharger changeover (17'000 ft ??) point, it suffered greatly. Purely by conversation with the Yorkshire Aviation museum personnel, the later war Hercules Halifax performance improvements were down to all the 'bits' that were changed over time, with the nose turret removal a prime example. If you've never seen a Halifax in the flesh, it's a big beast - I fly the BBMF Lanc, and the Halibag is a far bigger aircraft, wider and greater cross section, I really ought to look at empty weights for both frames.

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2 hours ago, isaneng said:

I have only spoken with one veteran (Flight Engineer) who flew both Merlin and Hercules 'engined' Lancasters - in fact he was shot down in a B-II. He told me the B-II was a rocket ship at low level, great speed and climb performance even at MAUW. It lost power at altitude due to the supercharger settings, and after the B-I/III supercharger changeover (17'000 ft ??) point, it suffered greatly. Purely by conversation with the Yorkshire Aviation museum personnel, the later war Hercules Halifax performance improvements were down to all the 'bits' that were changed over time, with the nose turret removal a prime example. If you've never seen a Halifax in the flesh, it's a big beast - I fly the BBMF Lanc, and the Halibag is a far bigger aircraft, wider and greater cross section, I really ought to look at empty weights for both frames.

Thanks for this information.  It confirms what I suspected from looking at the engine performance characteristics.

 

My goodness, you fly the BBMF Lancaster. 

 

Ray

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However, all the improvements seen on the Hercules Halifax were also present on late production Merlin ones, without apparently improving the loss rates.  Perhaps these were never properly analysed in Harris's determination to get rid of the Halifax and the looming presence of the Mk.III?    

 

The comments made about the Lancaster Mk.II's lack of performance after the change of supercharger gearing mirror those made about the Merlin-engined Halifax, and its inability to maintain cruise speeds up to 20,000ft.  Geoffrey comments above that its payload/range performance was much the same as that of the Hercules Halifax.  However, given the better aerodynamics of the Lancaster, it should have been superior.  I still feel that its problems have not been fully explained.

Edited by Graham Boak
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26 minutes ago, Graham Boak said:

Perhaps these were never properly analysed in Harris's determination to get rid of the Halifax and the looming presence of the Mk.III? 

Graham have you read this paper by Stephen J. Harris "The Lancaster and Halifax in Canadian Service"? Very interesting paper with much reference to Air Marshall Arthur Harris's thoughts on the matter.

 

https://scholars.wlu.ca/cgi/viewcontent.cgi?article=1432&context=cmh

 

Ray

Edited by Ray_W
More info
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Thank you, no, although I am familiar with  AVM Harris's opinions.

 

EDITED to help remove confusion - I hadn't registered the identical names.  Thanks Ray.

 

RE-EDIT  Now read the paper.  It would have been very interesting to see just what was this supposed unknown design fault, and a little operational analysis given to some of these claimed ratios.  From my own experience in the field, I know that small changes in the requirements can make dramatic differences in the results if it involves stepping over a limit affecting one option above another.

 

I do however feel that those on the spot at the time probably had a better grasp of the real limitations of production capacities than a few throw-away comments made more recently.

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18 minutes ago, Ray_W said:

Very interesting paper with much reference to Harris's thoughts on the matter.

I suppose I should of been clearer seeing there can be confusion with the author's name. Will edit to read "a very interesting paper with much reference to Air Marshall Arthur Harris's thoughts on the matter." 

 

Ray

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Once again some really fascinating information, which will repay careful study. Thank you isaneng, RayW and Graham B  and others for all this.  The effect of supercharger design selection/setting on higher altitude performance I had overlooked, foolishly.  Very important and an area largely ignored in many discussions.

(As is the impact of better fuel availability and higher octane fuel supply on aircraft performance & capability during the war. Some years ago I read a fascinating history of allied fuel supplies and the various mixings and chemical concoctions necessary to keep supplies going as various oilfields and refineries fell in and out of our hands. It showed how vital good chemists were to the war effort and how important some individual tanker deliveries of specialised products were.)   

 

 

Especially intrigued to read that Canadian paper, and see more of Harris' views. A fellow pilot whose father worked closely with Harris had some interesting insights, though I still feel he was allowed far too much freedom.

 

And -  wow - how lucky you are to to get to fly in the BBMF Lancaster, 'isaneng' ! 'Impressive to see but I bet crews in WW2 felt like a target just sitting there droning along for so many hours. Not sure I could have done that; takes a certain type of cold bravery.  

 

John B

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A fascinating thread, thanks to everyone for their input. 

 

On the subject of Hercules or Merlin, I recall a similar issue with the Beaufighter. Designed to use the Hercules, shortages due to priority application on the Stirling and Halifax resulted in the Mk II receiving Merlin XX engines. This was generally considered, from all I have read, to be a retrograde step.  It would seem that changing engines from those intended by the design team is not always as successful as expected. 

 

 

 

 

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There is a good chance the front turret on the Lancaster II was a big part of the extra drag versus the Halifax III arrangement, which would help even performance.

 

I assume someone has a good idea when the square fins were made the production standard for the different lines, Handley Page, London Aircraft Production, English Electric, Rootes Speke, and Fairey.

 

Thanks Ray for finding the report, agreed it is an omission the unspecified design problem is not mentioned, only that it could not be found or corrected at the time, so it is not things like the tail and other control surfaces.  It is also odd the exhaust shrouds on Halifax Merlins were reported less effective than those on Lancasters, clearly being more visible must have made interceptions easier and that is not strictly an aircraft performance issue, though the problems in taking evasive action clearly is.

 

It is odd the report does not mention the clearly better performing Halifax VI, though of course it did not arrive until the second half of 1944.  Reading between the lines it looks like the early mark III did not have the extended wing, and possibly problems with the engines, but that soon changed if the anecdotal evidence of climbing to 25,000 feet is correct, assuming it is not really a mark VI.

 

Not sure what to make of the comments about Lancaster turret hydraulic lines being more vulnerable equals the Halifax being more robust, agreed the consensus is liquid cooled engines were more vulnerable to damage than air cooled ones

 

As for the comment on the flak guns, The average for aircraft returning damaged by flak on night raids February to December 1942 was 6.5%.  Before the RAF introduced window Bomber Command was recording that around 6 to 9% of returning aircraft on night missions had flak damage, March to July 1943.  This dropped to 2.85% in August making the average for all of 1943 5.8%, damaged,  rates averaged 2.3% for all of 1944 and 1.4% for 1945.  Window remained effective against the fire control radars for the remainder of the war.

 

For a few months in 1944 Bomber Command's statistics separated out the Halifax II and V from the III.  Cat = Category, A = Enemy Action, N = Not Enemy Action.  And of course the sortie figures for the Halifax all marks and Halifax II and V are small.  Night bombing sorties only.  Cut and paste into your spreadsheet of choice.
The raw data, record ID number / Month / Aircraft / despatched sorties / effective sorties / Missing / Cat E A / Cat E N / Cat B A / Cat B N / Cat AC A / Cat AC N / % missing

 

1 / Jul-44 / Hali III / 2328 / 2189 / 46 / 1 / 8 / 2 / 1 / 15 / 7 / 2.10

2 / Jul-44 / Lanc / 5449 / 5023 / 220 / 5 / 8 / 5 / 4 / 67 / 13 / 4.38

3 / Jun-44 / Hali II/V / 152 / 119 /  /  /  / 1 /  /  /  / 0.00

4 / Jun-44 / Hali III / 4137 / 3855 / 100 / 4 / 9 / 4 / 1 / 19 / 11 / 2.59

5 / Jun-44 / Lanc / 7531 / 6845 / 205 / 6 / 4 / 6 /  / 42 / 10 / 2.99

6 / May-44 / Hali II/V / 127 / 123 / 1 /  /  /  / 1 / 1 / 1 / 0.81

7 / May-44 / Hali III / 2349 / 2219 / 50 / 2 / 3 / 4 / 4 / 9 / 8 / 2.25

8 / May-44 / Lanc / 6044 / 5407 / 197 / 4 / 6 / 5 / 7 / 53 / 14 / 3.64

9 / Apr-44 / Hali II/V / 404 / 393 / 6 / 1 /  / 1 /  / 2 /  / 1.53

10 / Apr-44 / Hali III / 2198 / 2137 / 59 / 1 / 2 / 1 / 8 / 13 / 9 / 2.76

11 / Apr-44 / Lanc / 4836 / 4645 / 120 / 6 / 10 / 3 / 4 / 49 / 33 / 2.58

12 / Mar-44 / Hali II/V / 850 / 758 / 5 /  / 3 / 1 / 1 / 1 / 1 / 0.66

13 / Mar-44 / Hali III / 1868 / 1657 / 93 / 2 / 11 / 4 / 1 / 15 / 13 / 5.61

14 / Mar-44 / Lanc / 4319 / 4080 / 180 / 3 / 10 / 7 / 3 / 71 / 32 / 4.41

15 / Feb-44 / Hali II/V / 269 / 231 / 30 /  / 1 /  / 1 / 8 / 3 / 12.99

16 / Feb-44 / Hali III / 720 / 609 / 37 /  / 5 /  / 1 / 2 / 11 / 6.08

17 / Feb-44 / Lanc / 2642 / 2472 / 117 /  / 15 / 4 /  / 27 / 13 / 4.73

18 / Jan-44 / Hali / 865 / 742 / 86 / 3 / 13 / 2 / 7 / 15 / 4 / 11.59

19 / Jan-44 / Lanc / 3954 / 3712 / 228 / 3 / 5 / 7 / 3 / 48 / 21 / 6.14

20 / Dec-43 / Hali / 754 / 660 / 52 /  / 3 / 3 / 2 / 9 / 3 / 7.88

21 / Dec-43 / Lanc / 2507 / 2299 / 113 / 1 / 37 / 14 / 7 / 40 / 11 / 4.92

 

The overall totals say Halifax 9.84% missing rate, with around 19% of aircraft missing or known to have been hit by enemy fire returning to Britain, Halifax II and V 4.12% missing and 23%, Halifax III 3.04% and 20.3%, Lancaster 4% and 25.6%.  Note the missing trend though as the year progresses Halifax III versus Lancaster.  Of course the loss rate declined from April 1944 onwards and the Halifax II and V were deliberately sent to less dangerous targets from late February.  Having said that it is interesting that a higher percentage of combat damaged Lancasters made it back to Britain, which says it was more robust though again the trend was for the Halifax III to match or exceed the Lancaster later in 1944.  Having reserve power is usually a good thing when coping with combat damage.

 

According to Bomber Command it had 32 Halifax III on strength on 1 January 1944 versus 258 mark II/V, the Halifax force becomes half mark III in the first week of February and mark II/V still make up around a quarter of the strength in early April 1944, down to 10% around mid May, gone from front line service in mid July.  I have no idea when the larger wing became the majority of the mark III.

 

The rest is from AVIA 46/112 Halifax Type Biography.

 

Sir Henry Tizard, 29 June 1942, based on the performance of the Halifax, Stirling and Manchester losses and bombs dropped June 1941 to May 1942, "there is no case for the fading out of the Stirling, but I think there may well be a case for the fading out of the Halifax as the Lancaster comes into full production."

 

Other quotes from the file.  "Everything but the barest necessities was eliminated from the first prototype; it was only required to fly; and fly it must at the earliest possible moment, in order to pin down and eradicate those inevitable aerodynamic teething troubles which best the path of every type, however carefully designed."  The prototype arrived at Boscombe Down without bomb doors, they were fitted there.  Self sealing tanks and armour plating were not in the original specification, trials were done using the first prototype.  The second prototype had gun turrets, items like fuel jettison gear, de icing etc., components delivered to Radlett for assembly on 31 July 1940, to A&AEE 11 September 1940, accepted 24 February 1941.  Two months delay to the prototype's first flight date was caused by the decision to disassemble it and transfer it from Handley Page to the bigger airfield at Bicester.  Aerodynamic troubles with the first prototype were not cured until July 1940.  By the time war broke out the decision was "Ultimately to concentrate on the the production of the Halifax as the standard aircraft for the bomber force"

 

The 4 gun mid upper turret, trial ordered in November 1941, decision to put it into production in May 1942, first fitted on Handley page line February 1943.  H2S work began in January 1942, final form production at Handley page and London Aircraft Production in September and October 1943

 

After complaints in April 1942 new bomb bay doors were designed and tested, they could close around an 8,000 pound bomb but were thicker, encroaching on the bomb bay and seriously cut down the stowage available for small bombs.  Smaller doors were designed that could enclose a 4,000 pound but not 8,000 pound bombs, flight testing revealed interference with H2S, as a result the design was dropped in December 1943.

 

Halifax I as first produced, Merlin X, 55,000 pounds maximum weight, 13,000 pounds bomb load, twin nose turret, quadruple tail turret, two manually operated guns on each beam, during production fuel increased from 1,552 to 1,636 gallons, a carrier fitted to carry 2x4,000 pound or 1x8,000 pound bombs, undercarriage strengthened to bring allowed all up weight to 60,000 pounds.  While the first 100 Halifaxes were to have Merlin X the change over was after the 87th machine.

 

Halifax II, Merlin XX replace Merlin X, then after "about the first 20" the Hudson type upper turret replaced the beam guns and an extra fuel tank was added in each wing.

 

Halifax II Series IA, a response to the performance complaints made in August 1942, front turret removed, replaced by fairing and ultimately the perspex nose, a 4 gun mid upper turret set lower in the fuselage, astrodome lowered, better low drag flame dampeners, "a number of drag producing excresences were removed or modified", "These changes were eventually associated with the designation Halifax II series IA, though in point of fact this really applied to a change of radiator with took place at about the same time." First production delivered February 1943, some fitted with H2S.

 

Halifax II Series II, engine nacelles lowered relative to the wing which was expected to increase performance, engines to be Merlin 61 which were later fitted, one prototype built and tested April/May 1943 showing a worthwhile improvement in performance, not proceeded with as in February 1943 the decision had been made to change over to Hercules engines due to the uncertainty of Merlin production.

 

Halifax III, in July 1941 the decision was taken to try the Hercules engine but at a low priority, prototype flew in October 1942.  In February 1943 the following improvements associated with the mark IV version were proposed and were "accordingly introduced" into the mark III, span increased to 104 feet, retractable tail wheel, fuel capacity increased by the addition of two 90 gallon tanks which could be fitted in two of the wing bomb cells giving the cell space the option of fuel or bombs.  All up weight to 63,000 pounds, which required more wing strength particularly in the longer span version, in March 1944 further strengthening was introduced to enable maximum weight of 65,000 pounds but this weight was not cleared until July 1944.  A redesigned bomb bay was dropped in favour of carrying H2S.  So the query is if the longer wing was a modification, when was it introduced to each of the 5 production lines?

 

In July 1943 the RAF made an urgent demand for a gun with a field of fire vertically downwards to something below dead astern.  A single hand operated 0.5 inch gun was tried out in the under turret hole and by January 1944 it was in production on aircraft not fitted with H2S.  The gun was later displaced by fitting H2S on all aircraft.

 

Halifax IV proposal, Merlin 60, 104 foot wing span, redesigned bomb bay enabling carriage of 4,000 pound bombs with the doors closed and 8,000 pound bombs with the doors nearly closed.  Contract issued in September 1942 but abandoned in February 1943 due to the uncertainty of Merlin production and the decision to go with Hercules.

 

Halifax V, as per mark II with different undercarriage.

 

Halifax VI, Hercules 100 fitted to mark III plus rearranged and simplified fuel system enabling more fuel (150 gallon tanks replacing the 90 gallon ones fitted in the mark III) but reducing maximum bomb load by 1,000 pounds, all up weight to 65,000 pounds with more wing strengthening.  In November 1944 the RAF made an urgent request to clear it at greater weights due to increases in tare weight reducing bomb load to less than the mark III.  In February 1945 the weight was raised to 68,000 pounds, this was also done for the mark VII.

 

Halifax VII, Hercules XVI fitted to mark VI airframes.

 

The Halifax II Series IA bomb load for a raid on Berlin is put at 2,000 pounds, the VI 9,000 pounds.

 

The file also has a Halifax versus Lancaster section, the inferior ceiling, bomb load and range, lower altitudes increased vulnerability and also "made their use impossible on many nights owing to inability to get above the clouds."  The shorter range reduced evasive routing and forced the Lancasters to conform.

 

Provision for doing glider towing had been built in almost from the start, but not used for years.  In June 1941 there was a trial requested for use in dropping paratroopers, the hole provided for the under turret was used and fittings for the role were incorporated in production aircraft from November 1942.

 

In October 1941 the urgent operational need for a paratroop version meant 3 mark II were converted (nose and mid upper turret removed, two extra 80 gallon fuel tanks added, other non essential drag producing equipment removed, and had "certain special features".  The fuel tanks had been designed in June 1941 to meet a Bomber Command request for a quick way of increasing the range of early versions that did not have the extra wing tanks.  Two SOE squadrons eventually equipped with this type, maximum weight 61,700 pounds.

 

January 1943 Coastal Command long range reconnaissance mark II, nose turret removed and replaced by a firing with two hand operated guns mounted on it, mid upper turret removed, two 80 gallon fuel tanks added, ASV fitted instead of H2S.  In July 1943 Meteorological Reconnaissance mark V were added, with similar modifications.  All up weight 61,700 pounds.

 

March 1943 trials with rocket projectiles, installation not entirely satisfactory, but no further action done from October 1943 as the requirement had been dropped.

 

The Halifax A.III and A.VII, nose gun and mid upper turret removed, H2S, which covered the jumping hole removed, paratroop and glider towing equipment permanently fitted, Rebecca fitted.  Later a large jumping hole fitted along with changes to the fuselage floor, twin 0.5 inch tail turret, "These aircraft were basically a mark VI" now called A.X.

 

Transport version design began in December 1943, scheme A was simple conversion removing items like the armament and other unnecessary equipment, making the C.III, C,VI and C.VII.  Scheme B was the production version, the C.VIII, armament removed, provision for bulky freight, a deep pannier slung in the bomb bay.

 

"Of the first 300 Halifaxes built hardly any two were similar and the series of production drawings was not sealed until 26 September 1941."  Interview with Mr. L.F. Fox of R.D.L.2 20 March 1943, "the first 300 Halifaxes off the line were all different and largely hand made, before the aeroplane was standardised."  After that most of the modifications were equipment but also a different undercarriage, tropical cooling, different engines, turrets etc.

 

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16 hours ago, John B (Sc) said:

'I must find a copy of 'Not Much of an Engineer'.

 

Hi John,

I downloaded one onto my Kindle from Amazon.

Ray

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