Editing Napier Sabre (section)

===Production===
[[File:Hawker Typhoon 2 ExCC.jpg|thumb|The [[Hawker Typhoon]] was the first operational Sabre-powered aircraft, entering service with the RAF in mid-1941. Problems with both the Sabre engine and the airframe nearly led to the Typhoon's withdrawal from service.]]
Problems arose as soon as mass production began. Prototype engines had been hand-assembled by Napier craftsmen and it proved to be difficult to adapt it to assembly-line production techniques. The sleeves often failed due to the way they were manufactured from chrome-molybdenum steel, leading to seized cylinders, which caused the loss of the sole prototype [[Martin-Baker MB 3]].<ref name="Flinov45">Flight 1945, p.550.</ref><ref>Aeroplane 2010, pp. 65–66.</ref> The Ministry of Aircraft Production was responsible for the development of the engine and arranged for sleeves to be machined by the [[Bristol Aeroplane Company]] from its Taurus engine forgings. These nitrided austenitic steel sleeves were the result of many years of intensive sleeve development, experience that Napier did not have. Air filters had to be fitted when a new sleeve problem appeared in 1944 when aircraft were operating from Normandy soil with its abrasive, gritty dust.<ref>I Kept No Diary-60 Years with Marine Diesels, Automobile and Aero Engines, F.R. Banks 1978, Airlife Publications, {{ISBN|0 9504543 9 7}}, p.133</ref>

Quality control proved to be inadequate, engines were often delivered with improperly cleaned castings, broken piston rings and machine cuttings left inside the engine.<ref name="tempest">[http://www.hawkertempest.se/NapierSabre1.htm Napier Sabre] {{webarchive|url=https://web.archive.org/web/20120623153341/http://www.hawkertempest.se/NapierSabre1.htm |date=23 June 2012 }} Retrieved on 17 July 2009.</ref> Mechanics were overworked trying to keep the Sabres running and during cold weather they had to run them every two hours during the night so that the engine oil would not congeal and prevent the engine from starting the next day.{{#tag:ref|Unlike current "multigrade" [[motor oil]]s, the lubricants in use in the 1940s thickened up at low temperatures, thus preventing the Sabre from "picking-up" when started.|group=nb}} These problems took too long to remedy and the engine gained a bad reputation. To make matters worse, mechanics and pilots unfamiliar with the different nature of the engine, tended to blame the Sabre for problems that were caused by not following correct procedures. This was exacerbated by the representatives of the competing Rolls-Royce company, which had its own agenda. In 1944, Rolls-Royce produced a similar design prototype called the [[Rolls-Royce Eagle (1944)|Eagle]].

Napier seemed complacent and tinkered with the design for better performance. In 1942, it started a series of projects to improve its high-altitude performance, with the addition of a three-speed, two-stage [[supercharger]], when the basic engine was still not running reliably. In December 1942, the company was purchased by the [[English Electric|English Electric Company]], which ended the supercharger project immediately and devoted the whole company to solving the production problems, which was achieved quickly.

[[File:Napier Sabre on truck.png|thumb|A 2,400hp Sabre inside a mock-up of an aircraft nose, mounted on a truck for display purposes |alt=The truck has signs reading "2,400 Horsepower!! The power behind the Typhoon & Tempest fighters" and "Napier Sabre - The most powerful aero engine in service in the world", plus the Napier logo]]

By 1944, the Sabre V was delivering {{convert|2,400|hp|kW|abbr=off}} consistently and the reputation of the engine started to improve. This was the last version to enter service, being used in the [[Hawker Typhoon]] and its derivative, the [[Hawker Tempest]]. Without the advanced supercharger, the engine's performance over {{convert|20000|ft|m|abbr=on}} fell off rapidly and pilots flying Sabre-powered aircraft, were generally instructed to enter combat only below this altitude. At low altitude, both planes were formidable. As air superiority over Continental Europe was slowly gained, Typhoons were increasingly used as [[fighter-bomber]]s, notably by the [[RAF Second Tactical Air Force]]. The Tempest became the principal destroyer of the [[V-1 flying bomb]] ([[Fieseler Fi 103]]), since it was the fastest of all the Allied fighters at low levels. Later, the Tempest destroyed about 20 [[Messerschmitt Me 262]] jet aircraft.

Development continued and the later Sabre VII delivered {{convert|3,500|hp|kW|abbr=on}} with a new supercharger. By the end of World War II, there were several engines in the same power class. The [[Pratt & Whitney R-4360 Wasp Major]] four-row, 28-cylinder radial produced {{convert|3,000|hp|kW|abbr=on}} at first and later types produced {{convert|3,800|hp|kW|abbr=on}}, but these required almost twice the displacement in order to do so, 4,360 cubic inches (71 litres).