Editing Avro Lancaster (section)

===Armament===

====Defensive armament====
[[File:Lancaster Mk I gun positions.jpg|thumb|upright=1.3|left|Battle of Britain Flight Lancaster Mk I ''PA474'' in flight showing nose, dorsal and tail .303 Browning gun positions]]
The Avro Lancaster was initially equipped with four [[Nash & Thompson]] [[Frazer Nash]] [[Hydraulic machinery|hydraulically]] operated turrets mounted in the nose, tail, mid-upper and underside. The original tail turret was equipped with four [[M1919 Browning machine gun#Browning .303 Mark II|Browning .303 Mark II]] machine guns and all other turrets with two such machine guns.<ref name="Lanc Story">Jacobs 1996{{page needed|date=January 2012}}</ref><ref name="Franks">Franks 2000, p. 83.</ref><ref name="goul garb 16"/>

Late on in the war, [[Freeman Dyson]] (as a 19-year-old who had yet to win a degree) put forward a case for the removal of the majority of the Lancaster's defensive armament. He argued that this would reduce the loss rate by increasing the Lancaster's cruising speed by up to {{cvt|50|mph}} (assuming the bomb load was not increased), making the bomber harder to intercept.<ref>Iveson 2009, p. 222.</ref> He also claimed reducing defensive air gunners would reduce human losses incurred with each aircraft lost.<ref>[[Freeman Dyson]], "The Children's Crusade" in ''Disturbing the Universe'', 1979.</ref> However this neglects the fact that the two main Luftwaffe [[night fighter]]s of the time, the [[Messerschmitt Bf 110]] and the [[Junkers Ju 88]] night fighters were capable of over {{cvt|300|mph}}, thus a {{cvt|50|mph}} increase over the Lancaster's normal cruising speed of around {{cvt|180|mph}}, giving a speed of {{cvt|230|mph}}, still left the Lancaster vulnerable to interception. The introduction of the [[Heinkel He 219]] and the jet-powered [[Messerschmitt Me 262]] erased any speed advantage and would have left the aircraft undefended. Consequently, Dyson's proposal was not adopted.

=====Nose turret=====
{{multiple image|align=right|total_width=380
|image1=A gun turret on a restored WW2 Lancaster bomber -b.jpg| width1=453|image_caption1=Mk.X nose with twin .303 Brownings in turret over bomb-aimer's position
|image2=Lancaster mk X-IMG 6218.jpg|width2=473|image_caption2=Nose turret from above, and bomber aimer's station
}}
Only the FN-5A<ref name="Lanc Story" /> nose turret which was similar to the FN-5 used on the preceding [[Avro Manchester]], the [[Vickers Wellington]] and the [[Short Stirling]] remained unchanged during the life of the design, except where it was removed.

=====Ventral turret=====
The ventral (underside) FN-64 turret quickly proved to be dead weight, being both difficult to sight because it relied on a periscope which limited the gunner's view to a 20-degree arc,<ref name="Lanc Story" /> and too slow to keep a target within its sights.{{NoteTag|Similar view and speed problems were commonplace in the era, having particularly afflicted the ventral turret in the [[North American B-25 Mitchell]] and other bombers.{{citation needed|date=July 2015}}}} Aside from early B.Is and the prototype B.IIs, the FN-64 was almost never used. When the [[Luftwaffe]] began using ''[[Schräge Musik]]'' to make attacks from below in the winter of 1943/1944, modifications were made, including downward observation blisters mounted behind the bomb aimer's blister<ref>Mod 913, Avro Manufacturing Drawing Z2511</ref> and official<ref>Mod 925, shown on Avro Manufacturing Drawing X815</ref> and unofficial mounts for {{cvt|.50|in|1}} machine guns or even {{cvt|20|mm}} cannon, firing through the ventral holes of the removed FN-64. The fitting of these guns was hampered as the same ventral position was used for mounting the [[H2S radar|H2S]] blister, which limited installations to those aircraft fitted with bulged bomb bays which interfered with the H2S.<ref name="Lanc Story" />

=====Mid-upper turret=====
[[File:A No. 57 Squadron Lancaster mid-upper gunner in his turret, February 1943. CH8795.jpg|thumb|Gunner in Fraser Nash FN50 mid-upper turret with twin .303 Brownings, February 1943]]
The mid-upper (dorsal or top) turret was an FN-50<ref name="Lanc Story" /><ref name="Franks" /> on early examples and the very similar FN-150 with improved sights and controls<ref name="Lanc Story" /> on later examples. On all but the earliest examples, this turret was surrounded by a coaming which provided a track for a cam-operated interrupter device which prevented the gunner from shooting the tail of his own aircraft.<ref name="Lanc Story" /> The Mk.VII and late Mk.X Lancasters used the heavier, electrically controlled Martin 250 CE 23A turret equipped with two {{cvt|.50|in}} machine guns<ref name="Lanc Story" /> which was mounted further forward to preserve the aircraft's longitudinal balance, and because it had an internal mechanism to prevent firing on the aircraft itself, it did not require a coaming.{{NoteTag|The Martin 250 CE 23A turret was the same unit which had been equipped upon many American bombers, such as the [[Consolidated B-24 Liberator]].{{citation needed|date=July 2015}}}}<ref name="Lanc Story" /> Other experimental turrets were tried out, including the FN-79 and the Boulton-Paul Type H barbette system.<ref name="Lanc Story" />

=====Tail turret=====
[[File:Lancaster tail gunner IWM CH 12776.jpg|thumb|upright|Gunner in the Nash & Thompson FN20 tail turret]]

The tail turret was the most important defensive position and carried the heaviest armament. Despite this, the turrets used, starting with the FN-20, were never entirely satisfactory and numerous designs were tried. The FN-20 was replaced by the very similar FN-120 which used an improved [[Gyro gunsight|gyroscopic gun sight]] (GGS).<ref name="Lanc Story" /> Many rear gunners insisted on having the centre section of [[Acrylic glass|perspex]] removed from the turret to improve visibility. The transparencies were difficult to see through at night, particularly when trying to keep watch for enemy night fighters that appeared without notice astern and below the aircraft when getting into position to open fire. This removal of perspex from the turret was called the "[[Gransden Lodge Airfield|Gransden Lodge]]" modification. Ammunition for the tail turret was 2,500 rounds per gun. Due to the weight, the ammunition was stored in tanks situated near the mid-upper turret's position and fed rearward in runways down the back of the fuselage to the turret.<ref>Stiriling, Neil. [http://www.wwiiaircraftperformance.org/Lancaster/Lancaster_I_III_ADS-b.jpg "Lancaster I/III data card."] ''wwiiaircraftperformance.org.'' Retrieved: 6 August 2013.</ref>

[[File:Rose Gun Turret RAF Museum London.JPG|thumb|left|The [[Rose turret]]]]
Gunners using both the FN-20 and 120 removed perspex and armour from the turret to improve visibility, but trials by the RAF showed that a [[de Havilland Mosquito]] night fighter was still able to get within a very short distance of the tail gunner without being spotted, confirming what the Luftwaffe had already realised. The [[Rose turret]] attempted to improve on the FN turrets by being completely open to the rear (improving visibility and allowing easier emergency egress) and by being fitted with two {{cvt|.50|in}} machine guns. It was installed in a small number of Lancasters but never became common.<ref name="Lanc Story" />

Ultimately radar, rather than improved visibility, made the turret more effective. The FN-121 was the Automatic Gun Laying Turret (AGLT), an FN-120 fitted with [[Village Inn (codename)|'Village Inn']] gun-laying [[radar]].<ref name="Lanc Story" /> Aircraft fitted with Village Inn were used as bait, flying behind the main formations to confront the night fighters that followed the formations and shot down stragglers. This significantly reduced operational losses; and gun-laying radar was added to the last versions of the turret. Before the end of the war, Lancasters built in the UK standardised on the FN-82 fitted with two {{cvt|.50|in}} machine guns and a gun-laying radar as production allowed, which was also used on early models of the Avro Lincoln. The disadvantage of all radar and radio transmitting systems is that attacking forces can locate aircraft by picking up transmissions.{{citation needed|date=April 2017}}

====Bombs====
{{multiple image|image_caption_align=left
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 | image1 =The bomb bay of an Avro Lancaster of No. 9 Squadron RAF at Bardney, Lincolnshire, loaded with 1,000lb bombs before a night raid on Stettin, 5 January 1944. CH18554.jpg
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 | image_caption1 = ''"Abnormal"'' industrial demolition load of 14 1,000-pound [[General-purpose bomb|medium capacity]] high-explosive bombs
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 | image_caption2 =''"Usual"'' [[area bombardment]] load – a 4,000-pound [[Blockbuster bomb|"Cookie" blast bomb]] with 12 Small Bomb Containers, each with 236 4-lb incendiary bombs<ref>{{cite web | url=http://www.iwm.org.uk/collections/item/object/205210816 | title=Royal Air Force Bomber Command, 1942–1945. CH18371 | publisher=Imperial War Museum | access-date=16 January 2016}}</ref>
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An important feature of the Lancaster was its unobstructed {{cvt|33|ft}} long bomb bay. At first, the heaviest bomb carried was the {{cvt|4000|lb}} high capacity HC "[[Blockbuster bomb|Cookie]]".<ref>[https://books.google.com/books?id=0SkDAAAAMBAJ&pg=PA48-IA3 "The Kite That Smashed Berlin"]. ''Popular Sciences'', March 1944, pp. 48C–48H.</ref> Bulged doors were added to 30 per cent of B.Is to allow the aircraft to carry {{cvt|8000|lb}} and later {{cvt|12000|lb}} "Cookies". The Lancaster also carried a variety of smaller weapons, including the Small Bomb Container (SBC) which held 236 {{cvt|4|lb}} or 24 {{cvt|30|lb}} incendiary and explosive incendiary bomblets; {{cvt|500|lb}} and {{cvt|1000|lb}} [[General-purpose bomb|General Purpose High Explosive (GP/HE) bombs]] (these came in a variety of designs); {{cvt|1850|lb}} parachute deployed [[magnetic mine|magnetic]] or [[acoustic mine|acoustic]] mines, or {{cvt|2000|lb}} armour-piercing (AP) bombs; {{cvt|250|lb}} Semi-Armour-Piercing (SAP) bombs, used up to 1942 against submarines; post-1942: {{cvt|250|lb}} or {{cvt|500|lb}} anti-submarine [[depth charge]]s.{{citation needed|date=May 2016}}

In 1943, [[No. 617 Squadron RAF|617 Squadron]] was created to carry out [[Operation Chastise]], the raid against the Ruhr dams. This unit was equipped with B.III (Specials), officially designated the "Type 464 (Provisioning)", modified to carry the {{cvt|9250|lb}} [[Bouncing bomb|"Upkeep" bouncing bomb]].<ref>McKinstry 2009, p. 265.</ref>{{NoteTag|In period material, the "Upkeep" [[bouncing bomb]] was frequently referred to as being a [[naval mine|mine]], rather than as a bomb.{{citation needed|date=May 2016}}}} The bomb bay doors were removed and the ends of the bomb bay were covered with fairings. "Upkeep" was suspended on laterally pivoted, vee-shaped struts which sprang apart beamwise when the bomb-release button was pressed. A drive belt and pulley to rotate the bomb at 500 rpm was mounted on the starboard strut and driven by a hydraulic motor housed in the forward fairing. The mid-upper turret was removed and a more bulbous bomb aimer's blister was fitted; this, as "Mod. 780", later became standard on all Lancasters, while the bombsight was replaced by a simple aiming device that consisted of a simple triangle of wood with a peephole at one corner and a nail in each of the other corners such that at the correct distance the nails coincided with the towers on the dams. Because each dam was a different width between the towers, each plane carried two or three different sights.<ref name="auto">Brickhill 1951, {{page needed|date=June 2020}}.</ref><ref>McKinstry 2009, p. 268.</ref> Two [[Signal lamp|Aldis lights]] were fitted in the rear bomb bay fairing, aimed forward so the bomb aimer could see the converging lights below his blister in the nose; the optimum height for dropping "Upkeep" was {{cvt|60|ft}} and, when shone on the relatively smooth waters of the dam's reservoirs, the light beams converged into a figure 8 when the Lancaster was flying at the correct height.<ref name="auto"/><ref>McKinstry 2009, p. 275.</ref>
The Type 464 Lancaster was also fitted with [[VHF|VHF radios]] (normally reserved for fighters) so that [[Guy Gibson|Gibson]], the squadron leader, could control the operation while over the target,<ref>Leo McKinstry (2010) ''Lancaster'' John Murray Publishers {{ISBN| 978-0-7195-2363-2}}. p. 277</ref> an early example of what became the [[master bomber]] role.

After the 'Dam Busters' raid 617 Squadron was converted to a high-altitude precision bombing squadron in preparation for the arrival of Barnes Wallis's forthcoming Earthquake bombs for attacking special and hardened targets, and while they were training for this the bouncing bomb variants of B.I Specials had the spars and equipment removed and were then modified to carry the {{cvt|21|ft}} long {{cvt|12000|lb}} [[Tallboy (bomb)|"Tallboy"]] bomb, a scaled-down version of the upcoming {{cvt|25.5|ft}} long {{cvt|22000|lb}} [[Grand Slam (bomb)|"Grand Slam"]] "earthquake" bombs which were still being built. Aircraft intended to carry the "Grand Slam" required extensive modifications. These included the removal of the dorsal turret and of two guns from the rear turret, the removal of the cockpit armour plating (the pilot's seatback), and the installation of Rolls-Royce Merlin Mk 24 engines for better take-off performance. The bomb bay doors were removed and the rear end of the bomb bay cut away to clear the tail of the bomb. Later the nose turret was also removed to further improve performance. A strengthened undercarriage and stronger mainwheels, later used by the [[Avro Lincoln]], were fitted.<ref name="Granfilm" />{{NoteTag|The weight in kilograms of the "Tall Boy" and "Grand Slam" bombs differs according to their source. The figures given are the most common.{{citation needed|date=July 2015}}}}

Specific bomb loads were standardised and given code names by Bomber Command:<ref>Mason, Francis K.
[http://www.lancaster-archive.com/lanc_bomb_loads.htm "Lancaster: Bomb Loads."] ''The Avro Lancaster'', 1990, February 2008. Retrieved December 2011.</ref>
[[File:Lancaster I NG128 Dropping Load - Duisburg - Oct 14 - 1944.jpg|thumb|Lancaster B.I of [[No. 101 Squadron RAF]] dropping bundles of '[[Chaff (countermeasure)|Window]]' followed by {{cvt|30|lb}} incendiaries and a [[Blockbuster bomb|{{cvt|4000|lb}} "cookie"]]]]
[[File:Lancaster Bomber At The Main Gate, RAF Scampton - geograph.org.uk - 198631.jpg|thumb|[[Tallboy (bomb)|Tallboy]] bombs displayed with a standard ''R5868'' Lancaster at [[RAF Scampton]].]]

{| class="wikitable"
!Codename!!Type of raid or target!!Bomb load
|-
|"Arson"||incendiary area bombing ||14 SBC, each with 236 x {{cvt|4|lb}} Incendiary and Explosive Incendiary bomblets, total 3,304.
|-
|"Abnormal"||factories, railway yards, dockyards||14 x {{cvt|1000|lb}} [[General-purpose bomb|GP/HE bombs]] using both impact and long delay (up to 144 hours) fuses.
|-
|"Cookie"—or—"Plumduff"||Blast, demolition and fire||1 x [[Blockbuster bomb|{{cvt|4000|lb}} impact-fused HC bomb]]. 3 x {{cvt|1000|lb}} GP/HE bombs, and up to 6 SBCs with 1,416 incendiary bomblets.
|-
|"Gardening"||Mining of ports, canals, rivers and seaways||6 x {{cvt|1850|lb}} parachute mines.
|-
|"No-Ball"||[[V-1 flying bomb|V-1 flying bomb launch sites]]||1 x {{cvt|4000|lb}} impact fused HC and up to 18 x {{cvt|500|lb}} GP bombs, with both impact and delay fusing.
|-
|"Piece"||Docks, fortifications and ships||6 x {{cvt|2000|lb}} short-delay fused AP bombs, plus other GP/HE bombs based on local needs or availability.
|-
|"Plumduff-Plus"||Heavy industry||1 x {{cvt|8000|lb}} impact or barometric fused HC and up to 6 x {{cvt|500|lb}} impact or delay fused GP/HE bombs.
|-
|"Usual"||Blast and incendiary area bombing||1 x {{cvt|4000|lb}} impact-fused HC bomb, and 12 SBCs with a total of 2,832 incendiary bomblets.
|-
|no code name given||Medium-range low altitude tactical raids||6 x {{cvt|1000|lb}} short and long delay fused GP/HE bombs, additional {{cvt|250|lb}} GP/HE bombs sometimes added.
|-
|no code name given||Submarines|| (up to 1942): 5 x {{cvt|250|lb}} short-delay fuse SAP bombs for surfaced [[U-boat]]s; (post-1942): 6 x {{cvt|500|lb}} and 3 x {{cvt|250|lb}} anti-submarine depth charge bombs.
|}
[[File:Royal Air Force Bomber Command, 1942-1945. CH15375.jpg|thumb|A 617 Squadron Lancaster dropping a Grand Slam bomb on the [[Arnsberg]] viaduct, March 1945.]]
[[File:Bremen-Farge, Royal Air Force Bomber Command, 1942-1945 CL2607.jpg|thumb|An RAF officer inspects the hole left by a Grand Slam in the reinforced concrete roof of the [[Valentin submarine pens|Valentin submarine factory]] in [[Bremen]], Germany]]
{|class="wikitable"
! Special-purpose weapons and codenames!!Type of target!!Weapon
|-
|"Upkeep"||Dams||1 x {{cvt|9250|lb}}, hydrostatic-fused "Upkeep" mine.
|-
|"Tallboy"||Very strong or durable structures (e.g.: submarine pens); battleship [[German battleship Tirpitz|Tirpitz]]||1 x {{cvt|12000|lb}} short-delay fused "Tallboy" bomb.
|-
|"Grand Slam"||As well as direct hits on very strong or durable targets (such as submarine pens) it could be used indirectly to create a [[camouflet]] (cavern) that undermined structures such as bridges, viaducts and bunkers causing them to collapse.||1 x {{cvt|22000|lb}} short-delay fused "Grand Slam" bomb.
|}
{{clear left}}

=====Bombsights=====
Bombsights used on Lancasters included:<ref>{{citation |last=Black |first=Henry |url=http://lancaster-archive.com/bc-bombsights.html |archive-url=https://web.archive.org/web/20071020002531/http://lancaster-archive.com/bc-bombsights.html |archive-date=2007-10-20 |title=Bombsights |work=lancaster-archive.com |date=2001 |accessdate=14 November 2010}}</ref>
;Mark IX [[Course Setting Bomb Sight]] (CSBS).
:This was an early preset vector bombsight that involved squinting through wires that had to be manually set based on aircraft speed, altitude and bombload. This sight lacked tactical flexibility as it had to be manually adjusted if any of the parameters changed and was soon changed in favour of more advanced designs.
;[[Mark XIV bomb sight|Mark XIV bombsight]]
:A vector bombsight where the bomb aimer input details of the bombload, target altitude and wind direction and the analogue computer then continuously calculated the trajectory of the bombs and projected an inverted sword shape onto a sighting glass on the sighting head. Assuming the sight was set correctly when the target was in the crosshairs of the sword shape, the bomb aimer would be able to accurately release the bombs.
;T1 bombsight
:A Mark XIV bombsight modified for mass production and produced in the USA. Some of the pneumatic gyro drives on the Mk XIV sight were replaced with electronic gyros and other minor modifications were made.
;[[Stabilizing Automatic Bomb Sight]]
:Also known as "SABS", this was an advanced bombsight mainly used by 617 Squadron for precision raids. Like the American [[Norden bombsight]] it was a tachometric sight.