Geoffrey Sinclair

A reply from the USN Museum, verbatim, You asked, "Do the aircraft history cards for BuNos 3856 to 3874 give the engine as R-1830-76 or R-1830-86?" I checked all Bureau Numbers between 3856 and 3874, and they all list Engine Model R-1830-76. Additionally, BuNos 3861 & 3862 have "2 stage" handwritten next to the typed engine model number. BuNos 3863 and 3864 have "(2)" handwritten next to the engine number.

Thanks for taking the look, interesting to see how early the change was and by the looks of things the decision the wires were the solution rather than other changes to the vertical tail and rudder system. The Australian Archives system is for the control symbol to be what reference ID original agency used for the file/record. There is no control symbol 150/4/274 present, so it probably means contacting the RAAF history people for the slight chance the record has been kept by the RAAF. Advanced Search using 150/4/* as the control symbol (* being the wild card) plus Anson in the title results in 208 files but not 274. "150/4/" seems to be a standard reference for these sorts of instructions, so for example readable online A705 150/4/555 DTS [Directorate of Technical Services] - Publication of technical orders - Aircraft general instruction number F 3 - paints and varnishes for use on aircraft 1939 - 1940 item ID 3031143 A705 150/4/3999 DAM (AM7) - Technical Order - Publication of M/T Maintenance Instruction 2/34 - Camouflage Disruptive Painting - M/T Vehicles and Equipment 1943 - 1943 item ID 3091760 A705 150/4/5053 HQ [Headquarters] DRM [Directorate of Repairs and Maintenance] RAAF Headquarters - RM8 - Marine Craft Instruction 3/2 - Marine Craft Painting and Marking RAAF Crash and Rescue Launches 1944 - 1949 item ID 3107828

http://fdrlibrary.marist.edu/archives/collections/franklin/?p=collections/findingaid&id=502 Has a lot of files imaged and available to read, the downside being a non systematic collection as far as things like USN aircraft production is concerned and no index, you need to read through each file. There is probably some more in there about the early F4F but finding things takes a lot of time. The Lend-Lease section shows just how broad the system was, not just finished weapons. I am treating things as a good way to find titles etc. of reports to ask for/find in the USN and US archives. With regards to the F4F, items found so far, Lend lease April-July 1941 http://www.fdrlibrary.marist.edu/_resources/images/psf/psfa0142.pdf Page 217, FDR memo, originally allocated 30 Grumman to UK 19 March, reallocated to Greece 28 March, back to UK 22 May 1941. Reference (Lend Lease number?) 206 Navy - Reports & Bulletins, October 1940 - April 1941 Part 2 http://www.fdrlibrary.marist.edu/_resources/images/psf/b-psfc000129.pdf Page 65, 17 December 1940 Grumman awarded $36,250,455 contract for fighters and pare parts, which if compatible with the dates from the USN acceptances reports is probably the date of the first expansion of the second order. Though of course if the contract was all aircraft it would be a unit price of nearly $143,000, assuming half the value is spares it is still an expensive aircraft, even given the USAAF 1939-41 average P-40 reported cost of $60,562 and the P-39 at $77,159 are correct. Navy, July - December 1941 part 1 http://www.fdrlibrary.marist.edu/_resources/images/psf/b-psfc000073.pdf Page 93 USN aircraft orders and deliveries (acceptances?) as of 1 September 1941, report continues to part 2 of the file. Graphical and tabular it includes engine deliveries and the intended schedules. The 897 F4F under order as of 1 September 1941 consist of On 8 August 1939 the USN ordered 54 F4F-3, then date unknown added another 27 added, 1 to XF4F-4 and 2 to XF4F-5 1 XF4F-6 added to the original USN order dated 20 November 1940 5 August 1940 the USN placed its second order, for 243 F4F-4 Date unknown the USN added another 254 F4F-4 now believed to be 17 December 1940. On 23 June 1941 another 162 F4F-4 added On 28 July 1941 another 160 F4F-4 added This totals 901 aircraft, less the XF4F-4, the 2 XF4F-5 and the XF4F-6 = 897. The report indicates Grumman were around 100 aircraft ahead of schedule while Pratt and Whitney were behind schedule. Edit addition: Navy - Defense Aid Funds Report http://www.fdrlibrary.marist.edu/_resources/images/psf/b-psfc000102.pdf page 11, approved allocation, dated 3 April 1941, for 150 F4F-4B and 20% spares, total cost $10,980,000, $73,200 per F4F including spares. (50 PBM-4 with 20% spares $33,336,000, Also 25 April - 150 PBY-5 plus 20% spares $35,577,000, 50 PB2Y-3 plus 20% spares $34,236,000, 13 May - 50 Grumman airplanes including propellers and spares $5,150,000) The first F6F Hellcat order is dated 23 May 1942.

It is always a joy to discover yet another designation for a particular item in a different report. R-1830 Engine production from the US War production Board report, to end June 1940 the data I have is only total R-1830, no break down by sub types. Month 1-stage C3G, C4G / 2-stage C5G, C7G Jul-40 234 / 1 Aug-40 421 / 11 Sep-40 365 / 33 Oct-40 497 / 17 Nov-40 536 / 14 Dec-40 571 / 17 Jan-41 387 / 16 Feb-41 440 / 10 Mar-41 545 / 11 Apr-41 436 / 3 May-41 423 / 16 Jun-41 457 / 30 Jul-41 577 / 40 Aug-41 498 / 54 Sep-41 521 / 52 Oct-41 431 / 96 Nov-41 531 / 79 Dec-41 575 / 100 1-stage C3G, C4G used in B-24, C-47, C-93, PBY, Beaufort, AT- 12, P-35A 2-stage C5G, C7G used in F4F, FM-1, PB2Y. According to the data in Problems of Accelerating Aircraft Production During World War II there were 98 C5G/C7G engines built in 1940, the above comes to 93 in the second half of 1940. Buick built C4G engines except for 1,100 G9G in 1945, Chevrolet built C3G and C4G, Pratt and Whitney switched 2 stage production to the C9G in December 1943.

In 1939/40 the French ordering system gave a total number of which most were to be delivered as assembled aircraft and the remainder as the equivalent value in spares. The G-36A order was for 100, being 81 complete and the equivalent of 19 more as spares. The Anglo French letter of intent for Lockheed Lightning was for 800 aircraft, 667 complete and the equivalent of 133 more as spares. Acceptance means the aircraft has passed it tests, which introduces the statistical problem of what happens if it crashes while being tested. Generally date order is rolled out of factory, acceptance, delivery. For production aircraft the sequence usually took a few days or less in wartime, for prototypes it could take many months. Again whatever the Grumman construction numbers or BuNos when it comes to USN Wildcats the acceptance order is the first order F4F-3, the F4F-3A, the second order F4F-3, all the F4F-4, then the final 100 F4F-3 (ex planned F4F-7). If 19 F4F-3 from the second USN order were built before the F4F-3A an explanation is required for why they were not accepted for 2 to 3 months. 78 F4F-3 (ending February 1941), 95 F4F-3A (starting March 1941, ending May), 107 F4F-3 (starting May 1941, with 3 acceptances then another 28 in June), 1,169 F4F-4, 100 F4F-3. Look at the notes about the changes to the second USN order which started out as all F4F-4.

The XF4F-3 was officially accepted in August 1939. The two X4F-5 in July and August 1940. The X4F-6 in November 1940, the XF4F-4 in May 1941, the pair of XF4F-8 in December 1942 according to the USN, January 1943 according to the War Production Board. The first 2 F4F-3 were accepted in August 1940, so it is quite possible the X4F-5 officially arrived before any F4F-3, while the third F4F-3 was accepted in November, same month as the XF4F-6. I think you might have answered your own question, all production F4F had the prototype wing until December 1940, the same time period the XF4F-5 and -6 were built. In terms of engine fit the XF4F-6 was an F4F-3A. This does not really help, but US War Production board report, Grumman model G-36 F4F-3, -3A, -4, Wildcat (British Martlet I, II, III) P&W R-1830-76, -86, -90, Curtiss C-5315-S with either 10 foot model 614 blades or 9 foot 9 inches model 512 blades. F4F-4B Wright R-1820 G-200, Hamilton Standard 23E50 with 10 foot 1 inch model 6393A-18 blades. Martlet II, IV Wright R-1820 G-205A, Curtiss C-5315-S with 10 foot model 614 blades

This is more a thinking aloud piece than anything else. Is there any documentation on when specific C/N or BuNo came off the Grumman line, that is before acceptance? On 8 August 1939 the USN ordered 54 F4F-3, then dates unknown added another 27, and changed 1 to XF4F-4 and 2 to XF4F-5. The USN allocated 2 blocks of BuNos. Grumman 2 matching blocks of C/N. Date unknown the French order is placed, the French presumably allocated a block of serial numbers, Grumman allocated a matching block of C/N. According to the USN it ordered an XF4F-6 added to the original USN order but dated 20 November 1940. Grumman gave it the construction number between the last of the original USN order and the first of the second USN order. On 5 August 1940 the USN placed its second order, for 243 F4F-4, allocating a single block of BuNo, matched by a Grumman block of C/N. Date unknown the USN added another 254 F4F-4 to the second order, again a single block of BuNo, but Grumman allocate a block of 20 (following directly on the block for the 243 aircraft) and a block of 234 C/N. Britain places the order for 100 Martlet on 28 July 1940 but is allocated a block of C/N after those for the USN F4F-4. On 23 June 1941 another 162 F4F-4 added to the USN order, again single blocks of BuNo and C/N. On 28 July 1941 another 160 F4F-4 added to the USN order, again single blocks of BuNo and C/N. The 243+254 = 497 USN second order originally meant as F4F-4 end up being built as 107 F4F-3 (initially to be 67 but then another 40 added), 95 F4F-3A, 274 F4F-4 and 21 F4F-7 while the BuNo to C/N matching remains, that is lowest BuNo has the lowest C/N and so on through the sequence, their order is 19 F4F-3, 95 F4F-3A, 88 F4F-3, 274 F4F-4, 21 F4F-7. Acceptance order however is F4F-3A, F4F-3, F4F-4, with 2 F4F-7 accepted before the last of the F4F-4. If the first 19 F4F-3 did come off the line first they were not accepted until 2 to 3 months later. This looks like about the only time F4F from a given order where BuNo and C/N were apparently built out of sequence. The USN Record of acceptances states the original order F4F-3 had R-1830-76, while those from the second order had either a -76 or a -86. The visual changes are the move to an internal carburettor duct for the first F4F-3 of the second order, then to 8 cowl flaps on the 20th F4F-3 of the order. All F4F-4 had the -86 engine. In parallel to the above the British order for Martlet is built, such that by end 1941 the RN has received 10 fixed wing (accepted at the same time as the F4F-3A) and 50 folding wing (accepted after the F4F-3A finish), while the USN has accepted 5 folding wing versions. The USN says all the Martlet used the R-1830-S3C4G, basically equivalent to the R-1830-90, the 10 with fixed wings were redesignated Martlet III. The other 30 Martlet III were F4F-3A originally destined for Greece.

A note for Jumpei's web site. The F4F-4 and FM-1 length when resting on the undercarriage was exactly 29 feet, spinner tip to rudder tip. When in level flight the length was 28 feet 9 and 3/8 inches. According to the Bureau of Aeronautics.

As has been noted the S3C4-G is essentially equivalent R-1830-90. The USN record of acceptances notes all Martlett II as built were powered by an R-1830-S3C4G. US National Archives, Record Group 72 Entry 153 Box 1 Naval Aircraft Record of Acceptances 1935-1946, Bureau of Aeronautics, Navy Department, Washington D.C., NAVAER 15838 The sources were given in the message. The RAF Contract Cards and Serial Registers. The former tracks orders, listing serial numbers and details like when delivered etc. The latter is tracking the arrival of new aircraft and initial deployment. As the Fleet Air Arm had officially become independent in 1939 the RAF steadily stopped tracking RN aircraft, but do have entries for some of the Martlet orders. These are what have been quoted. Note for example agreement of shipping details for AM954 and AJ107, AJ109 to 111. Serial Registers, covering K1000 to RZ49, RAF Museum microfilm, 5 files MF-1 to 5. Similarly the contract cards for roughly the same period, 4 microfilms, MFC-78-1 to 4. The reported change over or pitot types, where the 46 AM serials had one type and the 54 AJ serials another, is interesting, as this does not match any break in acceptances or construction numbers, implying it was done at RN request.

Differences. RAF Contract Cards. Mark I Did not use serials AL231 to 235. Article lists AX824 to 829 as both Martlet I and III. The 81 Martlet I serials were AL236-AL262 (At RNAS Donibristle November and December 1940) , AX824-AX829 (at Scottish Aviation August 1940), BJ507-BJ527 (At Scottish Aviation September 1940 on) and BJ554-BJ570 while BT447-BT456 were allocated to the 10 lost at sea. AL231 to 235 cancelled, replaced by AX824 to 829, so 5 cancelled, 6 replacements. Mark II, minor point, the article lists the loss of AM954 in the mark II section, but the AM954 to 963 block "covered in the Mark III section." AM954 initially retained in US, lost at sea US/UK, S.65363, Movements 6, 23 Feb 42. RAF Contract Cards, mark II Lost at sea differences. Shipped direct from NY to Bombay 15 Mar 42, Shipping folder Enc 247/1 AJ100 to 102, 105, 106, 108 no mention of lost at sea. Lost at Sea, S.65363 Movements 6, 23 Feb 42, (en route to UK?) AJ107, AJ109 to 111 (RAF Serial Registers have blank entries for the AJ serials except AJ107, 109 to 111 marked lost at sea) AJ124 to 126, China Bay, allotment 1348/42, April 1942, no mention of lost at sea AJ138 to 145, China Bay, allotment UK 6400, 16 April 1942, no mention of lost at sea. (RAF records AM955 to 963 on strength May/June 1941, AM964 to 999 December 1941 to March 1942, AJ100 to 153 March to June 1942., acceptances in USN were 10 in March 1941, 1 in June, then 49 August to December 1941, 1 in February, 33 in March and 6 in April 1942) Mark III, RAF Serial registers, AX724 to AX747, AX753 to AX754, AX761 and HK840 to HK842, total 30. Serials allocated in Middle East. Import report 27 mark III arrived Middle East in July and 3 in October 1941. (AX748 to 752 Anson, 755 DC-2, 756 to 759 Lodestar, 760 DH.86) USN record of acceptances, Mark VI serials JV637 to JV924 and JW785 to 836, total 340, article is missing JV903 to 924, adds JZ860 to 889.

It should be pointed out that in construction number order the F4F/G-36 production is 54 F4F-3 (3 to experimental types), 27 F4F-3, 91 G-36, 19 F4F-3, 95 F4F-3A, 88 F4F-3, 41+20+212 F4F-4, 21 F4F-7, 10 G-36A (RN fixed wings Martlet mark II/III), 90 G-36B (Martlet II), 220 F4F-4B, 162+160+573 F4F-4, 2 XF4F-8, 100 F4F-3. Acceptance order by month is very different, see below, the 21 F4F-7 acceptances over 9 months in 1942 are omitted as are the prototypes. There is no real link between construction number and acceptance dates between the different versions except for the reversion from F4F-4 to F4F-3 and there are plenty of stories from non Wildact production about airframes waiting for key components like engines before acceptance. If the 19 F4F-3 BuNo 3856 to 3874, C/N 738 to 756 did come off the production line before any F4F-3A they spent 2 or 3 months at Grumman before acceptance and the question then becomes why? Acceptances Month \ G-36A \ F4F-3 Jul-40 \ 1 Aug-40 \ 30 \ 2 Sep-40 \ 29 Oct-40 \ 21 Month \ F4F-3 Nov-40 \ 1 Dec-40 \ 19 Jan-41 \ 31 Feb-41 \ 25 Month \ F4F-3 \ Martlet II/III \ Martlet III \ F4F-3A Mar-41 \ 0 \ 10 \ 30 \ 15 Apr-41 \ 0 \ 0 \ 0 \ 17 May-41 \ 3 \ 0 \ 0 \ 33 Month \ F4F-3 \ Martlet II/III Jun-41 \ 28 \ 1 Jul-41 \ 32 Aug-41 \ 29 \ 2 Sep-41 \ 15 \ 3 Oct-41 \ 0 \ 6 Month \ Martlet II/III \ F4F-4 \ F4F-4B Nov-41 \ 14 \ 1 Dec-41 \ 24 \ 4 Jan-42 \ 0 \ 62 Feb-42 \ 1 \ 79 \ 1 Mar-42 \ 33 \ 56 Apr-42 \ 6 \ 92 Month \ F4F-4 \ F4F-4B May-42 \ 105 Jun-42 \ 119 \ 10 Jul-42 \ 62 \ 36 Aug-42 \ 43 \ 90 Sep-42 \ 77 \ 43 Oct-42 \ 132 \ 28 Nov-42 \ 176 \ 12 Dec-42 \ 161 \ Month \ F4F-3 Jan-43 \ 21 Feb-43 \ 16 Mar-43 \ 24 Apr-43 \ 24 May-43 \ 15

According to the book The Ninth Air Force in World War II by Ken C. Rust the color markings generally came in after D-Day. The 363rd Group had them before its designation as a reconnaissance unit in September 1944. the Group used a black horizontal stripe on the tail plus the following nose band and spinner colours. 380th Squadron code A9, blue, 381st Squadron code B3, yellow, 382nd Squadron code C3, red. The example from the 382nd Squadron has the anti glare paint as olive drab and the aircraft name in black (44-63811, "Big Mac Junior").

No idea about the 5 or 6 digit numbers, if they are the same on each aircraft then it suggests a part number, serial numbers would be needed to confirm who built the aircraft, G and H do suggest Gloster and Hawker. BM969 was built as a IIB, it seems clear the B and C wings were interchangeable enough to allow field conversions. According to Eyes For The Phoenix by Geoffrey J. Thomas the CBI PR Hurricanes only carried fuselage cameras, the tactical reconnaissance IIB had the outboard 4 machine guns removed the IIC generally the outboard cannon, the photo reconnaissance versions had all armament removed. "Additional internal fuel tanks" installed. The book's caption of the BM969 photograph dates it to mid 1942, noting the 2 inch yellow bands around the upper wing markings. The book also notes the first PR Hurricanes in mid 1942 from the Middle East.

Ministry of Aircraft Production. Hydraulic, Rotol, 5 blade, propeller model numbers. In January 1944 Spitfire F.XIV, F.21, no model number given. In March 1944. Spitfire F.XIV, PR, R19/-, R14/4F5/1. Spitfire F.21, R24/4F5/2, R14/5F5/2 In July 1944. Spitfire F.XIV, PR, R19/-, R14/4F5/1. Spitfire F.21, Spiteful, R24/4F5/2, R14/5F5/2 In September 1944. Spitfire F.XIV, PR.XIX, R19/-, R14/4F5/1. Spitfire F.21, Spiteful F.XIV R24/4F5/2, R14/5F5/2 In November 1944. Spitfire F.XIV, PR.XIX, R19/4F5/1. Spitfire F.21, F.22, Spiteful F.XIV, Seafire N.7/44 R14/5F5/2 In December 1944. Spitfire F.XIV, FR.XVIII, PR.XIX R19/5F5/1. Spitfire F.21, F.22, Spiteful F.XIV, Seafire F.45 R14/5F5/2 In June 1945. Spitfire F.XIV, FR.XIV, F.XVIII, FR.XVIII, PR.XIX R19/5F5/1. Spitfire F.21, F.22, Spiteful F.XIV, Seafire F.45 R14/5F5/2

If anyone just happens to be in Canberra with some time to spare, Australian Archives Series Number A705 Control Symbol 150/4/363 DTS [Directorate of Technical Services] - Anson order number 3 - tail plane bracing [15 folios] Access status: Open Location: Canberra 1937 - 1938 ID number 3030139 Or in Melbourne, all files open, B5752 359A Avro Anson Cadet AV Roe and Co Ltd [Contains 27 drawings] 1931 - 1935 532052 B5752 360A Avro Anson Cadet AV Roe and Co Ltd [Contains 27 drawings] 1935 - 1935 532053 B5752 374A Avro Anson Tudor and Canadian AV Roe and Co Ltd [Contains 28 drawings] 1940 - 1941 532054 B5752 512A Avro Anson Cadet [Contains 1 drawing] 1940 - 1940 532055 B5752 543 Avro Anson Cadet and York Military [Contains 39 drawings] 1929 - 1948 532056 B5752 552A Avro Anson, Avro 19, Tutor, Cadet, York AV Roe and Co Ltd [Contains 81 drawings] 1941 - 1946 532057 B5752 359B Avro Anson Cadet AV Roe and Co Ltd [Contains 70 drawings] 1932 - 1947 852961 B5752 360B Avro Anson Cadet AV Roe and Co Ltd [Contains 48 drawings] 1935 - 1943 852966 B5752 360C Avro Anson Cadet AV Roe and Co Ltd [Contains 48 drawings] 1935 - 1935 852969 B5752 374B Avro Anson Tudor and Canadian AV Roe and Co Ltd [Contains 31 drawings] 1931 - 1945 852980 B5752 374C Avro Anson Tudor and Canadian AV Roe and Co Ltd [Contains 20 drawings] 1939 - 1947 852986 B5752 512B Avro Anson Cadet AV Roe and Co Ltd [Contains 254 drawings] 1931 - 1947 852996 B5752 552B Avro Anson, Avro 19, Tutor, Cadet, York AV Roe and Co Ltd [Contains 48 drawings] 1927 - 1948 853013 B5752 436 Avro Anson Cadet - AV Roe and Co Ltd [Contains 63 drawings] 1935 - 1942 1000871 B6118 30 PART 1 [AVRO 652A type ANSON; Manufacturer's diagrams - A V ROE & Co Ltd, Aeronautical Engineers, Manchester, London & Hamble; drawing numbers include: 132/F26S5; 5 & 6/Z2151; 3/ES10; Z2151; 6 & 7/E.76S; 4S/F.2696;10/E.S10; F2705; 3/F.2S21; Z1668; F.2685][Folder 1 of 4] circa1934 - circa1944 1834277 Access status: Not yet examined, so a request to open them has to be made, which will take time to resolve. B6118 30 PART 2 [AVRO 652A type ANSON; Manufacturer's diagrams - A V ROE & Co Ltd, Aeronautical Engineers, Manchester, London & Hamble; drawing numbers include: 132/F26S5; 5 & 6/Z2151; 3/ES10; Z2151; 6 & 7/E.76S; 4S/F.2696;10/E.S10; F2705; 3/F.2S21; Z1668; F.2685][75 x 100cm][Folder 2 of 4] circa1934 - circa1944 5945320 B6118 30 PART 3 [AVRO 652A type ANSON; Manufacturer's diagrams - A V ROE & Co Ltd, Aeronautical Engineers, Manchester, London & Hamble; drawing numbers include: 132/F26S5; 5 & 6/Z2151; 3/ES10; Z2151; 6 & 7/E.76S; 4S/F.2696;10/E.S10; F2705; 3/F.2S21; Z1668; F.2685][50 X 67cm][Folder 3 of 4] circa1934 - circa1944 5945321 B6118 30 PART 4 [AVRO 652A type ANSON; Manufacturer's diagrams - A V ROE & Co Ltd, Aeronautical Engineers, Manchester, London & Hamble; drawing numbers include: 132/F26S5; 5 & 6/Z2151; 3/ES10; Z2151; 6 & 7/E.76S; 4S/F.2696;10/E.S10; F2705; 3/F.2S21; Z1668; F.2685][50 X 67cm][Folder 4 of 4] circa1934 - circa1944 5945322 Readable online, A14487 12/AB/2365 Air Board Agenda 2365 (RAAF) - Spares for conversion of unflapped Avro Anson aircraft - Overseas Indent No. 685 1938 - 1939 24190307, from wood no flaps to metal with flaps. A14487 20/AB/3538 Air Board Agenda 3538 (RAAF) - Supply of Anson airframe spares - Demand Aircraft Production Commission No. 542 1941 - 1941 24380763 (contains a list) If in London, AVIA 14/64/12 Ministry of Aircraft Production and predecessors: Royal Aircraft Factory, later Royal Aircraft Establishment: Aircraft, Engine and Equipment Drawings. ANCILLARY EQUIPMENT. Aerodyramic data sheets. Avro Anson 18/35. Held by: The National Archives, Kew - Ministry of Aviation Date: 14 December 1936 Reference:

Thanks for the review and extra details, I quoted what the USN orders ended up as given the topic was the Martlet. I do not think I missed any. Contract 46973, 2 March 1936 became 63072, 3 October 1938, for 1 XF4F-3 (ex XF4F-1 and XF4F-2) P&W XR-1830-76. Notes: Carrier - Low wing monocoque - Replaces XF4F-1 design. Returned to contractors works for modification from XF4F-2 to XF4F-3 on August 1938. Delivered Anacostia April 1939 for trials as XF4F-3 C-63072. Returned to contractors works June 1939. Finally accepted August 1939. Contract 68219, 8 August 1939, for 78 F4F-3, P&W R1830-76, plus 1 X4F-4 with the same engine, 2 XF4F-5 with Wright R-1820-40 and 1 XF4F-6 with a furnished by contractor P&W R-1830-90. According to the USN record of acceptances 68219 consisted of 54 F4F-3 plus 1 XF4F-6 (Though its entry is dated 20 November 1940, versus 8 August 1939 for the F4F-3), 27 F4F-3 added, 3 cancelled, 1 XF4F-4 and 2 XF4F-5 added. Contract 75736, 5 August 1940, for 107 F4F-3 with P&W R-1830-76/86 plus 95 F4F-3A with P&W R-1830-90 and 596 F4F-4 with P&W R-1830-86 and 21 F4F-7 with P&W R-1830-86. Mathematics first, USN record of acceptances, contract for 67 F4F-3, 95 F4F-3A and 335 F4F-4. Notes: F4F-3, initially 67 with 40 added, Originally 243 F4F-4 contracted for, extended for 254 additional F4F-3, -3A and -4. F4F-3A, initially 95 with 30 cancelled (actually "Diverted to Greece, not included in Navy totals"), Originally 80 F4F-3A and 15 F4F-4A. Similar to British Martlet III. Carrier development of F4F-3. F4F-4 to the original 335 there were 162 additions and 40 cancellations, then 160 additions and 21 cancellations. Quantity reduced by 40 to be delivered as F4F-3, increased by supplemental contract to include 162 additional 23 June 1941, 21 diverted to F4F-7, increased by second supplementary contract to include 160 additional 28 July 1941. Carrier. Development of XF4F-4. Manually operated folding wings. No floatation. F4F-7 21 added to order. The above from the 1942 notes, the 1943 F4F-4 notes, originally 243 F4F-4 contracted for; extended for 254 additional F4F-3, -3A, -4. 95 diverted to F4F-3A and 67 to F4F-3. From total of 335, 40 were diverted to be delivered as F4F-3; 162 were added by supplemental contract 23 June 1941; 21 were diverted to F4F-7; 160 were added by a second supplementary contract 28 July 1942. Contract 99340, 16 May 1942, for 573 F4F-4 with P&W R-1830-86 plus 2 XF4F-8 with Wright R-1820-56 and 100 F4F-3 with P&W R-1830-86/76. Mathematics, 575 F4F-4 ordered, 2 cancelled, 2 XF4F-8 added, 100 F4F-3. Notes on F4F-3 These planes were changed from F4F-7 to F4F-3. Manufactured as landplanes, converted to F4F-3 (seaplane) by service personnel.

Pulling everything together, notes from RAF contract cards and USN record of acceptances. There are some disagreements with the web site’s Martlet article. Martlet I ex French order F-292, requisition 2/E1/40 for 95 mark I (14 mark III serials reported as mark I, AX725 to 38) Wright GR-1820-G205A-2, the 81 Martlet I serials were AL236-AL262 (At RNAS Donibristle November and December 1940) , AX824-AX829 (at Scottish Aviation August 1940), BJ507-BJ527 (At Scottish Aviation September 1940 on) and BJ554-BJ570 while BT447-BT456 were allocated to the 10 lost at sea. AL231 to 235 cancelled, replaced by AX824 to 829, so 5 cancelled, 6 replacements. Martlet II/F4F-3/G-36B, order A-1548, requisition 2/E1/40, P&W R-1830-S3C4G. AM954 to AM999 and AJ100 to AJ153, with AM954 to AM963 having fixed wings and later considered mark III, total 100. Contract cards have AM954, AJ107, 109 listed as lost at sea while AJ110 and 111 look like they share the fate of AJ109. A photograph of AM958 suggests it was not fitted with R-1830-76 but with single stage version R-1830-90 as it lacks the small bulge covering near the wing leading edge for the intercoolers. USN order 68219 F4F-3 production ended in February 1941, with the R-1830-76, order 75736 F4F-3A production March to May 1941 with the R-1830-90, F4F-3 production from May 1941 with the R-1830-76 or 86. Martlet II Order, 10 in March 1941 (became mark III), then June on, engine R-1830-S3C4G. So were the first 10 of the Martlet II order F4F-3A or a hybrid with fixed wings and the P&W R-1830-76, -86 or S3C4G? F4F-3A/Martlet III, Diversion from USN order 75736, requisition BSC.1465, P&W R-1830-90, AX724 to AX747, AX753 to AX754, AX761 and HK840 to HK842, total 30. Originally for Greece. AX725 to AX738 incorrectly listed as mark I in RAF Contract Card summary making the mark I order 95. AX741 to 747 and AX761 have RAF Serial Register entries. The import report has 27 Wildcat arriving in the Middle East in July 1941 and 3 more in October. Martlet IV/Wildcat IV/F4F-4B, order LL-83734, requisition BSC.154 for 150, requisition BSC.7207 for 70, total 220. Wright R-1820-G205A furnished by Britain, given the bottleneck engine supply was at the time it suggests the engines were available from a British engine order, saving on R-1830, plus providing compatibility for the Martlet I. Serials FN100 to FN319 with FN205 to 207, FN240 and FN241 lost at sea. Wildcat V/FM-1,from USN order 99036, requisition BSC N.4, P&W R-1830-86, the USN reports 311 accepted for RN as JV325 to JV636, which is 312 serials, BuNo. 15415/JV428 reported delivered to USN, then in 1943 to Britain. JV325 to 414 did not have USN BuNo. Wildcat VI/FM-2 from USN order NOa(s)-227 (99036), requisition BSC N.4, Wright R-1820-56/72W in 1943, -72W in 1944, -56W in 1945, serials JV637 to JV924 and JW785 to 836, total 340. The USN reports 98+242 = 340 FM-2 accepted for RN, indicating serials JZ860 to 899 were not used. FM-2 acceptances for Britain ceased in May 1945, which is 3 months before FM-2 production ended. USN orders, Contract 46973, 2 March 1936 became 63072, 3 October 1938, for 1 XF4F-3 (ex XF4F-1 and XF4F-2) P&W XR-1830-76 Contract 68219, 8 August 1939, for 78 F4F-3, P&W R1830-76, plus 1 X4F-4 with the same engine, 2 XF4F-5 with Wright R-1820-40 and 1 XF4F-6 with a furnished by contractor P&W R-1830-90 Contract 75736, 5 August 1940, for 107 F4F-3 with P&W R-1830-76/86 plus 95 F4F-3A with P&W R-1830-90 and 596 F4F-4 with P&W R-1830-86 and 21 F4F-7 with P&W R-1830-86 Contract 99340, 16 May 1942, for 573 F4F-4 with P&W R-1830-86 plus 2 XF4F-8 with Wright R-1820-56 and 100 F4F-3 with P&W R-1830-86/76. Contract 99036, 18 April 1942, for 1,150 FM-1 (311 for RN) with P&W R-1830-86 Contract NOa(s)-227 (99036), 31 December 1943, for 4,100 FM-2 (340 for RN) plus another 1,423 in 1945 of which 746 were cancelled, with Wright R-1820-56/72W in 1943, -72W only in 1944, -56W in 1945, a total of 4,777 built. Contract NOas-1662, N.A.M. 1107 for 3 XF2M-1 dated 31 October 1944, cancelled. Martlet I production July to October 1940, F4F-3 production 2 in August 1940, then November 1940 to February 1941, May to December 1941, February to March 1942, January to May 1943, F4F-3A production March to May 1941. F4F-4 production November 1941 to December 1942, F4F-7 production January, March, May to September, November and December 1942. FM-1 production September 1942 to December 1943. FM-2 production September 1943 to August 1945. Total production 7,905. From USN Aircraft performance charts, propellers F4F-3, F4F-7 Curtiss Elec. CS 3 Blade 9 ft 9 in, Blade Design No. 512 F4F-4, FM-1 Curtiss Elec. CS 3 Bl. 9 ft 9 in, Blade. Design No. 512-ICL-5-15 FM-2, Curtiss electric CS 3 blade 10 foot, blade design No. 109354-12 Admiralty Fleet Order 3186/1943 Martlet I and IV Aircraft Types of Engines Fitted. A.M.R. 2498/43. - 15 July 1943. Some confusion may at present exist concerning the types of Cyclone engines which can be fitted in Martlet I and IV, due to the large variety of type numbers which may be found stamped on the engine date plates. 2 (a) Engines suitable for the Martlet I : Cyclone G.205A, Cyclone G.205A-2 2 (b) Engines suitable for the Martlet IV : Cyclone G.205A-3, Cyclone G.251A, Cyclone R.1820-40B 3 Apart from minor differences between the engines listed in 2(a) and 2 (b) above, such as ignition harness elbows, tachometer drives etc., the main difference is that 2(a) are fitted with 3 jaw starter shaft dog suitable for an electric-inertia starter, while 2(b) are fitted with a 12 jaw starter shaft dog suitable for a cartridge starter. 4. Engines shown within groups 2(a) and 2(b) respectively are interchangeable with other engines shown in the same group. 5. All engines shown in group 2(b) are fitted with an external oil scavenge line running from the oil pump at the rear of the engine to the sump at the front of the engine. Engines in group 2(a) were not originally fitted with this external scavenge line, but are being fitted on overhaul by the incorporation of Mod. Cyclone/45 so that this line alone may NOT be taken as a criterion by which to identify Martlet IV engines.

From USN Aircraft performance charts, propellers F4F-3, F4F-7 Curtiss Elec. CS 3 Blade 9 ft 9 in, Blade Design No. 512 F4F-4, FM-1 Curtiss Elec. CS 3 Bl. 9 ft 9 in, Blade. Design No. 512-ICL-5-15 FM-2, Curtiss electric CS 3 blade 10 foot, blade design No. 109354-12 Notes from USN record of acceptances, engines XF4F-3 (ex XF4F-1 and XF4F-2) P&W XR-1830-76 Martlet I/G-36A, ex French order F-292, Wright GR-1820-G205A-2, no USN equivalent F4F-3 P&W R-1830-76 in 1940, -76 or -86 in 1941, -86 in 1942 F4F-3/G-36B/Martlet II P&W R-1830-S3C4G F4F-3A/Martlet III P&W R-1830-90 XF4F-4 P&W R-1830-76 F4F-4 P&W R-1830-86 F4F-4B/Wildcat IV Wright R-1820-G205A furnished by British. XF4F-5 Wright R-1820-40 XF4F-6 P&W R-1830-90, furnished by contractor. F4F-7 P&W R-1830-86 XF4F-8 Wright R-1820-56 FM-1/Wildcat V P&W R-1830-86 FM-2/Wildcat VI Wright R-1820-56/72W in 1943, -72W in 1944, -56W in 1945.

Z4018 was a IIB, last of its serial block, built by Hawker, Taken on Charge 27 July 1941. Z4022 was the first of its serial block, a Gloster built mark I, taken on charge 13 February 1941. All the Iceland Hurricanes were Gloster built mark I. 1423 flight officially disbanded in October 1943 at Ouston (Flying Units of the RAF by Alan Lake.) Z4575, Z4607, Z4617, Z4631, Z4639 and Z4702 were shipped on the Empire Energy, Code Name Alabaster dated 21 May 1941, reported with 1423 flight on 16 June, 6 days after the flight officially formed. 98 squadron summary of events says on 4 June 1941 a party was sent to Reykjavik to erect the Hurricanes which had arrived in crates, on 8 June the first two Hurricanes were flown to Kaladarnes arriving 20.30 hours. On 10 June the remaining 4 Hurricanes were flown in, along with the arrival of 14 new men as ground crew. The Hurricanes form a flight of 98 squadron. First scramble on 14 June. 98 squadron summary of events reports on 15 July the Hurricane flight personnel moved to Reykjavik, On 19 July WAR/CC/216 dated 23 May 1941 received from Air Ministry establishing 1423 flight with 8+2 Hurricanes and 2 Battles. Z4037, Z4045, Z4048 and Z4049 received in crates on 26 July 1941, as well the Hurricane flight personnel separated from the squadron to operate independently. Two of the newly arrived Hurricanes were air tested on 30 July. Z4037, Z4045, Z4048 and Z4049 all have a deleted En Route to ME entry, dated 8 July 1941, the next entry is Iceland, 1423 Flight 26 July. Z4607 Crashed at Ksja Iceland 23 September 1941, the rest returned to Britain, all reported at 47 MU on 11 February 1942. Z4575 and Z4671 ended up in India, Z4702 with the RN, Z4037 to Ireland, the others stayed in Britain. Z4048, 5 MU 12 Feb 41, 47 MU 25 Jun 41, En route ME 9 Jul 41 (Cancelled), Iceland 1423 Flt 26 Jul 41, 47 MU 11 Feb 42, RIW 24 Feb 42, 13 MU 9 May 42, 46 MU 19 May 42, 42 SLG 25 Jun 42, 22 MU 23 Jul 42, 289 Sqn 30 Aug 42, FA Cat AC 2 Nov 43, ROS 10 Nov 43, 289 Sqn 10 Dec 43, 22 MU 12 Apr 44, Cat E 23 Oct 44

For the Aircraft Serial Number Record to be incorrect it would only require making the notation on the adjacent page, given there are 100 serials to the page, so 57480 to 57579 then 57580 to 57679. Also all the other F4U-4C notes are typed, the ones for 57567 to 57569 are hand written. After hunting off and on for a while I have come to the conclusion the F4U-4C were in fact the F4U-4B which were built from April 1946. So far no serial list or individual card I have seen mentions F4U-4C in the F4U-4 Bureau numbers, 80764 to 82177 = 1,414 aircraft, 96752 to 97390 = 639 less 97296 and 97634 to XF4U-5 = 637 total 2,051 F4U-4B serials were 97391 to 97531 = 141 less 97435 to XF4U-5 = 140, accepted from 30 April to November 1946 and 62915 to 63071 = 157, accepted November 1946 to August 1947, total 297 of which 11 were accepted as F4U-4P (references dispute exactly which 11). A photograph of 97448, accepted 25 July 1946, has F4U-4C painted on the tail. I know there were problems with the US built 20mm cannon and the conversion of 47 F4U-1C back to -1D supports the idea that after the 200 F4U-1C the next batch of cannon armed F4U were the F4U-4B, which were originally designated F4U-4C. I assume there is a report that F4U-1D 50277 was converted to the -1C, not sure what "crash/cover aircraft as 82305" means, all I have is it was accepted as an F4U-1D on 19 October 1944.

Thanks for the check and correction, agreed on point 2 (the 90 should have been 79), but not point 1, as I am looking at the airplane serial number record.

Looking at the squadron records at the UK National Archives says 2 April 1941 P/O Briggs killed in flying accident at Washeton on patrol departed 10.45, no further details, no individual aircraft letter given. Your best chance is the file AIR 81/5662 Pilot Officer M F Briggs: killed; aircraft accident near Richmond, Yorkshire, Spitfire P8049, 41 Squadron, 2 April 1941 The file has not been scanned, you would need to visit the archives or pay for them to scan it for you.

Mark VI, R7120 prototype taken from the production line in January 1941. Actual mark VI production began in December 1941, finishing in November 1942, had a pressure cabin and used the extended wing. The mark VII prototype AB450 was officially a conversion, coming off the production line as a Vb probably in February 1942. Mark VII production September 1942 to May 1944. The mark VIII being the unpressurised VII hence the extended wing tips on some VIII. F.VIII production November 1942 to September 1943, plus 20 in November, LF.VIII production May 1943 to January 1945, HF.VIII production May to November 1944, plus the final VIII in March 1945. May to November mark VIII production was 359 LF and 159 HF. Supermarine built F.IX June 1942 to June 1943, plus 40 LF.IX February to June 1943. Castle Bromwich built F.IX February to October 1943, also 1 LF.IX in both April and June 1943 before starting full production in August 1943, finishing in August 1945. HF.IX production began in March 1944 finishing in June 1945, March 1944 to June 1945 production totals were 2,622 LF and 400 HF.IX.

Total PBJ-1 accepted, 50 C, 152 D, 1 G, 248 H, 255 J, total 706. USN Idea of contracts, NAer-10000-6 dated 14 January 1943, (from USAAF contracts AC-19341, 27930, 30478), for 300 aircraft less 48 reallocated, 50 C, 152 D, 49 J (under NAER-10000-6/79), 1 G (under NAer-10000-6), BuNo 34998 to 35249, also under NAER-10000-6/79 dated 17 April 1943, 200+48 H BuNo 35250 to 35297, 88872 to 89071. NAer-20000-25 dated 19 June 1944 for 83 J, BuNo 38980 to 39012, 64943 to 64992. NAer-30000-119 dated 19 January 1945 for 123 J BuNo 35798 to 35920. To see what the USAAF documentation says about PBJ From North American, Inglewood, B-25C/PBJ-1C 42-64502 to 64506, quantity 5, accepted in Feb-43, BuNo 34998 to 35002. NOTE: Not modified for allocation centre 42-64602 to 64621, quantity 20, accepted in Mar-43, BuNo 35003 to 22. NOTE: Initially to 2 to San Pedro, rest to NA Kansas 42-64708 to 64732, quantity 25, accepted in Apr-43, BuNo 35023 to 47. NOTE: Initially to Rosvelt, San Pedro, Louisville, Kansas City B-25G/PBJ-1G 42-65031 to 65031, quantity 1, accepted in Jul-43, BuNo 35097. NOTE: Initially to Anacosta B-25H/PBJ-1H 43-4471, quantity 1, accepted in Jan-44, BuNo 35280. NOTE: Initially to Omaha 43-4482, quantity 1, accepted in Jan-44, BuNo 35281. NOTE: Initially to Omaha 43-4492, quantity 1, accepted in Jan-44, BuNo 35282. NOTE: Initially to Omaha 43-4530, quantity 1, accepted in Feb-44, BuNo diverted to Navy, BuNo not given but is 88872. NOTE: Initially to NA Kansas 43-4542 to 4544, quantity 3, accepted in Feb-44, BuNo 35283 to 5. NOTE: Initially to NA Kansas 43-4591 to 4593, quantity 3, accepted in Feb-44, BuNo 35286 to 8. NOTE: Initially to NA Kansas 43-4638, quantity 1, accepted in Mar-44, BuNo 88873. NOTE: Initially to Omaha 43-4654 to 4656, quantity 3, accepted in Mar-44, BuNo 88874, 35292, 35259. NOTE: Initially to Omaha 43-4658 to 4661, quantity 4, accepted in Mar-44, BuNo 35293, 35250, 35251, 88875. NOTE: Initially to Omaha 43-4664 to 4667, quantity 4, accepted in Mar-44, BuNo 35294 to 6, 35252. NOTE: Initially to Omaha 43-4669 to 4673, quantity 5, accepted in Mar-44, BuNo 35253, 60, 54 to 56. NOTE: Initially to Omaha 43-4675 to 4676, quantity 2, accepted in Mar-44, BuNo 35261, 57. NOTE: Initially to Omaha 43-4682 to 4705, quantity 24, accepted in Mar-44, BuNo 35289 to 91, 62 to 79, 88876, 7, 89051. NOTE: Initially to Omaha 43-4709 to 4730, quantity 22, accepted in Mar-44, BuNo 35297, 58, 88878 to 97. NOTE: Initially to Omaha, except 43-4700, which has no modification centre entry. 43-4731, quantity 1, accepted in Apr-44, BuNo 88898. NOTE: Initially to Omaha 43-4732 to 4735, quantity 4, accepted in Mar-44, BuNo 88899 to 902. NOTE: Initially to Omaha 43-4736 to 4737, quantity 2, accepted in Apr-44, BuNo 88903 and 4. NOTE: Initially to Omaha 43-4738, quantity 1, accepted in Mar-44, BuNo 88905. NOTE: Initially to Omaha 43-4739 to 4835, quantity 97, accepted in Apr-44, BuNo 88906 to 89002. NOTE: Initially to Omaha 43-4836 to 4883, quantity 48, accepted in May-44, BuNo 89003 to 89050. NOTE: Initially to Omaha 43-5028 to 5038, quantity 11, accepted in Jun-44, BuNo 89052 to 62. NOTE: Initially to NA Kansas 43-5040 to 5048, quantity 9, accepted in Jun-44, BuNo 89064 to 71, 63. NOTE: Initially to NA Kansas From North American, Kansas City, B-25D/PBJ-1D 41-30730 to 30754, quantity 25, accepted in Jun-43, BuNo 35048 to 72. NOTE: Initially to NA Kansas 42-87157 to 87205, quantity 49, accepted in Jul-43, BuNo 35073 to 96, 98 to 122. NOTE: Initially to NA Kansas 43-3320 to 3344, quantity 25, accepted in Oct-43, BuNo 35123 to 47. NOTE: Initially to Martin Omaha 43-3570 to 3605, quantity 36, accepted in Dec-43, BuNo 35148 to 83. NOTE: Initially to Martin Omaha 43-3651, quantity 1, accepted in Dec-43, BuNo 35184. NOTE: Initially to Martin Omaha 43-3655, quantity 1, accepted in Dec-43, BuNo 35185. NOTE: Initially to Martin Omaha 43-3771 to 3778, quantity 8, accepted in Jan-44, BuNo 35186 to 93. NOTE: Initially to Omaha 43-3837 to 3843, quantity 7, accepted in Feb-44, BuNo 35196 to 202. NOTE: Initially to NA Kansas B-25J/PBJ-1J 43-3985 to 3986, quantity 2, accepted in Feb-44, BuNo 35194 and 5. NOTE: Initially to NA Kansas 43-27511 to 27515, quantity 5, accepted in Mar-44, BuNo 35203 to 7. NOTE: Initially to NA Kansas 43-27904 to 27910, quantity 7, accepted in May-44, BuNo 35215 to 21. NOTE: Initially to NA Kansas 43-27681 to 27687, quantity 7, accepted in Apr-44, BuNo 35208 to 14. NOTE: Initially to NA Kansas 43-28174 to 28180, quantity 7, accepted in Jun-44, BuNo 35222 to 8. NOTE: Initially to NA Kansas 44-28792 to 28801, quantity 10, accepted in Jul-44, BuNo 35229 to 38. NOTE: Initially to NA Kansas 44-29064 to 29073, quantity 10, accepted in Aug-44, BuNo 35239 to 48. 44-29276 to 29285, quantity 10, accepted in Sep-44, BuNo 35249 to 58. NOTE: Actual BuNo 35249, 38980 to 88 44-29290 to 29299, quantity 10, accepted in Sep-44, BuNo 35259 to 68. NOTE: Actual BuNo 38989 to 98 44-29510 to 29513, quantity 4, accepted in Nov-44, BuNo 64969 to 72. 44-29604 to 29623, quantity 20, accepted in Oct-44, BuNo 38999 to 39012, 64943 to 8. 44-29788 to 29794, quantity 7, accepted in Nov-44, BuNo 64949 to 55. 44-29801 to 29807, quantity 7, accepted in Nov-44, BuNo 64956 to 62. 44-29814 to 29819, quantity 6, accepted in Nov-44, BuNo 64963 to 8. 44-29870 to 29884, quantity 15, accepted in Nov-44, BuNo 64973 to 87. 44-29897 to 29901, quantity 5, accepted in Nov-44, BuNo 64988 to 92. 44-30353 to 30356, quantity 4, accepted in Feb-45, BuNo 35821 to 4. 44-30509 to 30531, quantity 23, accepted in Jan-45, BuNo 35798 to 820. 44-30693 to 30697, quantity 5, accepted in Feb-45, BuNo 35825 to 9. 44-30703 to 30710, quantity 8, accepted in Feb-45, BuNo 35830 to 7. 44-30716 to 30718, quantity 3, accepted in Feb-45, BuNo 35838 to 40. 44-30849 to 30851, quantity 3, accepted in Mar-45, BuNo 35877 to 9. 44-30856, quantity 1, accepted in Mar-45, BuNo 35880. 44-30961 to 30964, quantity 4, accepted in Mar-45, BuNo 35841 to 4. 44-30972 to 30975, quantity 4, accepted in Mar-45, BuNo 35845 to 8. 44-30980 to 30991, quantity 12, accepted in Mar-45, BuNo 35849 to 60. 44-31089 to 31098, quantity 10, accepted in Mar-45, BuNo 35861 to 70. 44-31099, quantity 1, accepted in Apr-45, BuNo 35871. 44-31100, quantity 1, accepted in Mar-45, BuNo 35872. 44-31101 to 31104, quantity 4, accepted in Apr-45, BuNo 35873 to 6. 44-31277 to 31296, quantity 20, accepted in May-45, BuNo 35881 to 900. 44-31444 to 31463, quantity 20, accepted in Jun-45, BuNo 35901 to 20. In September 1944 the USAAF records have the BuNo 35250 to 35268 for PBJ-1J, they were actually used for PBJ-1H, with the result the USAAF documents duplicate those serials. As note above 43-4700/BuNo 35277 is unique in its group, it did not go to a modification centre. The USAAF and USN documentation normally agree with each other in terms of monthly acceptances except for February to June 1944. One February and the June difference is probably B-25H 43-4530 which is marked diverted to Navy, it became BuNo 88872, accepted by the USAAF in February but did not leave the modification centre until June 1944, it is assumed the other differences are due to similar reasons

Can you please explain how the above two statements can be reconciled, given my quote "at the time there were 5 Halifax lines and it is unlikely the changes happened on all of them at the same time." Also what exactly are my assumed assumptions? Actually the biography says the new radiator was the reason for the designation change but clearly that normally came with a new engine. The Merlin 22 entered production in August 1942 with 283 built by the end of the year and 5,197 built in 1943. My quote was "This does not imply anything about any Halifax being built as mark II series 1 (special). I have no documentation to determine the proportion of built as versus modified to" how is a suggestion none were built? Please explain how this is your suggested suggestion. I reported the state of production as of end February 1943, in terms of numbers built and serial block being built. I know from RAF documentation that on a macro level the serial blocks were built in order, but there are always exceptions as some aircraft arrived earlier/later than the serials around them for a variety of reasons. Hence the flagging of the assumption built in serial order. As of February 1943 the Halifax Biography says the Handley Page line changed over to series 1a, after/around that you would expect the other lines to change, but no dates are given in any document I can find. I did provide an indication of the later serials in case someone with an interest, time and access to Halifax II and V photographs might want to see if they can narrow down the change over date, no earlier/later than sort of approach. Taken on charge dates, DT579 30 October 1943, DT635 21 November 1943, DT643 26 December 1943, DT792 3 February 1943. While most of the DT640 to 649 and 665 to 669 serials were taken on charge in late November 1942, DT643 and DT645 (1 January 1943) were delayed, appearing slightly later than the first DT700 serials, that is after most of the DT665 to 705 block. In macro terms in order but not in micro terms. So in February 1943 English Electric have about 30 DT serial aircraft with Taken on Charge dates between the 2nd and 16th plus 1 on the 28th, and a similar number of JB serial aircraft between the 19th and 28th. Official production for the month was 52.