Editing BMW 801 (section)

==Design and development==

===Precursor design===
In the 1930s, BMW took out a license to build the [[Pratt & Whitney Hornet]] engines. By the mid-30s they had introduced an improved version, the [[BMW 132]]. The BMW 132 was widely used, most notably on the [[Junkers Ju 52]], which it powered for much of that design's lifetime.

In 1935 the [[Reich Air Ministry|RLM]] funded prototypes of two much larger radial designs, one from [[Bramo]], the Bramo 329, and another from BMW, the [[BMW 139]]. BMW's design used many components from the BMW 132 to create a two-row engine with 14 cylinders,{{citation needed|reason=text documentation is known to exist for it being an 18-cylinder engine|date=January 2015}} supplying 1,550&nbsp;PS (1,529&nbsp;hp, 1,140&nbsp;kW). After BMW bought Bramo in 1939 both projects were merged into the BMW 801, learning from the problems encountered in both projects.

The BMW 139 was originally intended to be used in roles similar to those of the other German radials, namely [[bomber]]s and [[Military transport aircraft|transport aircraft]], but midway through the program the Focke-Wulf firm's chief designer, [[Kurt Tank]] suggested it for use in the [[Focke-Wulf Fw 190]] fighter project. Radial engines were rare in European designs as they were considered to have too large a frontal area for good [[wikt:streamline|streamlining]] and would not be suitable for high speed aircraft. They were most popular on naval aircraft, where their easier maintenance and improved reliability were highly valued. Efforts to improve these designs led to new [[cowling]] designs that reduced the concerns about drag. Tank felt that attention to detail could result in a streamlined radial that would not suffer undue drag, and would be competitive with inlines.

The main concern was providing cooling air over the cylinder heads, which generally required a very large opening at the front of the aircraft. Tank's solution for the BMW 139 was to use an engine-driven fan behind an oversized, flow-through hollow [[Spinner (aeronautics)|prop-spinner]] open at the extreme front, blowing air past the engine cylinders, with some of it being drawn through S-shaped ducts over a [[radiator (engine cooling)|radiator]] for oil cooling. However this system proved almost impossible to operate properly with the BMW 139; early prototypes of the Fw 190 demonstrated terrible cooling problems. Although the problems appeared to be fixable, since the engine was already fairly dated in terms of design, in 1938 BMW proposed an entirely new engine designed specifically for fan-cooling that could be brought to production quickly.

===801 emerges===
[[File:BMW 801 engine.JPG|thumb|BMW 801 engine, [[BMW Museum]], Munich, Germany (2013)]]
The new design was given the name BMW 801 after BMW was given a new block of "109-800" engine numbers by the [[Reich Air Ministry|RLM]] to use after their merger with Bramo. The 801 retained the 139's older-style single-valve intake and exhaust, while most in-line engines of the era had moved to either three (as [[Junkers]] had done)<ref>{{cite web |url=https://www.flightglobal.com/pdfarchive/view/1937/1937%20-%202509.html?search=three%20valve |title=Flight Magazine, September 9, 1937 |author=<!--Not stated--> |date=September 9, 1937 |page=265 |website=flightglobal.com |publisher=Flightglobal Archive |access-date=March 15, 2017 |quote=At the recent international meeting at Zürich, several of the successful German machines were fitted with the new Junkers 210 petrol engine...'''Three valves per cylinder are provided, two inlets and one exhaust,''' operated by push rods and rockers from a single camshaft.}}</ref><ref>{{cite web |url=http://www.enginehistory.org/German/Jumo213/Jumo213.shtml |title=The Junkers Jumo 213 Engine |last=Culy |first=Doug |date=April 4, 2012 |website=enginehistory.org |publisher=Aircraft Engine Historical Society |access-date=March 15, 2017 |quote=The Jumo 213 had a three-valve head, but a four-valve head was in development for the “J” version. However, the Jumo 213A is documented as itself having superior high altitude performance at that particular point in time, although the DB 603 was later developed with equal or better features. |url-status=dead |archive-url=https://web.archive.org/web/20161221130406/http://www.enginehistory.org/German/Jumo213/Jumo213.shtml |archive-date=December 21, 2016 }}</ref> or four valves per cylinder, or in [[United Kingdom|British]] use for their own radials, [[sleeve valve]]s. Several minor advances were worked into the design, including the use of [[sodium]]-cooled valves and a [[Gasoline direct injection|direct fuel injection]] system, manufactured by Friedrich Deckel AG of Munich.

The [[supercharger]] was rather basic in the early models, using a single-stage two-speed design directly geared to the engine (unlike the [[Daimler-Benz DB 601|DB 601]]'s [[hydraulic]]ally clutched version) which led to rather limited altitude performance, in keeping with its intended medium-altitude usage. One key advancement for the 801 was the ''Kommandogerät'' (command-device), a mechanical-hydraulic unit that automatically adjusted engine fuel flow, propeller pitch, supercharger setting, mixture and ignition timing in response to a single throttle lever, dramatically simplifying engine control.<ref name=g8/> The ''Kommandogerät'' could be considered to be a precursor to the [[engine control unit]]s used for many vehicles' internal combustion engines of the late 20th and early 21st centuries.

There was a considerable amount of [[wind tunnel]] work done on the engine and BMW-designed forward cowling (incorporating the engine's oil cooler) at the ''[[Luftfahrtforschungsanstalt]]'' (''LFA'') facility in [[Völkenrode]], leading to the conclusion it was possible to reduce drag equivalent to {{convert|150|-|200|hp|kW PS|abbr=on}}. It also maximized the use of positive air pressure to aid cooling of cylinders, heads, and other internal parts.<ref>Christopher (2013), pp. 80–81</ref>

=== 801A and 801B ===
The first BMW 801As ran in April 1939, only six months after starting work on the design, with production commencing in 1940.<ref name="Gunston">Gunston (2006), p. 29</ref> The 801B was to be identical to the 801A except for the gearbox, which reversed the direction of the propeller rotation to counterclockwise as seen from behind the engine. The A and B models were intended to be used in pairs on twin-engine designs, cancelling out net [[torque]] and making the plane easier to handle. There is no evidence the 801B ever left the prototype stage. The BMW 801A/B engines delivered 1,560&nbsp;PS (1,539&nbsp;hp, 1,147&nbsp;kW) for takeoff. Major applications of the 801A/L engines include multiple variants of the [[Junkers Ju 88]] and [[Dornier Do 217]].

==== 801C and 801L ====
The BMW 801C was developed for use in single- or multi-engined fighters and included a new hydraulic prop control and various changes intended to improve cooling, including cooling "gills" on the [[cowling]] behind the engine in place of the original slots. The 801C was almost exclusively used in early variants of the [[Focke-Wulf Fw 190]]A. The BMW 801L was an A model with the hydraulic prop control mechanism introduced with the 801C engine. The C and L models delivered the same power as the original A model.

=== 801D-2 and 801G-2 ===
[[File:BMW 801 D2.JPG|thumb|right|BMW 801 D2 at the ''Flugmuseum Aviaticum'', Austria (2007)]]
The 801C was replaced with the BMW 801 D-2 series engines in early 1942, which ran on C2/C3 100 [[octane]] fuel instead of the A/B/C/L's B4 87 octane, boosting takeoff power to 1,700 PS (1,677&nbsp;hp, 1,250&nbsp;kW). The BMW 801G-2 and H-2 models were D-2 engines modified for use in bomber roles with lower gear ratios for driving larger propellers, clockwise and counterclockwise respectively. As with the 801B engine design, however, the 801H-2 engine did not leave the prototype stage.

The newer, 100 octane D-2 series and its derivatives had higher gear ratios, and higher compression ratios, than the earlier, 87 octane versions. The compression ratio of the 100 octane series was raised to 7.2 from the 6.5 of the 87 octane versions. This was possible because of the better fuel and the better (domed) shape of the combustion chamber.<ref> Bingham (1998), p. 67,68</ref><ref> Vernaleken (2010)</ref>

The D-2 models were tested with a system for injecting a 50–50 water-methanol mixture known as [[MW50]] into the supercharger primarily for its anti-detonation effect, allowing the use of increased boost pressures. Secondary effects were cooling of the engine and charge cooling. Some performance was gained, but at the cost of engine service life. This was replaced by a system that injected fuel instead of MW50, known as C3-injection, and this was used until 1944. [[Oil Campaign of World War II|The serious fuel shortage in 1944]] forced installation of MW50 instead of C3-injection. With MW50 boosting turned on, takeoff power increased to 2,000&nbsp;PS (1,470&nbsp;kW), the C3-injection was initially only permitted for low altitude use and increased take-off power to 1,870 PS. Later C3-injection systems were permitted for low-to-medium altitude use and raised take-off power to more than 1,900 PS.

=== Supercharger development ===
[[File:BMW801 Kommandogerät (1939) MTU-Museum 20231112 08w.jpg|thumb|BMW-Kommandogerät, a single-lever power control device for the BMW801, designed by Heinrich Leibach.]]
With the engine being used in higher-altitude fighter roles, a number of attempts were made to address the limited performance of the original supercharger. The BMW 801E was a modification of the D-2 using different [[gear ratio]]s, of 6:1 at low speed and 8.3:1 at high speed, that tuned the supercharger for higher altitudes. Although takeoff power was unaffected, cruise power increased over 100&nbsp;hp (75&nbsp;kW) and "high power" modes for climb at nearly 1,500 to 1,650 PS; and combat were likewise improved by up to 150&nbsp;hp (110&nbsp;kW). The E model was also used as the basis for the BMW 801R, which included a much more complex and powerful two-stage four-speed supercharger, as well as [[Die casting|die cast]] [[hydronalium]] [[cylinder head]]s, strengthened crankshaft and pistons, and chromed cylinders and exhaust valves; it was anticipated this version would produce over {{convert|2000|hp|kW PS|abbr=on}}, or over {{convert|2600|hp|kW PS|abbr=on}} with [[MW 50]] [[methanol]]-water injection.<ref name="Christopher, p.81">Christopher (2013), p. 81</ref>

The 801R, with its 2-stage, 4-speed supercharger, had a critical altitude of 11,000 meters. Above that altitude, the R could use additional boost by nitrous-oxide (GM-1) injection. The R was also bi-fuel. At its critical altitude, the R could deliver 1,400 PS.<ref> Gersdorff (1995), p. 66 </ref>

In spite of these improvements, the E model was not widely used. Instead, continued improvements to the basic E model led to the BMW 801F, which dramatically improved performance across the board, with takeoff power increasing to 2,400&nbsp;hp (1,790&nbsp;kW), making the 801 the only German aviation engine of an existing type that had a producible subtype that could [[Luftwaffe#Engine development|exceed 1,500 kW]] from a proven military aircraft powerplant. It was planned to use the F on all late-model Fw 190s, but the war ended before production started.

The 801F's supercharger had higher critical altitude, than the earlier D-2 series. The improved gear ratios increased the engine's critical altitude to between 7,000 and 8,000 meters. The 801F also had a stronger crankshaft and a fuel-injector pump of higher capacity. The version also had larger intake- and exhaust-valves, with increased valve-overlap. The engine, in the TF powerplant form also had better internal and external aerodynamics. On the test bench, the 801F could deliver 2,600 PS in 1945.<ref> Gersdorff (1995), p. 66 </ref>

The 801F was 25 centimeters longer, than the earlier 801 versions. The reason for this was to keep the balance of gravity of the Ta 152 aircraft.<ref> Gersdorff (1995), p. 66 </ref>

In 1944, the strongest production version of the 801, the 801S went into production. It had the same gear ratios, as the 801E, and it's supercharger used swirl-throttling. It used the parts of the earlier D-2, and in some parts, the above mentioned more advanced versions (E and F). The S also had an improved and simplified master controller and different magneto timing. The 801S also had altered valve-timing. In special-emergency mode, it could deliver 2,200 PS at sea-level.<ref> Gersdorff (1995), p. 66 </ref>

===Importance of continued development===
[[File:Junkers Ju 88 RAF Hendon.jpg|thumb|right|A surviving Ju 88R-1 night fighter with ''[[Power-egg|Kraftei]]'' unitized-installation BMW 801 engines. [[Royal Air Force Museum London]] (2007)]]
BMW had been required to create priorities for the 14-cylinder production 801 radial, the 18-cylinder [[BMW 802]] and liquid-cooled 28-cylinder [[BMW 803]] radial engines.

The first priority was for the 801 to be developed "to its limits", with the second priority the 802's design and prototype construction, and lastly the complex 803 four-row radial only receiving attention to its design-development.<ref>{{cite magazine |last=Fedden |first=Sir Roy |date=December 6, 1945 |title=German Piston-Engine Progress |page=603 |magazine=Flight Magazine |location=London, UK |publisher=Flightglobal }}</ref>

By contrast, [[Allies of World War II|Allied]] equivalents such as the American [[Wright R-2600#Variants|Wright ''Twin Cyclone'']], and the Soviet [[Shvetsov ASh-82#Variants|Shvetsov ASh-82]] radials never needed to be developed beyond 1,500&nbsp;kW as these nations possessed larger-displacement 18-cylinder radial aviation engines capable of more power.

=== Turbocharger development ===

As just one result of the highest level of priority given to the successful 801 design's further development, a number of attempts were made to use [[turbocharger]]s on the BMW 801 series as well. The first used a modified BMW 801D to create the BMW 801J,<ref name="801J engine photo at Flightglobal">[http://www.flightglobal.com/pdfarchive/view/1945/1945%20-%202394.html 801J engine photo at Flightglobal] (accessed March 11, 2016)</ref> delivering 1,810 PS (1,785&nbsp;hp, 1,331&nbsp;kW) at takeoff and 1,500&nbsp;hp (1,103&nbsp;kW) at {{convert|12200|m|abbr=on}}, an altitude where the D was struggling to produce 630&nbsp;hp (463&nbsp;kW). The BMW 801E was likewise modified to create the BMW 801Q, delivering a superb 1,715&nbsp;hp (1,261&nbsp;kW) at {{convert|12200|m|abbr=on}}.

The turbocharger was fitted behind the engine at a 30° forward tilt off a vertical axis, possessed hollow turbine blades in the exhaust section,<ref name="Christopher, p.81"/> and in a photo from ''Flight'' magazine, appears to have intercooler units fitted around the inner circumference of the rear cowl, just behind the rear row of cylinders.<ref name="801J engine photo at Flightglobal"/>

Not many of these engines ever entered production due to high costs, and the various high-altitude designs based on them were forced to turn to other engines, typically the [[Junkers Jumo 213]].

=== Surviving and operational examples ===
[[File:Fw190A-5 of Flying Heritage Collection.jpg|thumb|right|The [[Flying Heritage & Combat Armor Museum]]'s airworthy Fw 190A-5, WkNr. 151 227, between flights with its original, restored BMW 801 radial.]]
A sizable number of BMW 801s exist in museums, some on display by themselves, with some 20 of them associated with [[List of surviving Focke-Wulf Fw 190s|surviving examples of the Focke-Wulf Fw 190s]] that they powered in World War II. The first original Fw 190 to be restored to flight condition in the 21st century is the Fw 190A-5 discovered near St. Petersburg, Russia in 1989, bearing ''Werknummer'' 151 227 and formerly serving with [[Jagdgeschwader 54|JG 54]], was restored to flight condition along with its original BMW 801 powerplant. As of 2011, it is once again airworthy and located in [[Seattle]], [[Washington (state)|Washington]], [[United States|USA]].<ref>{{cite web |title=Focke-Wulf Fw 190 A-5 |url=http://www.flyingheritage.org/Explore/The-Collection/Germany/Focke-Wulf-Fw-190-A-5.aspx |website=Flying Heritage & Combat Armor Museum |access-date=17 November 2022}}</ref> The sole surviving [[Junkers Ju 388#Survivors|Ju 388]], in the hands of the [[Udvar-Hazy Center]] of the Smithsonian, has a pair of complete BMW 801J turbocharged engines still in its nacelles.

There is an 801-ML (801L) on display mounted in a Dornier 217 nacelle, essentially a complete surviving ''Motoranlage'' unitized powerplant, at the [[New England Air Museum]], [[Bradley International Airport]], Windsor Locks, CT.<ref>{{Cite web|url=http://neam.org/index.php?option=com_content&view=article&id=1072|title = New England Air Museum}}</ref> Likewise, the Ju 88R-1 night fighter at the
[[Royal Air Force Museum London]] (see photo above) also has unitized BMW 801 radials installed.